import { State } from './State';
import * as _ from 'lodash';
import { CanvasEngine } from '../CanvasEngine';
import { BaseEvent, BaseListener, BaseObserver } from '../core/BaseObserver';

export interface StateMachineListener extends BaseListener {
	stateChanged?: (event: BaseEvent & { newState: State }) => any;
}

export class StateMachine extends BaseObserver<StateMachineListener> {
	protected currentState: State;
	protected stateStack: State[];
	protected engine: CanvasEngine;

	constructor(engine: CanvasEngine) {
		super();
		this.engine = engine;
		this.stateStack = [];
	}

	getCurrentState() {
		return this.currentState;
	}

	pushState(state: State) {
		this.stateStack.push(state);
		this.setState(state);
	}

	popState() {
		this.stateStack.pop();
		this.setState(_.last(this.stateStack));
	}

	setState(state: State) {
		state.setEngine(this.engine);

		// if no state object, get the initial state
		if (this.currentState) {
			this.currentState.deactivated(state);
		}
		const old = this.currentState;
		this.currentState = state;
		if (this.currentState) {
			this.currentState.activated(old);
			this.fireEvent<'stateChanged'>(
				{
					newState: state
				},
				'stateChanged'
			);
		}
	}
}