// pathfinder/demo2/pathfinder.ts
//
// Copyright © 2018 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

import COVER_VERTEX_SHADER_SOURCE from "./cover.vs.glsl";
import COVER_FRAGMENT_SHADER_SOURCE from "./cover.fs.glsl";
import OPAQUE_VERTEX_SHADER_SOURCE from "./opaque.vs.glsl";
import OPAQUE_FRAGMENT_SHADER_SOURCE from "./opaque.fs.glsl";
import STENCIL_VERTEX_SHADER_SOURCE from "./stencil.vs.glsl";
import STENCIL_FRAGMENT_SHADER_SOURCE from "./stencil.fs.glsl";
import AREA_LUT from "../resources/textures/area-lut.png";
import {Matrix2D, Size2D} from "./geometry";
import {SVGPath, TILE_SIZE} from "./tiling";
import {staticCast, unwrapNull} from "./util";

const SVGPath: (path: string) => SVGPath = require('svgpath');

const STENCIL_FRAMEBUFFER_SIZE: Size2D = {
    width: TILE_SIZE.width * 128,
    height: TILE_SIZE.height * 256,
};

const QUAD_VERTEX_POSITIONS: Uint8Array = new Uint8Array([
    0, 0,
    1, 0,
    1, 1,
    0, 1,
]);

const FILL_INSTANCE_SIZE: number = 20;
const TILE_INSTANCE_SIZE: number = 16;

interface Color {
    r: number;
    g: number;
    b: number;
    a: number;
}

type Edge = 'left' | 'top' | 'right' | 'bottom';

class App {
    private canvas: HTMLCanvasElement;
    private openButton: HTMLInputElement;
    private areaLUT: HTMLImageElement;

    private gl: WebGL2RenderingContext;
    private disjointTimerQueryExt: any;
    private areaLUTTexture: WebGLTexture;
    private stencilTexture: WebGLTexture;
    private stencilFramebuffer: WebGLFramebuffer;
    private fillProgram: Program<'FramebufferSize' | 'TileSize' | 'AreaLUT',
                                    'TessCoord' | 'From' | 'To' | 'TileIndex'>;
    private solidTileProgram: Program<'FramebufferSize' | 'TileSize',
                                   'TessCoord' | 'TileOrigin' | 'Color'>;
    private maskTileProgram:
        Program<'FramebufferSize' | 'TileSize' | 'StencilTexture' | 'StencilTextureSize',
                'TessCoord' | 'TileOrigin' | 'TileIndex' | 'Backdrop' | 'Color'>;
    private quadVertexBuffer: WebGLBuffer;
    private fillVertexBuffer: WebGLBuffer;
    private fillVertexArray: WebGLVertexArrayObject;
    private tileVertexBuffer: WebGLBuffer;
    private instanceIDVertexBuffer: WebGLBuffer;
    private solidIndexBuffer: WebGLBuffer;
    private solidVertexArray: WebGLVertexArrayObject;
    private maskIndexBuffer: WebGLBuffer;
    private maskVertexArray: WebGLVertexArrayObject;

    private fillPrimitiveCount: number;
    private totalTileCount: number;
    private solidTileCount: number;
    private maskTileCount: number;

    constructor(areaLUT: HTMLImageElement) {
        const canvas = staticCast(document.getElementById('canvas'), HTMLCanvasElement);
        const openButton = staticCast(document.getElementById('open'), HTMLInputElement);
        this.canvas = canvas;
        this.openButton = openButton;
        this.areaLUT = areaLUT;

        this.openButton.addEventListener('change', event => this.loadFile(), false);

        const devicePixelRatio = window.devicePixelRatio;
        canvas.width = window.innerWidth * devicePixelRatio;
        canvas.height = window.innerHeight * devicePixelRatio;
        canvas.style.width = window.innerWidth + "px";
        canvas.style.height = window.innerHeight + "px";

        const gl = unwrapNull(this.canvas.getContext('webgl2', {antialias: false}));
        this.gl = gl;
        gl.getExtension('EXT_color_buffer_float');
        this.disjointTimerQueryExt = gl.getExtension('EXT_disjoint_timer_query');

        this.areaLUTTexture = unwrapNull(gl.createTexture());
        gl.bindTexture(gl.TEXTURE_2D, this.areaLUTTexture);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, areaLUT);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        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);

        this.stencilTexture = unwrapNull(gl.createTexture());
        gl.bindTexture(gl.TEXTURE_2D, this.stencilTexture);
        gl.texImage2D(gl.TEXTURE_2D,
                      0,
                      gl.R16F,
                      STENCIL_FRAMEBUFFER_SIZE.width,
                      STENCIL_FRAMEBUFFER_SIZE.height,
                      0,
                      gl.RED,
                      gl.HALF_FLOAT,
                      null);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
        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);

        this.stencilFramebuffer = unwrapNull(gl.createFramebuffer());
        gl.bindFramebuffer(gl.FRAMEBUFFER, this.stencilFramebuffer);
        gl.framebufferTexture2D(gl.FRAMEBUFFER,
                                gl.COLOR_ATTACHMENT0,
                                gl.TEXTURE_2D,
                                this.stencilTexture,
                                0);
        if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE)
            throw new Error("Stencil framebuffer incomplete!");

        const maskTileProgram = new Program(gl,
                                         COVER_VERTEX_SHADER_SOURCE,
                                         COVER_FRAGMENT_SHADER_SOURCE,
                                         [
                                             'FramebufferSize',
                                             'TileSize',
                                             'StencilTexture',
                                             'StencilTextureSize'
                                         ],
                                         [
                                             'TessCoord',
                                             'TileOrigin',
                                             'TileIndex',
                                             'Backdrop',
                                             'Color',
                                         ]);
        this.maskTileProgram = maskTileProgram;

        const solidTileProgram = new Program(gl,
                                             OPAQUE_VERTEX_SHADER_SOURCE,
                                             OPAQUE_FRAGMENT_SHADER_SOURCE,
                                             ['FramebufferSize', 'TileSize'],
                                             ['TessCoord', 'TileOrigin', 'Color']);
        this.solidTileProgram = solidTileProgram;

        const fillProgram = new Program(gl,
                                           STENCIL_VERTEX_SHADER_SOURCE,
                                           STENCIL_FRAGMENT_SHADER_SOURCE,
                                           ['FramebufferSize', 'TileSize', 'AreaLUT'],
                                           ['TessCoord', 'From', 'To', 'TileIndex']);
        this.fillProgram = fillProgram;

        // Initialize quad VBO.
        this.quadVertexBuffer = unwrapNull(gl.createBuffer());
        gl.bindBuffer(gl.ARRAY_BUFFER, this.quadVertexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, QUAD_VERTEX_POSITIONS, gl.STATIC_DRAW);

        // Initialize fill VBOs.
        this.fillVertexBuffer = unwrapNull(gl.createBuffer());

        // Initialize fill VAO.
        this.fillVertexArray = unwrapNull(gl.createVertexArray());
        gl.bindVertexArray(this.fillVertexArray);
        gl.useProgram(this.fillProgram.program);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.quadVertexBuffer);
        gl.vertexAttribPointer(fillProgram.attributes.TessCoord,
                               2,
                               gl.UNSIGNED_BYTE,
                               false,
                               0,
                               0);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.fillVertexBuffer);
        gl.vertexAttribPointer(fillProgram.attributes.From,
                               2,
                               gl.FLOAT,
                               false,
                               FILL_INSTANCE_SIZE,
                               0);
        gl.vertexAttribDivisor(fillProgram.attributes.From, 1);
        gl.vertexAttribPointer(fillProgram.attributes.To,
                               2,
                               gl.FLOAT,
                               false,
                               FILL_INSTANCE_SIZE,
                               8);
        gl.vertexAttribDivisor(fillProgram.attributes.To, 1);
        gl.vertexAttribIPointer(fillProgram.attributes.TileIndex,
                                1,
                                gl.UNSIGNED_INT,
                                FILL_INSTANCE_SIZE,
                                16);
        gl.vertexAttribDivisor(fillProgram.attributes.TileIndex, 1);
        gl.enableVertexAttribArray(fillProgram.attributes.TessCoord);
        gl.enableVertexAttribArray(fillProgram.attributes.From);
        gl.enableVertexAttribArray(fillProgram.attributes.To);
        gl.enableVertexAttribArray(fillProgram.attributes.TileIndex);

        // Initialize tile VBOs and IBOs.
        this.tileVertexBuffer = unwrapNull(gl.createBuffer());
        this.instanceIDVertexBuffer = unwrapNull(gl.createBuffer());
        this.solidIndexBuffer = unwrapNull(gl.createBuffer());
        this.maskIndexBuffer = unwrapNull(gl.createBuffer());

        // Initialize solid tile VAO.
        this.solidVertexArray = unwrapNull(gl.createVertexArray());
        gl.bindVertexArray(this.solidVertexArray);
        gl.useProgram(this.solidTileProgram.program);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.quadVertexBuffer);
        gl.vertexAttribPointer(solidTileProgram.attributes.TessCoord,
                               2,
                               gl.UNSIGNED_BYTE,
                               false,
                               0,
                               0);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.tileVertexBuffer);
        gl.vertexAttribPointer(solidTileProgram.attributes.TileOrigin,
                               2,
                               gl.FLOAT,
                               false,
                               TILE_INSTANCE_SIZE,
                               0);
        gl.vertexAttribDivisor(solidTileProgram.attributes.TileOrigin, 1);
        gl.vertexAttribPointer(solidTileProgram.attributes.Color,
                               4,
                               gl.UNSIGNED_BYTE,
                               true,
                               TILE_INSTANCE_SIZE,
                               12);
        gl.vertexAttribDivisor(solidTileProgram.attributes.Color, 1);
        gl.enableVertexAttribArray(solidTileProgram.attributes.TessCoord);
        gl.enableVertexAttribArray(solidTileProgram.attributes.TileOrigin);
        gl.enableVertexAttribArray(solidTileProgram.attributes.Color);

        // Initialize mask tile VAO.
        this.maskVertexArray = unwrapNull(gl.createVertexArray());
        gl.bindVertexArray(this.maskVertexArray);
        gl.useProgram(this.maskTileProgram.program);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.quadVertexBuffer);
        gl.vertexAttribPointer(maskTileProgram.attributes.TessCoord,
                               2,
                               gl.UNSIGNED_BYTE,
                               false,
                               0,
                               0);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.tileVertexBuffer);
        gl.vertexAttribPointer(maskTileProgram.attributes.TileOrigin,
                               2,
                               gl.FLOAT,
                               false,
                               TILE_INSTANCE_SIZE,
                               0);
        gl.vertexAttribDivisor(maskTileProgram.attributes.TileOrigin, 1);
        gl.vertexAttribPointer(maskTileProgram.attributes.Backdrop,
                               1,
                               gl.FLOAT,
                               false,
                               TILE_INSTANCE_SIZE,
                               8);
        gl.vertexAttribDivisor(maskTileProgram.attributes.Backdrop, 1);
        gl.vertexAttribPointer(maskTileProgram.attributes.Color,
                               4,
                               gl.UNSIGNED_BYTE,
                               true,
                               TILE_INSTANCE_SIZE,
                               12);
        gl.vertexAttribDivisor(maskTileProgram.attributes.Color, 1);
        gl.bindBuffer(gl.ARRAY_BUFFER, this.tileVertexBuffer);
        gl.vertexAttribIPointer(maskTileProgram.attributes.TileIndex, 1, gl.UNSIGNED_SHORT, 10, 4);
        gl.vertexAttribDivisor(maskTileProgram.attributes.TileIndex, 1);
        gl.enableVertexAttribArray(maskTileProgram.attributes.TessCoord);
        gl.enableVertexAttribArray(maskTileProgram.attributes.TileOrigin);
        gl.enableVertexAttribArray(maskTileProgram.attributes.TileIndex);
        gl.enableVertexAttribArray(maskTileProgram.attributes.Color);

        // Set up event handlers.
        this.canvas.addEventListener('click', event => this.onClick(event), false);

        this.fillPrimitiveCount = 0;
        this.totalTileCount = 0;
        this.solidTileCount = 0;
        this.maskTileCount = 0;
    }

    redraw(): void {
        const gl = this.gl, canvas = this.canvas;

        // Start timer.
        let timerQuery = null;
        if (this.disjointTimerQueryExt != null) {
            timerQuery = unwrapNull(gl.createQuery());
            gl.beginQuery(this.disjointTimerQueryExt.TIME_ELAPSED_EXT, timerQuery);
        }

        // Fill.
        gl.bindFramebuffer(gl.FRAMEBUFFER, this.stencilFramebuffer);
        gl.viewport(0, 0, STENCIL_FRAMEBUFFER_SIZE.width, STENCIL_FRAMEBUFFER_SIZE.height);
        gl.clearColor(0.0, 0.0, 0.0, 0.0);
        gl.clear(gl.COLOR_BUFFER_BIT);

        gl.bindVertexArray(this.fillVertexArray);
        gl.useProgram(this.fillProgram.program);
        gl.uniform2f(this.fillProgram.uniforms.FramebufferSize,
                     STENCIL_FRAMEBUFFER_SIZE.width,
                     STENCIL_FRAMEBUFFER_SIZE.height);
        gl.uniform2f(this.fillProgram.uniforms.TileSize, TILE_SIZE.width, TILE_SIZE.height);
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, this.areaLUTTexture);
        gl.uniform1i(this.fillProgram.uniforms.AreaLUT, 0);
        gl.blendEquation(gl.FUNC_ADD);
        gl.blendFunc(gl.ONE, gl.ONE);
        gl.enable(gl.BLEND);
        gl.drawArraysInstanced(gl.TRIANGLE_FAN, 0, 4, unwrapNull(this.fillPrimitiveCount));
        gl.disable(gl.BLEND);

        // Read back stencil and dump it.
        //this.dumpStencil();

        // Draw solid tiles.
        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
        const framebufferSize = {width: canvas.width, height: canvas.height};
        gl.viewport(0, 0, framebufferSize.width, framebufferSize.height);
        gl.clearColor(0.85, 0.85, 0.85, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);

        gl.bindVertexArray(this.solidVertexArray);
        gl.useProgram(this.solidTileProgram.program);
        gl.uniform2f(this.solidTileProgram.uniforms.FramebufferSize,
                     framebufferSize.width,
                     framebufferSize.height);
        gl.uniform2f(this.solidTileProgram.uniforms.TileSize, TILE_SIZE.width, TILE_SIZE.height);
        gl.disable(gl.BLEND);
        gl.drawArraysInstanced(gl.TRIANGLE_FAN, 0, 4, this.solidTileCount);

        /*
        // Draw masked tiles.
        gl.bindVertexArray(this.maskVertexArray);
        gl.useProgram(this.maskTileProgram.program);
        gl.uniform2f(this.maskTileProgram.uniforms.FramebufferSize,
                     framebufferSize.width,
                     framebufferSize.height);
        gl.uniform2f(this.maskTileProgram.uniforms.TileSize, TILE_SIZE.width, TILE_SIZE.height);
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, this.stencilTexture);
        gl.uniform1i(this.maskTileProgram.uniforms.StencilTexture, 0);
        gl.uniform2f(this.maskTileProgram.uniforms.StencilTextureSize,
                     STENCIL_FRAMEBUFFER_SIZE.width,
                     STENCIL_FRAMEBUFFER_SIZE.height);
        gl.blendEquation(gl.FUNC_ADD);
        gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);
        gl.enable(gl.BLEND);
        gl.drawArraysInstanced(gl.TRIANGLE_FAN, 0, 4, this.maskTileCount);
        gl.disable(gl.BLEND);
        */

        // End timer.
        if (timerQuery != null) {
            gl.endQuery(this.disjointTimerQueryExt.TIME_ELAPSED_EXT);
            waitForQuery(gl, this.disjointTimerQueryExt, timerQuery);
        }
    }

    private dumpStencil(): void {
        const gl = this.gl;

        const totalStencilFramebufferSize = STENCIL_FRAMEBUFFER_SIZE.width *
            STENCIL_FRAMEBUFFER_SIZE.height * 4;
        const stencilData = new Float32Array(totalStencilFramebufferSize);
        gl.readPixels(0, 0,
                      STENCIL_FRAMEBUFFER_SIZE.width, STENCIL_FRAMEBUFFER_SIZE.height,
                      gl.RGBA,
                      gl.FLOAT,
                      stencilData);
        const stencilDumpData = new Uint8ClampedArray(totalStencilFramebufferSize);
        for (let i = 0; i < stencilData.length; i++)
            stencilDumpData[i] = stencilData[i] * 255.0;
        const stencilDumpCanvas = document.createElement('canvas');
        stencilDumpCanvas.width = STENCIL_FRAMEBUFFER_SIZE.width;
        stencilDumpCanvas.height = STENCIL_FRAMEBUFFER_SIZE.height;
        stencilDumpCanvas.style.width =
            (STENCIL_FRAMEBUFFER_SIZE.width / window.devicePixelRatio) + "px";
        stencilDumpCanvas.style.height =
            (STENCIL_FRAMEBUFFER_SIZE.height / window.devicePixelRatio) + "px";
        const stencilDumpCanvasContext = unwrapNull(stencilDumpCanvas.getContext('2d'));
        const stencilDumpImageData = new ImageData(stencilDumpData,
                                                   STENCIL_FRAMEBUFFER_SIZE.width,
                                                   STENCIL_FRAMEBUFFER_SIZE.height);
        stencilDumpCanvasContext.putImageData(stencilDumpImageData, 0, 0);
        document.body.appendChild(stencilDumpCanvas);
        //console.log(stencilData);
    }

    private loadFile(): void {
        console.log("loadFile");
        // TODO(pcwalton)
        const file = unwrapNull(unwrapNull(this.openButton.files)[0]);
        const reader = new FileReader;
        reader.addEventListener('loadend', () => {
            const gl = this.gl;
            const arrayBuffer = staticCast(reader.result, ArrayBuffer);
            const root = new RIFFChunk(new DataView(arrayBuffer));
            for (const subchunk of root.subchunks()) {
                let bindPoint, buffer;
                let countFieldName: 'fillPrimitiveCount' | 'totalTileCount' | 'solidTileCount' |
                    'maskTileCount';
                let instanceSize;
                const id = subchunk.stringID();
                switch (id) {
                case 'fill':
                    bindPoint = gl.ARRAY_BUFFER;
                    buffer = this.fillVertexBuffer;
                    countFieldName = 'fillPrimitiveCount';
                    instanceSize = FILL_INSTANCE_SIZE;
                    break;
                case 'tile':
                    bindPoint = gl.ARRAY_BUFFER;
                    buffer = this.tileVertexBuffer;
                    countFieldName = 'totalTileCount';
                    instanceSize = TILE_INSTANCE_SIZE;
                    break;
                case 'soli':
                    bindPoint = gl.ELEMENT_ARRAY_BUFFER;
                    buffer = this.solidIndexBuffer;
                    countFieldName = 'solidTileCount';
                    instanceSize = 4;
                    break;
                case 'mask':
                    bindPoint = gl.ELEMENT_ARRAY_BUFFER;
                    buffer = this.maskIndexBuffer;
                    countFieldName = 'maskTileCount';
                    instanceSize = 4;
                    break;
                default:
                    throw new Error("Unexpected subchunk ID: " + id);
                }

                gl.bindBuffer(bindPoint, buffer);
                gl.bufferData(bindPoint, subchunk.contents(), gl.DYNAMIC_DRAW);
                this[countFieldName] = subchunk.length() / instanceSize;
            }

            this.regenerateInstanceIDBuffer();
            this.redraw();
        }, false);
        reader.readAsArrayBuffer(file);
    }

    private regenerateInstanceIDBuffer(): void {
        const instanceIDs = new Uint32Array(this.totalTileCount);
        for (let instanceID = 0; instanceID < this.totalTileCount; instanceID++)
            instanceIDs[instanceID] = instanceID;

        const gl = this.gl;
        gl.bindBuffer(gl.ARRAY_BUFFER, this.instanceIDVertexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, instanceIDs, gl.DYNAMIC_DRAW);
    }

    private onClick(event: MouseEvent): void {
        this.redraw();
    }
}

class Program<U extends string, A extends string> {
    program: WebGLProgram;
    uniforms: {[key in U]: WebGLUniformLocation | null};
    attributes: {[key in A]: number};

    private vertexShader: WebGLShader;
    private fragmentShader: WebGLShader;

    constructor(gl: WebGL2RenderingContext,
                vertexShaderSource: string,
                fragmentShaderSource: string,
                uniformNames: U[],
                attributeNames: A[]) {
        this.vertexShader = unwrapNull(gl.createShader(gl.VERTEX_SHADER));
        gl.shaderSource(this.vertexShader, vertexShaderSource);
        gl.compileShader(this.vertexShader);
        if (!gl.getShaderParameter(this.vertexShader, gl.COMPILE_STATUS)) {
            console.error(gl.getShaderInfoLog(this.vertexShader));
            throw new Error("Vertex shader compilation failed!");
        }

        this.fragmentShader = unwrapNull(gl.createShader(gl.FRAGMENT_SHADER));
        gl.shaderSource(this.fragmentShader, fragmentShaderSource);
        gl.compileShader(this.fragmentShader);
        if (!gl.getShaderParameter(this.fragmentShader, gl.COMPILE_STATUS)) {
            console.error(gl.getShaderInfoLog(this.fragmentShader));
            throw new Error("Fragment shader compilation failed!");
        }

        this.program = unwrapNull(gl.createProgram());
        gl.attachShader(this.program, this.vertexShader);
        gl.attachShader(this.program, this.fragmentShader);
        gl.linkProgram(this.program);
        if (!gl.getProgramParameter(this.program, gl.LINK_STATUS)) {
            console.error(gl.getProgramInfoLog(this.program));
            throw new Error("Program linking failed!");
        }

        const uniforms: {[key in U]?: WebGLUniformLocation | null} = {};
        for (const uniformName of uniformNames)
            uniforms[uniformName] = gl.getUniformLocation(this.program, "u" + uniformName);
        this.uniforms = uniforms as {[key in U]: WebGLUniformLocation | null};

        const attributes: {[key in A]?: number} = {};
        for (const attributeName of attributeNames) {
            attributes[attributeName] = unwrapNull(gl.getAttribLocation(this.program,
                                                                        "a" + attributeName));
        }
        this.attributes = attributes as {[key in A]: number};
    }
}

class RIFFChunk {
    private data: DataView;

    constructor(data: DataView) {
        this.data = data;
    }

    stringID(): string {
        return String.fromCharCode(this.data.getUint8(0),
                                   this.data.getUint8(1),
                                   this.data.getUint8(2),
                                   this.data.getUint8(3));
    }

    length(): number {
        return this.data.getUint32(4, true);
    }

    contents(): DataView {
        return new DataView(this.data.buffer, this.data.byteOffset + 8, this.length());
    }

    subchunks(): RIFFChunk[] {
        const subchunks = [];
        const contents = this.contents(), length = this.length();
        let offset = 4;
        while (offset < length) {
            const subchunk = new RIFFChunk(new DataView(contents.buffer,
                                                        contents.byteOffset + offset,
                                                        length - offset));
            subchunks.push(subchunk);
            offset += subchunk.length() + 8;
        }
        return subchunks;
    }
}

function waitForQuery(gl: WebGL2RenderingContext, disjointTimerQueryExt: any, query: WebGLQuery):
                      void {
    const queryResultAvailable = disjointTimerQueryExt.QUERY_RESULT_AVAILABLE_EXT;
    const queryResult = disjointTimerQueryExt.QUERY_RESULT_EXT;
    if (!disjointTimerQueryExt.getQueryObjectEXT(query, queryResultAvailable)) {
        setTimeout(() => waitForQuery(gl, disjointTimerQueryExt, query), 10);
        return;
    }
    const elapsed = disjointTimerQueryExt.getQueryObjectEXT(query, queryResult) / 1000000.0;
    console.log(elapsed + "ms elapsed");
}

function loadAreaLUT(): Promise<HTMLImageElement> {
    return new Promise((resolve, reject) => {;
        const image = new Image;
        image.src = AREA_LUT;
        image.addEventListener('load', event => resolve(image), false);
    });
}

function main(): void {
    loadAreaLUT().then(image => new App(image));
}

document.addEventListener('DOMContentLoaded', () => main(), false);