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

    function Int32ToFourCC(value: number) {
        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 FOURCC_DX10 = FourCCToInt32("DX10");
    var FOURCC_D3DFMT_R16G16B16A16F = 113;
    var FOURCC_D3DFMT_R32G32B32A32F = 116;

    var DXGI_FORMAT_R16G16B16A16_FLOAT = 10;
    var DXGI_FORMAT_B8G8R8X8_UNORM = 88;

    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;
    // var off_caps3 = 29;
    // var off_caps4 = 30;
    var off_dxgiFormat = 32

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

    export class DDSTools {
        public static StoreLODInAlphaChannel = false;

        public static GetDDSInfo(arrayBuffer: any): DDSInfo {
            var header = new Int32Array(arrayBuffer, 0, headerLengthInt);
            var extendedHeader = new Int32Array(arrayBuffer, 0, headerLengthInt + 4);

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

            var fourCC = header[off_pfFourCC];
            var dxgiFormat = (fourCC === FOURCC_DX10) ? extendedHeader[off_dxgiFormat] : 0;
            var textureType = Engine.TEXTURETYPE_UNSIGNED_INT;

            switch (fourCC) {
                case FOURCC_D3DFMT_R16G16B16A16F:  
                    textureType = Engine.TEXTURETYPE_HALF_FLOAT;                           
                    break;
                case FOURCC_D3DFMT_R32G32B32A32F:
                    textureType = Engine.TEXTURETYPE_FLOAT;
                    break;                    
                case FOURCC_DX10:
                    if (dxgiFormat === DXGI_FORMAT_R16G16B16A16_FLOAT) {
                        textureType = Engine.TEXTURETYPE_HALF_FLOAT;
                        break;
                    }
            }
  
            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,
                isCompressed: (fourCC === FOURCC_DXT1 || fourCC === FOURCC_DXT3 || FOURCC_DXT1 === FOURCC_DXT5),
                dxgiFormat: dxgiFormat,
                textureType: textureType
            };
        }

        // ref: http://stackoverflow.com/questions/32633585/how-do-you-convert-to-half-floats-in-javascript
        private static _FloatView: Float32Array;
        private static _Int32View: Int32Array;
        private static _ToHalfFloat(value: number): number {
            if (!DDSTools._FloatView) {
                DDSTools._FloatView = new Float32Array(1);
                DDSTools._Int32View = new Int32Array(DDSTools._FloatView.buffer);
            }
            
            DDSTools._FloatView[0] = value;
            var x = DDSTools._Int32View[0];

            var bits = (x >> 16) & 0x8000; /* Get the sign */
            var m = (x >> 12) & 0x07ff; /* Keep one extra bit for rounding */
            var e = (x >> 23) & 0xff; /* Using int is faster here */

            /* If zero, or denormal, or exponent underflows too much for a denormal
            * half, return signed zero. */
            if (e < 103) {
                return bits;
            }

            /* If NaN, return NaN. If Inf or exponent overflow, return Inf. */
            if (e > 142) {
                bits |= 0x7c00;
                /* If exponent was 0xff and one mantissa bit was set, it means NaN,
                * not Inf, so make sure we set one mantissa bit too. */
                bits |= ((e == 255) ? 0 : 1) && (x & 0x007fffff);
                return bits;
            }

            /* If exponent underflows but not too much, return a denormal */
            if (e < 113) {
                m |= 0x0800;
                /* Extra rounding may overflow and set mantissa to 0 and exponent
                * to 1, which is OK. */
                bits |= (m >> (114 - e)) + ((m >> (113 - e)) & 1);
                return bits;
            }

            bits |= ((e - 112) << 10) | (m >> 1);
            bits += m & 1;
            return bits;
        }

        private static _FromHalfFloat(value: number): number {
            var s = (value & 0x8000) >> 15;
            var e = (value & 0x7C00) >> 10;
            var f = value & 0x03FF;

            if(e === 0) {
                return (s ? -1 : 1) * Math.pow(2, -14) * (f / Math.pow(2, 10));
            } else if (e == 0x1F) {
                return f ? NaN : ((s ? -1 : 1) * Infinity);
            }

            return (s ? -1 : 1) * Math.pow(2, e-15) * (1 + (f / Math.pow(2, 10)));
        }

        private static _GetHalfFloatAsFloatRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer, lod: number): Float32Array {   
            var destArray = new Float32Array(dataLength);
            var srcData = new Uint16Array(arrayBuffer, dataOffset);
            var index = 0;
            for (var y = 0; y < height; y++) {
                for (var x = 0; x < width; x++) {
                    var srcPos = (x + y * width) * 4;
                    destArray[index] = DDSTools._FromHalfFloat(srcData[srcPos]);
                    destArray[index + 1] = DDSTools._FromHalfFloat(srcData[srcPos + 1]);
                    destArray[index + 2] = DDSTools._FromHalfFloat(srcData[srcPos + 2]);
                    if (DDSTools.StoreLODInAlphaChannel) {
                        destArray[index + 3] = lod;
                    } else {
                        destArray[index + 3] = DDSTools._FromHalfFloat(srcData[srcPos + 3]);
                    }
                    index += 4;
                }
            }

            return destArray;
        } 
    
        private static _GetHalfFloatRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer, lod: number): Uint16Array {   
            if (DDSTools.StoreLODInAlphaChannel) {
                var destArray = new Uint16Array(dataLength);
                var srcData = new Uint16Array(arrayBuffer, dataOffset);
                var index = 0;
                for (var y = 0; y < height; y++) {
                    for (var x = 0; x < width; x++) {
                        var srcPos = (x + y * width) * 4;
                        destArray[index] = srcData[srcPos];
                        destArray[index + 1] = srcData[srcPos + 1];
                        destArray[index + 2] = srcData[srcPos + 2];
                        destArray[index + 3] = DDSTools._ToHalfFloat(lod)
                        index += 4;
                    }
                }

                return destArray;
            }

            return new Uint16Array(arrayBuffer, dataOffset, dataLength);
        }           

        private static _GetFloatRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer, lod: number): Float32Array {
            if (DDSTools.StoreLODInAlphaChannel) {
                var destArray = new Float32Array(dataLength);
                var srcData = new Float32Array(arrayBuffer, dataOffset);
                var index = 0;
                for (var y = 0; y < height; y++) {
                    for (var x = 0; x < width; x++) {
                        var srcPos = (x + y * width) * 4;
                        destArray[index] = srcData[srcPos];
                        destArray[index + 1] = srcData[srcPos + 1];
                        destArray[index + 2] = srcData[srcPos + 2];
                        destArray[index + 3] = lod;
                        index += 4;
                    }
                }

                return destArray;
            }            
            return new Float32Array(arrayBuffer, dataOffset, dataLength);
        }

        private static _GetFloatAsUIntRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer, lod: number): Float32Array {   
            var destArray = new Uint8Array(dataLength);
            var srcData = new Float32Array(arrayBuffer, dataOffset);
            var index = 0;
            for (var y = 0; y < height; y++) {
                for (var x = 0; x < width; x++) {
                    var srcPos = (x + y * width) * 4;
                    destArray[index] = Scalar.Clamp(srcData[srcPos]) * 255;
                    destArray[index + 1] = Scalar.Clamp(srcData[srcPos + 1]) * 255;
                    destArray[index + 2] = Scalar.Clamp(srcData[srcPos + 2]) * 255;
                    if (DDSTools.StoreLODInAlphaChannel) {
                        destArray[index + 3] = lod;
                    } else {
                        destArray[index + 3] = Scalar.Clamp(srcData[srcPos + 3]) * 255;
                    }
                    index += 4;
                }
            }

            return destArray;
        }

        private static _GetHalfFloatAsUIntRGBAArrayBuffer(width: number, height: number, dataOffset: number, dataLength: number, arrayBuffer: ArrayBuffer, lod: number): Float32Array {   
            var destArray = new Uint8Array(dataLength);
            var srcData = new Uint16Array(arrayBuffer, dataOffset);
            var index = 0;
            for (var y = 0; y < height; y++) {
                for (var x = 0; x < width; x++) {
                    var srcPos = (x + y * width) * 4;
                    destArray[index] = Scalar.Clamp(DDSTools._FromHalfFloat(srcData[srcPos])) * 255;
                    destArray[index + 1] = Scalar.Clamp(DDSTools._FromHalfFloat(srcData[srcPos + 1])) * 255;
                    destArray[index + 2] = Scalar.Clamp(DDSTools._FromHalfFloat(srcData[srcPos + 2])) * 255;
                    if (DDSTools.StoreLODInAlphaChannel) {
                        destArray[index + 3] = lod;
                    } else {
                        destArray[index + 3] = Scalar.Clamp(DDSTools._FromHalfFloat(srcData[srcPos + 3])) * 255;
                    }
                    index += 4;
                }
            }

            return destArray;
        }

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

            return byteArray;
        }

        public static UploadDDSLevels(engine: Engine, gl:WebGLRenderingContext, arrayBuffer: any, info: DDSInfo, loadMipmaps: boolean, faces: number, lodIndex = -1): void {
            var ext = engine.getCaps().s3tc;

            var header = new Int32Array(arrayBuffer, 0, headerLengthInt),
                fourCC, width, height, dataLength, dataOffset,
                byteArray, mipmapCount, mip;
            let internalFormat = 0;
            let format = 0;
            let blockBytes = 1;

            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.isCompressed && !ext) {
                Tools.Error("Compressed textures are not supported on this platform.");
                return;
            }

            var bpp = header[off_RGBbpp];
            dataOffset = header[off_size] + 4;

            let computeFormats = false;

            if (info.isFourCC && ext) {
                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;
                case FOURCC_D3DFMT_R16G16B16A16F:  
                    computeFormats = true;
                    break;
                case FOURCC_D3DFMT_R32G32B32A32F:
                    computeFormats = true;
                    break;                    
                case FOURCC_DX10:
                    // There is an additionnal header so dataOffset need to be changed
                    dataOffset += 5 * 4; // 5 uints

                    let supported = false;
                    switch (info.dxgiFormat) {
                        case DXGI_FORMAT_R16G16B16A16_FLOAT:
                            computeFormats = true;
                            supported = true;
                            break;
                        case DXGI_FORMAT_B8G8R8X8_UNORM:
                            info.isRGB = true;
                            info.isFourCC = false;
                            bpp = 32;
                            supported = true;
                            break;                        
                    }

                    if (supported) {
                        break;
                    }
                default:
                    console.error("Unsupported FourCC code:", Int32ToFourCC(fourCC));
                    return;
                }
            }

            if (computeFormats) {
                format = engine._getWebGLTextureType(info.textureType);    
                internalFormat = engine._getRGBABufferInternalSizedFormat(info.textureType);
            }

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

                for (mip = 0; mip < mipmapCount; ++mip) {
                    if (lodIndex === -1 || lodIndex === mip) {
                        // In case of fixed LOD, if the lod has just been uploaded, early exit.
                        const i = (lodIndex === -1) ? mip : 0;

                        if (!info.isCompressed && info.isFourCC) {
                            dataLength = width * height * 4;
                            var FloatArray: Nullable<ArrayBufferView> = null;

                            if (engine.badOS || engine.badDesktopOS || (!engine.getCaps().textureHalfFloat && !engine.getCaps().textureFloat)) { // Required because iOS has many issues with float and half float generation
                                if (bpp === 128) {
                                    FloatArray = DDSTools._GetFloatAsUIntRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer, i);                                    
                                }
                                else if (bpp === 64) {
                                    FloatArray = DDSTools._GetHalfFloatAsUIntRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer, i);
                                }

                                info.textureType = Engine.TEXTURETYPE_UNSIGNED_INT;
                                format = engine._getWebGLTextureType(info.textureType);
                                internalFormat = engine._getRGBABufferInternalSizedFormat(info.textureType);
                            }
                            else {
                                if (bpp === 128) {
                                    FloatArray = DDSTools._GetFloatRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer, i);
                                } else if (bpp === 64 && !engine.getCaps().textureHalfFloat) {
                                    FloatArray = DDSTools._GetHalfFloatAsFloatRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer, i);

                                    info.textureType = Engine.TEXTURETYPE_FLOAT;
                                    format = engine._getWebGLTextureType(info.textureType);    
                                    internalFormat = engine._getRGBABufferInternalSizedFormat(info.textureType);                            
                                } else { // 64
                                    FloatArray = DDSTools._GetHalfFloatRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer, i);
                                }
                            }

                            if (FloatArray) {
                                engine._uploadDataToTexture(sampler, i, internalFormat, width, height, gl.RGBA, format, FloatArray);
                            }
                        } else if (info.isRGB) {
                            if (bpp === 24) {
                                dataLength = width * height * 3;
                                byteArray = DDSTools._GetRGBArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                                engine._uploadDataToTexture(sampler, i, gl.RGB, width, height, gl.RGB, gl.UNSIGNED_BYTE, byteArray);
                            } else { // 32
                                dataLength = width * height * 4;
                                byteArray = DDSTools._GetRGBAArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                                engine._uploadDataToTexture(sampler, i, gl.RGBA, width, height, gl.RGBA, gl.UNSIGNED_BYTE, byteArray);
                            }
                        } else if (info.isLuminance) {
                            var unpackAlignment = gl.getParameter(gl.UNPACK_ALIGNMENT);
                            var unpaddedRowSize = width;
                            var paddedRowSize = Math.floor((width + unpackAlignment - 1) / unpackAlignment) * unpackAlignment;
                            dataLength = paddedRowSize * (height - 1) + unpaddedRowSize;

                            byteArray = DDSTools._GetLuminanceArrayBuffer(width, height, dataOffset, dataLength, arrayBuffer);
                            engine._uploadDataToTexture(sampler, i, gl.LUMINANCE, width, height, 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);
                            engine._uploadCompressedDataToTexture(sampler, i, internalFormat, width, height, byteArray);
                        }
                    }
                    dataOffset += width * height * (bpp / 8);
                    width *= 0.5;
                    height *= 0.5;

                    width = Math.max(1.0, width);
                    height = Math.max(1.0, height);
                }
            }
        }
    }
}