var CONST = require('../../const');

/**
 * TextureGarbageCollector. This class manages the GPU and ensures that it does not get clogged up with textures that are no longer being used.
 *
 * @class
 * @memberof PIXI
 * @param renderer {PIXI.WebGLRenderer} The renderer this manager works for.
 */
function TextureGarbageCollector(renderer)
{
    this.renderer = renderer;

    this.count = 0;
    this.checkCount = 0;
    this.maxIdle = 60 * 60;
    this.checkCountMax = 60 * 10;

    this.mode = CONST.GC_MODES.DEFAULT;
}

TextureGarbageCollector.prototype.constructor = TextureGarbageCollector;
module.exports = TextureGarbageCollector;

/**
 * Checks to see when the last time a texture was used
 * if the texture has not been used for a specified amount of time it will be removed from the GPU
 */
TextureGarbageCollector.prototype.update = function()
{
    this.count++;

    if(this.mode === CONST.GC_MODES.MANUAL)
    {
        return;
    }

    this.checkCount++;


    if(this.checkCount > this.checkCountMax)
    {
        this.checkCount = 0;

        this.run();
    }
};

/**
 * Checks to see when the last time a texture was used
 * if the texture has not been used for a specified amount of time it will be removed from the GPU
 */
TextureGarbageCollector.prototype.run = function()
{
    var tm = this.renderer.textureManager;
    var managedTextures =  tm._managedTextures;
    var wasRemoved = false;
    var i,j;

    for (i = 0; i < managedTextures.length; i++)
    {
        var texture = managedTextures[i];

        // only supports non generated textures at the moment!
        if (!texture._glRenderTargets && this.count - texture.touched > this.maxIdle)
        {
            tm.destroyTexture(texture, true);
            managedTextures[i] = null;
            wasRemoved = true;
        }
    }

    if (wasRemoved)
    {
        j = 0;

        for (i = 0; i < managedTextures.length; i++)
        {
            if (managedTextures[i] !== null)
            {
                managedTextures[j++] = managedTextures[i];
            }
        }

        managedTextures.length = j;
    }
};

/**
 * Removes all the textures within the specified displayObject and its children from the GPU
 *
 * @param displayObject {PIXI.DisplayObject} the displayObject to remove the textures from.
 */
TextureGarbageCollector.prototype.unload = function( displayObject )
{
    var tm = this.renderer.textureManager;

    if(displayObject._texture)
    {
        tm.destroyTexture(displayObject._texture, true);
    }

    for (var i = displayObject.children.length - 1; i >= 0; i--) {

        this.unload(displayObject.children[i]);

    }
};