/* https://github.com/mrdoob/glsl-sandbox */

if (!window.requestAnimationFrame) {

    window.requestAnimationFrame = (function () {

        return window.webkitRequestAnimationFrame ||
            window.mozRequestAnimationFrame ||
            window.oRequestAnimationFrame ||
            window.msRequestAnimationFrame ||
            function (callback, element) {

                window.setTimeout(callback, 1000 / 60);

            };

    })();

}

// Get older browsers safely through init code, so users can read the
// message about how to download newer browsers.
if (!Date.now) {
    Date.now = function () {
        return +new Date();
    };
}

var quality = 1, quality_levels = [0.5, 1, 2, 4, 8];
var toolbar, compileButton, fullscreenButton, compileTimer, errorLines = [];
var canvas, gl, buffer, currentProgram, vertexPosition, screenVertexPosition,
    parameters = { startTime: Date.now(), time: 0, mouseX: 0.5, mouseY: 0.5, screenWidth: 0, screenHeight: 0 },
    surface = { centerX: 0, centerY: 0, width: 1, height: 1, isPanning: false, isZooming: false, lastX: 0, lastY: 0 },
    frontTarget, backTarget, screenProgram, getWebGL, resizer = {}, compileOnChangeCode = true;

function init() {

    console.log('initializing...');

    if (!document.addEventListener) {
        return;
    }

    canvas = document.createElement('canvas');
    document.body.appendChild(canvas);

    // Initialise WebGL

    try {

        gl = canvas.getContext('experimental-webgl', { preserveDrawingBuffer: true });

    } catch (error) { }

    if (gl) {

        // enable dFdx, dFdy, fwidth
        gl.getExtension('OES_standard_derivatives');

        // Create vertex buffer (2 triangles)

        buffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([- 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);

        // Create surface buffer (coordinates at screen corners)

        surface.buffer = gl.createBuffer();
    }

    var clientXLast, clientYLast;

    document.addEventListener('mousemove', function (event) {

        var clientX = event.clientX;
        var clientY = event.clientY;

        if (clientXLast == clientX && clientYLast == clientY)
            return;

        clientXLast = clientX;
        clientYLast = clientY;

        parameters.mouseX = clientX / window.innerWidth;
        parameters.mouseY = 1 - clientY / window.innerHeight;

    }, false);

    onWindowResize();
    window.addEventListener('resize', onWindowResize, false);

    compile();
    compileScreenProgram();

}

function computeSurfaceCorners() {

    if (gl) {

        surface.width = surface.height * parameters.screenWidth / parameters.screenHeight;

        var halfWidth = surface.width * 0.5, halfHeight = surface.height * 0.5;

        gl.bindBuffer(gl.ARRAY_BUFFER, surface.buffer);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
            surface.centerX - halfWidth, surface.centerY - halfHeight,
            surface.centerX + halfWidth, surface.centerY - halfHeight,
            surface.centerX - halfWidth, surface.centerY + halfHeight,
            surface.centerX + halfWidth, surface.centerY - halfHeight,
            surface.centerX + halfWidth, surface.centerY + halfHeight,
            surface.centerX - halfWidth, surface.centerY + halfHeight]), gl.STATIC_DRAW);

    }

}

function resetSurface() {

    surface.centerX = surface.centerY = 0;
    surface.height = 1;
    computeSurfaceCorners();

}

function compile() {

    console.log('compiling shader...');

    if (!gl) {

        return;

    }

    var program = gl.createProgram();
    var fragment = document.getElementById('shaderCode').textContent;
    var vertex = document.getElementById('surfaceVertexShader').textContent;

    var vs = createShader(vertex, gl.VERTEX_SHADER);
    var fs = createShader(fragment, gl.FRAGMENT_SHADER);

    if (vs == null || fs == null) return null;

    gl.attachShader(program, vs);
    gl.attachShader(program, fs);

    gl.deleteShader(vs);
    gl.deleteShader(fs);

    gl.linkProgram(program);

    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {

        var error = gl.getProgramInfoLog(program);

        compileButton.title = error;
        console.error(error);

        console.error('VALIDATE_STATUS: ' + gl.getProgramParameter(program, gl.VALIDATE_STATUS), 'ERROR: ' + gl.getError());
        compileButton.style.color = '#ff0000';
        compileButton.textContent = 'compiled with errors';

        return;

    }

    if (currentProgram) {

        gl.deleteProgram(currentProgram);

    }

    currentProgram = program;

    // Cache uniforms

    cacheUniformLocation(program, 'time');
    cacheUniformLocation(program, 'mouse');
    cacheUniformLocation(program, 'resolution');
    cacheUniformLocation(program, 'backbuffer');
    cacheUniformLocation(program, 'surfaceSize');

    // Load program into GPU

    gl.useProgram(currentProgram);

    // Set up buffers

    surface.positionAttribute = gl.getAttribLocation(currentProgram, "surfacePosAttrib");
    gl.enableVertexAttribArray(surface.positionAttribute);

    vertexPosition = gl.getAttribLocation(currentProgram, "position");
    gl.enableVertexAttribArray(vertexPosition);

    console.log('compilation finished');

}

function compileScreenProgram() {

    console.log('compiling screen program...');

    if (!gl) { return; }

    var program = gl.createProgram();
    var fragment = document.getElementById('fragmentShader').textContent;
    var vertex = document.getElementById('vertexShader').textContent;

    var vs = createShader(vertex, gl.VERTEX_SHADER);
    var fs = createShader(fragment, gl.FRAGMENT_SHADER);

    gl.attachShader(program, vs);
    gl.attachShader(program, fs);

    gl.deleteShader(vs);
    gl.deleteShader(fs);

    gl.linkProgram(program);

    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {

        console.error('VALIDATE_STATUS: ' + gl.getProgramParameter(program, gl.VALIDATE_STATUS), 'ERROR: ' + gl.getError());

        return;

    }

    screenProgram = program;

    gl.useProgram(screenProgram);

    cacheUniformLocation(program, 'resolution');
    cacheUniformLocation(program, 'texture');

    screenVertexPosition = gl.getAttribLocation(screenProgram, "position");
    gl.enableVertexAttribArray(screenVertexPosition);

    console.log('compilation finished');

}

function cacheUniformLocation(program, label) {

    if (program.uniformsCache === undefined) {

        program.uniformsCache = {};

    }

    program.uniformsCache[label] = gl.getUniformLocation(program, label);

}

//

function createTarget(width, height) {

    var target = {};

    target.framebuffer = gl.createFramebuffer();
    target.renderbuffer = gl.createRenderbuffer();
    target.texture = gl.createTexture();

    // set up framebuffer

    gl.bindTexture(gl.TEXTURE_2D, target.texture);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);

    gl.bindFramebuffer(gl.FRAMEBUFFER, target.framebuffer);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, target.texture, 0);

    // set up renderbuffer

    gl.bindRenderbuffer(gl.RENDERBUFFER, target.renderbuffer);

    gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, width, height);
    gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, target.renderbuffer);

    // clean up

    gl.bindTexture(gl.TEXTURE_2D, null);
    gl.bindRenderbuffer(gl.RENDERBUFFER, null);
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);

    return target;

}

function createRenderTargets() {

    frontTarget = createTarget(parameters.screenWidth, parameters.screenHeight);
    backTarget = createTarget(parameters.screenWidth, parameters.screenHeight);

}

//

var dummyFunction = function () { };


//

function htmlEncode(str) {

    return String(str)
        .replace(/&/g, '&')
        .replace(/"/g, '"')
        .replace(/'/g, ''')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;');

}

//

function createShader(src, type) {

    var shader = gl.createShader(type);
    var line, lineNum, lineError, index = 0, indexEnd;

    gl.shaderSource(shader, src);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {

        var error = gl.getShaderInfoLog(shader);

        // Remove trailing linefeed, for FireFox's benefit.
        while ((error.length > 1) && (error.charCodeAt(error.length - 1) < 32)) {
            error = error.substring(0, error.length - 1);
        }

        console.error(error);

        return null;

    }

    return shader;

}

//

function onWindowResize(event) {

    var isMaxWidth = ((resizer.currentWidth === resizer.maxWidth) || (resizer.currentWidth === resizer.minWidth)),
        isMaxHeight = ((resizer.currentHeight === resizer.maxHeight) || (resizer.currentHeight === resizer.minHeight));

    canvas.width = window.innerWidth / quality;
    canvas.height = window.innerHeight / quality;

    canvas.style.width = window.innerWidth + 'px';
    canvas.style.height = window.innerHeight + 'px';

    parameters.screenWidth = canvas.width;
    parameters.screenHeight = canvas.height;

    computeSurfaceCorners();

    if (gl) {

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

        createRenderTargets();

    }
}

//

function animate() {

    requestAnimationFrame(animate);
    render();

}

function render() {

    if (!currentProgram) return;

    parameters.time = Date.now() - parameters.startTime;

    // Set uniforms for custom shader

    gl.useProgram(currentProgram);

    gl.uniform1f(currentProgram.uniformsCache['time'], parameters.time / 1000);
    gl.uniform2f(currentProgram.uniformsCache['mouse'], parameters.mouseX, parameters.mouseY);
    gl.uniform2f(currentProgram.uniformsCache['resolution'], parameters.screenWidth, parameters.screenHeight);
    gl.uniform1i(currentProgram.uniformsCache['backbuffer'], 0);
    gl.uniform2f(currentProgram.uniformsCache['surfaceSize'], surface.width, surface.height);

    gl.bindBuffer(gl.ARRAY_BUFFER, surface.buffer);
    gl.vertexAttribPointer(surface.positionAttribute, 2, gl.FLOAT, false, 0, 0);

    gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
    gl.vertexAttribPointer(vertexPosition, 2, gl.FLOAT, false, 0, 0);

    gl.activeTexture(gl.TEXTURE0);
    gl.bindTexture(gl.TEXTURE_2D, backTarget.texture);

    // Render custom shader to front buffer

    gl.bindFramebuffer(gl.FRAMEBUFFER, frontTarget.framebuffer);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.TRIANGLES, 0, 6);

    // Set uniforms for screen shader

    gl.useProgram(screenProgram);

    gl.uniform2f(screenProgram.uniformsCache['resolution'], parameters.screenWidth, parameters.screenHeight);
    gl.uniform1i(screenProgram.uniformsCache['texture'], 1);

    gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
    gl.vertexAttribPointer(screenVertexPosition, 2, gl.FLOAT, false, 0, 0);

    gl.activeTexture(gl.TEXTURE1);
    gl.bindTexture(gl.TEXTURE_2D, frontTarget.texture);

    // Render front buffer to screen

    gl.bindFramebuffer(gl.FRAMEBUFFER, null);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.TRIANGLES, 0, 6);

    // Swap buffers

    var tmp = frontTarget;
    frontTarget = backTarget;
    backTarget = tmp;

}