Created
May 8, 2022 16:50
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| interface Machine<State extends string, Event extends string> { | |
| initialState: State; | |
| transition(currentState: State, event: Event): State; | |
| } | |
| interface MachineDefinition<State extends string, Event extends string> { | |
| initialState: State; | |
| states: Record<State, { | |
| entry?(): void; | |
| exit?(): void; | |
| on?: Record<Event, { | |
| target?: State; | |
| action?(): void; | |
| }>; | |
| }>; | |
| } | |
| function createMachine<State extends string, Event extends string>(definition: MachineDefinition<State, Event>): Machine<State, Event> { | |
| return { | |
| initialState: definition.initialState, | |
| transition(currentState, event) { | |
| const currentStateDefinition = definition.states[currentState]; | |
| const destinationTransition = currentStateDefinition?.on?.[event]; | |
| if (!destinationTransition) { | |
| return currentState; | |
| } | |
| const destinationState = destinationTransition.target ?? currentState; | |
| const destinationStateDefinition = definition.states[destinationState]; | |
| destinationTransition.action?.(); | |
| currentStateDefinition.exit?.(); | |
| destinationStateDefinition.entry?.(); | |
| return destinationState; | |
| } | |
| } | |
| } | |
| const machine = createMachine({ | |
| initialState: 'green', | |
| states: { | |
| green: { | |
| entry() { | |
| console.log('green: entry'); | |
| }, | |
| on: { | |
| TIME_ELAPSED: { | |
| target: 'yellow' | |
| } | |
| } | |
| }, | |
| yellow: { | |
| entry() { | |
| console.log('yellow: entry'); | |
| }, | |
| on: { | |
| TIME_ELAPSED: { | |
| target: 'red' | |
| } | |
| } | |
| }, | |
| red: { | |
| entry() { | |
| console.log('red: entry'); | |
| }, | |
| on: { | |
| TIME_ELAPSED: { | |
| target: 'green' | |
| } | |
| } | |
| } | |
| } | |
| }); | |
| let state = machine.initialState; | |
| console.log('current state:', state); | |
| state = machine.transition(state, 'TIME_ELAPSED'); | |
| console.log('current state:', state); | |
| state = machine.transition(state, 'TIME_ELAPSED'); | |
| console.log('current state:', state); | |
| state = machine.transition(state, 'TIME_ELAPSED'); | |
| console.log('current state:', state); |
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