/*
 * Copyright (c) 2011 Apple Inc. All rights reserved.
 * Copyright (C) 2012-2013 Erik de Castro Lopo <erikd@mega-nerd.com>
 *
 * @APPLE_APACHE_LICENSE_HEADER_START@
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @APPLE_APACHE_LICENSE_HEADER_END@
 */

/*
	File:		ALACDecoder.cpp
*/

#include <stdlib.h>
#include <stddef.h>
#include <string.h>

#include "alac_codec.h"

#include "dplib.h"
#include "aglib.h"
#include "matrixlib.h"

#include "ALACBitUtilities.h"
#include "EndianPortable.h"

typedef enum
{	false = 0,
	true = 1
} bool ;

// constants/data
const uint32_t kMaxBitDepth = 32;			// max allowed bit depth is 32


// prototypes
static int32_t	alac_fill_element (struct BitBuffer * bits) ;
static int32_t	alac_data_stream_element (struct BitBuffer * bits) ;

static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride );


/*
	Init()
	- initialize the decoder with the given configuration
*/
int32_t
alac_decoder_init (ALAC_DECODER *p, void * inMagicCookie, uint32_t inMagicCookieSize)
{
	int32_t		status = ALAC_noErr;
    ALACSpecificConfig theConfig;
    uint8_t * theActualCookie = (uint8_t *)inMagicCookie;
    uint32_t theCookieBytesRemaining = inMagicCookieSize;

    // For historical reasons the decoder needs to be resilient to magic cookies vended by older encoders.
    // As specified in the ALACMagicCookieDescription.txt document, there may be additional data encapsulating
    // the ALACSpecificConfig. This would consist of format ('frma') and 'alac' atoms which precede the
    // ALACSpecificConfig.
    // See ALACMagicCookieDescription.txt for additional documentation concerning the 'magic cookie'

    // skip format ('frma') atom if present
    if (theActualCookie[4] == 'f' && theActualCookie[5] == 'r' && theActualCookie[6] == 'm' && theActualCookie[7] == 'a')
    {
        theActualCookie += 12;
        theCookieBytesRemaining -= 12;
    }

    // skip 'alac' atom header if present
    if (theActualCookie[4] == 'a' && theActualCookie[5] == 'l' && theActualCookie[6] == 'a' && theActualCookie[7] == 'c')
    {
        theActualCookie += 12;
        theCookieBytesRemaining -= 12;
    }

    // read the ALACSpecificConfig
    if (theCookieBytesRemaining >= sizeof(ALACSpecificConfig))
    {
        theConfig.frameLength = psf_get_be32 (theActualCookie, offsetof (ALACSpecificConfig, frameLength)) ;

		if (theConfig.frameLength > ALAC_FRAME_LENGTH)
			return fALAC_FrameLengthError ;

        theConfig.compatibleVersion = theActualCookie [offsetof (ALACSpecificConfig, compatibleVersion)] ;
        theConfig.bitDepth = theActualCookie [offsetof (ALACSpecificConfig, bitDepth)] ;
        theConfig.pb = theActualCookie [offsetof (ALACSpecificConfig, pb)] ;
        theConfig.mb = theActualCookie [offsetof (ALACSpecificConfig, mb)] ;
        theConfig.kb = theActualCookie [offsetof (ALACSpecificConfig, kb)] ;
        theConfig.numChannels = theActualCookie [offsetof (ALACSpecificConfig, numChannels)] ;
        theConfig.maxRun = psf_get_be16 (theActualCookie, offsetof (ALACSpecificConfig, maxRun)) ;
        theConfig.maxFrameBytes = psf_get_be32 (theActualCookie, offsetof (ALACSpecificConfig, maxFrameBytes)) ;
        theConfig.avgBitRate = psf_get_be32 (theActualCookie, offsetof (ALACSpecificConfig, avgBitRate)) ;
        theConfig.sampleRate = psf_get_be32 (theActualCookie, offsetof (ALACSpecificConfig, sampleRate)) ;

        p->mConfig = theConfig;

        RequireAction( p->mConfig.compatibleVersion <= kALACVersion, return kALAC_ParamError; );

        RequireAction( (p->mMixBufferU != NULL) && (p->mMixBufferV != NULL) && (p->mPredictor != NULL),
                        status = kALAC_MemFullError; goto Exit; );
     }
    else
    {
        status = kALAC_ParamError;
    }

    // skip to Channel Layout Info
    // theActualCookie += sizeof(ALACSpecificConfig);

    // Currently, the Channel Layout Info portion of the magic cookie (as defined in the
    // ALACMagicCookieDescription.txt document) is unused by the decoder.

Exit:
	return status;
}

/*
	Decode()
	- the decoded samples are interleaved into the output buffer in the order they arrive in
	  the bitstream
*/
int32_t
alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, int32_t * sampleBuffer, uint32_t numSamples, uint32_t numChannels, uint32_t * outNumSamples)
{
	BitBuffer			shiftBits;
	uint32_t            bits1, bits2;
	uint8_t				tag;
	uint8_t				elementInstanceTag;
	AGParamRec			agParams;
	uint32_t				channelIndex;
	int16_t				coefsU[32];		// max possible size is 32 although NUMCOEPAIRS is the current limit
	int16_t				coefsV[32];
	uint8_t				numU, numV;
	uint8_t				mixBits;
	int8_t				mixRes;
	uint16_t			unusedHeader;
	uint8_t				escapeFlag;
	uint32_t			chanBits;
	uint8_t				bytesShifted;
	uint32_t			shift;
	uint8_t				modeU, modeV;
	uint32_t			denShiftU, denShiftV;
	uint16_t			pbFactorU, pbFactorV;
	uint16_t			pb;
	int32_t *			out32;
	uint8_t				headerByte;
	uint8_t				partialFrame;
	uint32_t			extraBits;
	int32_t				val;
	uint32_t			i, j;
	int32_t             status;

	RequireAction( (bits != NULL) && (sampleBuffer != NULL) && (outNumSamples != NULL), return kALAC_ParamError; );
	RequireAction( numChannels > 0, return kALAC_ParamError; );

	p->mActiveElements = 0;
	channelIndex	= 0;

	status = ALAC_noErr;
	*outNumSamples = numSamples;

	while ( status == ALAC_noErr )
	{
		// bail if we ran off the end of the buffer
    	RequireAction( bits->cur < bits->end, status = kALAC_ParamError; goto Exit; );

		// copy global decode params for this element
		pb = p->mConfig.pb;

		// read element tag
		tag = BitBufferReadSmall( bits, 3 );
		switch ( tag )
		{
			case ID_SCE:
			case ID_LFE:
			{
				// mono/LFE channel
				elementInstanceTag = BitBufferReadSmall( bits, 4 );
				p->mActiveElements |= (1u << elementInstanceTag);

				// read the 12 unused header bits
				unusedHeader = (uint16_t) BitBufferRead( bits, 12 );
				RequireAction( unusedHeader == 0, status = kALAC_ParamError; goto Exit; );

				// read the 1-bit "partial frame" flag, 2-bit "shift-off" flag & 1-bit "escape" flag
				headerByte = (uint8_t) BitBufferRead( bits, 4 );

				partialFrame = headerByte >> 3;

				bytesShifted = (headerByte >> 1) & 0x3u;
				RequireAction( bytesShifted != 3, status = kALAC_ParamError; goto Exit; );

				shift = bytesShifted * 8;

				escapeFlag = headerByte & 0x1;

				chanBits = p->mConfig.bitDepth - (bytesShifted * 8);

				// check for partial frame to override requested numSamples
				if ( partialFrame != 0 )
				{
					numSamples  = BitBufferRead( bits, 16 ) << 16;
					numSamples |= BitBufferRead( bits, 16 );
				}

				if ( escapeFlag == 0 )
				{
					// compressed frame, read rest of parameters
					mixBits	= (uint8_t) BitBufferRead( bits, 8 );
					mixRes	= (int8_t) BitBufferRead( bits, 8 );
					//Assert( (mixBits == 0) && (mixRes == 0) );		// no mixing for mono

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					modeU		= headerByte >> 4;
					denShiftU	= headerByte & 0xfu;

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					pbFactorU	= headerByte >> 5;
					numU		= headerByte & 0x1fu;

					for ( i = 0; i < numU; i++ )
						coefsU[i] = (int16_t) BitBufferRead( bits, 16 );

					// if shift active, skip the the shift buffer but remember where it starts
					if ( bytesShifted != 0 )
					{
						shiftBits = *bits;
						BitBufferAdvance( bits, (bytesShifted * 8) * numSamples );
					}

					// decompress
					set_ag_params( &agParams, p->mConfig.mb, (pb * pbFactorU) / 4, p->mConfig.kb, numSamples, numSamples, p->mConfig.maxRun );
					status = dyn_decomp( &agParams, bits, p->mPredictor, numSamples, chanBits, &bits1 );
					RequireNoErr( status, goto Exit; );

					if ( modeU == 0 )
					{
						unpc_block( p->mPredictor, p->mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
					}
					else
					{
						// the special "numActive == 31" mode can be done in-place
						unpc_block( p->mPredictor, p->mPredictor, numSamples, NULL, 31, chanBits, 0 );
						unpc_block( p->mPredictor, p->mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
					}
				}
				else
				{
					//Assert( bytesShifted == 0 );

					// uncompressed frame, copy data into the mix buffer to use common output code
					shift = 32 - chanBits;
					if ( chanBits <= 16 )
					{
						for ( i = 0; i < numSamples; i++ )
						{
							val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
							val = (val << shift) >> shift;
							p->mMixBufferU[i] = val;
						}
					}
					else
					{
						// BitBufferRead() can't read more than 16 bits at a time so break up the reads
						extraBits = chanBits - 16;
						for ( i = 0; i < numSamples; i++ )
						{
							val = (int32_t) BitBufferRead( bits, 16 );
							val = (val << 16) >> shift;
							p->mMixBufferU[i] = val | BitBufferRead( bits, (uint8_t) extraBits );
						}
					}

					mixBits = mixRes = 0;
					bits1 = chanBits * numSamples;
					bytesShifted = 0;
				}

				// now read the shifted values into the shift buffer
				if ( bytesShifted != 0 )
				{
					shift = bytesShifted * 8;
					//Assert( shift <= 16 );

					for ( i = 0; i < numSamples; i++ )
						p->mShiftBuffer[i] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
				}

				// convert 32-bit integers into output buffer
				switch ( p->mConfig.bitDepth )
				{
					case 16:
						out32 = sampleBuffer + channelIndex;
						for ( i = 0, j = 0; i < numSamples; i++, j += numChannels )
							out32[j] = p->mMixBufferU[i] << 16;
						break;
					case 20:
						out32 = sampleBuffer + channelIndex;
						copyPredictorTo20( p->mMixBufferU, out32, numChannels, numSamples );
						break;
					case 24:
						out32 = sampleBuffer + channelIndex;
						if ( bytesShifted != 0 )
							copyPredictorTo24Shift( p->mMixBufferU, p->mShiftBuffer, out32, numChannels, numSamples, bytesShifted );
						else
							copyPredictorTo24( p->mMixBufferU, out32, numChannels, numSamples );
						break;
					case 32:
						out32 = sampleBuffer + channelIndex;
						if ( bytesShifted != 0 )
							copyPredictorTo32Shift( p->mMixBufferU, p->mShiftBuffer, out32, numChannels, numSamples, bytesShifted );
						else
							copyPredictorTo32( p->mMixBufferU, out32, numChannels, numSamples);
						break;
				}

				channelIndex += 1;
				*outNumSamples = numSamples;
				break;
			}

			case ID_CPE:
			{
				// if decoding this pair would take us over the max channels limit, bail
				if ( (channelIndex + 2) > numChannels )
					goto NoMoreChannels;

				// stereo channel pair
				elementInstanceTag = BitBufferReadSmall( bits, 4 );
				p->mActiveElements |= (1u << elementInstanceTag);

				// read the 12 unused header bits
				unusedHeader = (uint16_t) BitBufferRead( bits, 12 );
				RequireAction( unusedHeader == 0, status = kALAC_ParamError; goto Exit; );

				// read the 1-bit "partial frame" flag, 2-bit "shift-off" flag & 1-bit "escape" flag
				headerByte = (uint8_t) BitBufferRead( bits, 4 );

				partialFrame = headerByte >> 3;

				bytesShifted = (headerByte >> 1) & 0x3u;
				RequireAction( bytesShifted != 3, status = kALAC_ParamError; goto Exit; );

				shift = bytesShifted * 8;

				escapeFlag = headerByte & 0x1;

				chanBits = p->mConfig.bitDepth - (bytesShifted * 8) + 1;

				// check for partial frame length to override requested numSamples
				if ( partialFrame != 0 )
				{
					numSamples  = BitBufferRead( bits, 16 ) << 16;
					numSamples |= BitBufferRead( bits, 16 );
				}

				if ( escapeFlag == 0 )
				{
					// compressed frame, read rest of parameters
					mixBits		= (uint8_t) BitBufferRead( bits, 8 );
					mixRes		= (int8_t) BitBufferRead( bits, 8 );

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					modeU		= headerByte >> 4;
					denShiftU	= headerByte & 0xfu;

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					pbFactorU	= headerByte >> 5;
					numU		= headerByte & 0x1fu;
					for ( i = 0; i < numU; i++ )
						coefsU[i] = (int16_t) BitBufferRead( bits, 16 );

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					modeV		= headerByte >> 4;
					denShiftV	= headerByte & 0xfu;

					headerByte	= (uint8_t) BitBufferRead( bits, 8 );
					pbFactorV	= headerByte >> 5;
					numV		= headerByte & 0x1fu;
					for ( i = 0; i < numV; i++ )
						coefsV[i] = (int16_t) BitBufferRead( bits, 16 );

					// if shift active, skip the interleaved shifted values but remember where they start
					if ( bytesShifted != 0 )
					{
						shiftBits = *bits;
						BitBufferAdvance( bits, (bytesShifted * 8) * 2 * numSamples );
					}

					// decompress and run predictor for "left" channel
					set_ag_params( &agParams, p->mConfig.mb, (pb * pbFactorU) / 4, p->mConfig.kb, numSamples, numSamples, p->mConfig.maxRun );
					status = dyn_decomp( &agParams, bits, p->mPredictor, numSamples, chanBits, &bits1 );
					RequireNoErr( status, goto Exit; );

					if ( modeU == 0 )
					{
						unpc_block( p->mPredictor, p->mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
					}
					else
					{
						// the special "numActive == 31" mode can be done in-place
						unpc_block( p->mPredictor, p->mPredictor, numSamples, NULL, 31, chanBits, 0 );
						unpc_block( p->mPredictor, p->mMixBufferU, numSamples, &coefsU[0], numU, chanBits, denShiftU );
					}

					// decompress and run predictor for "right" channel
					set_ag_params( &agParams, p->mConfig.mb, (pb * pbFactorV) / 4, p->mConfig.kb, numSamples, numSamples, p->mConfig.maxRun );
					status = dyn_decomp( &agParams, bits, p->mPredictor, numSamples, chanBits, &bits2 );
					RequireNoErr( status, goto Exit; );

					if ( modeV == 0 )
					{
						unpc_block( p->mPredictor, p->mMixBufferV, numSamples, &coefsV[0], numV, chanBits, denShiftV );
					}
					else
					{
						// the special "numActive == 31" mode can be done in-place
						unpc_block( p->mPredictor, p->mPredictor, numSamples, NULL, 31, chanBits, 0 );
						unpc_block( p->mPredictor, p->mMixBufferV, numSamples, &coefsV[0], numV, chanBits, denShiftV );
					}
				}
				else
				{
					//Assert( bytesShifted == 0 );

					// uncompressed frame, copy data into the mix buffers to use common output code
					chanBits = p->mConfig.bitDepth;
					shift = 32 - chanBits;
					if ( chanBits <= 16 )
					{
						for ( i = 0; i < numSamples; i++ )
						{
							val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
							val = (val << shift) >> shift;
							p->mMixBufferU[i] = val;

							val = (int32_t) BitBufferRead( bits, (uint8_t) chanBits );
							val = (val << shift) >> shift;
							p->mMixBufferV[i] = val;
						}
					}
					else
					{
						// BitBufferRead() can't read more than 16 bits at a time so break up the reads
						extraBits = chanBits - 16;
						for ( i = 0; i < numSamples; i++ )
						{
							val = (int32_t) BitBufferRead( bits, 16 );
							val = (val << 16) >> shift;
							p->mMixBufferU[i] = val | BitBufferRead( bits, (uint8_t)extraBits );

							val = (int32_t) BitBufferRead( bits, 16 );
							val = (val << 16) >> shift;
							p->mMixBufferV[i] = val | BitBufferRead( bits, (uint8_t)extraBits );
						}
					}

					bits1 = chanBits * numSamples;
					bits2 = chanBits * numSamples;
					mixBits = mixRes = 0;
					bytesShifted = 0;
				}

				// now read the shifted values into the shift buffer
				if ( bytesShifted != 0 )
				{
					shift = bytesShifted * 8;
					//Assert( shift <= 16 );

					for ( i = 0; i < (numSamples * 2); i += 2 )
					{
						p->mShiftBuffer[i + 0] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
						p->mShiftBuffer[i + 1] = (uint16_t) BitBufferRead( &shiftBits, (uint8_t) shift );
					}
				}

				// un-mix the data and convert to output format
				// - note that mixRes = 0 means just interleave so we use that path for uncompressed frames
				switch ( p->mConfig.bitDepth )
				{
					case 16:
						out32 = sampleBuffer + channelIndex;
						unmix16( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples, mixBits, mixRes );
						break;
					case 20:
						out32 = sampleBuffer + channelIndex;
						unmix20( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples, mixBits, mixRes );
						break;
					case 24:
						out32 = sampleBuffer + channelIndex;
						unmix24( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples,
									mixBits, mixRes, p->mShiftBuffer, bytesShifted );
						break;
					case 32:
						out32 = sampleBuffer + channelIndex;
						unmix32( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples,
									mixBits, mixRes, p->mShiftBuffer, bytesShifted );
						break;
				}

				channelIndex += 2;
				*outNumSamples = numSamples;
				break;
			}

			case ID_CCE:
			case ID_PCE:
			{
				// unsupported element, bail
				//AssertNoErr( tag );
				status = kALAC_ParamError;
				break;
			}

			case ID_DSE:
			{
				// data stream element -- parse but ignore
				status = alac_data_stream_element (bits) ;
				break;
			}

			case ID_FIL:
			{
				// fill element -- parse but ignore
				status = alac_fill_element (bits) ;
				break;
			}

			case ID_END:
			{
				// frame end, all done so byte align the frame and check for overruns
				BitBufferByteAlign( bits, false );
				//Assert( bits->cur == bits->end );
				goto Exit;
			}
		}

#if 0 // ! DEBUG
		// if we've decoded all of our channels, bail (but not in debug b/c we want to know if we're seeing bad bits)
		// - this also protects us if the config does not match the bitstream or crap data bits follow the audio bits
		if ( channelIndex >= numChannels )
			break;
#endif
	}

NoMoreChannels:

	// if we get here and haven't decoded all of the requested channels, fill the remaining channels with zeros
	for ( ; channelIndex < numChannels; channelIndex++ )
	{
		int32_t *	fill32 = sampleBuffer + channelIndex;
		Zero32( fill32, numSamples, numChannels );
	}

Exit:
	return status;
}

#if PRAGMA_MARK
#pragma mark -
#endif

/*
	FillElement()
	- they're just filler so we don't need 'em
*/
static int32_t
alac_fill_element (struct BitBuffer * bits)
{
	int16_t		count;

	// 4-bit count or (4-bit + 8-bit count) if 4-bit count == 15
	// - plus this weird -1 thing I still don't fully understand
	count = BitBufferReadSmall( bits, 4 );
	if ( count == 15 )
		count += (int16_t) BitBufferReadSmall( bits, 8 ) - 1;

	BitBufferAdvance( bits, count * 8 );

	RequireAction( bits->cur <= bits->end, return kALAC_ParamError; );

	return ALAC_noErr;
}

/*
	DataStreamElement()
	- we don't care about data stream elements so just skip them
*/
static int32_t
alac_data_stream_element (struct BitBuffer * bits)
{
	int32_t		data_byte_align_flag;
	uint16_t		count;

	// the tag associates this data stream element with a given audio element

	/* element_instance_tag = */ BitBufferReadSmall( bits, 4 );

	data_byte_align_flag = BitBufferReadOne( bits );

	// 8-bit count or (8-bit + 8-bit count) if 8-bit count == 255
	count = BitBufferReadSmall( bits, 8 );
	if ( count == 255 )
		count += BitBufferReadSmall( bits, 8 );

	// the align flag means the bitstream should be byte-aligned before reading the following data bytes
	if ( data_byte_align_flag )
		BitBufferByteAlign( bits, false );

	// skip the data bytes
	BitBufferAdvance( bits, count * 8 );

	RequireAction( bits->cur <= bits->end, return kALAC_ParamError; );

	return ALAC_noErr;
}

/*
	ZeroN()
	- helper routines to clear out output channel buffers when decoding fewer channels than requested
*/
static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride )
{
	uint32_t indx;

	if ( stride == 1 )
	{
		memset( buffer, 0, numItems * sizeof(int32_t) );
	}
	else
	{
		for ( indx = 0; indx < (numItems * stride); indx += stride )
			buffer[indx] = 0;
	}
}
