service

type Config struct {
	Name        string   // Required name of the service. No spaces suggested.
	DisplayName string   // Display name, spaces allowed.
	Description string   // Long description of service.
	UserName    string   // Run as username.
	Arguments   []string // Run with arguments.

	// Optional field to specify the executable for service.
	// If empty the current executable is used.
	Executable string

	// Array of service dependencies.
	// Not yet implemented on Linux or OS X.
	Dependencies []string

	// The following fields are not supported on Windows.
	WorkingDirectory string // Initial working directory.
	ChRoot           string

	// System specific options.
	//  * OS X
	//    - KeepAlive     bool (true)
	//    - RunAtLoad     bool (false)
	//    - UserService   bool (false) - Install as a current user service.
	//    - SessionCreate bool (false) - Create a full user session.
	//  * POSIX
	//    - RunWait      func() (wait for SIGNAL) - Do not install signal but wait for this function to return.
	//    - ReloadSignal string () [USR1, ...] - Signal to send on reaload.
	//    - PIDFile     string () [/run/prog.pid] - Location of the PID file.
	Option KeyValue
}

type Interface interface {
	// Start provides a place to initiate the service. The service doesn't not
	// signal a completed start until after this function returns, so the
	// Start function must not take more then a few seconds at most.
	Start(s Service) error

	// Stop provides a place to clean up program execution before it is terminated.
	// It should not take more then a few seconds to execute.
	// Stop should not call os.Exit directly in the function.
	Stop(s Service) error
}

type KeyValue map[string]interface{}

type Logger interface {
	Error(v ...interface{}) error
	Warning(v ...interface{}) error
	Info(v ...interface{}) error

	Errorf(format string, a ...interface{}) error
	Warningf(format string, a ...interface{}) error
	Infof(format string, a ...interface{}) error
}

type Service interface {
	// Run should be called shortly after the program entry point.
	// After Interface.Stop has finished running, Run will stop blocking.
	// After Run stops blocking, the program must exit shortly after.
	Run() error

	// Start signals to the OS service manager the given service should start.
	Start() error

	// Stop signals to the OS service manager the given service should stop.
	Stop() error

	// Restart signals to the OS service manager the given service should stop then start.
	Restart() error

	// Install setups up the given service in the OS service manager. This may require
	// greater rights. Will return an error if it is already installed.
	Install() error

	// Uninstall removes the given service from the OS service manager. This may require
	// greater rights. Will return an error if the service is not present.
	Uninstall() error

	// Status returns nil if the given service is running.
	// Will return an error if the service is not running or is not present.
	Status() error

	// Opens and returns a system logger. If the user program is running
	// interactively rather then as a service, the returned logger will write to
	// os.Stderr. If errs is non-nil errors will be sent on errs as well as
	// returned from Logger's functions.
	Logger(errs chan<- error) (Logger, error)

	// SystemLogger opens and returns a system logger. If errs is non-nil errors
	// will be sent on errs as well as returned from Logger's functions.
	SystemLogger(errs chan<- error) (Logger, error)

	// String displays the name of the service. The display name if present,
	// otherwise the name.
	String() string
}

type System interface {
	// String returns a description of the system.
	String() string

	// Detect returns true if the system is available to use.
	Detect() bool

	// Interactive returns false if running under the system service manager
	// and true otherwise.
	Interactive() bool

	// New creates a new service for this system.
	New(i Interface, c *Config) (Service, error)
}