/*
 * GJay, copyright (c) 2002-3 Chuck Groom <cgroom@users.sourceforge.net>
 *       Copyright (c) 2010 Craig Small <csmall@enc.com.au>
 *
 * mp3.c: Functions for handling MP3 files and most MP3 data
 * structure manipulation.
 *
 * MP3 info manipulation taken from mp3info package's mp3tech.c, which is
 * copyright (C) 2000-2001  Cedric Tefft <cedric@earthling.net>, which is
 * in turn based in part on:
 *    MP3Info 0.5 by Ricardo Cerqueira <rmc@rccn.net>
 *    MP3Stat 0.9 by Ed Sweetman <safemode@voicenet.com> and 
 *     	             Johannes Overmann <overmann@iname.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 1, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "gjay.h"
#include "mp3.h"
#include "i18n.h"

/* MIN_CONSEC_GOOD_FRAMES defines how many consecutive valid MP3 frames
   we need to see before we decide we are looking at a real MP3 file */
#define MIN_CONSEC_GOOD_FRAMES 4
#define FRAME_HEADER_SIZE 4
#define MIN_FRAME_SIZE 21
#define NUM_SAMPLES 4
#define TEXT_FIELD_LEN  30
#define INT_FIELD_LEN   4

#define NUM_TAGS 16
#define TITLE_CHAR  "t"
#define ARTIST_CHAR "c"
#define ALBUM_CHAR  "a"
static char * id3_tag[NUM_TAGS] = {
    "TT2",  TITLE_CHAR,
    "TIT2", TITLE_CHAR,
    "TP1",  ARTIST_CHAR,
    "TPE1", ARTIST_CHAR,
    "TCM",  ARTIST_CHAR,
    "TCOM", ARTIST_CHAR,
    "TAL",  ALBUM_CHAR,
    "TALB", ALBUM_CHAR
};
    

int get_header(FILE *file,mp3header *header);
int frame_length(mp3header *header);
int header_layer(mp3header *h);
int header_bitrate(mp3header *h);
int sameConstant(mp3header *h1, mp3header *h2);
int get_id3(mp3info *mp3);
char *pad(char *string, int length);
char *unpad(char *string);
int write_tag(mp3info *mp3);
int header_frequency(mp3header *h);
char *header_emphasis(mp3header *h);
char *header_mode(mp3header *h);
int get_first_header(mp3info *mp3,long startpos);
int get_next_header(mp3info *mp3);


int layer_tab[4]= {0, 3, 2, 1};

int frequencies[3][4] = {
   {22050,24000,16000,50000},  /* MPEG 2.0 */
   {44100,48000,32000,50000},  /* MPEG 1.0 */
   {11025,12000,8000,50000}    /* MPEG 2.5 */
};

int bitrate[2][3][14] = { 
  { /* MPEG 2.0 */
    {32,48,56,64,80,96,112,128,144,160,176,192,224,256},  /* layer 1 */
    {8,16,24,32,40,48,56,64,80,96,112,128,144,160},       /* layer 2 */
    {8,16,24,32,40,48,56,64,80,96,112,128,144,160}        /* layer 3 */
  },

  { /* MPEG 1.0 */
    {32,64,96,128,160,192,224,256,288,320,352,384,416,448}, /* layer 1 */
    {32,48,56,64,80,96,112,128,160,192,224,256,320,384},    /* layer 2 */
    {32,40,48,56,64,80,96,112,128,160,192,224,256,320}      /* layer 3 */
  }
};

int frame_size_index[] = {24000, 72000, 72000};


char *mode_text[] = {
   "stereo", "joint stereo", "dual channel", "mono"
};

char *emphasis_text[] = {
  "none", "50/15 microsecs", "reserved", "CCITT J 17"
};


int get_mp3_info(mp3info *mp3,int scantype, int fullscan_vbr)
{
    int had_error = 0;
    int frame_type[15]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    float seconds=0,total_rate=0;
    int frames=0,frame_types=0,frames_so_far=0;
    int l,vbr_median=-1;
    int bitrate,lastrate;
    int counter=0;
    mp3header header;
    struct stat filestat;
    off_t sample_pos,data_start=0;

    stat(mp3->filename,&filestat);
    mp3->datasize=filestat.st_size;
    get_id3(mp3);

    if(scantype == SCAN_QUICK) {
	if(get_first_header(mp3,0L)) {
            data_start=ftell(mp3->file);
            lastrate=15-mp3->header.bitrate;
            while((counter < NUM_SAMPLES) && lastrate) {
                sample_pos=(counter*(mp3->datasize/NUM_SAMPLES+1))+data_start;
                if(get_first_header(mp3,sample_pos)) {
                    bitrate=15-mp3->header.bitrate;
                } else {
                    bitrate=-1;
                }
		
                if(bitrate != lastrate) {
                    mp3->vbr=1;
                    if(fullscan_vbr) {
                        counter=NUM_SAMPLES;
                        scantype=SCAN_FULL;
                    }
                }
                lastrate=bitrate;
                counter++;
			
            }
            if(!(scantype == SCAN_FULL)) {
                mp3->frames=(mp3->datasize-data_start)/(l=frame_length(&mp3->header));
                mp3->seconds = (int)((float)(frame_length(&mp3->header)*mp3->frames)/
                                     (float)(header_bitrate(&mp3->header)*125)+0.5);
                mp3->vbr_average = (float)header_bitrate(&mp3->header);
            }
	}

    }

    if(scantype == SCAN_FULL) {
  	if(get_first_header(mp3,0L)) {
            data_start=ftell(mp3->file);
            while((bitrate=get_next_header(mp3))) {
                frame_type[15-bitrate]++;
                frames++;
            }
            memcpy(&header,&(mp3->header),sizeof(mp3header));
            for(counter=0;counter<15;counter++) {
                if(frame_type[counter]) {
                    frame_types++;
                    header.bitrate=counter;
                    frames_so_far += frame_type[counter];
                    seconds += (float)(frame_length(&header)*frame_type[counter])/
                        (float)(header_bitrate(&header)*125);
                    total_rate += (float)((header_bitrate(&header))*frame_type[counter]);
                    if((vbr_median == -1) && (frames_so_far >= frames/2))
                        vbr_median=counter;
                }
            }
            mp3->seconds=(int)(seconds+0.5);
            mp3->header.bitrate=vbr_median;
            mp3->vbr_average=total_rate/(float)frames;
            mp3->frames=frames;
            if(frame_types > 1) {
                mp3->vbr=1;
            }
	}
    }
    return had_error;
}


int get_first_header(mp3info *mp3, long startpos) 
{
    int k, l=0,c;
    mp3header h, h2;
    long valid_start=0;
  
    fseek(mp3->file,startpos,SEEK_SET);
    while (1) {
        while((c=fgetc(mp3->file)) != 255 && (c != EOF));
        if(c == 255) {
            ungetc(c,mp3->file);
            valid_start=ftell(mp3->file);
            if((l=get_header(mp3->file,&h))) {
                fseek(mp3->file,l-FRAME_HEADER_SIZE,SEEK_CUR);
                for(k=1; (k < MIN_CONSEC_GOOD_FRAMES) && (mp3->datasize-ftell(mp3->file) >= FRAME_HEADER_SIZE); k++) {
                    if(!(l=get_header(mp3->file,&h2))) break;
                    if(!sameConstant(&h,&h2)) break;
                    fseek(mp3->file,l-FRAME_HEADER_SIZE,SEEK_CUR);
                }
                if(k == MIN_CONSEC_GOOD_FRAMES) {
                    fseek(mp3->file,valid_start,SEEK_SET);
                    memcpy(&(mp3->header),&h2,sizeof(mp3header));
                    mp3->header_isvalid=1;
                    return 1;
                } 
            }
        } else {
            return 0;
        }
    }

    return 0;  
}

/* get_next_header() - read header at current position or look for 
   the next valid header if there isn't one at the current position
*/
int get_next_header(mp3info *mp3) 
{
    int l=0,c,skip_bytes=0;
    mp3header h;
  
    while(1) {
        while((c=fgetc(mp3->file)) != 255 && (ftell(mp3->file) < mp3->datasize)) skip_bytes++;
        if(c == 255) {
            ungetc(c,mp3->file);
            if((l=get_header(mp3->file,&h))) {
                if(skip_bytes) mp3->badframes++;
                fseek(mp3->file,l-FRAME_HEADER_SIZE,SEEK_CUR);
                return 15-h.bitrate;
            } else {
		skip_bytes += FRAME_HEADER_SIZE;
            }
        } else {
            if(skip_bytes) mp3->badframes++;
            return 0;
        }
    }
}


/* Get next MP3 frame header.
   Return codes:
   positive value = Frame Length of this header
   0 = No, we did not retrieve a valid frame header
*/

int get_header(FILE *file,mp3header *header)
{
    unsigned char buffer[FRAME_HEADER_SIZE];
    int fl;

    if(fread(&buffer,FRAME_HEADER_SIZE,1,file)<1) {
	header->sync=0;
	return 0;
    }
    header->sync=(((int)buffer[0]<<4) | ((int)(buffer[1]&0xE0)>>4));
    if(buffer[1] & 0x10) header->version=(buffer[1] >> 3) & 1;
    else header->version=2;
    header->layer=(buffer[1] >> 1) & 3;
    header->bitrate=(buffer[2] >> 4) & 0x0F;
    if((header->sync != 0xFFE) || (header->layer != 1) || (header->bitrate == 0xF)) {
	header->sync=0;
	return 0;
    }
    header->crc=buffer[1] & 1;
    header->freq=(buffer[2] >> 2) & 0x3;
    header->padding=(buffer[2] >>1) & 0x1;
    header->extension=(buffer[2]) & 0x1;
    header->mode=(buffer[3] >> 6) & 0x3;
    header->mode_extension=(buffer[3] >> 4) & 0x3;
    header->copyright=(buffer[3] >> 3) & 0x1;
    header->original=(buffer[3] >> 2) & 0x1;
    header->emphasis=(buffer[3]) & 0x3;

    /* Final sanity checks: bitrate 1111b and frequency 11b are reserved (invalid) */
    if (header->bitrate == 0x0f || header->bitrate == 0) {
      g_warning( _("Invalid bitrate %0x in mp3 header.\n"), header->bitrate);
      return 0;
    }

    if (header->freq == 0x03) {
      g_warning(_("Invalid frequency %0x in mp3 header.\n"), header->freq);
      return 0;
    }
    return ((fl=frame_length(header)) >= MIN_FRAME_SIZE ? fl : 0); 
}

int frame_length(mp3header *header) {
    return header->sync == 0xFFE ? 
        (frame_size_index[3-header->layer]*((header->version&1)+1)*
         header_bitrate(header)/header_frequency(header))+
        header->padding : 1;
}

int header_layer(mp3header *h) {return layer_tab[h->layer];}

int header_bitrate(mp3header *h) {
    assert(h->bitrate > 0);
    return bitrate[h->version & 1][3-h->layer][h->bitrate-1];
}

int header_frequency(mp3header *h) {
    return frequencies[h->version][h->freq];
}

char *header_emphasis(mp3header *h) {
    return emphasis_text[h->emphasis];
}

char *header_mode(mp3header *h) {
    return mode_text[h->mode];
}

int sameConstant(mp3header *h1, mp3header *h2) {
    if((*(uint*)h1) == (*(uint*)h2)) return 1;

    if((h1->version       == h2->version         ) &&
       (h1->layer         == h2->layer           ) &&
       (h1->crc           == h2->crc             ) &&
       (h1->freq          == h2->freq            ) &&
       (h1->mode          == h2->mode            ) &&
       (h1->copyright     == h2->copyright       ) &&
       (h1->original      == h2->original        ) &&
       (h1->emphasis      == h2->emphasis        )) 
        return 1;
    else return 0;
}


int get_id3(mp3info *mp3) {
  char fbuf[4];

  if(mp3->datasize < 128) {
    g_warning(_("mp3 file '%s' is smaller than 128 bytes.\n"),
        mp3->filename);
    return 4;
  }
	if(fseek(mp3->file, -128, SEEK_END )) {
    g_warning(_("Couldn't read last 128 bytes of '%s'\n"),mp3->filename);
    return 4;
  } 
  fread(fbuf,1,3,mp3->file); fbuf[3] = '\0';
  mp3->id3.genre[0]=255;

  if (memcmp("TAG", fbuf, 3) != 0) {
    return 4;
  }

  mp3->id3_isvalid=1;
  mp3->datasize -= 128;
  fseek(mp3->file, -125, SEEK_END);
  fread(mp3->id3.title,1,30,mp3->file); mp3->id3.title[30] = '\0';
  fread(mp3->id3.artist,1,30,mp3->file); mp3->id3.artist[30] = '\0';
  fread(mp3->id3.album,1,30,mp3->file); mp3->id3.album[30] = '\0';
  fread(mp3->id3.year,1,4,mp3->file); mp3->id3.year[4] = '\0';
  fread(mp3->id3.comment,1,30,mp3->file); mp3->id3.comment[30] = '\0';
  if (mp3->id3.comment[28] == '\0') {
    mp3->id3.track[0] = mp3->id3.comment[29];
  }
  fread(mp3->id3.genre,1,1,mp3->file);
  unpad(mp3->id3.title);
  unpad(mp3->id3.artist);
  unpad(mp3->id3.album);
  unpad(mp3->id3.year);
  unpad(mp3->id3.comment);
  return 0;
}

char *pad(char *string, int length) {
  int l;

  l=strlen(string);
  while(l<length) {
      string[l] = ' ';
      l++;
  }

  string[l]='\0';
  return string;
}

/* Remove trailing whitespace from the end of a string */

char *unpad(char *string) {
  char *pos=string+strlen(string)-1;

  while(pos >= string && isspace(pos[0]))
    (pos--)[0]='\0';
  return string;
}

/*
 * Build an ID3 tag and write it to the file
 * Returns positive int on success, 0 on failure
 */

int write_tag(mp3info *mp3) {

    char buf[129];

    strcpy(buf,"TAG");
    pad(mp3->id3.title,TEXT_FIELD_LEN);
    strncat(buf,mp3->id3.title,TEXT_FIELD_LEN);
    pad(mp3->id3.artist,TEXT_FIELD_LEN);
    strncat(buf,mp3->id3.artist,TEXT_FIELD_LEN);
    pad(mp3->id3.album,TEXT_FIELD_LEN);
    strncat(buf,mp3->id3.album,TEXT_FIELD_LEN);
    pad(mp3->id3.year,INT_FIELD_LEN);
    strncat(buf,mp3->id3.year,INT_FIELD_LEN);
    pad(mp3->id3.comment,TEXT_FIELD_LEN);
    strncat(buf,mp3->id3.comment,TEXT_FIELD_LEN);
    strncat(buf,(char*)(mp3->id3.genre),1);
    if (mp3->id3.track[0] != '\0') {
        buf[125]='\0';
        buf[126]=mp3->id3.track[0];
    }
    fseek(mp3->file,-128*mp3->id3_isvalid,SEEK_END);
    return (int)fwrite(buf,1,128,mp3->file);
}


/*
 * Try to read the mp3 ID3 tags from file fp. Return 0 on success.
 */
int get_id3_tags( FILE   * fp, 
                  gchar ** title,
                  gchar ** artist,
                  gchar ** album) {
    unsigned char buffer[BUFFER_SIZE];    
    int k, off, len, s;
    char tag[BUFFER_SIZE];
    int result = 1;

    assert(artist && album && title);

    if (!fp)
        return 1;

    rewind(fp);

    if (fread(buffer, 1, BUFFER_SIZE, fp) == 0)
        return 1;
    if (memcmp(buffer, "ID3", 3) == 0) {
        result = 0; // success
        for (off = 10; off < 1024; ) {
            for (k = 0; k < NUM_TAGS; k+=2) {
                if (strcasecmp((char*)(buffer + off), id3_tag[k]) == 0) {
                    if (buffer[off + 5]) {
                        s = 7;
                        len = buffer[off + 5] - 1;
                    } else if (buffer[off + 7]) {
                        s = 11;
                        len = buffer[off + 7] - 1;
                    } else {
                        /* Well, we tried and failed... */
                        continue;
                    }
                    bzero(tag, BUFFER_SIZE);
                    memcpy(tag, buffer + off + s, len);
                    if (id3_tag[k+1][0] == TITLE_CHAR[0]) {
                        *title = strdup_to_utf8(tag);
                    } else if (id3_tag[k+1][0] == ARTIST_CHAR[0]) {
                        *artist = strdup_to_utf8(tag);
                    } else if (id3_tag[k+1][0] == ALBUM_CHAR[0]) {
                        *album = strdup_to_utf8(tag);
                    } 
                    off += s + len;
                    break;
                }
            }
            if (k < NUM_TAGS)
                continue;
            if (isalpha(buffer[off]) &&
                isalpha(buffer[off + 1]) &&
                isalpha(buffer[off + 2])) {
                off += 6 + buffer[off + 5];
            } else {
                break;
            }
        }
    } else {
        fseek(fp, -128, SEEK_END);
        fread(buffer, 1, 128, fp);
        if (strncmp((char*)buffer, "TAG", 3) == 0) {
            result = 0; // success

            bzero(tag, TEXT_FIELD_LEN + 1);
            memcpy(tag, buffer + 3, TEXT_FIELD_LEN);
            *title = strdup_to_utf8(tag);

            bzero(tag, TEXT_FIELD_LEN + 1);
            memcpy(tag, buffer + 3 + TEXT_FIELD_LEN, TEXT_FIELD_LEN);
            *artist = strdup_to_utf8(tag);

            bzero(tag, TEXT_FIELD_LEN + 1);
            memcpy(tag, buffer + 3 + TEXT_FIELD_LEN*2, TEXT_FIELD_LEN);
            *album = strdup_to_utf8(tag);
        }
    }    
    return result;
}

gboolean
read_mp3_file_type( gchar    * path,
                      gint     * length,
                      gchar   ** title,
                      gchar   ** artist,
                      gchar   ** album)
{
  mp3info mp3;

  memset(&mp3, 0, sizeof(mp3info));
  mp3.filename = path;
  mp3.file = fopen(path, "r");
  if (!mp3.file) {
    g_warning(_("Unable to read song data for '%s'\n"), path);
    return FALSE;
  }
  if ( get_mp3_info(&mp3, SCAN_QUICK, 1) == 0)
  {
    *length = mp3.seconds;
    if (mp3.id3_isvalid) 
    {
      *artist = strdup_to_utf8(mp3.id3.artist);
      *album = strdup_to_utf8(mp3.id3.album);
      *title = strdup_to_utf8(mp3.id3.title);
    } else {
      /* Use alternate methods of looking for ID3 tags 
       * This is needed to support, among other things, 
       * mp3s generated by iTunes */
      get_id3_tags(mp3.file, title, artist, album);
    }
  }
  fclose(mp3.file);
  if (mp3.header_isvalid)
    return TRUE;
  return FALSE;
}