machine

package
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 Go to latest Published: Feb 21, 2026 License: MIT Imports: 18 Imported by: 24

README

🦾 /pkg/machine

cd /

[!NOTE] asyncmachine-go is a batteries-included graph control flow library (AOP, actor model, state-machine).

/pkg/machine is a nondeterministic, multi-state, clock-based, relational, optionally accepting, and non-blocking state machine. It's a form of a rules engine that can orchestrate blocking APIs into fully controllable async state-machines. Write ops are state mutations, read ops are state checking, and subscriptions are state waiting. It's dependency-free and a building block of a larger project.

Installation

import am "github.com/pancsta/asyncmachine-go/pkg/machine"

Features

Features are explained using Mermaid flow diagrams, and headers link to relevant sections of the manual.

Multi-state

Many states can be active at the same time.

Clock and state contexts

States have clocks that produce contexts (odd = active; even = inactive).

Queue

Queue of mutations enable lock-free Actor Model.

AOP handlers

States are Aspects with Enter, State, Exit, and End handlers.

Negotiation

Transitions are cancellable (during the negotiation phase).

Relations

States are connected via Require, Remove, and Add relations.

Subscriptions

Channel-broadcast waiting on clock values.

Error handling

Error is a state, handled just like any other mutation.

val, err := someOp()
if err != nil {
    mach.AddErr(err, nil)
    return // no err needed
}
Tracers

Synchronous tracers for internal events.

TransitionInit TransitionStart TransitionEnd HandlerStart HandlerEnd
MachineInit MachineDispose NewSubmachine QueueEnd SchemaChange VerifyStates

Usage

Raw Strings
// ProcessingFile to FileProcessed
// 1 async and 1 sync state
package main

import am "github.com/pancsta/asyncmachine-go/pkg/machine"

func main() {
    // init the state machine
    mach := am.New(nil, am.Schema{
        "ProcessingFile": { // async
            Remove: am.S{"FileProcessed"},
        },
        "FileProcessed": { // async
            Remove: am.S{"ProcessingFile"},
        },
        "InProgress": { // sync
            Auto:    true,
            Require: am.S{"ProcessingFile"},
        },
    }, nil)
    mach.BindHandlers(&Handlers{
        Filename: "README.md",
    })
    // change the state
    mach.Add1("ProcessingFile", nil)
    // wait for completed
    select {
    case <-time.After(5 * time.Second):
        println("timeout")
    case <-mach.WhenErr(nil):
        println("err:", mach.Err())
    case <-mach.When1("FileProcessed", nil):
        println("done")
    }
}

type Handlers struct {
    Filename string
}

// negotiation handler
func (h *Handlers) ProcessingFileEnter(e *am.Event) bool {
    // read-only ops
    // decide if moving fwd is ok
    // no blocking
    // lock-free critical section
    return true
}

// final handler
func (h *Handlers) ProcessingFileState(e *am.Event) {
    // read & write ops
    // no blocking
    // lock-free critical section
    mach := e.Machine
    // clock-based expiration context
    stateCtx := mach.NewStateCtx("ProcessingFile")
    // unblock
    go func() {
        // re-check the state ctx
        if stateCtx.Err() != nil {
            return // expired
        }
        // blocking call
        err := processFile(h.Filename, stateCtx)
        // re-check the state ctx after a blocking call
        if stateCtx.Err() != nil {
            return // expired
        }
        if err != nil {
            mach.AddErr(err, nil)
            return
        }
        // move to the next state in the flow
        mach.Add1("FileProcessed", nil)
    }()
}
Waiting

Subscriptions do not allocate goroutines.

// wait until FileDownloaded becomes active
<-mach.When1("FileDownloaded", nil)

// wait until FileDownloaded becomes inactive
<-mach.WhenNot1("DownloadingFile", nil)

// wait for EventConnected to be activated with an arg ID=123
<-mach.WhenArgs("EventConnected", am.A{"ID": 123}, nil)

// wait for Foo to have a tick >= 6
<-mach.WhenTime1("Foo", 6, nil)

// wait for Foo to have a tick >= 6 and Bar tick >= 10
<-mach.WhenTime(am.S{"Foo", "Bar"}, am.Time{6, 10}, nil)

// wait for DownloadingFile to have a tick increased by 2 since now
<-mach.WhenTicks("DownloadingFile", 2, nil)

// wait for a mutation to execute
<-mach.WhenQueue(mach.Add1("Foo", nil))

// wait for an error
<-mach.WhenErr(nil)
Schema File
// BasicStatesDef contains all the states of the Basic state machine.
type BasicStatesDef struct {
    *am.StatesBase

    // ErrNetwork indicates a generic network error.
    ErrNetwork string
    // ErrHandlerTimeout indicates one of state machine handlers has timed out.
    ErrHandlerTimeout string

    // Start indicates the machine should be working. Removing start can force
    // stop the machine.
    Start string
    // Ready indicates the machine meets criteria to perform work, and requires
    // Start.
    Ready string
    // Healthcheck is a periodic request making sure that the machine is still
    // alive.
    Healthcheck string
}

var BasicSchema = am.Schema{

    // Errors

    ssB.ErrNetwork:        {Require: S{Exception}},
    ssB.ErrHandlerTimeout: {Require: S{Exception}},

    // Basics

    ssB.Start:       {},
    ssB.Ready:       {Require: S{ssB.Start}},
    ssB.Healthcheck: {},
}
Passing Args
// Example with typed state names (ssS) and typed arguments (A).
mach.Add1(ssS.KillingWorker, Pass(&A{
    ConnAddr:   ":5555",
    WorkerAddr: ":5556",
}))
Mutations and Relations

While mutations are the heartbeat of asyncmachine, it's the relations which define the rules of the flow. Check out the relations playground and quiz yourself (maybe a fancier playground).

mach := newMach("DryWaterWet", am.Schema{
    "Wet": {
        Require: am.S{"Water"},
    },
    "Dry": {
        Remove: am.S{"Water"},
    },
    "Water": {
        Add:    am.S{"Wet"},
        Remove: am.S{"Dry"},
    },
})
mach.Add1("Dry", nil)
mach.Add1("Water", nil)
// TODO quiz: is Wet active?

Demos

go run github.com/pancsta/asyncmachine-go/tools/cmd/am-dbg@latest \
  --import-data https://pancsta.github.io/assets/asyncmachine-go/am-dbg-exports/secai-cook.gob.br \
  mach://cook

Examples

All examples and benchmarks can be found in /examples.

Dev Tools

Apps

Documentation

API

The most common API methods are listed below. There's more for local state machines, but all of these are also implemented in the transparent RPC layer.

// TODO update
// A (arguments) is a map of named arguments for a Mutation.
type A map[string]any
// S (state names) is a string list of state names.
type S []string
type Time []uint64
type Clock map[string]uint64
type Result int
type Schema = map[string]State

// Api is a subset of Machine for alternative implementations.
type Api interface {
    // ///// REMOTE

    // Mutations (remote)

    Add1(state string, args A) Result
    Add(states S, args A) Result
    Remove1(state string, args A) Result
    Remove(states S, args A) Result
    AddErr(err error, args A) Result
    AddErrState(state string, err error, args A) Result
    Toggle(states S, args A) Result
    Toggle1(state string, args A) Result
    Set(states S, args A) Result

    // Traced mutations (remote)

    EvAdd1(event *Event, state string, args A) Result
    EvAdd(event *Event, states S, args A) Result
    EvRemove1(event *Event, state string, args A) Result
    EvRemove(event *Event, states S, args A) Result
    EvAddErr(event *Event, err error, args A) Result
    EvAddErrState(event *Event, state string, err error, args A) Result
    EvToggle(event *Event, states S, args A) Result
    EvToggle1(event *Event, state string, args A) Result

    // Waiting (remote)

    WhenArgs(state string, args A, ctx context.Context) <-chan struct{}

    // Getters (remote)

    Err() error

    // ///// LOCAL

    // Checking (local)

    IsErr() bool
    Is(states S) bool
    Is1(state string) bool
    Any(states ...S) bool
    Any1(state ...string) bool
    Not(states S) bool
    Not1(state string) bool
    IsTime(time Time, states S) bool
    WasTime(time Time, states S) bool
    IsClock(clock Clock) bool
    WasClock(clock Clock) bool
    Has(states S) bool
    Has1(state string) bool
    CanAdd(states S, args A) Result
    CanAdd1(state string, args A) Result
    CanRemove(states S, args A) Result
    CanRemove1(state string, args A) Result
    CountActive(states S) int

    // Waiting (local)

    When(states S, ctx context.Context) <-chan struct{}
    When1(state string, ctx context.Context) <-chan struct{}
    WhenNot(states S, ctx context.Context) <-chan struct{}
    WhenNot1(state string, ctx context.Context) <-chan struct{}
    WhenTime(states S, times Time, ctx context.Context) <-chan struct{}
    WhenTime1(state string, tick uint64, ctx context.Context) <-chan struct{}
    WhenTicks(state string, ticks int, ctx context.Context) <-chan struct{}
    WhenQuery(query func(clock Clock) bool, ctx context.Context) <-chan struct{}
    WhenErr(ctx context.Context) <-chan struct{}
    WhenQueue(tick Result) <-chan struct{}

    // Getters (local)

    StateNames() S
    StateNamesMatch(re *regexp.Regexp) S
    ActiveStates() S
    Tick(state string) uint64
    Clock(states S) Clock
    Time(states S) Time
    TimeSum(states S) uint64
    QueueTick() uint64
    NewStateCtx(state string) context.Context
    Export() *Serialized
    Schema() Schema
    Switch(groups ...S) string
    Groups() (map[string][]int, []string)
    Index(states S) []int
    Index1(state string) int

    // Misc (local)

    Id() string
    ParentId() string
    Tags() []string
    Ctx() context.Context
    String() string
    StringAll() string
    Log(msg string, args ...any)
    SemLogger() SemLogger
    Inspect(states S) string
    BindHandlers(handlers any) error
    DetachHandlers(handlers any) error
    HasHandlers() bool
    StatesVerified() bool
    Tracers() []Tracer
    DetachTracer(tracer Tracer) error
    BindTracer(tracer Tracer) error
    AddBreakpoint1(added string, removed string, strict bool)
    AddBreakpoint(added S, removed S, strict bool)
    Dispose()
    WhenDisposed() <-chan struct{}
    IsDisposed() bool
}

Tests

It's very easy to get a grasp of how asyncmachine works by reading the idiomatic test suite. Consider the example below of a method used to wait for certain arguments passing via a state activation:

func TestWhenArgs(t *testing.T) {
    // init
    m := NewRels(t, nil)

    // bind
    whenCh := m.WhenArgs("B", A{"foo": "bar"}, nil)

    // incorrect args
    m.Add1("B", A{"foo": "foo"})
    select {
    case <-whenCh:
        t.Fatal("whenCh shouldnt be selected")
    default:
        // pass
    }

    // correct args
    m.Add1("B", A{"foo": "bar"})
    select {
    case <-whenCh:
        // pass
    default:
        t.Fatal("whenCh should be selected")
    }

    // dispose
    m.Dispose()
    <-m.WhenDisposed()
}

Status

Release Candidate, semantically versioned, partially optimized.

Concepts

asyncmachine is loosely based on the following concepts:

monorepo

Go back to the monorepo root to continue reading.

Documentation

Overview

Package machine is a nondeterministic, multi-state, clock-based, relational, optionally-accepting, and non-blocking state machine.

Index

Examples

Constants

View Source 
const (
	// EnvAmDebug enables a simple debugging mode (eg long timeouts).
	// "2" logs to stdout (where applicable)
	// "1" | "2" | "" (default)
	EnvAmDebug = "AM_DEBUG"
	// EnvAmTestRunner indicates a CI test runner.
	EnvAmTestRunner = "AM_TEST_RUNNER"
	// EnvAmLog sets the log level.
	// "1" | "2" | "3" | "4" | "5" | "" (default)
	EnvAmLog = "AM_LOG"
	// EnvAmDetectEval detects evals directly in handlers (use in tests).
	EnvAmDetectEval = "AM_DETECT_EVAL"
	// EnvAmTraceFilter will remove its contents from stack traces, shortening
	// them .
	EnvAmTraceFilter = "AM_TRACE_FILTER"
	// EnvAmTestDebug activates debugging in tests.
	EnvAmTestDebug = "AM_TEST_DEBUG"
	// EnvAmTestDbgAddr enables test loop integration (no parallel and dbg relay)
	EnvAmTestDbgAddr = "AM_TEST_DBG_ADDR"
	SuffixEnter      = "Enter"
	SuffixExit       = "Exit"
	SuffixState      = "State"
	SuffixEnd        = "End"
	PrefixErr        = "Err"
	// StateAny is a name of a meta-state used in catch-all handlers.
	StateAny = "Any"
	// StateException is the name of the predefined Exception state.
	StateException = "Exception"
	// StateHeartbeat is the name of the predefined Heartbeat state.
	StateHeartbeat = "Heartbeat"
	// StateHealthcheck is the name of the predefined Healthcheck state.
	StateHealthcheck = "Healthcheck"
	// StateStart is the name of the predefined Start state.
	StateStart = "Start"
	// StateDisposing is the name of the predefined Disposing state.
	StateDisposing = "Disposing"
	// StateReady is the name of the predefined Ready state.
	StateReady = "Ready"
	// StateMachineRestored is the name of the predefined MachineRestored state.
	StateMachineRestored = "MachineRestored"
)

Variables

View Source 
var (
	// ErrStateUnknown indicates that the state is unknown.
	ErrStateUnknown = errors.New("state unknown")
	// ErrStateInactive indicates that a necessary state isn't active.
	ErrStateInactive = errors.New("state not active")
	// ErrCanceled indicates that a transition was canceled.
	ErrCanceled = errors.New("transition canceled")
	// ErrQueued indicates that a mutation was queued. Queuing is a feature, not
	// an error, but it may be considered as such in certain cases.
	ErrQueued = errors.New("transition queued")
	// ErrInvalidArgs indicates that arguments are invalid.
	ErrInvalidArgs = errors.New("invalid arguments")
	// ErrHandlerTimeout indicates that a mutation timed out.
	ErrHandlerTimeout = errors.New("handler timeout")
	// ErrEvalTimeout indicates that an eval func timed out.
	ErrEvalTimeout = errors.New("eval timeout")
	// ErrTimeout indicates that a generic timeout occurred.
	ErrTimeout = errors.New("timeout")
	// ErrStateMissing indicates that states are missing.
	ErrStateMissing = errors.New("missing states")
	// ErrRelation indicates that a relation definition is invalid.
	ErrRelation = errors.New("relation error")
	// ErrDisposed indicates that the machine has been disposed.
	ErrDisposed = errors.New("machine disposed")
	// ErrSchema indicates an issue with the machine schema.
	ErrSchema = errors.New("schema error")
	// ErrInternal happens for internal errors in the machine. These should be
	// reported as bugs.
	ErrInternal = errors.New("internal error")
)
View Source 
var CtxKey = &CtxKeyName{}
View Source 
var LogArgs = []string{
	"name", "id", "port", "addr", "err", "path", "url",
	"uri",
}

LogArgs is a list of common argument names to be logged. Useful for debugging.

View Source 
var LogArgsMaxLen = 20

LogArgsMaxLen is the default maximum length of the arg's string representation.

Functions

func AMerge added in v0.9.0 

func AMerge[K comparable, V any](maps ...map[K]V) map[K]V

AMerge merges 2 or more maps into 1. Useful for passing args from many packages.

func IsActiveTick added in v0.5.0 

func IsActiveTick(tick uint64) bool

IsActiveTick returns true if the tick represents an active state (odd number).

func IsHandler added in v0.8.0 

func IsHandler(states S, method string) (string, string)

IsHandler checks if a method name is a handler method, by returning a state name.

func IsQueued added in v0.15.0 

func IsQueued(result Result) bool

IsQueued returns true if the mutation has been queued, and the result represents the queue time it will be processed.

func ListHandlers added in v0.8.0 

func ListHandlers(handlers any, states S) ([]string, error)

ListHandlers returns a list of handler method names from a handler struct, limited to [states].

func MockClock added in v0.7.0 

func MockClock(mach *Machine, clock Clock)

MockClock mocks the internal clock of the machine. Only for testing.

func MutationFormatArgs added in v0.15.0 

func MutationFormatArgs(matched map[string]string) string

func NewLogArgsMapper added in v0.18.0 

func NewLogArgsMapper(
	maxLen int, names []string,
) func(args A) map[string]string

NewLogArgsMapper returns a matcher function for [Opts.LogArgs]. Useful for debugging untyped argument maps. Usually [names] extend defaults from LogArgs.

maxLen: maximum length of the arg's string representation). Defaults to LogArgsMaxLen,

func NewStateGroups added in v0.8.0 

func NewStateGroups[G any](groups G, mixins ...any) G

func NewStates added in v0.8.0 

func NewStates[G States](states G) G

func StatesEqual added in v0.8.0 

func StatesEqual(states1 S, states2 S) bool

StatesEqual returns true if states1 and states2 are equal, regardless of order.

func StatesToIndex added in v0.12.0 

func StatesToIndex(index S, states S) []int

StatesToIndex returns a subset of [index] that matches [states]. Unknown states are represented by -1.

Types

type A 

type A map[string]any

A (arguments) is a map of named arguments for a Mutation.

func Pass added in v0.8.0 

func Pass(args *AT) A

Pass prepares A from AT, to pass to further mutations.

func PassMerge added in v0.8.0 

func PassMerge(existing A, args *AT) A

PassMerge prepares A from AT and existing A, to pass to further mutations.

type AT added in v0.8.0 

type AT struct {
	Err          error
	ErrTrace     string
	Panic        *ExceptionArgsPanic
	TargetStates S
	CalledStates S
	TimeBefore   Time
	TimeAfter    Time
	Event        *Event
	// MutDone chan gets closed by the machine once it's processed. Can cause chan
	// leaks when misused. Only for Can* checks.
	CheckDone *CheckDone
}

AT represents typed arguments of pkg/machine, extracted from Event.Args via ParseArgs, or created manually to for Pass.

func ParseArgs added in v0.8.0 

func ParseArgs(args A) *AT

ParseArgs extracts AT from A.

type ATRpc added in v0.17.1 

type ATRpc struct {
	Err          error
	ErrTrace     string
	Panic        *ExceptionArgsPanic
	TargetStates S
	CalledStates S
	TimeBefore   Time
	TimeAfter    Time
	Event        *Event
}

type Api added in v0.8.0 

type Api interface {

	// Add1 is [Machine.Add1].
	Add1(state string, args A) Result
	// Add is [Machine.Add].
	Add(states S, args A) Result
	// Remove1 is [Machine.Remove1].
	Remove1(state string, args A) Result
	// Remove is [Machine.Remove].
	Remove(states S, args A) Result
	// AddErr is [Machine.AddErr].
	AddErr(err error, args A) Result
	// AddErrState is [Machine.AddErrState].
	AddErrState(state string, err error, args A) Result
	// Toggle is [Machine.Toggle].
	Toggle(states S, args A) Result
	// Toggle1 is [Machine.Toggle1].
	Toggle1(state string, args A) Result
	// Set is [Machine.Set].
	Set(states S, args A) Result

	// EvAdd1 is [Machine.EvAdd1].
	EvAdd1(event *Event, state string, args A) Result
	// EvAdd is [Machine.EvAdd].
	EvAdd(event *Event, states S, args A) Result
	// EvRemove1 is [Machine.EvRemove1].
	EvRemove1(event *Event, state string, args A) Result
	// EvRemove is [Machine.EvRemove].
	EvRemove(event *Event, states S, args A) Result
	// EvAddErr is [Machine.EvAddErr].
	EvAddErr(event *Event, err error, args A) Result
	// EvAddErrState is [Machine.EvAddErrState].
	EvAddErrState(event *Event, state string, err error, args A) Result
	// EvToggle is [Machine.Toggle].
	EvToggle(event *Event, states S, args A) Result
	// EvToggle1 is [Machine.Toggle1].
	EvToggle1(event *Event, state string, args A) Result

	// WhenArgs is [Machine.WhenArgs].
	WhenArgs(state string, args A, ctx context.Context) <-chan struct{}

	// Err is [Machine.Err].
	Err() error

	// IsErr is [Machine.IsErr].
	IsErr() bool
	// Is is [Machine.Is].
	Is(states S) bool
	// Is1 is [Machine.Is1].
	Is1(state string) bool
	// Any is [Machine.Any].
	Any(states ...S) bool
	// Any1 is [Machine.Any1].
	Any1(state ...string) bool
	// Not is [Machine.Not].
	Not(states S) bool
	// Not1 is [Machine.Not1].
	Not1(state string) bool
	// IsTime is [Machine.IsTime].
	IsTime(time Time, states S) bool
	// WasTime is [Machine.WasTime].
	WasTime(time Time, states S) bool
	// IsClock is [Machine.IsClock].
	IsClock(clock Clock) bool
	// WasClock is [Machine.WasClock].
	WasClock(clock Clock) bool
	// Has is [Machine.Has].
	Has(states S) bool
	// Has1 is [Machine.Has1].
	Has1(state string) bool
	// CanAdd is [Machine.CanAdd].
	CanAdd(states S, args A) Result
	// CanAdd1 is [Machine.CanAdd1].
	CanAdd1(state string, args A) Result
	// CanRemove is [Machine.CanRemove].
	CanRemove(states S, args A) Result
	// CanRemove1 is [Machine.CanRemove1].
	CanRemove1(state string, args A) Result
	// Transition is [Machine.Transition].
	Transition() *Transition

	// When is [Machine.When].
	When(states S, ctx context.Context) <-chan struct{}
	// When1 is [Machine.When1].
	When1(state string, ctx context.Context) <-chan struct{}
	// WhenNot is [Machine.WhenNot].
	WhenNot(states S, ctx context.Context) <-chan struct{}
	// WhenNot1 is [Machine.WhenNot1].
	WhenNot1(state string, ctx context.Context) <-chan struct{}
	// WhenTime is [Machine.WhenTime].
	WhenTime(states S, times Time, ctx context.Context) <-chan struct{}
	// WhenTime1 is [Machine.WhenTime1].
	WhenTime1(state string, tick uint64, ctx context.Context) <-chan struct{}
	// WhenTicks is [Machine.WhenTicks].
	WhenTicks(state string, ticks int, ctx context.Context) <-chan struct{}
	// WhenQuery is [Machine.WhenQuery].
	WhenQuery(query func(clock Clock) bool, ctx context.Context) <-chan struct{}
	// WhenErr is [Machine.WhenErr].
	WhenErr(ctx context.Context) <-chan struct{}
	// WhenQueue is [Machine.WhenQueue].
	WhenQueue(tick Result) <-chan struct{}

	// StateNames is [Machine.StateNames].
	StateNames() S
	// StateNamesMatch is [Machine.StateNamesMatch].
	StateNamesMatch(re *regexp.Regexp) S
	// ActiveStates is [Machine.ActiveStates].
	ActiveStates(states S) S
	// Tick is [Machine.Tick].
	Tick(state string) uint64
	// Clock is [Machine.Clock].
	Clock(states S) Clock
	// Time is [Machine.Time].
	Time(states S) Time
	// QueueTick is [Machine.QueueTick].
	QueueTick() uint64
	// MachineTick is [Machine.MachineTick].
	MachineTick() uint32
	// QueueLen is [Machine.QueueLen].
	QueueLen() uint16
	// NewStateCtx is [Machine.NewStateCtx].
	NewStateCtx(state string) context.Context
	// Export is [Machine.Export].
	Export() (*Serialized, Schema, error)
	// Schema is [Machine.Schema].
	Schema() Schema
	// Switch is [Machine.Switch].
	Switch(groups ...S) string
	// Groups is [Machine.Groups].
	Groups() (map[string][]int, []string)
	// Index is [Machine.Index].
	Index(states S) []int
	// Index1 is [Machine.Index1].
	Index1(state string) int

	// Id is [Machine.Id].
	Id() string
	// ParentId is [Machine.ParentId].
	ParentId() string
	// ParseStates is [Machine.ParseStates].
	ParseStates(states S) S
	// Tags is [Machine.Tags].
	Tags() []string
	// Ctx is [Machine.Ctx].
	Context() context.Context
	// String is [Machine.String].
	String() string
	// StringAll is [Machine.StringAll].
	StringAll() string
	// Log is [Machine.Log].
	Log(msg string, args ...any)
	// SemLogger is [Machine.SemLogger].
	SemLogger() SemLogger
	// Inspect is [Machine.Inspect].
	Inspect(states S) string
	// BindHandlers is [Machine.BindHandlers].
	BindHandlers(handlers any) error
	// DetachHandlers is [Machine.DetachHandlers].
	DetachHandlers(handlers any) error
	// HasHandlers is [Machine.HasHandlers].
	HasHandlers() bool
	// StatesVerified is [Machine.StatesVerified].
	StatesVerified() bool
	// Tracers is [Machine.Tracers].
	Tracers() []Tracer
	// DetachTracer is [Machine.DetachTracer].
	DetachTracer(tracer Tracer) error
	// BindTracer is [Machine.BindTracer].
	BindTracer(tracer Tracer) error
	// AddBreakpoint is [Machine.AddBreakpoint].
	AddBreakpoint(added S, removed S, strict bool)
	// AddBreakpoint1 is [Machine.AddBreakpoint1].
	AddBreakpoint1(added string, removed string, strict bool)
	// Dispose is [Machine.Dispose].
	Dispose()
	// WhenDisposed is [Machine.WhenDisposed].
	WhenDisposed() <-chan struct{}
	// IsDisposed is [Machine.IsDisposed].
	IsDisposed() bool
	// OnDispose is [Machine.OnDispose].
	OnDispose(fn HandlerDispose)
}

Api is a subset of Machine for alternative implementations.

type CheckDone added in v0.15.0 

type CheckDone struct {
	// TODO close these on dispose and deadline
	Ch chan struct{}
	// Was the mutation canceled?
	Canceled bool
}

type Clock added in v0.7.0 

type Clock map[string]uint64

Clock is a map of state names to their tick values. It's like Time but indexed by string, instead of int. See TimeIndex for a more advanced data structure.

type CtxBinding added in v0.8.0 

type CtxBinding struct {
	Ctx    context.Context
	Cancel context.CancelFunc
}

type CtxKeyName added in v0.8.0 

type CtxKeyName struct{}

type CtxValue added in v0.8.0 

type CtxValue struct {
	Id    string
	State string
	Tick  uint64
}

type DefaultRelationsResolver 

type DefaultRelationsResolver struct {
	// TODO replace with TimeIndex, log(), Schema
	//   - for netmach mut filtering
	//   - for alternative impls
	Machine    *Machine
	Transition *Transition
	Index      S
	// contains filtered or unexported fields
}

DefaultRelationsResolver is the default implementation of the RelationsResolver with Add, Remove, Require and After. It can be overridden using Opts.Resolver. TODO refac RelationsDefault

func (*DefaultRelationsResolver) InboundRelationsOf added in v0.12.0 

func (rr *DefaultRelationsResolver) InboundRelationsOf(toState string) (
	S, error,
)

InboundRelationsOf returns a list of states pointing to [toState]. Not thread safe.

func (*DefaultRelationsResolver) NewAutoMutation added in v0.12.0 

func (rr *DefaultRelationsResolver) NewAutoMutation() (*Mutation, S)

NewAutoMutation implements RelationsResolver.GetAutoMutation.

func (*DefaultRelationsResolver) NewSchema added in v0.12.0 

func (rr *DefaultRelationsResolver) NewSchema(schema Schema, states S)

func (*DefaultRelationsResolver) RelationsBetween added in v0.12.0 

func (rr *DefaultRelationsResolver) RelationsBetween(
	fromState, toState string,
) ([]Relation, error)

RelationsBetween returns a list of outbound relations between fromState -> toState. Not thread safe.

func (*DefaultRelationsResolver) RelationsOf added in v0.12.0 

func (rr *DefaultRelationsResolver) RelationsOf(fromState string) (
	[]Relation, error,
)

RelationsOf returns a list of relation types of the given state. Not thread safe.

func (*DefaultRelationsResolver) SortStates 

func (rr *DefaultRelationsResolver) SortStates(states S)

SortStates implements RelationsResolver.SortStates.

func (*DefaultRelationsResolver) TargetStates added in v0.12.0 

func (rr *DefaultRelationsResolver) TargetStates(
	t *Transition, statesToSet, index S,
) S

TargetStates implements RelationsResolver.TargetStates.

type Event 

type Event struct {
	// Ctx is an optional context this event is constrained by.
	Ctx context.Context
	// Name of the handler method (eg FooState).
	Name string
	// MachineId is the ID of the parent machine.
	MachineId string
	// TransitionId is the ID of the parent transition.
	TransitionId string
	// Args is a map of named arguments for a Mutation.
	Args A
	// IsCheck is true if this event is a check event, fired by one of Can*()
	// methods. Useful for avoiding flooding the log with errors.
	IsCheck bool
	// contains filtered or unexported fields
}

Event struct represents a single event of a Mutation within a Transition. One event can have 0-n handlers.

func NewEvent added in v0.17.0 

func NewEvent(mach *Machine, machApi Api) *Event

NewEvent creates a new Event struct with private fields initialized.

func (*Event) Clone added in v0.9.0 

func (e *Event) Clone() *Event

Clone clones the event struct, making it writable.

func (*Event) Export added in v0.15.0 

func (e *Event) Export() *Event

Export clones only the essential data of the Event. Useful for tracing vs GC.

func (*Event) IsValid added in v0.10.1 

func (e *Event) IsValid() bool

IsValid confirm this event should still be processed. Useful for negotiation handlers, which can't use state context.

func (*Event) Machine 

func (e *Event) Machine() *Machine

func (*Event) Mutation added in v0.5.0 

func (e *Event) Mutation() *Mutation

Mutation returns the Mutation of an Event.

func (*Event) String added in v0.15.0 

func (e *Event) String() string

func (*Event) SwapArgs added in v0.15.0 

func (e *Event) SwapArgs(args A) *Event

SwapArgs clone the event and assign new args.

func (*Event) Transition added in v0.5.0 

func (e *Event) Transition() *Transition

Transition returns the Transition of an Event.

type ExceptionArgsPanic 

type ExceptionArgsPanic struct {
	CalledStates S
	StatesBefore S
	Transition   *Transition
	LastStep     *Step
	StackTrace   string
}

ExceptionArgsPanic is an optional argument ["panic"] for the StateException state which describes a panic within a Transition handler.

type ExceptionHandler 

type ExceptionHandler struct{}

ExceptionHandler provide a basic StateException state support, as should be embedded into handler structs in most of the cases. Because ExceptionState will be called after [Machine.HandlerDeadline], it should handle locks on its own (to not race with itself).

func (*ExceptionHandler) ExceptionState 

func (eh *ExceptionHandler) ExceptionState(e *Event)

ExceptionState is a final entry handler for the StateException state. Args: - err error: The error that caused the StateException state. - panic *ExceptionArgsPanic: Optional details about the panic.

type HandlerChange added in v0.15.0 

type HandlerChange func(mach *Machine, before, after Time)

type HandlerDispose added in v0.9.0 

type HandlerDispose func(id string, ctx context.Context)

HandlerDispose is a machine disposal handler func signature.

type HandlerError added in v0.13.0 

type HandlerError func(mach *Machine, err error)

type HandlerFinal added in v0.8.0 

type HandlerFinal func(e *Event)

HandlerFinal is a final transition handler func signature.

type HandlerNegotiation added in v0.8.0 

type HandlerNegotiation func(e *Event) bool

HandlerNegotiation is a negotiation transition handler func signature.

type IndexStateCtx added in v0.7.0 

type IndexStateCtx map[string]*CtxBinding

IndexStateCtx is a map of (single) state names to a context cancel function

type IndexWhen added in v0.7.0 

type IndexWhen map[string][]*WhenBinding

IndexWhen is a map of (single) state names to a list of activation or de-activation bindings

type IndexWhenArgs added in v0.7.0 

type IndexWhenArgs map[string][]*WhenArgsBinding

IndexWhenArgs is a map of (single) state names to a list of args value bindings

type IndexWhenTime added in v0.7.0 

type IndexWhenTime map[string][]*WhenTimeBinding

IndexWhenTime is a map of (single) state names to a list of time bindings

type InternalCheckFunc added in v0.15.1 

type InternalCheckFunc func(states S) bool

type InternalLogFunc added in v0.15.1 

type InternalLogFunc func(level LogLevel, msg string, args ...any)

type LastTxTracer added in v0.12.0 

type LastTxTracer struct {
	*TracerNoOp
	// contains filtered or unexported fields
}

TODO add TTL, ctx

func NewLastTxTracer added in v0.12.0 

func NewLastTxTracer() *LastTxTracer

NewLastTxTracer returns a Tracer that logs the last transition.

func (*LastTxTracer) Load added in v0.12.0 

func (t *LastTxTracer) Load() *Transition

Load returns the last transition.

func (*LastTxTracer) String added in v0.12.0 

func (t *LastTxTracer) String() string

func (*LastTxTracer) TransitionEnd added in v0.12.0 

func (t *LastTxTracer) TransitionEnd(transition *Transition)

type LogArgsMapperFn added in v0.15.0 

type LogArgsMapperFn func(args A) map[string]string

LogArgsMapperFn is a function that maps arguments to be logged. Useful for debugging. See NewLogArgsMapper.

type LogEntry added in v0.6.0 

type LogEntry struct {
	Level LogLevel
	Text  string
}

type LogLevel 

type LogLevel int

LogLevel defines the level of details in the produced log (0-5). 

const (
	// LogNothing means no logging, including external msgs.
	LogNothing LogLevel = iota
	// LogExternal will show ony external user msgs.
	LogExternal
	// LogChanges means logging state changes and external msgs.
	LogChanges
	// LogOps means LogChanges + logging all the operations.
	LogOps
	// LogDecisions means LogOps + logging all the decisions behind them.
	LogDecisions
	// LogEverything means LogDecisions + all event and handler names, and more.
	LogEverything
)

func EnvLogLevel added in v0.7.0 

func EnvLogLevel(name string) LogLevel

EnvLogLevel returns a log level from an environment variable, AM_LOG by default.

func (LogLevel) Level added in v0.18.0 

func (l LogLevel) Level() string

Level returns a number form of a log level.

func (LogLevel) String added in v0.3.0 

func (l LogLevel) String() string

String returns a human form of a log level.

type LoggerFn added in v0.15.0 

type LoggerFn func(level LogLevel, msg string, args ...any)

LoggerFn is a logging function for the machine.

type Machine 

type Machine struct {
	// Maximum number of mutations that can be queued. Default: 1000.
	QueueLimit uint16
	// HandlerTimeout defined the time for a handler to execute before it causes
	// StateException. Default: 1s. See also [Opts.HandlerTimeout].
	// Using HandlerTimeout can cause race conditions, unless paired with
	// [Event.IsValid].
	HandlerTimeout time.Duration
	// HandlerDeadline is a grace period after a handler timeout, before the
	// machine moves on.
	HandlerDeadline time.Duration
	// LastHandlerDeadline stores when the last HandlerDeadline was hit.
	LastHandlerDeadline atomic.Pointer[time.Time]
	// HandlerBackoff is the time after a [HandlerDeadline], during which the
	// machine will return [Canceled] to any mutation.
	HandlerBackoff time.Duration
	// EvalTimeout is the time the machine will try to execute an eval func.
	// Like any other handler, eval func also has [HandlerTimeout]. Default: 1s.
	EvalTimeout time.Duration
	// If true, the machine will log stack traces of errors. Default: true.
	// Requires an ExceptionHandler binding and [Machine.PanicToException] set.
	LogStackTrace bool
	// If true, the machine will catch panic and trigger the [StateException]
	// state. Default: true. Can be disabled via AM_DEBUG=1.
	PanicToException bool
	// DisposeTimeout specifies the duration to wait for the queue to drain during
	// disposal. Default 1s.
	DisposeTimeout time.Duration
	// contains filtered or unexported fields
}

Machine provides a state machine API with mutations, state schema, handlers, subscriptions, tracers, and helpers methods. It also holds a queue of mutations to execute.

func New 

func New(ctx context.Context, schema Schema, opts *Opts) *Machine

New creates a new Machine instance, bound to context and modified with optional Opts.

Example 
ctx := context.TODO()
mach := New(ctx, Schema{
	"Foo": {Require: S{"Bar"}},
	"Bar": {},
}, nil)
mach.Add1("Foo", nil)
mach.Is1("Foo") // false

func NewCommon added in v0.5.0 

func NewCommon(
	ctx context.Context, id string, stateSchema Schema, stateNames S,
	handlers any, parent Api, opts *Opts,
) (*Machine, error)

NewCommon creates a new Machine instance with all the common options set.

Example 
// define (tip: use am-gen instead)
stateStruct := Schema{
	"Foo": {Require: S{"Bar"}},
	"Bar": {},
}
stateNames := []string{"Foo", "Bar"}
type Handlers struct{}
// func (h *Handlers) FooState(e *Event) {
// 	args := e.Args
// 	mach := e.Machine()
// 	ctx := mach.NewStateCtx("Foo")
// 	// unblock
// 	go func() {
// 		if ctx.Err() != nil {
// 			return // expired
// 		}
// 		// blocking calls...
// 		if ctx.Err() != nil {
// 			return // expired
// 		}
// 		mach.Add1("Bar", nil)
// 	}()
// }

// init
ctx := context.TODO()
mach, err := NewCommon(ctx, "mach-id",
	stateStruct, stateNames,
	&Handlers{}, nil, nil)
if err != nil {
	panic(err)
}
mach.SemLogger().SetLevel(LogOps)

func (*Machine) ActiveStates 

func (m *Machine) ActiveStates(states S) S

ActiveStates returns a copy of the currently active states when states is nil, optionally limiting the results to a subset of states.

func (*Machine) Add 

func (m *Machine) Add(states S, args A) Result

Add activates a list of states in the machine, returning the result of the transition (Executed, Queued, Canceled). Like every mutation method, it will resolve relations and trigger handlers.

func (*Machine) Add1 added in v0.5.0 

func (m *Machine) Add1(state string, args A) Result

Add1 is a shorthand method to add a single state with the passed args. See Add().

func (*Machine) AddBreakpoint added in v0.8.0 

func (m *Machine) AddBreakpoint(added S, removed S, strict bool)

AddBreakpoint adds a breakpoint for an outcome of mutation (added and removed states) checked by mutation equality. Once such a mutation happens, a log message will be printed out. We can set an IDE's breakpoint on this line and see the mutation's sync stack trace. If [Machine.LogStackTrace] is set, the stack trace will be printed out as well. Many breakpoints can be added, but none removed.

Breakpoints are useful to find the caller of a mutation, but don't work with Machine.Set.

strict: strict skips already active / inactive (for strict of diff equality).

func (*Machine) AddBreakpoint1 added in v0.15.0 

func (m *Machine) AddBreakpoint1(added string, removed string, strict bool)

func (*Machine) AddErr 

func (m *Machine) AddErr(err error, args A) Result

AddErr is a dedicated method to add the StateException state with the passed error and optional arguments. Like every mutation method, it will resolve relations and trigger handlers. AddErr produces a stack trace of the error, if LogStackTrace is enabled.

func (*Machine) AddErrState added in v0.7.0 

func (m *Machine) AddErrState(state string, err error, args A) Result

AddErrState adds a dedicated error state, along with the build in StateException state. Like every mutation method, it will resolve relations and trigger handlers. AddErrState produces a stack trace of the error, if LogStackTrace is enabled.

func (*Machine) Any 

func (m *Machine) Any(states ...S) bool

Any is a group call to Is, returns true if any of the params return true from Is. 

machine.StringAll() // ()[Foo:0 Bar:0 Baz:0]
machine.Add(S{"Foo"})
// is(Foo, Bar) or is(Bar)
machine.Any(S{"Foo", "Bar"}, S{"Bar"}) // false
// is(Foo) or is(Bar)
machine.Any(S{"Foo"}, S{"Bar"}) // true

func (*Machine) Any1 added in v0.5.0 

func (m *Machine) Any1(states ...string) bool

Any1 is group call to Machine.Is1, returns true if any of the params return true from Machine.Is1.

func (*Machine) Backoff added in v0.13.0 

func (m *Machine) Backoff() bool

Backoff is true in case the machine had a recent HandlerDeadline. During a backoff, all mutations will be Canceled.

func (*Machine) BindHandlers 

func (m *Machine) BindHandlers(handlers any) error

BindHandlers binds a struct of handler methods to machine's states, based on the naming convention, eg `FooState(e *Event)`. Negotiation handlers can optionally return bool.

func (*Machine) BindTracer added in v0.8.0 

func (m *Machine) BindTracer(tracer Tracer) error

BindTracer binds a Tracer to the machine. Tracers can cause StateException in submachines, before any handlers are bound. Use the Err() getter to examine such errors.

func (*Machine) CanAdd added in v0.5.0 

func (m *Machine) CanAdd(states S, args A) Result

CanAdd checks if [states] can be added and returns Executed or [AT.CheckDone] if a dry run mutation passes. Useful for reducing failed negotiations.

func (*Machine) CanAdd1 added in v0.15.0 

func (m *Machine) CanAdd1(state string, args A) Result

CanAdd1 is Machine.CanAdd for a single state.

func (*Machine) CanRemove added in v0.5.0 

func (m *Machine) CanRemove(states S, args A) Result

CanRemove checks if [states] can be removed and returns Executed or [AT.CheckDone] if a dry run mutation passes. Useful for reducing failed negotiations.

func (*Machine) CanRemove1 added in v0.15.0 

func (m *Machine) CanRemove1(state string, args A) Result

CanRemove1 is Machine.CanRemove for a single state.

func (*Machine) Clock 

func (m *Machine) Clock(states S) Clock

Clock returns current machine's clock, a state-keyed map of ticks. If states are passed, only the ticks of the passed states are returned.

func (*Machine) Context added in v0.18.0 

func (m *Machine) Context() context.Context

Context returns the machine's parent context. This context lives longer then the internal graceful dispose context.

func (*Machine) DetachHandlers added in v0.8.0 

func (m *Machine) DetachHandlers(handlers any) error

DetachHandlers detaches previously bound machine handlers.

func (*Machine) DetachTracer added in v0.8.0 

func (m *Machine) DetachTracer(tracer Tracer) error

DetachTracer tries to remove a tracer from the machine. Returns an error in case the tracer wasn't bound.

func (*Machine) Dispose 

func (m *Machine) Dispose()

Dispose disposes the machine and all its emitters. You can wait for the completion of the disposal with `<-mach.WhenDisposed()`. It's advised to use Dispose() func from pkg/helpers instead, which handles Disposed state mixing.

func (*Machine) DisposeForce added in v0.5.0 

func (m *Machine) DisposeForce()

DisposeForce disposes the machine and all its emitters, without waiting for the queue to drain. Will cause panics.

func (*Machine) Err 

func (m *Machine) Err() error

Err returns the last error.

func (*Machine) EvAdd added in v0.9.0 

func (m *Machine) EvAdd(event *Event, states S, args A) Result

EvAdd is like Add, but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvAdd1 added in v0.9.0 

func (m *Machine) EvAdd1(event *Event, state string, args A) Result

EvAdd1 is like Add1 but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvAddErr added in v0.9.0 

func (m *Machine) EvAddErr(event *Event, err error, args A) Result

EvAddErr is like AddErr, but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvAddErrState added in v0.9.0 

func (m *Machine) EvAddErrState(
	event *Event, state string, err error, args A,
) Result

EvAddErrState is like AddErrState, but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvRemove added in v0.9.0 

func (m *Machine) EvRemove(event *Event, states S, args A) Result

EvRemove is like Remove but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvRemove1 added in v0.9.0 

func (m *Machine) EvRemove1(event *Event, state string, args A) Result

EvRemove1 is like Remove1, but passed the source event as the 1st param, which results in traceable transitions.

func (*Machine) EvToggle added in v0.15.0 

func (m *Machine) EvToggle(e *Event, states S, args A) Result

EvToggle is a traced version of Machine.Toggle.

func (*Machine) EvToggle1 added in v0.15.0 

func (m *Machine) EvToggle1(e *Event, state string, args A) Result

EvToggle1 is a traced version of Machine.Toggle1.

func (*Machine) Eval added in v0.5.0 

func (m *Machine) Eval(source string, fn func(), ctx context.Context) bool

Eval executes a function on the machine's queue, allowing to avoid using locks for non-handler code. Blocking code should NOT be scheduled here. Eval cannot be called within a handler's critical zone, as both are using the same serial queue and will deadlock. Eval has a timeout of HandlerTimeout/2 and will return false in case it happens. Evals do not trigger consensus, thus are much faster than state mutations.

ctx: nil context defaults to machine's context.

Note: usage of Eval is discouraged. But if you have to, use AM_DETECT_EVAL in tests for deadlock detection. Most usages of eval can be replaced with atomics or returning from mutation via channels. Evals can be better then Multi states in some cases.

func (*Machine) Export added in v0.6.4 

func (m *Machine) Export() (*Serialized, Schema, error)

Export exports the machine state as Serialized: ID, machine time, and state names.

func (*Machine) Fork added in v0.18.0 

func (m *Machine) Fork(ctx context.Context, e *Event, fn func())

Fork is a syntax sugar method for a handler unblocking boilerplate. Fork can only by used in the handler body (while the event is valid). See Machine.Go for nested forking.

func (*Machine) Go added in v0.18.0 

func (m *Machine) Go(ctx context.Context, fn func())

Go is a syntax sugar method for a nested handler unblocking boilerplate.

func (*Machine) Groups added in v0.15.0 

func (m *Machine) Groups() (map[string][]int, []string)

func (*Machine) Has 

func (m *Machine) Has(states S) bool

Has return true is passed states are registered in the machine. Useful for checking if a machine implements a specific state set.

func (*Machine) Has1 added in v0.5.0 

func (m *Machine) Has1(state string) bool

Has1 is shorthand for Has. It returns true if the passed state is registered in the machine.

func (*Machine) HasHandlers added in v0.12.0 

func (m *Machine) HasHandlers() bool

HasHandlers returns true if this machine has bound handlers, and thus an allocated goroutine. It also makes it nondeterministic.

func (*Machine) Id added in v0.8.0 

func (m *Machine) Id() string

Id returns the machine's id.

func (*Machine) Import added in v0.6.4 

func (m *Machine) Import(data *Serialized) error

Import imports the machine state from Serialized. It's not safe to import into a machine which has already produces transitions and/or has telemetry connected (use Machine.SetSchema instead).

func (*Machine) Index added in v0.7.0 

func (m *Machine) Index(states S) []int

Index returns a list of state indexes in the machine's StateNames() list, with -1s for missing ones.

func (*Machine) Index1 added in v0.12.0 

func (m *Machine) Index1(state string) int

Index1 returns the index of a state in the machine's StateNames() list, or -1 when not found or machine has been disposed.

func (*Machine) Inspect 

func (m *Machine) Inspect(states S) string

Inspect returns a multi-line string representation of the machine (states, relations, clocks). states: param for ordered or partial results.

func (*Machine) Is 

func (m *Machine) Is(states S) bool

Is checks if all the passed states are currently active. 

machine.StringAll() // ()[Foo:0 Bar:0 Baz:0]
machine.Add(S{"Foo"})
machine.Is(S{"Foo"}) // true
machine.Is(S{"Foo", "Bar"}) // false

func (*Machine) Is1 added in v0.5.0 

func (m *Machine) Is1(state string) bool

Is1 is Machine.Is for a single state.

func (*Machine) IsClock 

func (m *Machine) IsClock(clock Clock) bool

IsClock checks if the machine has changed since the passed clock. Returns true if at least one state has changed.

func (*Machine) IsDisposed added in v0.8.0 

func (m *Machine) IsDisposed() bool

IsDisposed returns true if the machine has been disposed.

func (*Machine) IsErr 

func (m *Machine) IsErr() bool

IsErr checks if the machine has the StateException state currently active.

func (*Machine) IsQueued 

func (m *Machine) IsQueued(mutType MutationType, states S,
	withoutArgsOnly bool, statesStrictEqual bool, minQueueTick uint64,
	isCheck bool, position Position,
) (found bool, idx uint16, qTick uint64)

IsQueued checks if a particular mutation has been queued. Returns an index (idx, true), or (0, false), if not found.

mutType: add, remove, set

states: list of states used in the mutation

withoutArgsOnly: matches only mutation without the arguments object

statesStrictEqual: states of the mutation have to be exactly like `states` and not a superset.

minQueueTick: minimal queue tick assigned to the matched mutation

isCheck: the mutation has to be a [Mutation.IsCheck]

position: position in the queue, after applying the [startIndex]

func (*Machine) IsQueuedAbove added in v0.13.0 

func (m *Machine) IsQueuedAbove(threshold int, mutType MutationType,
	states S, withoutArgsOnly bool, statesStrictEqual bool, minQueueTick uint64,
) bool

IsQueuedAbove ... N times. This method allows for rate-limiting of mutations for specific states and a threshold.

func (*Machine) IsTime added in v0.7.0 

func (m *Machine) IsTime(t Time, states S) bool

IsTime checks if the machine has changed since the passed time (list of ticks). Returns true if at least one state has changed. The states param is optional and can be used to check only a subset of states.

func (*Machine) Log 

func (m *Machine) Log(msg string, args ...any)

Log logs an [extern] message unless LogNothing is set. Optionally redirects to a custom logger from SemLogger().SetLogger.

func (*Machine) MachineTick added in v0.16.0 

func (m *Machine) MachineTick() uint32

MachineTick is the number of times the machine has been started. Each start means an empty queue. Only set by Machine.Import.

func (*Machine) MustBindHandlers added in v0.8.0 

func (m *Machine) MustBindHandlers(handlers any)

MustBindHandlers is a panicking version of BindHandlers, useful in tests.

func (*Machine) NewStateCtx added in v0.5.0 

func (m *Machine) NewStateCtx(state string) context.Context

NewStateCtx returns a new sub-context, bound to the current clock's tick of the passed state.

Context cancels when the state has been deactivated, or right away, if it isn't currently active.

State contexts are used to check state expirations and should be checked often inside goroutines.

func (*Machine) Not 

func (m *Machine) Not(states S) bool

Not checks if **none** of the passed states are currently active. 

machine.StringAll()
// -> ()[A:0 B:0 C:0 D:0]
machine.Add(S{"A", "B"})

// not(A) and not(C)
machine.Not(S{"A", "C"})
// -> false

// not(C) and not(D)
machine.Not(S{"C", "D"})
// -> true

func (*Machine) Not1 added in v0.5.0 

func (m *Machine) Not1(state string) bool

Not1 is Machine.Not for a single state.

func (*Machine) OnChange added in v0.13.0 

func (m *Machine) OnChange(fn HandlerChange)

OnChange is the most basic state-change handler, useful for machines without any handlers.

func (*Machine) OnDispose added in v0.16.0 

func (m *Machine) OnDispose(fn HandlerDispose)

OnDispose adds a function to be called after the machine gets disposed. These functions will run synchronously just before WhenDisposed() channel gets closed. Considering it's a low-level feature, it's advised to handle disposal via dedicated states.

func (*Machine) OnError added in v0.13.0 

func (m *Machine) OnError(fn HandlerError)

OnError is the most basic error handler, useful for machines without any handlers.

func (*Machine) PanicToErr added in v0.7.0 

func (m *Machine) PanicToErr(args A)

PanicToErr will catch a panic and add the StateException state. Needs to be called in a defer statement, just like a recover() call.

func (*Machine) PanicToErrState added in v0.7.0 

func (m *Machine) PanicToErrState(state string, args A)

PanicToErrState will catch a panic and add the StateException state, along with the passed state. Needs to be called in a defer statement, just like a recover() call.

func (*Machine) ParentId added in v0.8.0 

func (m *Machine) ParentId() string

ParentId returns the ID of the parent machine (if any).

func (*Machine) ParseStates added in v0.16.0 

func (m *Machine) ParseStates(states S) S

ParseStates parses a list of states, removing unknown ones and duplicates. Use Machine.Has and Machine.Has1 to check if a state is defined for the machine.

func (*Machine) PrependMut added in v0.15.0 

func (m *Machine) PrependMut(mut *Mutation) Result

PrependMut prepends the mutation to the front of the queue. This is a special cases only method and should be used with caution, as it can create an infinite loop. It's useful for postponing mutations inside a negotiation handler. The returned Result can't be waited on, as prepended mutations don't create a queue tick.

func (*Machine) Queue 

func (m *Machine) Queue() []*Mutation

Queue returns a copy of the currently active states.

func (*Machine) QueueLen added in v0.13.0 

func (m *Machine) QueueLen() uint16

func (*Machine) QueueTick added in v0.15.0 

func (m *Machine) QueueTick() uint64

QueueTick is the number of times the queue has processed a mutation. Starts from [1], for easy comparison with Result.

func (*Machine) Remove 

func (m *Machine) Remove(states S, args A) Result

Remove deactivates a list of states in the machine, returning the result of the transition (Executed, Queued, Canceled). Like every mutation method, it will resolve relations and trigger handlers.

func (*Machine) Remove1 added in v0.5.0 

func (m *Machine) Remove1(state string, args A) Result

Remove1 is Machine.Remove1 for a single state.

func (*Machine) Resolver 

func (m *Machine) Resolver() RelationsResolver

Resolver returns the relation resolver, used to produce target states of transitions.

func (*Machine) Schema added in v0.11.0 

func (m *Machine) Schema() Schema

Schema returns a copy of machine's schema.

func (*Machine) SchemaVer added in v0.10.1 

func (m *Machine) SchemaVer() int

SchemaVer return the current version of the schema.

func (*Machine) SemLogger added in v0.15.0 

func (m *Machine) SemLogger() SemLogger

SemLogger returns the semantic logger of the machine

func (*Machine) Set 

func (m *Machine) Set(states S, args A) Result

Set deactivates a list of states in the machine, returning the result of the transition (Executed, Canceled, Queued). Like every mutation method, it will resolve relations and trigger handlers.

func (*Machine) SetGroups added in v0.15.0 

func (m *Machine) SetGroups(groups any, optStates States)

SetGroups organizes the schema into a tree using schema-v2 structs.

func (*Machine) SetGroupsString added in v0.15.0 

func (m *Machine) SetGroupsString(groups map[string]S, order []string)

SetGroupsString is like SetGroups, but work with the schema-v1 format.

func (*Machine) SetSchema added in v0.11.0 

func (m *Machine) SetSchema(newSchema Schema, names S) error

SetSchema sets the machine's schema. It will automatically call VerifyStates with the names param and handle EventSchemaChange if successful. The new schema has to be longer than the previous one (no relations-only changes). The length of the schema is also the version of the schema.

func (*Machine) SetTags added in v0.10.1 

func (m *Machine) SetTags(tags []string)

SetTags updates the machine's tags with the provided slice of strings.

func (*Machine) StateNames 

func (m *Machine) StateNames() S

StateNames returns a SHARED copy of all the state names.

func (*Machine) StateNamesMatch added in v0.12.0 

func (m *Machine) StateNamesMatch(re *regexp.Regexp) S

TODO docs

func (*Machine) StatesVerified added in v0.5.0 

func (m *Machine) StatesVerified() bool

StatesVerified returns true if the state names have been ordered using VerifyStates.

func (*Machine) String 

func (m *Machine) String() string

String returns a one line representation of the currently active states, with their clock values. Inactive states are omitted. Eg: (Foo:1 Bar:3)

func (*Machine) StringAll 

func (m *Machine) StringAll() string

StringAll returns a one line representation of all the states, with their clock values. Inactive states are in square brackets. 

(Foo:1 Bar:3) [Baz:2]

func (*Machine) Switch added in v0.3.0 

func (m *Machine) Switch(groups ...S) string

Switch returns the first state from the passed list that is currently active, making it handy for switch statements. Useful for state groups. 

switch mach.Switch(ss.GroupPlaying) {
case "Playing":
case "Paused":
case "Stopped":
}

func (*Machine) Tags added in v0.5.0 

func (m *Machine) Tags() []string

Tags returns machine's tags, a list of unstructured strings without spaces.

func (*Machine) Tick added in v0.7.0 

func (m *Machine) Tick(state string) uint64

Tick return the current tick for a given state.

func (*Machine) Time 

func (m *Machine) Time(states S) Time

Time returns machine's time, a list of ticks per state. Returned value includes the specified states, or all the states if nil.

func (*Machine) Toggle added in v0.10.1 

func (m *Machine) Toggle(states S, args A) Result

Toggle deactivates a list of states in case all are active, or activates them otherwise. Returns the result of the transition (Executed, Queued, Canceled).

func (*Machine) Toggle1 added in v0.8.0 

func (m *Machine) Toggle1(state string, args A) Result

Toggle1 activates or deactivates a single state, depending on its current state. Returns the result of the transition (Executed, Queued, Canceled).

func (*Machine) Tracers added in v0.5.0 

func (m *Machine) Tracers() []Tracer

Tracers return a copy of currenty attached tracers.

func (*Machine) Transition 

func (m *Machine) Transition() *Transition

Transition returns the current transition, if any.

func (*Machine) VerifyStates added in v0.3.0 

func (m *Machine) VerifyStates(states S) error

VerifyStates verifies an array of state names and returns an error in case at least one isn't defined. It also retains the order and uses it for StateNames. Verification can be checked via Machine.StatesVerified.

func (*Machine) WasClock added in v0.12.0 

func (m *Machine) WasClock(clock Clock) bool

WasClock checks if the passed time has happened (or happening right now). Returns false if at least one state is too early.

func (*Machine) WasTime added in v0.12.0 

func (m *Machine) WasTime(t Time, states S) bool

WasTime checks if the passed time has happened (or happening right now). Returns false if at least one state is too early. The states param is optional and can be used to check only a subset of states.

func (*Machine) When 

func (m *Machine) When(states S, ctx context.Context) <-chan struct{}

When returns a channel that will be closed when all the passed states become active or the machine gets disposed.

ctx: optional context that will close the channel early.

func (*Machine) When1 added in v0.5.0 

func (m *Machine) When1(state string, ctx context.Context) <-chan struct{}

When1 is an alias to When() for a single state. See When.

func (*Machine) WhenArgs added in v0.5.0 

func (m *Machine) WhenArgs(
	state string, args A, ctx context.Context,
) <-chan struct{}

WhenArgs returns a channel that will be closed when the passed state becomes active with all the passed args. Args are compared using the native '=='. It's meant to be used with async Multi states, to filter out a specific call.

ctx: optional context that will close the channel when handler loop ends.

func (*Machine) WhenDisposed added in v0.5.0 

func (m *Machine) WhenDisposed() <-chan struct{}

WhenDisposed returns a channel that will be closed when the machine is disposed.

func (*Machine) WhenErr 

func (m *Machine) WhenErr(disposeCtx context.Context) <-chan struct{}

WhenErr returns a channel that will be closed when the machine is in the StateException state.

ctx: optional context that will close the channel early.

func (*Machine) WhenNot 

func (m *Machine) WhenNot(states S, ctx context.Context) <-chan struct{}

WhenNot returns a channel that will be closed when all the passed states become inactive or the machine gets disposed.

ctx: optional context that will close the channel early.

func (*Machine) WhenNot1 added in v0.5.0 

func (m *Machine) WhenNot1(state string, ctx context.Context) <-chan struct{}

WhenNot1 is an alias to WhenNot() for a single state. See WhenNot.

func (*Machine) WhenQuery added in v0.16.0 

func (m *Machine) WhenQuery(
	clockCheck func(clock Clock) bool, ctx context.Context,
) <-chan struct{}

WhenQuery returns a channel that will be closed when the passed [clockCheck] function returns true. [clockCheck] should be a pure function and non-blocking.`

ctx: optional context that will close the channel early.

func (*Machine) WhenQueue added in v0.15.0 

func (m *Machine) WhenQueue(tick Result) <-chan struct{}

WhenQueue waits until the passed queueTick gets processed. TODO example

func (*Machine) WhenQueueEnds added in v0.5.0 

func (m *Machine) WhenQueueEnds() <-chan struct{}

WhenQueueEnds closes every time the queue ends, or the optional ctx expires.

ctx: optional context that will close the channel early.

func (*Machine) WhenTicks added in v0.5.0 

func (m *Machine) WhenTicks(
	state string, ticks int, ctx context.Context,
) <-chan struct{}

WhenTicks waits N ticks of a single state (relative to now). Uses WhenTime underneath.

ctx: optional context that will close the channel early.

func (*Machine) WhenTime added in v0.5.0 

func (m *Machine) WhenTime(
	states S, times Time, ctx context.Context,
) <-chan struct{}

WhenTime returns a channel that will be closed when all the passed states have passed the specified time. The time is a logical clock of the state. Machine time can be sourced from Machine.Time(), or Machine.Clock().

ctx: optional context that will close the channel early.

func (*Machine) WhenTime1 added in v0.11.0 

func (m *Machine) WhenTime1(
	state string, ticks uint64, ctx context.Context,
) <-chan struct{}

WhenTime1 waits till ticks for a single state equal the given value (or more).

ctx: optional context that will close the channel early.

func (*Machine) WillBe added in v0.8.0 

func (m *Machine) WillBe(states S, position ...Position) bool

WillBe returns true if the passed states are scheduled to be activated. Does not cover implied states, only called ones. See Machine.IsQueued to perform more detailed queries.

position: optional position assertion

func (*Machine) WillBe1 added in v0.8.0 

func (m *Machine) WillBe1(state string, position ...Position) bool

WillBe1 returns true if the passed state is scheduled to be activated. See IsQueued to perform more detailed queries.

func (*Machine) WillBeRemoved added in v0.8.0 

func (m *Machine) WillBeRemoved(states S, position ...Position) bool

WillBeRemoved returns true if the passed states are scheduled to be deactivated. Does not cover implied states, only called ones. See Machine.IsQueued to perform more detailed queries.

position: optional position assertion

func (*Machine) WillBeRemoved1 added in v0.8.0 

func (m *Machine) WillBeRemoved1(state string, position ...Position) bool

WillBeRemoved1 returns true if the passed state is scheduled to be deactivated. See IsQueued to perform more detailed queries.

type MutSource added in v0.9.0 

type MutSource struct {
	MachId string
	TxId   string
	// Machine time of the source machine BEFORE the event.
	MachTime uint64
}

type Mutation 

type Mutation struct {
	// add, set, remove
	Type MutationType
	// States explicitly passed to the mutation method, as their indexes. Use
	// Transition.CalledStates or IndexToStates to get the actual state names.
	Called []int
	// argument map passed to the mutation method (if any).
	Args A
	// this mutation has been triggered by an auto state
	// TODO rename to IsAuto
	IsAuto bool
	// Source is the source event for this mutation.
	Source *MutSource
	// IsCheck indicates that this mutation is a check, see [Machine.CanAdd].
	IsCheck bool

	// QueueTickNow is the queue tick during which this mutation was scheduled.
	QueueTickNow uint64
	// QueueLen is the length of the queue at the time when the mutation was
	// queued.
	QueueLen int32
	// QueueTokensLen is the amount of unexecuted queue tokens (priority queue).
	// TODO impl
	QueueTokensLen int32
	// QueueTick is the assigned queue tick at the time when the mutation was
	// queued. 0 for prepended mutations.
	QueueTick uint64
	// QueueToken is a unique ID, which is given to prepended mutations.
	// Tokens are assigned in a series but executed in random order.
	QueueToken uint64
	// contains filtered or unexported fields
}

Mutation represents an atomic change (or an attempt) of machine's active states. Mutation causes a Transition.

func (*Mutation) CalledIndex added in v0.12.0 

func (m *Mutation) CalledIndex(index S) *TimeIndex

func (*Mutation) IsCalled added in v0.12.0 

func (m *Mutation) IsCalled(idx int) bool

func (*Mutation) LogArgs added in v0.15.0 

func (m *Mutation) LogArgs(mapper LogArgsMapperFn) string

LogArgs returns a text snippet with arguments which should be logged for this Mutation.

func (*Mutation) MapArgs added in v0.15.0 

func (m *Mutation) MapArgs(mapper LogArgsMapperFn) map[string]string

MapArgs returns arguments of this Mutation which match the passed [mapper]. The returned map is never nil.

func (*Mutation) String added in v0.11.0 

func (m *Mutation) String() string

func (*Mutation) StringFromIndex added in v0.12.0 

func (m *Mutation) StringFromIndex(index S) string

type MutationType 

type MutationType int

MutationType enum 

const (
	MutationAdd MutationType = iota
	MutationRemove
	MutationSet
)

func (MutationType) String 

func (m MutationType) String() string

type Opts 

type Opts struct {
	// Unique ID of this machine. Default: random ID.
	Id string
	// Time for a handler to execute. Default: time.Second
	HandlerTimeout time.Duration
	// TODO docs
	HandlerDeadline time.Duration
	// If true, the machine will NOT print all exceptions to stdout.
	DontLogStackTrace bool
	// If true, the machine will die on panics.
	DontPanicToException bool
	// If true, the machine will NOT prefix its logs with its ID.
	DontLogId bool
	// Custom relations resolver. Default: *[DefaultRelationsResolver].
	Resolver RelationsResolver
	// Log level of the machine. Default: [LogNothing].
	LogLevel LogLevel
	// Tracer for the machine. Default: nil.
	Tracers []Tracer
	// LogArgs matching function for the machine. Default: nil.
	LogArgs LogArgsMapperFn
	// Parent machine, used to inherit certain properties, e.g. tracers.
	// Overrides ParentID. Default: nil.
	Parent Api
	// ParentID is the ID of the parent machine. Default: "".
	ParentId string
	// Tags is a list of tags for the machine. Default: nil.
	Tags []string
	// QueueLimit is the maximum number of mutations that can be queued.
	// Default: 1000.
	QueueLimit uint16
	// DetectEval will detect Eval calls directly in handlers, which causes a
	// deadlock. It works in similar way as -race flag in Go and can also be
	// triggered by setting either env var: AM_DEBUG=1 or AM_DETECT_EVAL=1.
	// Default: false.
	DetectEval     bool
	HandlerBackoff time.Duration
}

Opts struct is used to configure a new Machine.

func OptsWithDebug added in v0.5.0 

func OptsWithDebug(opts *Opts) *Opts

OptsWithDebug returns Opts with debug settings (DontPanicToException, long HandlerTimeout).

func OptsWithTracers added in v0.5.0 

func OptsWithTracers(opts *Opts, tracers ...Tracer) *Opts

OptsWithTracers returns Opts with the given tracers. Tracers are inherited by submachines (via Opts.Parent) when env.AM_DEBUG is set.

type Position added in v0.15.0 

type Position uint8

Position describes the item's position in a list. Used mostly for the queue in Machine.IsQueued. 

const (
	PositionAny Position = iota
	PositionFirst
	PositionLast
)

type Relation 

type Relation int8

Relation enum 

const (
	// TODO refac, 0 should be RelationNone, start from 1, udpate with dbg proto
	RelationAfter Relation = iota
	RelationAdd
	RelationRequire
	RelationRemove
)

func (Relation) String 

func (r Relation) String() string

type RelationsResolver 

type RelationsResolver interface {
	// TargetStates returns the target states after parsing the relations.
	TargetStates(t *Transition, calledStates, index S) S
	// NewAutoMutation returns an (optional) auto mutation which is appended to
	// the queue after the transition is executed. It also returns the names of
	// the called states.
	NewAutoMutation() (*Mutation, S)
	// SortStates sorts the states in the order their handlers should be
	// executed.
	SortStates(states S)
	// RelationsOf returns a list of relation types of the given state.
	RelationsOf(fromState string) ([]Relation, error)
	// RelationsBetween returns a list of relation types between the given
	// states.
	RelationsBetween(fromState, toState string) ([]Relation, error)
	InboundRelationsOf(toState string) (S, error)

	// NewSchema runs when Machine receives a new struct.
	NewSchema(schema Schema, states S)
}

RelationsResolver is an interface for parsing relations between states. Not thread-safe. TODO support custom relation types and additional state properties. TODO refac Relations

type Result 

type Result uint64

Result enum is the result of a state Transition. Queued is a virtual value and everything >= Queued (2) represents a queue tick on which the mutation will be processed. It's useful for queued negotiations. 

const (
	// Executed means that the transition was executed immediately and not
	// canceled.
	Executed Result = 0
	// Canceled means that the transition was canceled, by either relations or a
	// negotiation handler.
	Canceled Result = 1
	// Queued means that the transition was queued for later execution. Everything
	// above 2 also means Queued. The following methods can be used to wait for
	// the results:
	// - Machine.When
	// - Machine.WhenNot
	// - Machine.WhenArgs
	// - Machine.WhenTime
	// - Machine.WhenTime1
	// - Machine.WhenTicks
	// - Machine.WhenQueue
	// - Machine.WhenQueueEnds
	// See [Machine.QueueTick].
	Queued Result = 2
)

func (Result) String 

func (r Result) String() string

type S 

type S []string

S (state names) is a string list of state names.

func IndexToStates added in v0.12.0 

func IndexToStates(index S, states []int) S

IndexToStates decodes state indexes based on the provided index.

func SAdd added in v0.7.0 

func SAdd(states ...S) S

SAdd concatenates multiple state lists into one, removing duplicates. Useful for merging lists of states, eg a state group with other states involved in a relation.

func SRem added in v0.12.0 

func SRem(src S, states ...S) S

SRem removes groups > 1 from nr 1. TODO docs

func StatesDiff added in v0.17.0 

func StatesDiff(states1 S, states2 S) S

StatesDiff returns the states that are in states1 but not in states2.

func StatesShared added in v0.17.0 

func StatesShared(states1 S, states2 S) S

StatesShared return states present in both states1 and states2.

func (S) Filter added in v0.17.0 

func (s S) Filter(idxs []int) S

Filter returns a subset of S from specified indexes.

type Schema added in v0.10.2 

type Schema = map[string]State

Schema is a map of state names to state definitions.

func ParseSchema added in v0.12.0 

func ParseSchema(schema Schema) (Schema, error)

func SchemaClone added in v0.18.0 

func SchemaClone(schema Schema) Schema

SchemaClone deep clones the states struct and returns a copy.

func SchemaMerge added in v0.10.3 

func SchemaMerge(schemas ...Schema) Schema

SchemaMerge merges multiple state structs into one, overriding the previous state definitions. No relation-level merging takes place.

type SemConfig added in v0.15.0 

type SemConfig struct {
	// TODO
	Full     bool
	Steps    bool
	Graph    bool
	Can      bool
	Queued   bool
	Args     bool
	When     bool
	StateCtx bool
}

SemConfig defines a config for SemLogger.

type SemLogger added in v0.15.0 

type SemLogger interface {

	// AddPipeOut informs that [sourceState] has been piped out into [targetMach].
	// The name of the target state is unknown.
	AddPipeOut(addMut bool, sourceState, targetMach string)
	// AddPipeIn informs that [targetState] has been piped into this machine from
	// [sourceMach]. The name of the source state is unknown.
	AddPipeIn(addMut bool, targetState, sourceMach string)
	// RemovePipes removes all pipes for the passed machine ID.
	RemovePipes(machId string)

	// IsCan return true when the machine is logging Can* methods.
	IsCan() bool
	// EnableCan enables / disables logging of Can* methods.
	EnableCan(enable bool)
	// IsSteps return true when the machine is logging transition steps.
	IsSteps() bool
	// EnableSteps enables / disables logging of transition steps.
	EnableSteps(enable bool)
	// IsGraph returns true when the machine is logging graph structures.
	IsGraph() bool
	// EnableGraph enables / disables logging of graph structures.
	EnableGraph(enable bool)
	// EnableId enables or disables the logging of the machine's ID in log
	// messages.
	EnableId(val bool)
	// IsId returns true when the machine is logging the machine's ID in log
	// messages.
	IsId() bool
	// EnableQueued enables or disables the logging of queued mutations.
	EnableQueued(val bool)
	// IsQueued returns true when the machine is logging queued mutations.
	IsQueued() bool
	// EnableStateCtx enables or disables the logging of active state contexts.
	EnableStateCtx(val bool)
	// IsStateCtx returns true when the machine is logging active state contexts.
	IsStateCtx() bool
	// EnableWhen enables or disables the logging of "when" methods.
	EnableWhen(val bool)
	// IsWhen returns true when the machine is logging "when" methods.
	IsWhen() bool
	// EnableArgs enables or disables the logging known args.
	EnableArgs(val bool)
	// IsArgs returns true when the machine is logging known args.
	IsArgs() bool

	// SetLogger sets a custom logger function.
	SetLogger(logger LoggerFn)
	// Logger returns the current custom logger function or nil.
	Logger() LoggerFn
	// SetLevel sets the log level of the machine.
	SetLevel(lvl LogLevel)
	// Level returns the log level of the machine.
	Level() LogLevel
	// SetEmpty creates an empty logger that does nothing and sets the log
	// level in one call. Useful when combined with am-dbg. Requires LogChanges
	// log level to produce any output.
	SetEmpty(lvl LogLevel)
	// SetSimple takes log.Printf and sets the log level in one
	// call. Useful for testing. Requires LogChanges log level to produce any
	// output.
	SetSimple(logf func(format string, args ...any), level LogLevel)
	// SetArgsMapper accepts a function which decides which mutation arguments
	// to log. See NewLogArgsMapper or create one.
	SetArgsMapper(mapper LogArgsMapperFn)
	// SetArgsMapperDef binds and extends the default NewLogArgsMapper and LogArgs
	// with [additional] arguments to be logged.
	SetArgsMapperDef(additional ...string)
	// ArgsMapper returns the current log args mapper function.
	ArgsMapper() LogArgsMapperFn
}

SemLogger is a semantic logger for structured events. It's consist of: - enable / enabled methods - text logger utils - setters for external semantics (eg pipes) It's WIP, and eventually it will replace (but not remove) the text logger.

type Serialized added in v0.7.0 

type Serialized struct {
	// ID is the ID of a state machine.
	// TODO refac to Id with the new dbg telemetry protocol
	ID string `json:"id" yaml:"id" toml:"id"`
	// StateNames is an ordered list of state names.
	StateNames S `json:"state_names" yaml:"state_names" toml:"state_names"`
	// Time is the [Machine.Time] value.
	Time Time `json:"time" yaml:"time" toml:"time"`
	// QueueTick is a value of [Machine.QueueTick].
	QueueTick uint64 `json:"queue_tick" yaml:"queue_tick" toml:"queue_tick"`
	// MachineTick is a value of [Machine.MachineTick].
	// nolint:lll
	MachineTick uint32 `json:"machine_tick" yaml:"machine_tick" toml:"machine_tick"`
}

Serialized is a machine state serialized to a JSON/YAML/TOML compatible struct. One also needs the state Struct to re-create a state machine.

type State 

type State struct {
	Auto    bool     `json:"auto,omitempty"`
	Multi   bool     `json:"multi,omitempty"`
	Require S        `json:"require,omitempty"`
	Add     S        `json:"add,omitempty"`
	Remove  S        `json:"remove,omitempty"`
	After   S        `json:"after,omitempty"`
	Tags    []string `json:"tags,omitempty"`
}

State defines a single state of a machine, its properties and relations.

func StateAdd added in v0.7.0 

func StateAdd(source State, overlay State) State

StateAdd adds new states to relations of the source state, without removing existing ones. Useful for adjusting shared stated to a specific machine. Only "true" values for Auto and Multi are applied from [overlay]. 

ssS.HandshakeDone: StateAdd(
	SharedSchema[ssS.HandshakeDone],
	am.State{
		Require: S{ssS.ClientConnected},
		Remove: S{Exception},
	}),

func StateSet added in v0.7.0 

func StateSet(source State, auto, multi bool, overlay State) State

StateSet replaces passed relations and properties of the source state. Only relations in the overlay state are replaced, the rest is preserved. If [overlay] has all fields `nil`, then only [auto] and [multi] get applied. 

 ssS.HandshakeDone: StateSet(s, false, true, State{
		Remove: S{"C"},
	})

type StateIsActive added in v0.7.0 

type StateIsActive map[string]bool

TODO optimize with indexes

type States 

type States interface {
	// Names returns the state names of the state machine.
	Names() S
	// TODO
	StateGroups() (map[string][]int, []string)
	SetNames(S)
	SetStateGroups(map[string][]int, []string)
}

type StatesBase added in v0.8.0 

type StatesBase struct {
	// Exception is the only built-in state and mean a global error. All errors
	// have to [State.Require] the Exception state. If [Machine.PanicToErr] is
	// true, Exception will receive it.
	Exception string
	// contains filtered or unexported fields
}

func (*StatesBase) Names added in v0.8.0 

func (b *StatesBase) Names() S

func (*StatesBase) SetNames added in v0.8.0 

func (b *StatesBase) SetNames(names S)

func (*StatesBase) SetStateGroups added in v0.15.0 

func (b *StatesBase) SetStateGroups(groups map[string][]int, order []string)

func (*StatesBase) StateGroups added in v0.15.0 

func (b *StatesBase) StateGroups() (map[string][]int, []string)

type Step added in v0.5.0 

type Step struct {
	Type StepType
	// Only for Type == StepRelation.
	RelType Relation
	// marks a final handler (FooState, FooEnd)
	IsFinal bool
	// marks a self handler (FooFoo)
	IsSelf bool
	// marks an enter handler (FooState, but not FooEnd). Requires IsFinal.
	IsEnter bool
	// Deprecated, use GetFromState(). TODO remove
	FromState string
	// TODO implement
	FromStateIdx int
	// Deprecated, use GetToState(). TODO remove
	ToState string
	// TODO implement
	ToStateIdx int
	// Deprecated, use RelType. TODO remove
	Data any
}

Step struct represents a single step within a Transition, either a relation resolving step or a handler call.

func (*Step) GetFromState added in v0.9.0 

func (s *Step) GetFromState(index S) string

GetFromState returns the source state of a step. Optional, unless no GetToState().

func (*Step) GetToState added in v0.9.0 

func (s *Step) GetToState(index S) string

GetToState returns the target state of a step. Optional, unless no GetFromState().

func (*Step) StringFromIndex added in v0.12.0 

func (s *Step) StringFromIndex(idx S) string

type StepType added in v0.5.0 

type StepType int8

StepType enum 

const (
	StepRelation StepType = 1 << iota
	StepHandler
	// TODO rename to StepActivate
	StepSet
	// StepRemove indicates a step where a state goes active->inactive
	// TODO rename to StepDeactivate
	StepRemove
	// StepRemoveNotActive indicates a step where a state goes inactive->inactive
	// TODO rename to StepDeactivatePassive
	StepRemoveNotActive
	// TODO refac to StepCalled
	StepRequested
	StepCancel
)

TODO refac with dbg-proto-v2

func (StepType) String added in v0.5.0 

func (tt StepType) String() string

type Subscriptions added in v0.15.1 

type Subscriptions struct {
	// Mx locks the subscription manager. TODO optimize?
	Mx sync.Mutex
	// contains filtered or unexported fields
}

Subscriptions is an embed responsible for binding subscriptions, managing their indexes, processing triggers, and garbage collection.

func NewSubscriptionManager added in v0.15.1 

func NewSubscriptionManager(
	mach Api, clock Clock, is, not InternalCheckFunc, log InternalLogFunc,
) *Subscriptions

func (*Subscriptions) HasWhenArgs added in v0.15.1 

func (sm *Subscriptions) HasWhenArgs() bool

func (*Subscriptions) NewStateCtx added in v0.15.1 

func (sm *Subscriptions) NewStateCtx(state string) context.Context

NewStateCtx returns a new sub-context, bound to the current clock's tick of the passed state.

Context cancels when the state has been deactivated, or right away, if it isn't currently active.

State contexts are used to check state expirations and should be checked often inside goroutines.

func (*Subscriptions) ProcessStateCtx added in v0.15.1 

func (sm *Subscriptions) ProcessStateCtx(deactivated S) []context.CancelFunc

ProcessStateCtx collects all deactivated state contexts, and returns theirs cancel funcs. Uses transition caches.

func (*Subscriptions) ProcessWhen added in v0.15.1 

func (sm *Subscriptions) ProcessWhen(activated, deactivated S) []chan struct{}

ProcessWhen collects all the matched active state subscriptions, and returns theirs channels.

func (*Subscriptions) ProcessWhenArgs added in v0.15.1 

func (sm *Subscriptions) ProcessWhenArgs(e *Event) []chan struct{}

ProcessWhenArgs collects all the args-matching subscriptions, and returns theirs channels.

func (*Subscriptions) ProcessWhenQuery added in v0.16.0 

func (sm *Subscriptions) ProcessWhenQuery() []chan struct{}

func (*Subscriptions) ProcessWhenQueue added in v0.15.1 

func (sm *Subscriptions) ProcessWhenQueue(queueTick uint64) []chan struct{}

func (*Subscriptions) ProcessWhenQueueEnds added in v0.15.1 

func (sm *Subscriptions) ProcessWhenQueueEnds() []chan struct{}

ProcessWhenQueueEnds collects all queue-end subscriptions, and returns theirs channels.

func (*Subscriptions) ProcessWhenTime added in v0.15.1 

func (sm *Subscriptions) ProcessWhenTime(before Clock) []chan struct{}

ProcessWhenTime collects all the time-based subscriptions, and returns theirs channels.

func (*Subscriptions) QueueFlush added in v0.17.0 

func (sm *Subscriptions) QueueFlush()

QueueFlush means a new queue, and all the queue-related subs are expired and have to be closed.

func (*Subscriptions) SetClock added in v0.17.0 

func (sm *Subscriptions) SetClock(clock Clock)

SetClock sets a longer clock from an expanded schema.

func (*Subscriptions) When added in v0.15.1 

func (sm *Subscriptions) When(states S, ctx context.Context) <-chan struct{}

func (*Subscriptions) WhenArgs added in v0.15.1 

func (sm *Subscriptions) WhenArgs(
	state string, args A, ctx context.Context,
) <-chan struct{}

WhenArgs returns a channel that will be closed when the passed state becomes active with all the passed args. Args are compared using the native '=='. It's meant to be used with async Multi states, to filter out a specific call.

ctx: optional context that will close the channel when handler loop ends.

func (*Subscriptions) WhenNot added in v0.15.1 

func (sm *Subscriptions) WhenNot(
	states S, ctx context.Context,
) <-chan struct{}

WhenNot returns a channel that will be closed when all the passed states become inactive or the machine gets disposed.

ctx: optional context that will close the channel early.

func (*Subscriptions) WhenQuery added in v0.16.0 

func (sm *Subscriptions) WhenQuery(
	fn func(clock Clock) bool, ctx context.Context,
) <-chan struct{}

func (*Subscriptions) WhenQueue added in v0.15.1 

func (sm *Subscriptions) WhenQueue(tick Result) <-chan struct{}

WhenQueue waits until the passed queueTick gets processed.

func (*Subscriptions) WhenQueueEnds added in v0.15.1 

func (sm *Subscriptions) WhenQueueEnds() <-chan struct{}

WhenQueueEnds closes every time the queue ends, or the optional ctx expires. This function assumes the queue is running, and wont close early.

ctx: optional context that will close the channel early.

func (*Subscriptions) WhenTime added in v0.15.1 

func (sm *Subscriptions) WhenTime(
	states S, times Time, ctx context.Context,
) <-chan struct{}

WhenTime returns a channel that will be closed when all the passed states have passed the specified time. The time is a logical clock of the state. Machine time can be sourced from Machine.Time(), or Machine.Clock().

ctx: optional context that will close the channel early.

type Time added in v0.7.0 

type Time []uint64

Time is machine time, an ordered list of state ticks. It's like Clock, but indexed by int, instead of string. TODO use math/big?

func IndexToTime added in v0.12.0 

func IndexToTime(index S, active []int) Time

IndexToTime returns "virtual time" with selected states active. It's useful to use time methods on a list of states, eg the called ones.

func NewTime added in v0.17.0 

func NewTime(index Time, activeStates []int) Time

NewTime returns a Time of the same len as [index] with active states marked by indexes in [activeStates].

func (Time) ActiveStates added in v0.12.0 

func (t Time) ActiveStates(idxs []int) []int

ActiveStates returns a list of active state indexes in this machine time slice. When idxs isn't nil, only the passed indexes are considered.

func (Time) Add added in v0.10.3 

func (t Time) Add(t2 Time) Time

Add sums 2 instances of Time and returns a new one.

func (Time) After added in v0.16.0 

func (t Time) After(orEqual bool, time2 Time) bool

After returns true if at least 1 tick in time1 is after time2, optionally accepting equal values for true. Requires a deterministic states order, eg by using Machine.VerifyStates.

func (Time) Any added in v0.16.0 

func (t Time) Any(idxs ...[]int) bool

Any is Machine.Any but for an int-based time slice.

func (Time) Any1 added in v0.8.0 

func (t Time) Any1(idxs ...int) bool

Any1 is Machine.Any1 but for an int-based time slice.

func (Time) Before added in v0.16.0 

func (t Time) Before(orEqual bool, time2 Time) bool

Before returns true if at least 1 tick in time1 is before time2, optionally accepting equal values for true. Requires a deterministic states order, eg by using Machine.VerifyStates.

func (Time) DiffSince added in v0.10.3 

func (t Time) DiffSince(before Time) Time

DiffSince returns the number of ticks for each state in Time since the passed machine time.

func (Time) Equal added in v0.16.0 

func (t Time) Equal(strict bool, time2 Time) bool

Equal checks if time1 is equal to time2. Requires a deterministic states order, eg by using Machine.VerifyStates.

func (Time) Filter added in v0.16.0 

func (t Time) Filter(idxs []int) Time

Filter returns a subset of the Time slice for the given state indexes. It's not advised to slice an already sliced time slice.

func (Time) Increment added in v0.16.0 

func (t Time) Increment(idx int) Time

Increment adds 1 to a state's tick value

func (Time) Is added in v0.7.0 

func (t Time) Is(idxs []int) bool

Is is Machine.Is but for an int-based time slice.

func (Time) Is1 added in v0.7.0 

func (t Time) Is1(idx int) bool

Is1 is Machine.Is1 but for an int-based time slice.

func (Time) NonZeroStates added in v0.16.0 

func (t Time) NonZeroStates() []int

NonZeroStates returns a list of state indexes with non-zero ticks in this machine time slice.

func (Time) Not added in v0.12.0 

func (t Time) Not(idxs []int) bool

Not is Machine.Not but for an int-based time slice.

func (Time) Not1 added in v0.12.0 

func (t Time) Not1(idx int) bool

Not1 is Machine.Not1 but for an int-based time slice.

func (Time) String added in v0.8.0 

func (t Time) String() string

String returns an integer representation of the time slice.

func (Time) Sum added in v0.9.0 

func (t Time) Sum(idxs []int) uint64

Sum returns a sum of ticks for each state in Time, or narrowed down to [idxs].

func (Time) Tick added in v0.16.0 

func (t Time) Tick(idx int) uint64

Tick is Machine.Tick but for an int-based time slice.

func (Time) ToIndex added in v0.16.0 

func (t Time) ToIndex(index S) *TimeIndex

ToIndex returns a string-indexed version of Time.

type TimeIndex added in v0.12.0 

type TimeIndex struct {
	Time
	Index S
}

TimeIndex is Time with a bound state index (list of state names). It's not suitable for storage, use Time instead. See Clock for a simpler type with ticks indexes by state names.

func NewTimeIndex added in v0.12.0 

func NewTimeIndex(index S, activeStates []int) *TimeIndex

NewTimeIndex returns a TimeIndex of the same len as [index] with active states marked by indexes in [activeStates].

func (TimeIndex) ActiveStates added in v0.12.0 

func (t TimeIndex) ActiveStates(states S) S

ActiveStates is Machine.ActiveStates but for a string-based time slice.

func (TimeIndex) Any added in v0.16.0 

func (t TimeIndex) Any(states ...string) bool

Any is Machine.Any but for a string-based time slice.

func (TimeIndex) Any1 added in v0.12.0 

func (t TimeIndex) Any1(states ...string) bool

Any1 is Machine.Any1 but for a string-based time slice.

func (TimeIndex) Filter added in v0.16.0 

func (t TimeIndex) Filter(states S) *TimeIndex

Filter is Time.Filter but for a string-based time slice.

func (TimeIndex) Is added in v0.12.0 

func (t TimeIndex) Is(states S) bool

Is is Machine.Is but for a string-based time slice.

func (TimeIndex) Is1 added in v0.12.0 

func (t TimeIndex) Is1(state string) bool

Is1 is Machine.Is1 but for a string-based time slice.

func (TimeIndex) NonZeroStates added in v0.16.0 

func (t TimeIndex) NonZeroStates() S

NonZeroStates is Time.NonZeroStates but for a string-based time slice.

func (TimeIndex) Not added in v0.12.0 

func (t TimeIndex) Not(states S) bool

Not is Machine.Not but for a string-based time slice.

func (TimeIndex) Not1 added in v0.12.0 

func (t TimeIndex) Not1(state string) bool

Not1 is Machine.Not1 but for a string-based time slice.

func (TimeIndex) StateName added in v0.12.0 

func (t TimeIndex) StateName(idx int) string

StateName returns the name of the state at the given index.

func (TimeIndex) String added in v0.12.0 

func (t TimeIndex) String() string

String returns a string representation of the time slice.

func (TimeIndex) Sum added in v0.16.0 

func (t TimeIndex) Sum(states S) uint64

Sum is Time.Sum but for a string-based time slice.

type Tracer added in v0.5.0 

type Tracer interface {
	TransitionInit(transition *Transition)
	TransitionStart(transition *Transition)
	TransitionEnd(transition *Transition)
	MutationQueued(machine Api, mutation *Mutation)
	HandlerStart(transition *Transition, emitter string, handler string)
	HandlerEnd(transition *Transition, emitter string, handler string)
	// MachineInit is called only for machines with tracers added via
	// Opts.Tracers.
	MachineInit(machine Api) context.Context
	MachineDispose(machID string)
	NewSubmachine(parent, machine Api)
	Inheritable() bool
	QueueEnd(machine Api)
	SchemaChange(machine Api, old Schema)
	VerifyStates(machine Api)
}

Tracer is an interface for logging machine transitions and events, used by Opts.Tracers and Machine.BindTracer.

type TracerNoOp added in v0.17.0 

type TracerNoOp struct{}

TracerNoOp is a no-op implementation of Tracer, used for embedding.

func (*TracerNoOp) HandlerEnd added in v0.17.0 

func (t *TracerNoOp) HandlerEnd(
	transition *Transition, emitter string, handler string)

func (*TracerNoOp) HandlerStart added in v0.17.0 

func (t *TracerNoOp) HandlerStart(
	transition *Transition, emitter string, handler string)

func (*TracerNoOp) Inheritable added in v0.17.0 

func (t *TracerNoOp) Inheritable() bool

func (*TracerNoOp) MachineDispose added in v0.17.0 

func (t *TracerNoOp) MachineDispose(machID string)

func (*TracerNoOp) MachineInit added in v0.17.0 

func (t *TracerNoOp) MachineInit(machine Api) context.Context

func (*TracerNoOp) MutationQueued added in v0.17.0 

func (t *TracerNoOp) MutationQueued(machine Api, mutation *Mutation)

func (*TracerNoOp) NewSubmachine added in v0.17.0 

func (t *TracerNoOp) NewSubmachine(parent, machine Api)

func (*TracerNoOp) QueueEnd added in v0.17.0 

func (t *TracerNoOp) QueueEnd(machine Api)

func (*TracerNoOp) SchemaChange added in v0.17.0 

func (t *TracerNoOp) SchemaChange(machine Api, old Schema)

func (*TracerNoOp) TransitionEnd added in v0.17.0 

func (t *TracerNoOp) TransitionEnd(transition *Transition)

func (*TracerNoOp) TransitionInit added in v0.17.0 

func (t *TracerNoOp) TransitionInit(transition *Transition)

func (*TracerNoOp) TransitionStart added in v0.17.0 

func (t *TracerNoOp) TransitionStart(transition *Transition)

func (*TracerNoOp) VerifyStates added in v0.17.0 

func (t *TracerNoOp) VerifyStates(machine Api)

type Transition 

type Transition struct {
	// Id is a unique identifier of the transition.
	Id string
	// Steps is a list of steps taken by this transition (so far).
	Steps []*Step
	// HasStateChanged is true if the transition has changed the state of the
	// machine. TODO useful?
	// HasStateChanged bool
	// TimeBefore is the machine time from before the transition.
	TimeBefore Time
	// TimeAfter is the machine time from after the transition. If the transition
	// has been canceled, this will be the same as TimeBefore. This field is the
	// same as TimeBefore, until the negotiation phase finishes.
	TimeAfter Time
	// TargetIndexes is a list of indexes of the target states.
	TargetIndexes []int
	// Enters is a list of states activated in this transition.
	Enters S
	// Enters is a list of states deactivated in this transition.
	Exits S
	// Mutation call which caused this transition
	Mutation *Mutation
	// Machine is the parent machine of this transition.
	Machine *Machine
	// MachApi is a subset of Machine.
	// TODO call when applicable instead of calling Machine
	// TODO rename to MachApi
	MachApi Api
	// LogEntries are log msgs produced during the transition.
	LogEntries []*LogEntry
	// PreLogEntries are log msgs produced before during the transition.
	PreLogEntries []*LogEntry
	// QueueLen is the length of the queue after the transition.
	QueueLen uint16
	// InternalLogEntriesLock is used to lock the logs to be collected by Tracers.
	// TODO getter?
	InternalLogEntriesLock sync.Mutex
	// IsCompleted returns true when the execution of the transition has been
	// fully completed.
	IsCompleted atomic.Bool
	// IsAccepted returns true if the transition has been accepted, which can
	// change during the transition's negotiation phase and while resolving
	// relations.
	IsAccepted atomic.Bool
	// TODO true for panic and timeouts
	IsBroken atomic.Bool
	// TODO confirms relations resolved and negotiation ended
	IsSettled atomic.Bool
	// contains filtered or unexported fields
}

Transition represents processing of a single mutation within a machine.

func (*Transition) Args 

func (t *Transition) Args() A

Args returns the argument map passed to the mutation method (or an empty one).

func (*Transition) CalledStates 

func (t *Transition) CalledStates() S

CalledStates return explicitly called / requested states of the transition.

func (*Transition) CleanCache added in v0.13.0 

func (t *Transition) CleanCache()

func (*Transition) ClockAfter added in v0.7.0 

func (t *Transition) ClockAfter() Clock

ClockAfter return the Clock from before the transition.

func (*Transition) ClockBefore added in v0.7.0 

func (t *Transition) ClockBefore() Clock

ClockBefore return the Clock from before the transition.

func (*Transition) IsAuto 

func (t *Transition) IsAuto() bool

IsAuto returns true if the transition was triggered by an auto state. Thus, it cant trigger any other auto state mutations.

func (*Transition) IsHealth added in v0.13.0 

func (t *Transition) IsHealth() bool

IsHealth returns true if the transition was health-related (StateHealthcheck, StateHeartbeat).

func (*Transition) StatesBefore 

func (t *Transition) StatesBefore() S

StatesBefore is a list of states before the transition.

func (*Transition) String 

func (t *Transition) String() string

String representation of the transition and the steps taken so far.

func (*Transition) TargetStates 

func (t *Transition) TargetStates() S

TargetStates is a list of states after parsing the relations.

func (*Transition) TimeIndexAfter added in v0.15.0 

func (t *Transition) TimeIndexAfter() *TimeIndex

TimeIndexAfter return TimeAfter bound to an index, for easy querying.

func (*Transition) TimeIndexBefore added in v0.18.0 

func (t *Transition) TimeIndexBefore() *TimeIndex

TimeIndexBefore return TimeIndexBefore bound to an index, for easy querying.

func (*Transition) TimeIndexCalled added in v0.18.0 

func (t *Transition) TimeIndexCalled() *TimeIndex

TimeIndexCalled return CalledStates bound to an index, for easy querying.

func (*Transition) TimeIndexDiff added in v0.18.0 

func (t *Transition) TimeIndexDiff() (*TimeIndex, *TimeIndex)

TimeIndexDiff return 2 time indexes of added and removed states by this transition. Added include Multi states.

func (*Transition) TimeIndexTouched added in v0.18.0 

func (t *Transition) TimeIndexTouched() *TimeIndex

TimeIndexTouched return all the touched states as active. Requires [SemLogger.IsSteps] to be true.

func (*Transition) Type 

func (t *Transition) Type() MutationType

Type returns the type of the mutation (add, remove, set).

type WhenArgsBinding added in v0.7.0 

type WhenArgsBinding struct {
	// contains filtered or unexported fields
}

type WhenBinding added in v0.7.0 

type WhenBinding struct {
	Ch chan struct{}
	// means states are required to NOT be active
	Negation bool
	States   StateIsActive
	Matched  int
	Total    int
	Ctx      context.Context
}

type WhenTimeBinding added in v0.7.0 

type WhenTimeBinding struct {
	Ch chan struct{}
	// map of matched to their index positions
	// TODO optimize indexes
	Index map[string]int
	// number of matches so far TODO len(Index) ?
	Matched int
	// number of total matches needed
	Total int // TODO len(Times) ?
	// optional Time to match for completed from Index
	Times     Time
	Completed StateIsActive
	Ctx       context.Context
}

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