/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtCanvas3D module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL3$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPLv3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or later as published by the Free
** Software Foundation and appearing in the file LICENSE.GPL included in
** the packaging of this file. Please review the following information to
** ensure the GNU General Public License version 2.0 requirements will be
** met: http://www.gnu.org/licenses/gpl-2.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

Qt.include("/gl-matrix.js")

//
// Draws a cube that has a Qt Quick item as decal texture on each face.
// A simple per vertex lighting equation is used to emulate light landing on the rotating cube.
//

var gl;
var cubeTexture = 0;
var vertexPositionAttribute;
var textureCoordAttribute;
var vertexNormalAttribute;
var mvMatrix = mat4.create();
var pMatrix  = mat4.create();
var nMatrix  = mat4.create();
var pMatrixUniform;
var mvMatrixUniform;
var nUniform;
var width = 0;
var height = 0;
var canvas3d;
var pixelSize;
var canvasTextureProvider = null;
var textureSourceItem = null;

function initializeGL(canvas, textureSource) {
    canvas3d = canvas;
    textureSourceItem = textureSource;

    // Get the OpenGL context object that represents the API we call
    gl = canvas.getContext("canvas3d", {depth:true, antialias:true});

    // Setup the OpenGL state
    gl.enable(gl.DEPTH_TEST);
    gl.depthFunc(gl.LESS);
    gl.enable(gl.CULL_FACE);
    gl.cullFace(gl.BACK);
    gl.clearDepth(1.0);
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, false);

    // Use fully transparent clear color to allow other QML components to be seen through
    // Canvas3D where not obscured by the rotating cube.
    gl.clearColor(0.0, 0.0, 0.0, 0.0);

    // Set viewport
    gl.viewport(0, 0, canvas.width, canvas.height);

    // Initialize the shader program
    initShaders();

    // Initialize vertex and color buffers
    initBuffers();

    // Create a texture from the Qt Quick item
    canvasTextureProvider = gl.getExtension("QTCANVAS3D_texture_provider");
    cubeTexture = canvasTextureProvider.createTextureFromSource(textureSourceItem);

    gl.bindTexture(gl.TEXTURE_2D, cubeTexture);
}

function resizeGL(canvas)
{
    var pixelRatio = canvas.devicePixelRatio;
    canvas.pixelSize = Qt.size(canvas.width * pixelRatio,
                               canvas.height * pixelRatio);
}

function degToRad(degrees) {
    return degrees * Math.PI / 180;
}

function paintGL(canvas) {
    var pixelRatio = canvas.devicePixelRatio;
    var currentWidth = canvas.width * pixelRatio;
    var currentHeight = canvas.height * pixelRatio;
    if (currentWidth !== width || currentHeight !== height ) {
        width = currentWidth;
        height = currentHeight;
        gl.viewport(0, 0, width, height);
        mat4.perspective(pMatrix, degToRad(45), width / height, 0.1, 500.0);
        gl.uniformMatrix4fv(pMatrixUniform, false, pMatrix);
    }

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    mat4.identity(mvMatrix);
    mat4.translate(mvMatrix, mvMatrix, [(canvas.yRotAnim - 120.0) / 120.0,
                                        (canvas.xRotAnim -  60.0) / 50.0,
                                        -7.0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.xRotAnim), [0, 1, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.yRotAnim), [1, 0, 0]);
    mat4.rotate(mvMatrix, mvMatrix, degToRad(canvas.zRotAnim), [0, 0, 1]);
    gl.uniformMatrix4fv(mvMatrixUniform, false, mvMatrix);

    mat4.invert(nMatrix, mvMatrix);
    mat4.transpose(nMatrix, nMatrix);
    gl.uniformMatrix4fv(nUniform, false, nMatrix);

    gl.drawElements(gl.TRIANGLES, 36, gl.UNSIGNED_SHORT, 0);
}

function initBuffers()
{
    var cubeVertexPositionBuffer = gl.createBuffer();
    cubeVertexPositionBuffer.name = "cubeVertexPositionBuffer";
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
    gl.bufferData(
                gl.ARRAY_BUFFER,
                new Float32Array([// Front face
                                        -1.0, -1.0,  1.0,
                                        1.0, -1.0,  1.0,
                                        1.0,  1.0,  1.0,
                                        -1.0,  1.0,  1.0,

                                        // Back face
                                        -1.0, -1.0, -1.0,
                                        -1.0,  1.0, -1.0,
                                        1.0,  1.0, -1.0,
                                        1.0, -1.0, -1.0,

                                        // Top face
                                        -1.0,  1.0, -1.0,
                                        -1.0,  1.0,  1.0,
                                        1.0,  1.0,  1.0,
                                        1.0,  1.0, -1.0,

                                        // Bottom face
                                        -1.0, -1.0, -1.0,
                                        1.0, -1.0, -1.0,
                                        1.0, -1.0,  1.0,
                                        -1.0, -1.0,  1.0,

                                        // Right face
                                        1.0, -1.0, -1.0,
                                        1.0,  1.0, -1.0,
                                        1.0,  1.0,  1.0,
                                        1.0, -1.0,  1.0,

                                        // Left face
                                        -1.0, -1.0, -1.0,
                                        -1.0, -1.0,  1.0,
                                        -1.0,  1.0,  1.0,
                                        -1.0,  1.0, -1.0
                                       ]),
                gl.STATIC_DRAW);
    gl.vertexAttribPointer(vertexPositionAttribute, 3, gl.FLOAT, false, 0, 0);

    var cubeVertexIndexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER,
                  new Uint16Array([
                                            0,  1,  2,      0,  2,  3,    // front
                                            4,  5,  6,      4,  6,  7,    // back
                                            8,  9,  10,     8,  10, 11,   // top
                                            12, 13, 14,     12, 14, 15,   // bottom
                                            16, 17, 18,     16, 18, 19,   // right
                                            20, 21, 22,     20, 22, 23    // left
                                        ]),
                  gl.STATIC_DRAW);

    var cubeVerticesTextureCoordBuffer = gl.createBuffer();
    cubeVerticesTextureCoordBuffer.name = "cubeVerticesTextureCoordBuffer";
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesTextureCoordBuffer);
    var textureCoordinates = [
                // Front
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Back
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Top
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Bottom
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Right
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0,
                // Left
                1.0,  0.0,
                0.0,  0.0,
                0.0,  1.0,
                1.0,  1.0
            ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates),
                  gl.STATIC_DRAW);
    gl.vertexAttribPointer(textureCoordAttribute, 2, gl.FLOAT, false, 0, 0);

    var cubeVerticesNormalBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesNormalBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
                                                              // Front
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,
                                                              0.0,  0.0,  1.0,

                                                              // Back
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,
                                                              0.0,  0.0, -1.0,

                                                              // Top
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,
                                                              0.0,  1.0,  0.0,

                                                              // Bottom
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,
                                                              0.0, -1.0,  0.0,

                                                              // Right
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,
                                                              1.0,  0.0,  0.0,

                                                              // Left
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0,
                                                              -1.0,  0.0,  0.0
                                                          ]), gl.STATIC_DRAW);
    gl.vertexAttribPointer(vertexNormalAttribute, 3, gl.FLOAT, false, 0, 0);
}

function initShaders()
{
    var vertexShader = getShader(gl,
                                 "attribute highp vec3 aVertexNormal;    \
                                  attribute highp vec3 aVertexPosition;  \
                                  attribute highp vec2 aTextureCoord;    \
                                                                         \
                                  uniform highp mat4 uNormalMatrix;      \
                                  uniform mat4 uMVMatrix;                \
                                  uniform mat4 uPMatrix;                 \
                                                                         \
                                  varying mediump vec4 vColor;           \
                                  varying highp vec2 vTextureCoord;      \
                                  varying highp vec3 vLighting;          \
                                                                         \
                                  void main(void) {                      \
                                      gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0); \
                                      vTextureCoord = aTextureCoord;                                   \
                                      highp vec3 ambientLight = vec3(0.5, 0.5, 0.5);                   \
                                      highp vec3 directionalLightColor = vec3(0.75, 0.75, 0.75);       \
                                      highp vec3 directionalVector = vec3(0.85, 0.8, 0.75);            \
                                      highp vec4 transformedNormal = uNormalMatrix * vec4(aVertexNormal, 1.0); \
                                      highp float directional = max(dot(transformedNormal.xyz, directionalVector), 0.0); \
                                      vLighting = ambientLight + (directionalLightColor * directional); \
                                  }", gl.VERTEX_SHADER);

    var fragmentShader = getShader(gl,
                                   "varying highp vec2 vTextureCoord;  \
                                    varying highp vec3 vLighting;      \
                                                                       \
                                    uniform sampler2D uSampler;        \
                                                                       \
                                    void main(void) {                  \
                                        mediump vec3 texelColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t)).rgb; \
                                        gl_FragColor = vec4(texelColor * vLighting, 1.0);                                      \
                                    }", gl.FRAGMENT_SHADER);

    // Create the Program3D for shader
    var shaderProgram = gl.createProgram();

    // Attach the shader sources to the shader program
    gl.attachShader(shaderProgram, vertexShader);
    gl.attachShader(shaderProgram, fragmentShader);

    // Link the program
    gl.linkProgram(shaderProgram);

    // Check the linking status
    if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
        console.log("Could not initialize shaders");
        console.log(gl.getProgramInfoLog(shaderProgram));
    }

    // Take the shader program into use
    gl.useProgram(shaderProgram);

    // Look up where the vertex data needs to go
    vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
    gl.enableVertexAttribArray(vertexPositionAttribute);
    textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
    gl.enableVertexAttribArray(textureCoordAttribute);
    vertexNormalAttribute = gl.getAttribLocation(shaderProgram, "aVertexNormal");
    gl.enableVertexAttribArray(vertexNormalAttribute);

    // Get the uniform locations
    pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
    mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    nUniform = gl.getUniformLocation(shaderProgram, "uNormalMatrix");

    // Setup texture sampler uniform
    var textureSamplerUniform = gl.getUniformLocation(shaderProgram, "uSampler")
    gl.activeTexture(gl.TEXTURE0);
    gl.uniform1i(textureSamplerUniform, 0);
    gl.bindTexture(gl.TEXTURE_2D, 0);
}

function getShader(gl, str, type) {
    var shader = gl.createShader(type);
    gl.shaderSource(shader, str);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        console.log("JS:Shader compile failed");
        console.log(gl.getShaderInfoLog(shader));
        return null;
    }

    return shader;
}