@theatrejs/theatrejs
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🎮 A JavaScript 2D Game Engine focused on creating pixel art games.
278 lines (219 loc) • 6.47 kB
JavaScript
/**
* Creates finite state machines.
* @template {string} TypeGeneric The generic type of the names of a state.
*
* @example
*
* const toggle = new FiniteStateMachine([
*
* {
* $state: 'ON',
* $transitions: [{
*
* $state: 'OFF',
* $condition: ({$timer}) => ($timer >= 1000)
* }]
* },
* {
* $state: 'OFF',
* $transitions: [{
*
* $state: 'ON',
* $condition: ({$timer}) => ($timer >= 1000)
* }]
* }
* ]);
*
* toggle.tick(timetick);
*/
class FiniteStateMachine {
/**
* @callback TypeStateHandlerEnter A state entering handler.
* @param {object} $parameters The given parameters.
* @param {TypeGeneric} $parameters.$previous The previous state.
* @returns {void}
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* @callback TypeStateHandlerLeave A state leaving handler.
* @param {object} $parameters The given parameters.
* @param {number} $parameters.$timer The timer of the current state.
* @param {TypeGeneric} $parameters.$next The next state.
* @returns {void}
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* @callback TypeStateHandlerTick A state updating handler.
* @param {object} $parameters The given parameters.
* @param {number} $parameters.$timetick The tick duration (in ms).
* @param {number} $parameters.$timer The timer of the current state.
* @returns {void}
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* @callback TypeStateTransitionCondition A state transition condition.
* @param {object} $parameters The given parameters.
* @param {TypeGeneric} $parameters.$previous The previous state.
* @param {number} $parameters.$timer The timer of the current state.
* @returns {boolean}
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* @typedef {object} TypeStateTransition A transition to a state.
* @property {TypeStateTransitionCondition} $condition The condition to transition to given state.
* @property {TypeGeneric} $state The given state to transition to.
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* @typedef {object} TypeState A state.
* @property {TypeGeneric} $state The name of the state.
* @property {TypeStateHandlerEnter} [$onEnter] The handler to execute when entering the state.
* @property {TypeStateHandlerLeave} [$onLeave] The handler to execute when leaving the state.
* @property {TypeStateHandlerTick} [$onTick] The handler to execute when updating the state.
* @property {Array<TypeStateTransition>} [$transitions] The transitions to given states.
* @protected
*
* @memberof FiniteStateMachine
*/
/**
* Stores the initiated status.
* @type {boolean}
* @private
*/
$initiated;
/**
* Stores the previous state.
* @type {TypeState}
* @private
*/
$previous;
/**
* Stores the current state.
* @type {TypeState}
* @private
*/
$state;
/**
* Stores the states.
* @type {Map<TypeGeneric, TypeState>}
* @private
*/
$states;
/**
* Stores the timer of the current state.
* @type {number}
* @private
*/
$timer;
/**
* Gets the name of the current state.
* @type {TypeGeneric}
* @public
*/
get state() {
return this.$state.$state;
}
/**
* Gets the initiated status.
* @type {boolean}
* @public
*/
get initiated() {
return this.$initiated;
}
/**
* Creates a new finite state machine.
* @param {Array<TypeState>} $data The representation of the finite state machine.
*/
constructor($data) {
this.$initiated = false;
this.$states = new Map();
this.$timer = 0;
$data.forEach(($state) => {
this.$states.set($state.$state, $state);
});
}
/**
* Initiates the finite state machine.
* @param {TypeGeneric} $state The name of the state to initiate.
* @public
*/
initiate($state) {
if (this.$initiated === true) {
return;
}
this.$previous = this.$state;
this.$state = this.$states.get($state);
if (typeof this.$state.$onEnter === 'function') {
this.$state.$onEnter({
$previous: undefined
});
}
this.$initiated = true;
}
/**
* Updates the finite state machine by one tick update.
* @param {number} $timetick The tick duration (in ms).
* @public
*/
tick($timetick) {
if (this.$initiated === false) {
return;
}
this.$timer += $timetick;
if (typeof this.$state.$onTick === 'function') {
this.$state.$onTick({
$timer: this.$timer,
$timetick: $timetick
});
}
const transitions = this.$state.$transitions;
if (Array.isArray(transitions) === false) {
return;
}
for (const $transition of transitions) {
let previous;
if (typeof this.$previous !== 'undefined') {
previous = this.$previous.$state;
}
const current = this.$state.$state;
const next = $transition.$state;
const condition = $transition.$condition({
$previous: previous,
$timer: this.$timer
});
if (condition === true) {
if (typeof this.$state.$onLeave === 'function') {
this.$state.$onLeave({
$next: next,
$timer: this.$timer
});
}
this.$timer = 0;
this.$previous = this.$state;
this.$state = this.$states.get(next);
if (typeof this.$state.$onEnter === 'function') {
this.$state.$onEnter({
$previous: current
});
}
this.tick(0);
break;
}
}
}
}
export {
FiniteStateMachine
};
export default FiniteStateMachine;