API Reference

This document contains a description of the low-level API to define and execute processes.

FsmProcess Callbacks

Note: All callback methods return a function unregistering the callback.

• onStateCreate(handler: (state: FsmState) => void) - registers a function called each time a new state is created. This method should use the FsmState#onEnter/FsmState#onExit methods to activate/deactivate states. This method can be called multiple times to register various state handlers.
• onStateError(handler: (state: FsmState, error: unknown) => void | Promise<void>) - registers an error handler; this handler is called each time state activation/deactivation code raises an error.

FsmProcess Methods

• async dispatch(event: string): Promise<boolean> – dispatches the specified event and triggers state transitions in this process
• async dump(...args: unknown[]): Promise<FsmProcessDump> - creates a dump of this process; a new process can be restored in the current state using the FsmProcess#restore(...) method.
• async restore(dump: FsmProcessDump, ...args: unknown[]): Promise<void> - restores the process using the dumped data. Note that the process should not be started yet.
• async shutdown(event?: string): Promise<void> - shuts down the running process with an optional exit event

FsmState Callbacks

• onEnter(callback: () => void | Promise<void>) - registers a callback function used to activate this state. It can be an asynchronous callback - the process will wait until all registered state handlers are resolved.
• onExit(callback: () => void | Promise<void>) - registers a function to call when the process leaves this state. The process waits until all state handlers return control.
• onStateError(handler: FsmStateErrorHandler) - registers an error handler; this handler is called when onEnter or onExit methods raise an error
• dump(handler: (state: FsmState, dump: Record<string, unknown>) => void | Promise<void>) - registers a handler to call when the process dumps its internal current state; the handler receives the state to dump and an object where the internal data should be copied
• restore(handler: (state: FsmState, dump: Record<string, unknown>) => void | Promise<void>) - registers a handler restoring the current state; the handler receives the restored state and an object containing dumped information

FsmState Methods

• getData<T>(key: string, recursive: boolean = true): T | undefined - returns a state-specific data object associated with the specified string key; if this method cannot find information associated with the given key then it recursively searches the data in parent states.
• useData<T>(key: string): [ (recursive: boolean = true) => this.getData<T>(key, recursive), (value: T) => this.setData(key, value)] returns a pair of methods allowing to get and set data in the current state