var Class = require('../../utils/Class');
var Components = require('../components');
var Easing = require('../../math/easing');
var GetEaseFunction = require('../../tweens/builder/GetEaseFunction');
var MinMax2 = require('../../math/MinMax2');
var MinMax4 = require('../../math/MinMax4');
var Particle = require('./Particle');
var StableSort = require('../../utils/array/StableSort');
var GetRandomElement = require('../../utils/array/GetRandomElement');

var ParticleEmitter = new Class({

    Mixins: [
        Components.BlendMode,
        Components.RenderTarget,
        Components.ScrollFactor,
        Components.Visible
    ],

    initialize:

    function ParticleEmitter (manager, config)
    {
        if (config === undefined) { config = {}; }

        this.manager = manager;

        this.key = '';

        this.particleClass = Particle;

        this.frames = [];

        this.dead = [];
        this.alive = [];

        this.x = 0;
        this.y = 0;

        //  How can the emitter pick from a random frame OR a fixed frame?

        //  A radial emitter will emit particles in all directions between angle min and max
        //  A point emitter will emit particles only in the direction set by the speed values
        this.radial = true;

        this.speed = new MinMax4();

        this.scale = new MinMax4(1);

        this.gravity = new MinMax2();

        this.alpha = new MinMax2(1);

        this.angle = new MinMax2(0, 360);

        this.particleAngle = new MinMax2();

        //  The lifespan of the particles (in ms)
        this.lifespan = new MinMax2(1000);

        this.deathCallback = null;
        this.deathCallbackScope = null;

        //  Set to hard limit the amount of particle objects this emitter is allowed to create
        this.maxParticles = 0;

        //  How many particles are emitted each time the emitter updates
        this.emitCount = 1;

        //  How often a particle is emitted in ms (if emitter is a constant / flow emitter)
        //  If emitter is an explosion emitter this value will be -1.
        //  Anything > -1 sets this to be a flow emitter
        this.frequency = 0;

        //  Controls if the emitter is currently emitting particles. Already alive particles will continue to update until they expire.
        this.on = true;

        //  Newly emitted particles are added to the top of the particle list, i.e. rendered above those already alive. Set to false to send them to the back.
        this.particleBringToTop = true;

        this.timeScale = 1;

        this._counter = 0;

        //  Optional Particle emission zone - must be an object that supports a `getRandomPoint` function, such as a Rectangle, Circle, Path, etc.
        this.zone = null;

        // this.easingFunctionAlpha = Easing.Linear;
        // this.easingFunctionScale = Easing.Linear;
        // this.easingFunctionRotation = Easing.Linear;

        this.active = true;
    },

    getFrame: function ()
    {
        return GetRandomElement(this.frames);
    },

    //  Either a single frame (numeric / string based), or an array of frames to randomly pick from
    setFrame: function (frame)
    {
        this.manager.setEmitterFrames(frame, this);

        return this;
    },

    setRadial: function (value)
    {
        if (value === undefined) { value = true; }

        this.radial = value;

        return this;
    },

    setPosition: function (x, y)
    {
        this.x = x;
        this.y = y;

        return this;
    },

    /*
    setEase: function (easeName, easeParam)
    {
        var ease = GetEaseFunction(easeName, easeParam);

        this.easingFunctionAlpha = ease;
        this.easingFunctionScale = ease;
        this.easingFunctionRotation = ease;

        return this;
    },

    setAlphaEase: function (easeName, easeParam)
    {
        this.easingFunctionAlpha = GetEaseFunction(easeName, easeParam);

        return this;
    },

    setScaleEase: function (easeName, easeParam)
    {
        this.easingFunctionScale = GetEaseFunction(easeName, easeParam);

        return this;
    },

    setRotationEase: function (easeName, easeParam)
    {
        this.easingFunctionRotation = GetEaseFunction(easeName, easeParam);

        return this;
    },
    */

    //  Particle Emission

    setSpeed: function (xMin, xMax, yMin, yMax)
    {
        this.speed.set(xMin, xMax, yMin, yMax);

        return this;
    },

    setScale: function (xMin, xMax, yMin, yMax)
    {
        this.scale.set(xMin, xMax, yMin, yMax);

        return this;
    },

    setGravity: function (x, y)
    {
        this.gravity.set(x, y);

        return this;
    },

    setAlpha: function (min, max)
    {
        this.alpha.set(min, max);

        return this;
    },

    setAngle: function (min, max)
    {
        this.angle.set(min, max);

        return this;
    },

    setParticleAngle: function (min, max)
    {
        this.particleAngle.set(min, max);

        return this;
    },

    setLifespan: function (min, max)
    {
        this.lifespan.set(min, max);

        return this;
    },

    setFrequency: function (frequency)
    {
        this.frequency = frequency;
        this._counter = 0;

        return this;
    },

    //  The zone must have a function called `getRandomPoint` that takes an object and sets
    //  its x and y properties accordingly then returns that object
    setZone: function (zone)
    {
        if (zone === undefined)
        {
            this.zone = null;
        }
        else if (typeof zone.getRandomPoint === 'function')
        {
            this.zone = zone;
        }

        return this;
    },

    //  Particle Management

    reserve: function (particleCount)
    {
        var dead = this.dead;

        for (var i = 0; i < particleCount; i++)
        {
            dead.push(new this.particleClass());
        }

        return this;
    },

    getAliveParticleCount: function ()
    {
        return this.alive.length;
    },

    getDeadParticleCount: function ()
    {
        return this.dead.length;
    },

    getParticleCount: function ()
    {
        return this.getAliveParticleCount() + this.getDeadParticleCount();
    },

    atLimit: function ()
    {
        return (this.maxParticles > 0 && this.getParticleCount() === this.maxParticles);
    },

    onParticleDeath: function (callback, context)
    {
        if (callback === undefined)
        {
            //  Clear any previously set callback
            this.deathCallback = null;
            this.deathCallbackScope = null;
        }
        else if (typeof callback === 'function')
        {
            this.deathCallback = callback;

            if (context)
            {
                this.deathCallbackScope = context;
            }
        }

        return this;
    },

    killAll: function ()
    {
        var dead = this.dead;
        var alive = this.alive;

        while (alive.length > 0)
        {
            dead.push(alive.pop());
        }

        return this;
    },

    forEachAlive: function (callback, thisArg)
    {
        var alive = this.alive;
        var length = alive.length;

        for (var index = 0; index < length; ++index)
        {
            //  Sends the Particle and the Emitter
            callback.call(thisArg, alive[index], this);
        }

        return this;
    },

    forEachDead: function (callback, thisArg)
    {
        var dead = this.dead;
        var length = dead.length;

        for (var index = 0; index < length; ++index)
        {
            //  Sends the Particle and the Emitter
            callback.call(thisArg, dead[index], this);
        }

        return this;
    },

    start: function ()
    {
        this.on = true;

        this._counter = 0;

        return this;
    },

    pause: function ()
    {
        this.active = false;

        return this;
    },

    resume: function ()
    {
        this.active = true;

        return this;
    },

    flow: function (frequency, count)
    {
        if (count === undefined) { count = 1; }

        this.frequency = frequency;

        this.emitCount = count;

        return this.start();
    },

    explode: function (count, x, y)
    {
        this.frequency = -1;

        return this.emit(count, x, y);
    },

    emitAt: function (x, y, count)
    {
        return this.emit(count, x, y);
    },

    emit: function (count, x, y)
    {
        if (count === undefined) { count = 1; }

        var output = [];

        if (this.atLimit())
        {
            return output;
        }

        //  Store emitter coordinates in-case this was a placement explode, or emitAt

        var oldX = this.x;
        var oldY = this.y;

        if (x !== undefined)
        {
            this.x = x;
        }

        if (y !== undefined)
        {
            this.y = y;
        }

        var dead = this.dead;

        for (var i = 0; i < count; i++)
        {
            var particle;

            if (dead.length > 0)
            {
                particle = dead.pop();

                particle.reset();
            }
            else
            {
                particle = new this.particleClass();
            }

            particle.emit(this);

            if (this.particleBringToTop)
            {
                this.alive.push(particle);
            }
            else
            {
                this.alive.unshift(particle);
            }

            output.push(particle);

            if (this.atLimit())
            {
                break;
            }
        }

        this.x = oldX;
        this.y = oldY;

        return output;
    },

    preUpdate: function (time, delta)
    {
        //  Scale the delta
        delta *= this.timeScale;

        var step = (delta / 1000);
        var particles = this.alive;
        var length = particles.length;

        for (var index = 0; index < length; index++)
        {
            var particle = particles[index];

            //  update returns `true` if the particle is now dead (lifeStep < 0)
            if (particle.update(this, delta, step))
            {
                //  Moves the dead particle to the end of the particles array (ready for splicing out later)
                var last = particles[length - 1];

                particles[length - 1] = particle;
                particles[index] = last;

                index -= 1;
                length -= 1;
            }
        }

        //  Move dead particles to the dead array
        var deadLength = particles.length - length;

        if (deadLength > 0)
        {
            var rip = particles.splice(particles.length - deadLength, deadLength);

            var deathCallback = this.deathCallback;
            var deathCallbackScope = this.deathCallbackScope;

            if (deathCallback)
            {
                for (var i = 0; i < rip.length; i++)
                {
                    deathCallback.call(deathCallbackScope, rip[i]);
                }
            }

            this.dead.concat(rip);

            StableSort(particles, this.indexSort);
        }

        if (this.frequency > -1 && this.on)
        {
            this._counter -= delta;

            if (this._counter <= 0)
            {
                this.emit(this.emitCount);

                this._counter = this.frequency;
            }
        }
    },

    indexSort: function (a, b)
    {
        return a.index - b.index;
    }

});

module.exports = ParticleEmitter;