module BABYLON.Internals {
    // Based on demo done by Brandon Jones - http://media.tojicode.com/webgl-samples/dds.html
    // All values and structures referenced from:
    // http://msdn.microsoft.com/en-us/library/bb943991.aspx/
    var DDS_MAGIC = 0x20534444;

    var DDSD_CAPS = 0x1,
        DDSD_HEIGHT = 0x2,
        DDSD_WIDTH = 0x4,
        DDSD_PITCH = 0x8,
        DDSD_PIXELFORMAT = 0x1000,
        DDSD_MIPMAPCOUNT = 0x20000,
        DDSD_LINEARSIZE = 0x80000,
        DDSD_DEPTH = 0x800000;

    var DDSCAPS_COMPLEX = 0x8,
        DDSCAPS_MIPMAP = 0x400000,
        DDSCAPS_TEXTURE = 0x1000;

    var DDSCAPS2_CUBEMAP = 0x200,
        DDSCAPS2_CUBEMAP_POSITIVEX = 0x400,
        DDSCAPS2_CUBEMAP_NEGATIVEX = 0x800,
        DDSCAPS2_CUBEMAP_POSITIVEY = 0x1000,
        DDSCAPS2_CUBEMAP_NEGATIVEY = 0x2000,
        DDSCAPS2_CUBEMAP_POSITIVEZ = 0x4000,
        DDSCAPS2_CUBEMAP_NEGATIVEZ = 0x8000,
        DDSCAPS2_VOLUME = 0x200000;

    var DDPF_ALPHAPIXELS = 0x1,
        DDPF_ALPHA = 0x2,
        DDPF_FOURCC = 0x4,
        DDPF_RGB = 0x40,
        DDPF_YUV = 0x200,
        DDPF_LUMINANCE = 0x20000;

    function FourCCToInt32(value) {
        return value.charCodeAt(0) +
            (value.charCodeAt(1) << 8) +
            (value.charCodeAt(2) << 16) +
            (value.charCodeAt(3) << 24);
    }

    function Int32ToFourCC(value) {
        return String.fromCharCode(
            value & 0xff,
            (value >> 8) & 0xff,
            (value >> 16) & 0xff,
            (value >> 24) & 0xff
            );
    }

    var FOURCC_DXT1 = FourCCToInt32("DXT1");
    var FOURCC_DXT3 = FourCCToInt32("DXT3");
    var FOURCC_DXT5 = FourCCToInt32("DXT5");

    var headerLengthInt = 31; // The header length in 32 bit ints

    // Offsets into the header array
    var off_magic = 0;

    var off_size = 1;
    var off_flags = 2;
    var off_height = 3;
    var off_width = 4;

    var off_mipmapCount = 7;

    var off_pfFlags = 20;
    var off_pfFourCC = 21;
    var off_RGBbpp = 22;
    var off_RMask = 23;
    var off_GMask = 24;
    var off_BMask = 25;
    var off_AMask = 26;
    var off_caps1 = 27;
    var off_caps2 = 28;

    export interface DDSInfo {
        width: number;
        height: number;
        mipmapCount: number;
        isFourCC: boolean;
        isRGB: boolean;
        isLuminance: boolean;
        isCube: boolean
    };

    export class DDSTools {
        public static GetDDSInfo(arrayBuffer: any): DDSInfo {
            var header = new Int32Array(arrayBuffer, 0, headerLengthInt);

            var mipmapCount = 1;
            if (header[off_flags] & DDSD_MIPMAPCOUNT) {
                mipmapCount = Math.max(1, header[off_mipmapCount]);
            }

            return {
                width: header[off_width],
                height: header[off_height],
                mipmapCount: mipmapCount,
                isFourCC: (header[off_pfFlags] & DDPF_FOURCC) === DDPF_FOURCC,
                isRGB: (header[off_pfFlags] & DDPF_RGB) === DDPF_RGB,
                isLuminance: (header[off_pfFlags] & DDPF_LUMINANCE) === DDPF_LUMINANCE,
                isCube: (header[off_caps2] & DDSCAPS2_CUBEMAP) === DDSCAPS2_CUBEMAP
            };
        }

        private static GetRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer): Uint8Array {
            var byteArray = new Uint8Array(dataLength);
            var srcData = new Uint8Array(arrayBuffer);
            var index = 0;
            for (var y = height - 1; y >= 0; y--) {
                for (var x = 0; x < width; x++) {
                    var srcPos = dataOffset + (x + y * width) * 4;
                    byteArray[index + 2] = srcData[srcPos];
                    byteArray[index + 1] = srcData[srcPos + 1];
                    byteArray[index] = srcData[srcPos + 2];
                    byteArray[index + 3] = srcData[srcPos + 3];
                    index += 4;
                }
            }

            return byteArray;
        }

        private static GetRGBArrayBuffer(width: number, height: number, dataOffset:number, dataLength: number, arrayBuffer: ArrayBuffer): Uint8Array {            
            var byteArray = new Uint8Array(dataLength);
            var srcData = new Uint8Array(arrayBuffer);
            var index = 0;
            for (var y = height - 1; y >= 0; y--) {
                for (var x = 0; x < width; x++) {
                    var srcPos = dataOffset + (x + y * width) * 3;
                    byteArray[index + 2] = srcData[srcPos];
                    byteArray[index + 1] = srcData[srcPos + 1];
                    byteArray[index] = srcData[srcPos + 2];
                    index += 3;
                }
            }

            return byteArray;
        }

        private static GetLuminanceArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer): Uint8Array {
            var byteArray = new Uint8Array(dataLength);
            var srcData = new Uint8Array(arrayBuffer);
            var index = 0;
            for (var y = height - 1; y >= 0; y--) {
                for (var x = 0; x < width; x++) {
                    var srcPos = dataOffset + (x + y * width);
                    byteArray[index] = srcData[srcPos];
                    index++;
                }
            }

            return byteArray;
        }

        public static UploadDDSLevels(gl: WebGLRenderingContext, ext: any, arrayBuffer: any, info: DDSInfo, loadMipmaps: boolean, faces: number): void {
            var header = new Int32Array(arrayBuffer, 0, headerLengthInt),
                fourCC, blockBytes, internalFormat,
                width, height, dataLength, dataOffset,
                byteArray, mipmapCount, i;

            if (header[off_magic] != DDS_MAGIC) {
                Tools.Error("Invalid magic number in DDS header");
                return;
            }

            if (!info.isFourCC && !info.isRGB && !info.isLuminance) {
                Tools.Error("Unsupported format, must contain a FourCC, RGB or LUMINANCE code");
                return;
            }

            if (info.isFourCC) {
                fourCC = header[off_pfFourCC];
                switch (fourCC) {
                case FOURCC_DXT1:
                    blockBytes = 8;
                    internalFormat = ext.COMPRESSED_RGBA_S3TC_DXT1_EXT;
                    break;
                case FOURCC_DXT3:
                    blockBytes = 16;
                    internalFormat = ext.COMPRESSED_RGBA_S3TC_DXT3_EXT;
                    break;
                case FOURCC_DXT5:
                    blockBytes = 16;
                    internalFormat = ext.COMPRESSED_RGBA_S3TC_DXT5_EXT;
                    break;
                default:
                    console.error("Unsupported FourCC code:", Int32ToFourCC(fourCC));
                    return;
                }
            }

            mipmapCount = 1;
            if (header[off_flags] & DDSD_MIPMAPCOUNT && loadMipmaps !== false) {
                mipmapCount = Math.max(1, header[off_mipmapCount]);
            }
            
            var bpp = header[off_RGBbpp];

            for (var face = 0; face < faces; face++) {
                var sampler = faces == 1 ? gl.TEXTURE_2D : (gl.TEXTURE_CUBE_MAP_POSITIVE_X + face);

                width = header[off_width];
                height = header[off_height];
                dataOffset = header[off_size] + 4;

                for (i = 0; i < mipmapCount; ++i) {
                    if (info.isRGB) {
                        if (bpp == 24) {
                            dataLength = width * height * 3;
                            byteArray = DDSTools.GetRGBArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                            gl.texImage2D(sampler, i, gl.RGB, width, height, 0, gl.RGB, gl.UNSIGNED_BYTE, byteArray);
                        } else { // 32
                            dataLength = width * height * 4;
                            byteArray = DDSTools.GetRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                            gl.texImage2D(sampler, i, gl.RGBA, width, height, 0, gl.RGBA, gl.UNSIGNED_BYTE, byteArray);
                        }
                    } else if (info.isLuminance) {
                        dataLength = width * height;
                        byteArray = DDSTools.GetLuminanceArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                        gl.texImage2D(sampler, i, gl.LUMINANCE, width, height, 0, gl.LUMINANCE, gl.UNSIGNED_BYTE, byteArray);
                    } else {
                        dataLength = Math.max(4, width) / 4 * Math.max(4, height) / 4 * blockBytes;
                        byteArray = new Uint8Array(arrayBuffer, dataOffset, dataLength);
                        gl.compressedTexImage2D(sampler, i, internalFormat, width, height, 0, byteArray);
                    }
                    dataOffset += dataLength;
                    width *= 0.5;
                    height *= 0.5;
                }
            }
        }
    }
}