import BoundingRectangle from '../Core/BoundingRectangle.js';
import Check from '../Core/Check.js';
import Color from '../Core/Color.js';
import defined from '../Core/defined.js';
import destroyObject from '../Core/destroyObject.js';
import DeveloperError from '../Core/DeveloperError.js';
import PrimitiveType from '../Core/PrimitiveType.js';
import ViewportQuadVS from '../Shaders/ViewportQuadVS.js';
import ClearCommand from './ClearCommand.js';
import DrawCommand from './DrawCommand.js';
import Framebuffer from './Framebuffer.js';
import RenderState from './RenderState.js';
import ShaderProgram from './ShaderProgram.js';

    /**
     * @private
     */
    function ComputeEngine(context) {
        this._context = context;
    }

    var renderStateScratch;
    var drawCommandScratch = new DrawCommand({
        primitiveType : PrimitiveType.TRIANGLES
    });
    var clearCommandScratch = new ClearCommand({
        color : new Color(0.0, 0.0, 0.0, 0.0)
    });

    function createFramebuffer(context, outputTexture) {
        return new Framebuffer({
            context : context,
            colorTextures : [outputTexture],
            destroyAttachments : false
        });
    }

    function createViewportQuadShader(context, fragmentShaderSource) {
        return ShaderProgram.fromCache({
            context : context,
            vertexShaderSource : ViewportQuadVS,
            fragmentShaderSource : fragmentShaderSource,
            attributeLocations : {
                position : 0,
                textureCoordinates : 1
            }
        });
    }

    function createRenderState(width, height) {
        if ((!defined(renderStateScratch)) ||
            (renderStateScratch.viewport.width !== width) ||
            (renderStateScratch.viewport.height !== height)) {

            renderStateScratch = RenderState.fromCache({
                viewport : new BoundingRectangle(0, 0, width, height)
            });
        }
        return renderStateScratch;
    }

    ComputeEngine.prototype.execute = function(computeCommand) {
        //>>includeStart('debug', pragmas.debug);
        Check.defined('computeCommand', computeCommand);
        //>>includeEnd('debug');

        // This may modify the command's resources, so do error checking afterwards
        if (defined(computeCommand.preExecute)) {
            computeCommand.preExecute(computeCommand);
        }

        //>>includeStart('debug', pragmas.debug);
        if (!defined(computeCommand.fragmentShaderSource) && !defined(computeCommand.shaderProgram)) {
            throw new DeveloperError('computeCommand.fragmentShaderSource or computeCommand.shaderProgram is required.');
        }

        Check.defined('computeCommand.outputTexture', computeCommand.outputTexture);
        //>>includeEnd('debug');

        var outputTexture = computeCommand.outputTexture;
        var width = outputTexture.width;
        var height = outputTexture.height;

        var context = this._context;
        var vertexArray = defined(computeCommand.vertexArray) ? computeCommand.vertexArray : context.getViewportQuadVertexArray();
        var shaderProgram = defined(computeCommand.shaderProgram) ? computeCommand.shaderProgram : createViewportQuadShader(context, computeCommand.fragmentShaderSource);
        var framebuffer = createFramebuffer(context, outputTexture);
        var renderState = createRenderState(width, height);
        var uniformMap = computeCommand.uniformMap;

        var clearCommand = clearCommandScratch;
        clearCommand.framebuffer = framebuffer;
        clearCommand.renderState = renderState;
        clearCommand.execute(context);

        var drawCommand = drawCommandScratch;
        drawCommand.vertexArray = vertexArray;
        drawCommand.renderState = renderState;
        drawCommand.shaderProgram = shaderProgram;
        drawCommand.uniformMap = uniformMap;
        drawCommand.framebuffer = framebuffer;
        drawCommand.execute(context);

        framebuffer.destroy();

        if (!computeCommand.persists) {
            shaderProgram.destroy();
            if (defined(computeCommand.vertexArray)) {
                vertexArray.destroy();
            }
        }

        if (defined(computeCommand.postExecute)) {
            computeCommand.postExecute(outputTexture);
        }
    };

    ComputeEngine.prototype.isDestroyed = function() {
        return false;
    };

    ComputeEngine.prototype.destroy = function() {
        return destroyObject(this);
    };
export default ComputeEngine;