#include <opus/opus_types.h>
#include <ogg/ogg.h>

#import "TGDataItem.h"
#import "TGOggOpusWriter.h"

#ifdef ENABLE_NLS
#include <libintl.h>
#define _(X) gettext(X)
#else
#define _(X) (X)
#define textdomain(X)
#define bindtextdomain(X, Y)
#endif
#ifdef gettext_noop
#define N_(X) gettext_noop(X)
#else
#define N_(X) (X)
#endif

typedef struct
{
    void *readdata;
    opus_int64 total_samples_per_channel;
    int rawmode;
    int channels;
    long rate;
    int gain;
    int samplesize;
    int endianness;
    char *infilename;
    int ignorelength;
    int skip;
    int extraout;
    char *comments;
    int comments_length;
    int copy_comments;
} oe_enc_opt;

typedef struct
{
    int (*id_func)(unsigned char *buf, int len); /* Returns true if can load file */
    int id_data_len; /* Amount of data needed to id whether this can load the file */
    int (*open_func)(FILE *in, oe_enc_opt *opt, unsigned char *buf, int buflen);
    void (*close_func)(void *);
    char *format;
    char *description;
} input_format;

#include <opus/opus.h>

#include <ogg/ogg.h>
#include "opus_header.h"

static bool comment_init(char **comments, int* length, const char *vendor_string);
static bool comment_add(char **comments, int* length, char *tag, char *val);
static bool comment_pad(char **comments, int* length, int amount);

static inline int writeOggPage(ogg_page *page, TGDataItem *fileItem)
{
    int written = (int)(page->header_len + page->body_len);
    
    NSMutableData *data = [[NSMutableData alloc] init];
    [data appendBytes:page->header length:page->header_len];
    [data appendBytes:page->body length:page->body_len];
    [fileItem appendData:data];
    
    return MAX(0, written);
}

@interface TGOggOpusWriter ()
{
    TGDataItem *_dataItem;
    
    OpusEncoder *_encoder;
    uint8_t *_packet;
    
    oe_enc_opt inopt;
    
    ogg_stream_state os;
    ogg_page og;
    ogg_packet op;
    ogg_int64_t last_granulepos;
    ogg_int64_t enc_granulepos;
    int last_segments;
    int eos;
    OpusHeader header;
    
    ogg_int32_t _packetId;
    int size_segments;
    
    opus_int64 nb_encoded;
    opus_int64 bytes_written;
    opus_int64 pages_out;
    opus_int64 total_bytes;
    opus_int64 total_samples;
    opus_int32 nb_samples;
    opus_int32 peak_bytes;
    opus_int32 min_bytes;
    
    int max_frame_bytes;
    opus_int32 bitrate;
    opus_int32 rate;
    opus_int32 coding_rate;
    opus_int32 frame_size;
    int with_cvbr;
    int max_ogg_delay;
    int comment_padding;
    int serialno;
    opus_int32 lookahead;
}

@property (nonatomic) ogg_sync_state syncState;

@end

@implementation TGOggOpusWriter

- (instancetype)init
{
    self = [super init];
    if (self != nil)
    {
        bitrate = 30 * 1024;
        rate = 48000;
        coding_rate = 48000;
        frame_size = 960;
        with_cvbr = 1;
        max_ogg_delay = 48000;
        comment_padding = 512;
        
        _packetId = -1;
    }
    return self;
}

- (void)dealloc {
    [self cleanup];
}

- (void)cleanup
{
    if (_encoder != NULL)
    {
        opus_encoder_destroy(_encoder);
        _encoder = NULL;
    }
    
    ogg_stream_clear(&os);
    
    if (_packet != NULL)
    {
        free(_packet);
        _packet = NULL;
    }
}

- (bool)beginWithDataItem:(TGDataItem *)dataItem
{
    _dataItem = dataItem;
    
    inopt.channels = 1;
    inopt.rate = coding_rate=rate;
    inopt.gain = 0;
    inopt.samplesize = 16;
    inopt.endianness = 0;
    inopt.rawmode = 0;
    inopt.ignorelength = 0;
    inopt.copy_comments = 0;
    
    arc4random_buf(&serialno, sizeof(serialno));
    
    const char *opus_version = opus_get_version_string();
    comment_init(&inopt.comments, &inopt.comments_length, opus_version);
    
//    bitrate = 16 * 1024;

//    inopt.rawmode = 1;
//    inopt.ignorelength = 1;
//    inopt.samplesize = 16;
//    inopt.rate = 16000;
//    inopt.channels = 1;
    
    rate = (opus_int32)inopt.rate;
    inopt.skip = 0;
    
    // In order to code the complete length we'll need to do a little padding
    //setup_padder(&inopt, &original_samples);
    
    if (rate > 24000)
        coding_rate = 48000;
    else if (rate > 16000)
        coding_rate = 24000;
    else if (rate > 12000)
        coding_rate = 16000;
    else if (rate > 8000)
        coding_rate = 12000;
    else
        coding_rate = 8000;
    
    // Scale the resampler complexity, but only for 48000 output because the near-cutoff behavior matters a lot more at lower rates
    if (rate != coding_rate)
    {
        NSLog(@"Invalid rate");
        return false;
    }
    
    header.channels = 1;
    header.channel_mapping = 0;
    header.input_sample_rate = rate;
    header.gain = inopt.gain;
    header.nb_streams = 1;
    
    int result = OPUS_OK;
    _encoder = opus_encoder_create(coding_rate, 1, OPUS_APPLICATION_AUDIO, &result);
    if (result != OPUS_OK)
    {
        NSLog(@"Error cannot create encoder: %s", opus_strerror(result));
        return false;
    }
    
    min_bytes = max_frame_bytes = (1275 * 3 + 7) * header.nb_streams;
    _packet = malloc(max_frame_bytes);
    
    result = opus_encoder_ctl(_encoder, OPUS_SET_BITRATE(bitrate));
    if (result != OPUS_OK)
    {
        NSLog(@"Error OPUS_SET_BITRATE returned: %s", opus_strerror(result));
        return false;
    }
    
    /*result = opus_encoder_ctl(_encoder, OPUS_SET_VBR(1));
    if (result != OPUS_OK)
    {
        NSLog(@"Error OPUS_SET_VBR returned: %s", opus_strerror(result));
        return false;
    }*/
    
    /*ret = opus_multistream_encoder_ctl(st, OPUS_SET_VBR_CONSTRAINT(1));
    if (ret != OPUS_OK)
    {
        NSLog(@"Error OPUS_SET_VBR_CONSTRAINT returned: %s", opus_strerror(ret));
        return false;
    }*/
    
    /*ret = opus_multistream_encoder_ctl(st, OPUS_SET_COMPLEXITY(complexity));
    if(ret != OPUS_OK)
    {
        NSLog(@"Error OPUS_SET_COMPLEXITY returned: %s", opus_strerror(ret));
        return false;
    }*/
    
    /*result = opus_encoder_ctl(st, OPUS_SET_PACKET_LOSS_PERC(expect_loss));
    if (ret != OPUS_OK)
    {
        NSLog(@"Error OPUS_SET_PACKET_LOSS_PERC returned: %s", opus_strerror(ret));
        return false;
    }*/
    
#ifdef OPUS_SET_LSB_DEPTH
    result = opus_encoder_ctl(_encoder, OPUS_SET_LSB_DEPTH(MAX(8, MIN(24, inopt.samplesize))));
    if (result != OPUS_OK)
    {
        NSLog(@"Warning OPUS_SET_LSB_DEPTH returned: %s", opus_strerror(result));
    }
#endif
    
    // We do the lookahead check late so user CTLs can change it
    result = opus_encoder_ctl(_encoder, OPUS_GET_LOOKAHEAD(&lookahead));
    if (result != OPUS_OK)
    {
        NSLog(@"Error OPUS_GET_LOOKAHEAD returned: %s", opus_strerror(result));
        return false;
    }
    
    inopt.skip += lookahead;
    // Regardless of the rate we're coding at the ogg timestamping/skip is always timed at 48000.
    header.preskip = (int)(inopt.skip * (48000.0 / coding_rate));
    // Extra samples that need to be read to compensate for the pre-skip
    inopt.extraout = (int)(header.preskip * (rate / 48000.0));
    
    // Initialize Ogg stream struct
    if (ogg_stream_init(&os, serialno) == -1)
    {
        NSLog(@"Error: stream init failed");
        return false;
    }
    
    // Write header
    {
        unsigned char header_data[100];
        int packet_size = opus_header_to_packet(&header, header_data, 100);
        op.packet = header_data;
        op.bytes = packet_size;
        op.b_o_s = 1;
        op.e_o_s = 0;
        op.granulepos = 0;
        op.packetno = 0;
        ogg_stream_packetin(&os, &op);
        
        while ((result = ogg_stream_flush(&os, &og)))
        {
            if (!result)
                break;
            
            int pageBytesWritten = writeOggPage(&og, _dataItem);
            if (pageBytesWritten != og.header_len + og.body_len)
            {
                NSLog(@"Error: failed writing header to output stream");
                return false;
            }
            bytes_written += pageBytesWritten;
            pages_out++;
        }
        
        comment_pad(&inopt.comments, &inopt.comments_length, comment_padding);
        op.packet = (unsigned char *)inopt.comments;
        op.bytes = inopt.comments_length;
        op.b_o_s = 0;
        op.e_o_s = 0;
        op.granulepos = 0;
        op.packetno = 1;
        ogg_stream_packetin(&os, &op);
    }
    
    // Writing the rest of the opus header packets
    while ((result = ogg_stream_flush(&os, &og)))
    {
        if (result == 0)
            break;
        
        int writtenPageBytes = writeOggPage(&og, _dataItem);
        if (writtenPageBytes != og.header_len + og.body_len)
        {
            NSLog(@"Error: failed writing header to output stream");
            return false;
        }
        
        bytes_written += writtenPageBytes;
        pages_out++;
    }
    
    free(inopt.comments);
    
    return true;
}

- (bool)parseExistingOpusFile:(NSData *)data
{
    ogg_sync_init(&_syncState);
    
    char *buffer = ogg_sync_buffer(&_syncState, (long)data.length);
    memcpy(buffer, data.bytes, data.length);
    ogg_sync_wrote(&_syncState, (long)data.length);
    
    ogg_stream_state tempStream;
    ogg_page page;
    ogg_packet packet;
    bool headerParsed = false;
    bool foundStream = false;
    ogg_int64_t finalGranulePos = 0;
    
    while (ogg_sync_pageout(&_syncState, &page) == 1) {
        if (!foundStream) {
            serialno = ogg_page_serialno(&page);
            if (ogg_stream_init(&tempStream, serialno) != 0) {
                ogg_sync_clear(&_syncState);
                return false;
            }
            foundStream = true;
        }
        
        if (ogg_page_serialno(&page) == serialno) {
            ogg_stream_pagein(&tempStream, &page);
            
            if (ogg_page_granulepos(&page) != -1) {
                finalGranulePos = ogg_page_granulepos(&page);
            }
            
            while (ogg_stream_packetout(&tempStream, &packet) == 1) {
                if (!headerParsed && packet.packetno == 0) {
                    if (![self parseOpusHeader:packet.packet length:packet.bytes]) {
                        ogg_stream_clear(&tempStream);
                        ogg_sync_clear(&_syncState);
                        return false;
                    }
                    headerParsed = true;
                }
                
                _packetId = (ogg_int32_t)packet.packetno;
                if (packet.granulepos != -1) {
                    enc_granulepos = packet.granulepos;
                    last_granulepos = packet.granulepos;
                    finalGranulePos = packet.granulepos;
                }
            }
        }
    }
    
    if (finalGranulePos > header.preskip) {
         opus_int64 samples = finalGranulePos - header.preskip;
         total_samples = (samples * rate) / 48000;
     } else {
         total_samples = 0;
     }
    
    ogg_stream_clear(&tempStream);
    ogg_sync_clear(&_syncState);
    
    if (!headerParsed) {
        return false;
    }
    
    return true;
}

- (bool)parseOpusHeader:(unsigned char *)data length:(long)length
{
    if (length < 19) {
        NSLog(@"Opus header too short");
        return false;
    }
    
    if (memcmp(data, "OpusHead", 8) != 0) {
        NSLog(@"Invalid Opus header signature");
        return false;
    }
    
    header.channels = data[9];
    header.preskip = data[10] | (data[11] << 8);
    header.input_sample_rate = data[12] | (data[13] << 8) | (data[14] << 16) | (data[15] << 24);
    header.gain = (signed short)(data[16] | (data[17] << 8));
    header.channel_mapping = data[18];
    
    if (header.channels == 0) {
        return false;
    }
    
    rate = header.input_sample_rate;
    coding_rate = rate;
    
    if (rate > 24000)
        coding_rate = 48000;
    else if (rate > 16000)
        coding_rate = 24000;
    else if (rate > 12000)
        coding_rate = 16000;
    else if (rate > 8000)
        coding_rate = 12000;
    else
        coding_rate = 8000;
    
    header.nb_streams = 1;
    
    return true;
}

- (bool)initializeEncoderForAppend
{
    bytes_written = _dataItem.data.length;
    
    inopt.channels = header.channels;
    inopt.rate = rate;
    inopt.gain = header.gain;
    inopt.samplesize = 16;
    inopt.endianness = 0;
    inopt.rawmode = 0;
    inopt.ignorelength = 0;
    inopt.copy_comments = 0;
    
    int result = OPUS_OK;
    _encoder = opus_encoder_create(coding_rate, header.channels, OPUS_APPLICATION_AUDIO, &result);
    if (result != OPUS_OK) {
        NSLog(@"Error cannot create encoder: %s", opus_strerror(result));
        return false;
    }
    
    bitrate = 30 * 1024;
    frame_size = 960;
    
    opus_encoder_ctl(_encoder, OPUS_SET_BITRATE(bitrate));
    
#ifdef OPUS_SET_LSB_DEPTH
    opus_encoder_ctl(_encoder, OPUS_SET_LSB_DEPTH(16));
#endif
    
    opus_encoder_ctl(_encoder, OPUS_GET_LOOKAHEAD(&lookahead));
    
    if (ogg_stream_init(&os, serialno) == -1) {
        NSLog(@"Error: stream init failed");
        return false;
    }
    
    max_frame_bytes = (1275 * 3 + 7) * header.nb_streams;
    _packet = malloc(max_frame_bytes);
        
    return true;
}


- (bool)beginAppendWithDataItem:(TGDataItem *)dataItem
{
    if (dataItem.data.length == 0) {
        return [self beginWithDataItem:dataItem];
    }
    
    _dataItem = dataItem;
    
    if (![self parseExistingOpusFile:_dataItem.data]) {
        return false;
    }
    
    return [self initializeEncoderForAppend];
}

- (bool)writeFrame:(uint8_t *)framePcmBytes frameByteCount:(NSUInteger)frameByteCount
{
    // Main encoding loop (one frame per iteration)
    nb_samples = -1;

    int cur_frame_size = frame_size;
    _packetId++;
    
    if (nb_samples < 0)
    {
        nb_samples = (opus_int32)(frameByteCount / 2);
        total_samples += nb_samples;
        if (nb_samples < frame_size)
            op.e_o_s = 1;
        else
            op.e_o_s = 0;
    }
    op.e_o_s |= eos;
    
    int nbBytes = 0;
    
    if (nb_samples != 0)
    {
        uint8_t *paddedFrameBytes = framePcmBytes;
        bool freePaddedFrameBytes = false;
        
        if (nb_samples < cur_frame_size)
        {
            paddedFrameBytes = malloc(cur_frame_size * 2);
            freePaddedFrameBytes = true;
            
            memcpy(paddedFrameBytes, framePcmBytes, frameByteCount);
            memset(paddedFrameBytes + nb_samples * 2, 0, cur_frame_size * 2 - nb_samples * 2);
        }
        
        // Encode current frame
        nbBytes = opus_encode(_encoder, (opus_int16 *)paddedFrameBytes, cur_frame_size, _packet, max_frame_bytes / 10);
        if (freePaddedFrameBytes)
        {
            free(paddedFrameBytes);
            paddedFrameBytes = NULL;
        }
        
        if (nbBytes < 0)
        {
            NSLog(@"Encoding failed: %s. Aborting.", opus_strerror(nbBytes));
            return false;
        }
        
        nb_encoded += cur_frame_size;
        enc_granulepos += cur_frame_size * 48000 / coding_rate;
        total_bytes += nbBytes;
        size_segments = (nbBytes + 255) / 255;
        peak_bytes = MAX(nbBytes, peak_bytes);
        min_bytes = MIN(nbBytes, min_bytes);
    }
    
    // Flush early if adding this packet would make us end up with a continued page which we wouldn't have otherwise
    while ((((size_segments<=255)&&(last_segments+size_segments>255)) ||
            (enc_granulepos-last_granulepos>max_ogg_delay)) &&
           ogg_stream_flush_fill(&os, &og, 255 * 255))
    {
        if (ogg_page_packets(&og) != 0)
            last_granulepos = ogg_page_granulepos(&og);
        
        last_segments -= og.header[26];
        int writtenPageBytes = writeOggPage(&og, _dataItem);
        if (writtenPageBytes != og.header_len + og.body_len)
        {
            NSLog(@"Error: failed writing data to output stream");
            return false;
        }
        bytes_written += writtenPageBytes;
        pages_out++;
    }
    
    if (framePcmBytes != NULL) {
        op.packet = (unsigned char *)_packet;
        op.bytes = nbBytes;
        op.b_o_s = 0;
        op.granulepos = enc_granulepos;
    
        if (op.e_o_s)
        {
            /* We compute the final GP as ceil(len*48k/input_rate). When a resampling
             decoder does the matching floor(len*input/48k) conversion the length will
             be exactly the same as the input.
             */
            op.granulepos = ((total_samples * 48000 + rate - 1) / rate) + header.preskip;
        }
        op.packetno = 2 + _packetId;
        ogg_stream_packetin(&os, &op);
        last_segments += size_segments;
    }
    
    // If the stream is over or we're sure that the delayed flush will fire, go ahead and flush now to avoid adding delay
    while ((op.e_o_s || (enc_granulepos + (frame_size * 48000 / coding_rate) - last_granulepos > max_ogg_delay) ||
            (last_segments >= 255)) ? ogg_stream_flush_fill(&os, &og, 255 * 255) : ogg_stream_pageout_fill(&os, &og, 255 * 255))
    {
        if (ogg_page_packets(&og) != 0)
            last_granulepos = ogg_page_granulepos(&og);
        last_segments -= og.header[26];
        int writtenPageBytes = writeOggPage(&og, _dataItem);
        if (writtenPageBytes != og.header_len + og.body_len)
        {
            NSLog(@"Error: failed writing data to output stream");
            return false;
        }
        bytes_written += writtenPageBytes;
        pages_out++;
    }
    
    return true;
}

- (NSUInteger)encodedBytes
{
    return (NSUInteger)bytes_written;
}

- (NSTimeInterval)encodedDuration
{
    return total_samples / (NSTimeInterval)coding_rate;
}

- (NSDictionary *)pause
{
    [self flushPages];
    return [self saveState];
}

- (bool)resumeWithDataItem:(TGDataItem *)dataItem encoderState:(NSDictionary *)state
{
    if (![self restoreState:state withDataItem:dataItem])
        return false;
    
    _packetId++;
    
    return true;
}

- (bool)flushPages
{
    while (ogg_stream_flush_fill(&os, &og, 255 * 255))
    {
        if (ogg_page_packets(&og) != 0)
            last_granulepos = ogg_page_granulepos(&og);
        
        last_segments -= og.header[26];
        int writtenPageBytes = writeOggPage(&og, _dataItem);
        if (writtenPageBytes != og.header_len + og.body_len)
        {
            NSLog(@"Error: failed writing data to output stream");
            return false;
        }
        bytes_written += writtenPageBytes;
        pages_out++;
    }
    return true;
}

- (NSDictionary *)saveState
{
    NSMutableDictionary *state = [NSMutableDictionary dictionary];
    
    [state setObject:@(_packetId) forKey:@"packetId"];
    [state setObject:@(enc_granulepos) forKey:@"enc_granulepos"];
    [state setObject:@(last_granulepos) forKey:@"last_granulepos"];
    [state setObject:@(last_segments) forKey:@"last_segments"];
    [state setObject:@(nb_encoded) forKey:@"nb_encoded"];
    [state setObject:@(bytes_written) forKey:@"bytes_written"];
    [state setObject:@(pages_out) forKey:@"pages_out"];
    [state setObject:@(total_bytes) forKey:@"total_bytes"];
    [state setObject:@(total_samples) forKey:@"total_samples"];
    [state setObject:@(serialno) forKey:@"serialno"];
    
    [state setObject:@(rate) forKey:@"rate"];
    [state setObject:@(coding_rate) forKey:@"coding_rate"];
    [state setObject:@(frame_size) forKey:@"frame_size"];
    [state setObject:@(bitrate) forKey:@"bitrate"];
    [state setObject:@(with_cvbr) forKey:@"with_cvbr"];
    [state setObject:@(lookahead) forKey:@"lookahead"];
    
    NSDictionary *headerDict = @{
        @"channels": @(header.channels),
        @"channel_mapping": @(header.channel_mapping),
        @"input_sample_rate": @(header.input_sample_rate),
        @"gain": @(header.gain),
        @"nb_streams": @(header.nb_streams),
        @"preskip": @(header.preskip)
    };
    [state setObject:headerDict forKey:@"header"];
    
    return state;
}

- (bool)restoreState:(NSDictionary *)state withDataItem:(TGDataItem *)dataItem
{
    if (state == nil || dataItem == nil)
        return false;
    
    [self cleanup];
    
    _dataItem = dataItem;
    
    _packetId = [state[@"packetId"] intValue];
    enc_granulepos = [state[@"enc_granulepos"] longLongValue];
    last_granulepos = [state[@"last_granulepos"] longLongValue];
    last_segments = [state[@"last_segments"] intValue];
    nb_encoded = [state[@"nb_encoded"] longLongValue];
    bytes_written = [state[@"bytes_written"] longLongValue];
    pages_out = [state[@"pages_out"] longLongValue];
    total_bytes = [state[@"total_bytes"] longLongValue];
    total_samples = [state[@"total_samples"] longLongValue];
    serialno = [state[@"serialno"] intValue];
    
    rate = [state[@"rate"] intValue];
    coding_rate = [state[@"coding_rate"] intValue];
    frame_size = [state[@"frame_size"] intValue];
    bitrate = [state[@"bitrate"] intValue];
    with_cvbr = [state[@"with_cvbr"] intValue];
    lookahead = [state[@"lookahead"] intValue];
    
    NSDictionary *headerDict = state[@"header"];
    header.channels = [headerDict[@"channels"] intValue];
    header.channel_mapping = [headerDict[@"channel_mapping"] intValue];
    header.input_sample_rate = [headerDict[@"input_sample_rate"] intValue];
    header.gain = [headerDict[@"gain"] intValue];
    header.nb_streams = [headerDict[@"nb_streams"] intValue];
    header.preskip = [headerDict[@"preskip"] intValue];
    
    int result = OPUS_OK;
    _encoder = opus_encoder_create(coding_rate, header.channels, OPUS_APPLICATION_AUDIO, &result);
    if (result != OPUS_OK)
    {
        NSLog(@"Error cannot create encoder: %s", opus_strerror(result));
        return false;
    }
    
    opus_encoder_ctl(_encoder, OPUS_SET_BITRATE(bitrate));
    
#ifdef OPUS_SET_LSB_DEPTH
    opus_encoder_ctl(_encoder, OPUS_SET_LSB_DEPTH(16));
#endif
    
    if (ogg_stream_init(&os, serialno) == -1)
    {
        NSLog(@"Error: stream init failed");
        return false;
    }
    
    min_bytes = max_frame_bytes = (1275 * 3 + 7) * header.nb_streams;
    _packet = malloc(max_frame_bytes);
    
    return true;
}

@end

/*
 Comments will be stored in the Vorbis style.
 It is describled in the "Structure" section of
    http://www.xiph.org/ogg/vorbis/doc/v-comment.html

 However, Opus and other non-vorbis formats omit the "framing_bit".

The comment header is decoded as follows:
  1) [vendor_length] = read an unsigned integer of 32 bits
  2) [vendor_string] = read a UTF-8 vector as [vendor_length] octets
  3) [user_comment_list_length] = read an unsigned integer of 32 bits
  4) iterate [user_comment_list_length] times {
     5) [length] = read an unsigned integer of 32 bits
     6) this iteration's user comment = read a UTF-8 vector as [length] octets
     }
  7) done.
*/

#define readint(buf, base) (((buf[base+3]<<24)&0xff000000)| \
                           ((buf[base+2]<<16)&0xff0000)| \
                           ((buf[base+1]<<8)&0xff00)| \
                           (buf[base]&0xff))
#define writeint(buf, base, val) do{ buf[base+3]=((val)>>24)&0xff; \
                                     buf[base+2]=((val)>>16)&0xff; \
                                     buf[base+1]=((val)>>8)&0xff; \
                                     buf[base]=(val)&0xff; \
                                 }while(0)

static bool comment_init(char **comments, int *length, const char *vendor_string)
{
    // The 'vendor' field should be the actual encoding library used
    int vendor_length = (int)strlen(vendor_string);
    int user_comment_list_length = 0;
    int len = 8 + 4 + vendor_length + 4;
    char *p = (char *)malloc(len);
    memcpy(p, "OpusTags", 8);
    writeint(p, 8, vendor_length);
    memcpy(p + 12, vendor_string, vendor_length);
    writeint(p, 12 + vendor_length, user_comment_list_length);
    *length = len;
    *comments = p;
    
    return true;
}

__unused bool comment_add(char **comments, int* length, char *tag, char *val)
{
    char *p = *comments;
    int vendor_length = readint(p, 8);
    int user_comment_list_length = readint(p, 8 + 4 + vendor_length);
    int tag_len = (tag ? (int)strlen(tag) + 1 : 0);
    int val_len = (int)strlen(val);
    int len = (*length) + 4 + tag_len + val_len;
    
    p = (char *)realloc(p, len);
    
    writeint(p, *length, tag_len+val_len);      /* length of comment */
    if (tag)
    {
        memcpy(p + *length + 4, tag, tag_len);        /* comment tag */
        (p+*length+4)[tag_len-1] = '=';           /* separator */
    }
    memcpy(p + *length + 4 + tag_len, val, val_len);  /* comment */
    writeint(p, 8 + 4 + vendor_length, user_comment_list_length + 1);
    *comments = p;
    *length = len;
    
    return true;
}

static bool comment_pad(char **comments, int* length, int amount)
{
    if (amount > 0)
    {
        char *p = *comments;
        // Make sure there is at least amount worth of padding free, and round up to the maximum that fits in the current ogg segments
        int newlen = (*length + amount + 255) / 255 * 255 - 1;
        p = realloc(p, newlen);
        for (int i = *length; i < newlen; i++)
        {
            p[i] = 0;
        }
        *comments = p;
        *length = newlen;
    }
    
    return true;
}

#undef readint
#undef writeint