/*    
 *	 PVRLoader
 *   Author: pierre lepers
 *   Date: 17/09/2014 11:09
 *
 *	 PVR v2 (legacy) parser
 *   TODO : Add Support for PVR v3 format
 *   TODO : implement loadMipmaps option
 */


THREE.PVRLoader = function () {
	this._parser = THREE.PVRLoader.parse;
};

THREE.PVRLoader.prototype = Object.create( THREE.CompressedTextureLoader.prototype );
THREE.PVRLoader.prototype.constructor = THREE.PVRLoader;


THREE.PVRLoader.parse = function ( buffer, loadMipmaps ) {
	var headerLengthInt = 13;
	var header = new Uint32Array( buffer, 0, headerLengthInt );

	var pvrDatas = {
		buffer: buffer,
		header : header,
		loadMipmaps : loadMipmaps
	};

	// PVR v3
	if ( header[0] === 0x03525650 ) {
		return THREE.PVRLoader._parseV3( pvrDatas );
	} 
	// PVR v2
	else if ( header[11] === 0x21525650) {
		return THREE.PVRLoader._parseV2( pvrDatas );

	} else {
		throw new Error( "[THREE.PVRLoader] Unknown PVR format" );
	}

};

THREE.PVRLoader._parseV3 = function ( pvrDatas ) {
	
	var header = pvrDatas.header;
	var bpp, format;
	

	var metaLen 	  = header[12],
		pixelFormat   =  header[2],
		height        =  header[6],
		width         =  header[7],
		numSurfs      =  header[9],
		numFaces      =  header[10],
		numMipmaps    =  header[11];

	switch ( pixelFormat ) {
		case 0 : // PVRTC 2bpp RGB
			bpp = 2;
			format = THREE.RGB_PVRTC_2BPPV1_Format;
			break;
		case 1 : // PVRTC 2bpp RGBA
			bpp = 2
			format = THREE.RGBA_PVRTC_2BPPV1_Format;
			break;
		case 2 : // PVRTC 4bpp RGB
			bpp = 4
			format = THREE.RGB_PVRTC_4BPPV1_Format;
			break;
		case 3 : // PVRTC 4bpp RGBA
			bpp = 4
			format = THREE.RGBA_PVRTC_4BPPV1_Format;
			break;
		default :
			throw new Error( "pvrtc - unsupported PVR format " + pixelFormat);
	}

	pvrDatas.dataPtr 	 = 52 + metaLen;
	pvrDatas.bpp 		 = bpp;
	pvrDatas.format 	 = format;
	pvrDatas.width 		 = width;
	pvrDatas.height 	 = height;
	pvrDatas.numSurfaces = numFaces;
	pvrDatas.numMipmaps  = numMipmaps;

	pvrDatas.isCubemap 	= (numFaces === 6);

	return THREE.PVRLoader._extract( pvrDatas );
};

THREE.PVRLoader._parseV2 = function ( pvrDatas ) {

	var header = pvrDatas.header;

	var headerLength  =  header[0],
		height        =  header[1],
		width         =  header[2],
		numMipmaps    =  header[3],
		flags         =  header[4],
		dataLength    =  header[5],
		bpp           =  header[6],
		bitmaskRed    =  header[7],
		bitmaskGreen  =  header[8],
		bitmaskBlue   =  header[9],
		bitmaskAlpha  =  header[10],
		pvrTag        =  header[11],
		numSurfs      =  header[12];


	var TYPE_MASK = 0xff
	var PVRTC_2 = 24,
		PVRTC_4 = 25

	var formatFlags = flags & TYPE_MASK;



	var bpp, format;
	var _hasAlpha = bitmaskAlpha > 0;

	if (formatFlags === PVRTC_4 ) {
		format = _hasAlpha ? THREE.RGBA_PVRTC_4BPPV1_Format : THREE.RGB_PVRTC_4BPPV1_Format;
		bpp = 4;
	}
	else if ( formatFlags === PVRTC_2) {
		format = _hasAlpha ? THREE.RGBA_PVRTC_2BPPV1_Format : THREE.RGB_PVRTC_2BPPV1_Format;
		bpp = 2;
	}
	else
		throw new Error( "pvrtc - unknown format " + formatFlags);
	


	pvrDatas.dataPtr 	 = headerLength;
	pvrDatas.bpp 		 = bpp;
	pvrDatas.format 	 = format;
	pvrDatas.width 		 = width;
	pvrDatas.height 	 = height;
	pvrDatas.numSurfaces = numSurfs;
	pvrDatas.numMipmaps  = numMipmaps + 1;

  	// guess cubemap type seems tricky in v2
  	// it juste a pvr containing 6 surface (no explicit cubemap type)
	pvrDatas.isCubemap 	= (numSurfs === 6);

	return THREE.PVRLoader._extract( pvrDatas );

};


THREE.PVRLoader._extract = function ( pvrDatas ) {
	
	var pvr = {
		mipmaps: [], 
		width: pvrDatas.width, 
		height: pvrDatas.height, 
		format: pvrDatas.format, 
		mipmapCount: pvrDatas.numMipmaps, 
		isCubemap : pvrDatas.isCubemap 
	};

	var buffer = pvrDatas.buffer;



	// console.log( "--------------------------" );

	// console.log( "headerLength ", headerLength);
	// console.log( "height       ", height      );
	// console.log( "width        ", width       );
	// console.log( "numMipmaps   ", numMipmaps  );
	// console.log( "flags        ", flags       );
	// console.log( "dataLength   ", dataLength  );
	// console.log( "bpp          ", bpp         );
	// console.log( "bitmaskRed   ", bitmaskRed  );
	// console.log( "bitmaskGreen ", bitmaskGreen);
	// console.log( "bitmaskBlue  ", bitmaskBlue );
	// console.log( "bitmaskAlpha ", bitmaskAlpha);
	// console.log( "pvrTag       ", pvrTag      );
	// console.log( "numSurfs     ", numSurfs    );




	var dataOffset = pvrDatas.dataPtr,
		bpp = pvrDatas.bpp,
		numSurfs = pvrDatas.numSurfaces,
		dataSize = 0,
		blockSize = 0,
		blockWidth = 0,
		blockHeight = 0,
		widthBlocks = 0,
		heightBlocks = 0;



	if ( bpp === 2 ) {
		blockWidth = 8;
		blockHeight = 4;
	} else {
		blockWidth = 4;
		blockHeight = 4;
	}

	blockSize = (blockWidth * blockHeight) * bpp / 8;

	pvr.mipmaps.length = pvrDatas.numMipmaps * numSurfs;

	var mipLevel = 0;

	while (mipLevel < pvrDatas.numMipmaps) {

		var sWidth = pvrDatas.width >> mipLevel,
		sHeight = pvrDatas.height >> mipLevel;

		widthBlocks = sWidth / blockWidth;
		heightBlocks = sHeight / blockHeight;

		// Clamp to minimum number of blocks
		if (widthBlocks < 2)
			widthBlocks = 2;
		if (heightBlocks < 2)
			heightBlocks = 2;

		dataSize = widthBlocks * heightBlocks * blockSize;


		for ( var surfIndex = 0; surfIndex < numSurfs; surfIndex ++ ) {

			var byteArray = new Uint8Array( buffer, dataOffset, dataSize );

			var mipmap = { 
				data: byteArray, 
				width: sWidth, 
				height: sHeight 
			};

			pvr.mipmaps[ surfIndex * pvrDatas.numMipmaps + mipLevel] = mipmap;

			dataOffset += dataSize;


		}

		mipLevel ++;

	}


	return pvr;
}