export default class Updater {
    constructor(options) {
        this.options = Object.assign({}, Updater.DefaultOptions, options || {});

        this.callbacks = [];

        this.start = Date.now();
        this.last = Date.now();

        this.interval = setInterval(() => this.update(), this.options.updateRate);
    }

    static install(Vue, options) {
        let instance = Vue.prototype.$updater;
        if (!instance) {
            instance = new Updater(options);
        }

        Vue.prototype.$updater = instance;
    }

    addListener(callback) {
        if (-1 !== this.callbacks.indexOf(callback) && (true !== this.options.mute)) {
            console.warn('Duplicate updater handler detected.');
        }

        if (typeof(callback) !== 'function') {
            throw new Error('Expected argument one to be a function, got ' + typeof(callback));
        }

        this.callbacks.push(callback);
    }

    removeListener(callback) {
        do {
            let index = this.callbacks.indexOf(callback);
            if (-1 !== index) {
                this.callbacks.splice(index, 1);
            }
        } while(-1 !== index);
    }

    update() {
        const now = Date.now();

        const deltaTime = now - this.last;
        const fromStart = now - this.start;

        for (let k in this.callbacks) {
            this.callbacks[k].call(this, deltaTime, fromStart, now);
        }

        this.last = now;
    }
}

Updater.DefaultOptions = {
    updateRate: 33
};