const { Scheduler } = require('./Scheduler')
, Rx = require('rxjs')
, Observable = Rx.Observable
, empty = Rx.empty
, { take } = require('rxjs/operators')
, { Schedule, ScheduleEvent, PreliminaryScheduleEvent } = require('./Schedule')
, symbolIntervalEvent = Symbol('intervalEvent');
/**
* @author Sebastian Hönel <development@hoenel.net>
*/
class Interval extends Schedule {
/**
*
* @template T
* @param {number} msecs
* @param {producerHandler.<T|Promise.<T>>} [itemProducer] Optional. Defaults to
* null. A function that produces an item that shall then be signaled
* by the scheduler. If the item is not of importance, then you may
* just supply an empty function or null (will be converted to an empty
* function then).
* @param {boolean} waitforFinishProduction if true, the interval will
* be reset only when the itemProducer finished producing its item. If
* this is false, the interval will be reset right away if it elapses.
* This makes sense if producing an item takes considerable amounts of time.
* @param {number} maxNumTriggers the maximum amount of times this interval
* shall trigger. Supply a negative value or Number.MAX_SAFE_INTEGER to not
* limit this interval to any amount of occurrences.
* @param {boolean} triggerInitially if true, will trigger this interval
* right away, instead of waiting for the timeout to elapse once.
* @param {boolean} enabled if true, this Interval is enabled. Otherwise,
* its events are ignored until it get enabled.
*/
constructor(msecs, itemProducer = null, maxNumTriggers = -1, waitforFinishProduction = true, triggerInitially = false, enabled = true) {
super(!!enabled);
if (itemProducer === null) {
itemProducer = () => {};
}
if (isNaN(msecs) || msecs < 1) {
throw new Error(`Interval smaller than 1 ms are forbidden.`);
}
if (typeof itemProducer !== 'function') {
throw new Error('The itemProducer must be a function.');
}
if (Object.prototype.toString.call(maxNumTriggers) !== '[object Number]'
|| isNaN(maxNumTriggers)) {
throw new Error(`The value "${maxNumTriggers}" is invalid for the parameter maxNumTriggers.`);
}
this.msecs = msecs;
this.itemProducer = itemProducer;
this.maxNumTriggers = maxNumTriggers < 0 || maxNumTriggers >= Number.MAX_SAFE_INTEGER ?
Number.MAX_SAFE_INTEGER : Math.ceil(maxNumTriggers);
this.waitforFinishProduction = !!waitforFinishProduction;
this.triggerInitially = !!triggerInitially;
this.numOccurred = 0;
};
get isFinished() {
return this.numOccurred === this.maxNumTriggers;
};
/**
* This method will ultimately set the number of occurences equal to the
* number of how many times this Interval should have been triggered.
* This leads to this Interval reporting that it is finished.
* Attempting to finish an unbounded Interval will throw an Error.
*
* @throws {Error} if this is an unbounded Interval
* @returns {this} this
*/
finish() {
if (this.maxNumTriggers === Number.MAX_SAFE_INTEGER) {
throw new Error('Finishing an Interval is only supported for limited Intervals.');
}
this.numOccurred = this.maxNumTriggers;
return this;
};
/**
* Additionally to finish(), this method also disables this Interval.
*
* @returns {this} this
*/
finalize() {
this.isEnabled = false;
return this.finish();
};
/**
* @inheritdoc
* @param {Date} after Required.
* @param {Date} before
* @returns {IterableIterator.<PreliminaryScheduleEvent.<Interval, undefined>>}
*/
*preliminaryEvents(after, before) {
if (!(after instanceof Date && before instanceof Date)) {
throw new Error('after and/or before must be Date objects. Interval does not support unbounded intervals.');
}
let triggers = 0, start = +after, end = +before;
if (start > end) {
throw new Error('The Date for after happens after the Date for before.');
}
if (this.triggerInitially) {
yield new PreliminaryScheduleEvent(after, this);
triggers++;
}
start += this.msecs;
while (triggers < this.maxNumTriggers && start <= end) {
yield new PreliminaryScheduleEvent(new Date(start), this);
start += this.msecs;
triggers++;
}
};
};
class IntervalEventSimple extends ScheduleEvent {
/**
* @template T
* @param {Interval} interval
* @param {T} item
*/
constructor(interval, item) {
super(interval, item);
};
};
/**
* @author Sebastian Hönel <development@hoenel.net>
*/
class IntervalScheduler extends Scheduler {
constructor() {
super(symbolIntervalEvent);
/** @type {Array.<Interval>} */
this.intervals = [];
/** @type {Object.<string, Interval>} */
this._intervalIds = {};
this._intervalId = 0;
/** @type {Object.<string, number>} */
this._timeouts = {};
};
/**
* @param {Interval} interval
* @throws {Error} if interval is not of type Interval
* @returns {boolean}
*/
_isInterval(interval) {
if (!(interval instanceof Interval)) {
throw new Error('The given interval is not an instance of Interval');
}
return true;
};
/**
* @param {string} id
* @param {Interval} interval
* @param {boolean} [triggerOnce] Optional. Defaults to false.
*/
async _scheduleInterval(id, interval, triggerOnce = false) {
/** @param {boolean} wait */
const triggerInterval = async wait => {
if (!interval.isEnabled || interval.isFinished) {
return;
}
let item = interval.itemProducer();
if (wait && item instanceof Promise) {
item = await item;
}
this.emit(symbolIntervalEvent, new IntervalEventSimple(interval, item));
interval.numOccurred++;
};
const triggerOncePromise = triggerOnce ?
triggerInterval(interval.waitforFinishProduction) : Promise.resolve();
if (interval.waitforFinishProduction) {
await triggerOncePromise;
}
this._timeouts[id] = setTimeout(async () => {
clearTimeout(this._timeouts[id]);
this._timeouts[id] = null;
delete this._timeouts[id];
// It may have been removed in the meantime:
if (!this.hasInterval(interval)) {
return;
}
if (!interval.isFinished && interval.isEnabled) {
// .. then actually execute its trigger:
let triggerPromise = triggerInterval(interval.waitforFinishProduction);
if (interval.waitforFinishProduction) {
await triggerPromise;
}
}
// The Interval should be scheduled consecutively, but its execution
// is conditional, because the scheduler is not notified when an
// Interval gets dis- or enabled.
this._scheduleInterval(id, interval, false);
}, interval.msecs);
};
/**
* @param {Interval} interval
* @returns {string}
*/
_getIntervalId(interval) {
this._isInterval(interval);
if (!this.hasInterval(interval)) {
throw new Error('This interval was not previously added.');
}
for (let key of Object.keys(this._intervalIds)) {
if (this._intervalIds[key] === interval) {
return key;
}
}
throw new Error(`There is no ID for the interval.`);
};
/**
* Calls hasInterval() with the given Schedule.
*
* @param {Interval} schedule
* @returns {boolean}
*/
hasSchedule(schedule) {
return this.hasInterval(schedule);
};
/**
* @param {Interval} interval
* @returns {boolean}
*/
hasInterval(interval) {
return this._isInterval(interval) &&
this.intervals.findIndex(i => i === interval) >= 0;
};
/**
* Calls addInterval() with the given Schedule.
*
* @param {Interval} schedule
* @returns {this}
*/
addSchedule(schedule) {
return this.addInterval(schedule);
};
/**
* @param {Interval} interval
* @returns {this}
*/
addInterval(interval) {
if (this.hasInterval(interval)) {
throw new Error('This interval has been added already.');
}
this.intervals.push(interval);
const id = `i_${this._intervalId++}`;
this._timeouts[id] = null;
this._intervalIds[id] = interval;
this._scheduleInterval(id, interval, interval.triggerInitially);
return this;
};
/**
* Calls removeInterval() with the given schedule.
*
* @param {Interval} schedule
* @returns {this}
*/
removeSchedule(schedule) {
return this.removeInterval(schedule);
};
/**
* Removes all Intervals and returns them. This will lead to the
* un-scheduling of all Intervals.
*
* @inheritDoc
* @returns {Array.<Interval>}
*/
removeAllSchedules() {
const intervals = this.intervals.slice(0);
intervals.forEach(i => this.removeSchedule(i));
return intervals;
};
/**
* @param {Interval} interval
* @returns {this}
*/
removeInterval(interval) {
if (!this.hasInterval(interval)) {
throw new Error('This interval was not previously added.');
}
const id = this._getIntervalId(interval);
if (this._timeouts[id] !== null) {
clearTimeout(this._timeouts[id]);
this._timeouts[id] = null;
delete this._timeouts[id];
}
delete this._intervalIds[id];
this.intervals.splice(this.intervals.findIndex(i => i === interval), 1);
return this;
};
/**
* @returns {Observable.<IntervalEventSimple>}
*/
get observable() {
return super.observable;
};
/**
* Returns an Observable for the given Interval. Note that, for
* finished Intervals, an empty Observable is returned.
*
* @param {Schedule|Interval} interval Must be an instance of Interval
* @returns {Observable.<IntervalEventSimple>}
*/
getObservableForSchedule(interval) {
if (interval.isFinished) {
return empty();
}
return super.getObservableForSchedule(interval)
.pipe(take(interval.maxNumTriggers - interval. numOccurred));
};
/**
* @inheritdoc
* @param {Date} after
* @param {Date} before
* @returns {IterableIterator.<PreliminaryScheduleEvent.<Interval, undefined>>}
*/
*preliminaryEvents(after, before) {
for (const interval of this.intervals) {
for (const pre of interval.preliminaryEvents(...arguments)) {
yield pre;
}
}
};
};
module.exports = Object.freeze({
Interval,
IntervalScheduler,
IntervalEventSimple,
symbolIntervalEvent
});