sprite

package
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Published: Jul 12, 2026 License: MIT Imports: 6 Imported by: 0

Documentation

Overview

Package sprite is a thread-safe, in-memory model of Sprites and their checkpoint/restore semantics. It owns the canonical state; callers receive copies so that concurrent reads and writes never share mutable memory.

A sprite's filesystem is modeled as a path -> contents map. exec runs a small scripted interpreter (see exec.go) that can write or modify an fs key, so a checkpoint (a deep copy of the fs under a server-assigned version id) and a later restore (replace the fs with that copy) are observable. This mirrors the behavior of chant's in-process Sprites fake rather than real code execution.

Checkpoints are addressed by a server-assigned version id (v1, v2, …), not by a caller label. The caller supplies only an optional comment; the store assigns the id sequentially per sprite in creation order.

Index

Constants

This section is empty.

Variables

View Source
var (
	// ErrNotFound is returned for a sprite that was never created or has been
	// destroyed. A destroyed sprite is treated as absent, matching the fake.
	ErrNotFound = errors.New("sprite not found")
	// ErrCheckpointNotFound is returned by Restore for an unknown checkpoint id.
	ErrCheckpointNotFound = errors.New("checkpoint not found")
)

Sentinel errors returned by the store.

Functions

This section is empty.

Types

type Checkpoint added in v0.2.0

type Checkpoint struct {
	ID         string
	Comment    string
	CreateTime string
	IsAuto     bool
	FS         map[string]string
}

Checkpoint is a captured filesystem snapshot: a server-assigned version id (v1, v2, …), the caller-supplied comment, the creation timestamp, whether it was created automatically, and a full copy of the fs at checkpoint time.

type CheckpointInfo added in v0.2.0

type CheckpointInfo struct {
	ID         string `json:"id"`
	Comment    string `json:"comment"`
	CreateTime string `json:"create_time"`
	IsAuto     bool   `json:"is_auto"`
}

CheckpointInfo is the metadata projection of a checkpoint, without its fs copy. It is what the list endpoint, the individual GET, and the sprite view expose so a client can pick a checkpoint by id (or, for compensation, by the newest matching comment). The JSON tags match the real Sprites checkpoint shape: id, comment, create_time, is_auto.

type ExecResult

type ExecResult struct {
	Stdout   string
	Stderr   string
	ExitCode int
}

ExecResult is the outcome of running a command in a sprite. The server's control-WebSocket exec handler carries these three fields to the client as framed messages: stdout as StreamStdout, stderr as StreamStderr, and the exit code as the StreamExit frame's single payload byte.

type Sprite

type Sprite struct {
	ID          string
	Status      Status
	URL         string
	FS          map[string]string
	Checkpoints []Checkpoint
	Policy      any
	// CreatedAt is stamped from the injected clock at creation. It is internal
	// bookkeeping and is not part of the wire contract.
	CreatedAt string
}

Sprite is a single sprite: its lifecycle status, its addressable URL, its filesystem, and its checkpoints (an ordered list, each a full copy of the fs at checkpoint time under a sequential v<N> id).

type Status

type Status string

Status is the lifecycle state of a sprite.

const (
	StatusStarting  Status = "starting"
	StatusRunning   Status = "running"
	StatusPaused    Status = "paused"
	StatusDestroyed Status = "destroyed"
)

The sprite lifecycle states. A sprite is created running; destroy moves it to destroyed, after which every operation on it reports ErrNotFound.

type Store

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

Store holds sprites keyed by id.

func New

func New(clk clock.Clock) *Store

New returns an empty store. A nil clock is replaced with a real one.

func (*Store) Checkpoint

func (s *Store) Checkpoint(id, comment string) (string, error)

Checkpoint deep-copies the sprite's current filesystem under a fresh, server-assigned version id and returns that id. Ids are assigned sequentially per sprite: "v1", "v2", …, one past the current checkpoint count. The caller controls only the comment, which may be empty. It returns ErrNotFound for a missing or destroyed sprite.

func (*Store) Create

func (s *Store) Create(id, url string, policy any) Sprite

Create records a new running sprite under id, with an empty filesystem and no checkpoints. Like the fake, it overwrites any existing sprite with the same id. It returns a copy of the created sprite.

func (*Store) Destroy

func (s *Store) Destroy(id string) error

Destroy marks the sprite destroyed. It returns ErrNotFound if the sprite is missing or already destroyed.

func (*Store) Exec

func (s *Store) Exec(id, cmd string) (ExecResult, error)

Exec runs cmd against the sprite's filesystem and returns the result. It returns ErrNotFound for a missing or destroyed sprite.

func (*Store) Get

func (s *Store) Get(id string) (View, error)

Get returns a read-only view of the sprite. It returns ErrNotFound for a missing or destroyed sprite.

func (*Store) GetCheckpoint added in v0.3.0

func (s *Store) GetCheckpoint(id, checkpointID string) (CheckpointInfo, error)

GetCheckpoint returns a single checkpoint's metadata projection. It returns ErrNotFound for a missing or destroyed sprite, and ErrCheckpointNotFound for an unknown id.

func (*Store) ListCheckpoints added in v0.2.0

func (s *Store) ListCheckpoints(id string) ([]CheckpointInfo, error)

ListCheckpoints returns the sprite's checkpoints as {id, comment} projections in creation order (oldest first), so a client can pick the newest deterministically. It returns ErrNotFound for a missing or destroyed sprite.

func (*Store) Restore

func (s *Store) Restore(id, checkpointID string) error

Restore replaces the sprite's filesystem with the identified checkpoint's copy and sets its status back to running. The checkpoint is addressed by its server-assigned version id (v1, v2, …). It returns ErrNotFound for a missing or destroyed sprite, and ErrCheckpointNotFound for an unknown id.

type View

type View struct {
	ID          string            `json:"id"`
	Status      Status            `json:"status"`
	URL         string            `json:"url"`
	FS          map[string]string `json:"fs"`
	Checkpoints []CheckpointInfo  `json:"checkpoints"`
}

View is the read-only projection returned by GET /v1/sprites/{id}: the checkpoints are exposed as an ordered list of {id, comment} projections, not their fs copies.

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