/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
   It is considered beerware. Prost. Skol. Cheers or whatever. */

#include "trackerlogic.h"

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <unistd.h>
#include <time.h>
#include <math.h>
#include <glob.h>

#include <errno.h>
#include "scan.h"
#include "byte.h"

#if defined( WANT_CLOSED_TRACKER ) || defined( WANT_BLACKLIST )
#include <sys/stat.h>
#endif

/* GLOBAL VARIABLES */
static ot_vector all_torrents[256];
#ifdef WANT_CLOSED_TRACKER
int g_closedtracker = 1;
static ot_torrent* const OT_TORRENT_NOT_ON_WHITELIST = (ot_torrent*)1;
#endif

#ifdef WANT_BLACKLIST
int g_check_blacklist = 1;
static ot_torrent* const OT_TORRENT_ON_BLACKLIST = (ot_torrent*)2;
#endif

/* Converter function from memory to human readable hex strings
   - definitely not thread safe!!!
*/
static char ths[2+2*20]="-";static char*to_hex(ot_byte*s){const char*m="0123456789ABCDEF";char*e=ths+41;char*t=ths+1;while(t<e){*t++=m[*s>>4];*t++=m[*s++&15];}*t=0;return ths+1;}

/* This function gives us a binary search that returns a pointer, even if
   no exact match is found. In that case it sets exactmatch 0 and gives
   calling functions the chance to insert data
*/
static void *binary_search( const void * const key, const void * base, const size_t member_count, const size_t member_size,
                            size_t compare_size, int *exactmatch ) {
  size_t mc = member_count;
  ot_byte *lookat = ((ot_byte*)base) + member_size * (member_count >> 1);
  *exactmatch = 1;

  while( mc ) {
    int cmp = memcmp( lookat, key, compare_size);
    if (cmp == 0) return (void *)lookat;
    if (cmp < 0) {
      base = (void*)(lookat + member_size);
      --mc;
    }
    mc >>= 1;
    lookat = ((ot_byte*)base) + member_size * (mc >> 1);
  }
  *exactmatch = 0;
  return (void*)lookat;
}

/* This is the generic insert operation for our vector type.
   It tries to locate the object at "key" with size "member_size" by comparing its first "compare_size" bytes with
   those of objects in vector. Our special "binary_search" function does that and either returns the match or a
   pointer to where the object is to be inserted. vector_find_or_insert makes space for the object and copies it,
   if it wasn't found in vector. Caller needs to check the passed "exactmatch" variable to see, whether an insert
   took place. If resizing the vector failed, NULL is returned, else the pointer to the object in vector.
*/
static void *vector_find_or_insert( ot_vector *vector, void *key, size_t member_size, size_t compare_size, int *exactmatch ) {
  ot_byte *match = binary_search( key, vector->data, vector->size, member_size, compare_size, exactmatch );

  if( *exactmatch ) return match;

  if( vector->size + 1 >= vector->space ) {
    size_t   new_space = vector->space ? OT_VECTOR_GROW_RATIO * vector->space : OT_VECTOR_MIN_MEMBERS;
    ot_byte *new_data = realloc( vector->data, new_space * member_size );
    if( !new_data ) return NULL;

    /* Adjust pointer if it moved by realloc */
    match = new_data + (match - (ot_byte*)vector->data);

    vector->data = new_data;
    vector->space = new_space;
  }
  memmove( match + member_size, match, ((ot_byte*)vector->data) + member_size * vector->size - match );
  vector->size++;
  return match;
}

/* This is the non-generic delete from vector-operation specialized for peers in pools.
   Set hysteresis == 0 if you expect the vector not to ever grow again.
   It returns 0 if no peer was found (and thus not removed)
              1 if a non-seeding peer was removed
              2 if a seeding peer was removed
*/
static int vector_remove_peer( ot_vector *vector, ot_peer *peer, int hysteresis ) {
  int      exactmatch;
  size_t   shrink_thresh = hysteresis ? OT_VECTOR_SHRINK_THRESH : OT_VECTOR_SHRINK_RATIO;
  ot_peer *end = ((ot_peer*)vector->data) + vector->size;
  ot_peer *match;

  if( !vector->size ) return 0;
  match = binary_search( peer, vector->data, vector->size, sizeof( ot_peer ), OT_PEER_COMPARE_SIZE, &exactmatch );

  if( !exactmatch ) return 0;
  exactmatch = ( OT_FLAG( match ) & PEER_FLAG_SEEDING ) ? 2 : 1;
  memmove( match, match + 1, sizeof(ot_peer) * ( end - match - 1 ) );
  if( ( --vector->size * shrink_thresh < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
    vector->space /= OT_VECTOR_SHRINK_RATIO;
    vector->data = realloc( vector->data, vector->space * sizeof( ot_peer ) );
  }
  if( !vector->size ) {
    /* for peer pools its safe to let them go,
       in 999 of 1000 this happens in older pools, that won't ever grow again */
    free( vector->data );
    vector->data = NULL;
    vector->space = 0;
  }
  return exactmatch;
}

static void free_peerlist( ot_peerlist *peer_list ) {
  size_t i;
  for( i=0; i<OT_POOLS_COUNT; ++i )
    if( peer_list->peers[i].data )
      free( peer_list->peers[i].data );
  free( peer_list );
}

/* This is the non-generic delete from vector-operation specialized for torrents in buckets.
   it returns 0 if the hash wasn't found in vector
              1 if the torrent was removed from vector
*/
static int vector_remove_torrent( ot_vector *vector, ot_hash *hash ) {
  int exactmatch;
  ot_torrent *end = ((ot_torrent*)vector->data) + vector->size;
  ot_torrent *match;

  if( !vector->size ) return 0;

  match = binary_search( hash, vector->data, vector->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  if( !exactmatch ) return 0;

  /* If this is being called after a unsuccessful malloc() for peer_list
     in add_peer_to_torrent, match->peer_list actually might be NULL */
  if( match->peer_list) free_peerlist( match->peer_list );

  memmove( match, match + 1, sizeof(ot_torrent) * ( end - match - 1 ) );
  if( ( --vector->size * OT_VECTOR_SHRINK_THRESH < vector->space ) && ( vector->space > OT_VECTOR_MIN_MEMBERS ) ) {
    vector->space /= OT_VECTOR_SHRINK_RATIO;
    vector->data = realloc( vector->data, vector->space * sizeof( ot_torrent ) );
  }
  return 1;
}

/* This function deallocates all timedouted pools and shifts all other pools
   it Returns 1 if torrent itself has not seen an announce for more than OT_TORRENT_TIMEOUT time units
              0 if torrent is not yet timed out
   Note: We expect NOW as a parameter since calling time() may be expensive
*/
static int clean_peerlist( time_t time_now, ot_peerlist *peer_list ) {
  int i, timedout = (int)( time_now - peer_list->base );

  if( !timedout ) return 0;
  if( timedout > OT_POOLS_COUNT ) timedout = OT_POOLS_COUNT;

  for( i = OT_POOLS_COUNT - timedout; i < OT_POOLS_COUNT; ++i )
    free( peer_list->peers[i].data);

  memmove( peer_list->peers + timedout, peer_list->peers, sizeof( ot_vector ) * (OT_POOLS_COUNT-timedout) );
  byte_zero( peer_list->peers, sizeof( ot_vector ) * timedout );

  memmove( peer_list->seed_count + timedout, peer_list->seed_count, sizeof( size_t ) * ( OT_POOLS_COUNT - timedout) );
  byte_zero( peer_list->seed_count, sizeof( size_t ) * timedout );

  if( timedout == OT_POOLS_COUNT )
    return time_now - peer_list->base > OT_TORRENT_TIMEOUT;

  peer_list->base = time_now;
  return 0;
}

ot_torrent *add_peer_to_torrent( ot_hash *hash, ot_peer *peer ) {
  int          exactmatch;
  ot_torrent *torrent;
  ot_peer    *peer_dest;
  ot_vector  *torrents_list = &all_torrents[*hash[0]], *peer_pool;
#if defined( WANT_CLOSED_TRACKER ) || defined( WANT_BLACKLIST )
  struct stat dummy_sb;
  char       *fn = to_hex( (ot_byte*)hash );
#endif

#ifdef WANT_CLOSED_TRACKER
  if( g_closedtracker && stat( fn, &dummy_sb ) )
    return OT_TORRENT_NOT_ON_WHITELIST;
#endif

#ifdef WANT_BLACKLIST
  if( g_check_blacklist && !stat( fn - 1, &dummy_sb ) )
    return OT_TORRENT_ON_BLACKLIST;
#endif

  torrent = vector_find_or_insert( torrents_list, (void*)hash, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  if( !torrent ) return NULL;

  if( !exactmatch ) {
    /* Create a new torrent entry, then */
    memmove( &torrent->hash, hash, sizeof( ot_hash ) );

    if( !( torrent->peer_list = malloc( sizeof (ot_peerlist) ) ) ) {
      vector_remove_torrent( torrents_list, hash );
      return NULL;
    }

    byte_zero( torrent->peer_list, sizeof( ot_peerlist ) );
    torrent->peer_list->base = NOW;
  } else
    clean_peerlist( NOW, torrent->peer_list );

  /* Sanitize flags: Whoever claims to have completed download, must be a seeder */
  if( ( OT_FLAG( peer ) & ( PEER_FLAG_COMPLETED | PEER_FLAG_SEEDING ) ) == PEER_FLAG_COMPLETED )
    OT_FLAG( peer ) ^= PEER_FLAG_COMPLETED;

  peer_pool = &torrent->peer_list->peers[0];
  peer_dest = vector_find_or_insert( peer_pool, (void*)peer, sizeof( ot_peer ), OT_PEER_COMPARE_SIZE, &exactmatch );

  /* If we hadn't had a match in current pool, create peer there and
     remove it from all older pools */
  if( !exactmatch ) {
    int i;
    memmove( peer_dest, peer, sizeof( ot_peer ) );

    if( OT_FLAG( peer ) & PEER_FLAG_COMPLETED )
      torrent->peer_list->downloaded++;

    if( OT_FLAG(peer) & PEER_FLAG_SEEDING )
      torrent->peer_list->seed_count[0]++;

    for( i=1; i<OT_POOLS_COUNT; ++i ) {
      switch( vector_remove_peer( &torrent->peer_list->peers[i], peer, 0 ) ) {
        case 0: continue;
        case 2: torrent->peer_list->seed_count[i]--;
        case 1: default: return torrent;
      }
    }
  } else {
    if( (OT_FLAG(peer_dest) & PEER_FLAG_SEEDING ) && !(OT_FLAG(peer) & PEER_FLAG_SEEDING ) )
      torrent->peer_list->seed_count[0]--;
    if( !(OT_FLAG(peer_dest) & PEER_FLAG_SEEDING ) && (OT_FLAG(peer) & PEER_FLAG_SEEDING ) )
      torrent->peer_list->seed_count[0]++;
    if( !(OT_FLAG( peer_dest ) & PEER_FLAG_COMPLETED ) && (OT_FLAG( peer ) & PEER_FLAG_COMPLETED ) )
      torrent->peer_list->downloaded++;
    if( OT_FLAG( peer_dest ) & PEER_FLAG_COMPLETED )
      OT_FLAG( peer ) |= PEER_FLAG_COMPLETED;

    memmove( peer_dest, peer, sizeof( ot_peer ) );
  }

  return torrent;
}

/* Compiles a list of random peers for a torrent
   * reply must have enough space to hold 92+6*amount bytes
   * Selector function can be anything, maybe test for seeds, etc.
   * RANDOM may return huge values
   * does not yet check not to return self
*/
size_t return_peers_for_torrent( ot_torrent *torrent, size_t amount, char *reply, int is_tcp ) {
  char  *r = reply;
  size_t peer_count, seed_count, index;

#ifdef WANT_CLOSED_TRACKER
  if( torrent == OT_TORRENT_NOT_ON_WHITELIST ) {
    const char * const notvalid = "d14:failure reason43:This torrent is not served by this tracker.e";
    memmove( reply, notvalid, sizeof(notvalid));
    return sizeof(notvalid);
  }
#endif

#ifdef WANT_BLACKLIST
  if( torrent == OT_TORRENT_ON_BLACKLIST ) {
    const char * const blacklisted = "d14:failure reason29:This torrent is black listed.e";
    memmove( reply, blacklisted, sizeof(blacklisted));
    return sizeof(blacklisted);
  }
#endif

  for( peer_count = seed_count = index = 0; index < OT_POOLS_COUNT; ++index ) {
    peer_count += torrent->peer_list->peers[index].size;
    seed_count += torrent->peer_list->seed_count[index];
  }
  if( peer_count < amount ) amount = peer_count;

  if( is_tcp )
    r += sprintf( r, "d8:completei%zde10:incompletei%zde8:intervali%ie5:peers%zd:", seed_count, peer_count-seed_count, OT_CLIENT_REQUEST_INTERVAL_RANDOM, 6*amount );
  else {
    *(unsigned long*)(r+0) = htonl( OT_CLIENT_REQUEST_INTERVAL_RANDOM );
    *(unsigned long*)(r+4) = htonl( peer_count );
    *(unsigned long*)(r+8) = htonl( seed_count );
    r += 12;
  }

  if( amount ) {
    unsigned int pool_offset, pool_index = 0;;
    unsigned int shifted_pc = peer_count;
    unsigned int shifted_step = 0;
    unsigned int shift = 0;

    /* Make fixpoint arithmetic as exact as possible */
#define MAXPRECBIT (1<<(8*sizeof(int)-3))
    while( !(shifted_pc & MAXPRECBIT ) ) { shifted_pc <<= 1; shift++; }
    shifted_step = shifted_pc/amount;
#undef MAXPRECBIT

    /* Initialize somewhere in the middle of peers so that
       fixpoint's aliasing doesn't alway miss the same peers */
    pool_offset = random() % peer_count;

    for( index = 0; index < amount; ++index ) {
      /* This is the aliased, non shifted range, next value may fall into */
      unsigned int diff = ( ( ( index + 1 ) * shifted_step ) >> shift ) -
                          ( (   index       * shifted_step ) >> shift );
      pool_offset += 1 + random() % diff;

      while( pool_offset >= torrent->peer_list->peers[pool_index].size ) {
        pool_offset -= torrent->peer_list->peers[pool_index].size;
        pool_index = ( pool_index + 1 ) % OT_POOLS_COUNT;
      }

      memmove( r, ((ot_peer*)torrent->peer_list->peers[pool_index].data) + pool_offset, 6 );
      r += 6;
    }
  }
  if( is_tcp )
    *r++ = 'e';

  return r - reply;
}

/* Fetch full scrape info for all torrents */
size_t return_fullscrape_for_tracker( char **reply ) {
  size_t torrent_count = 0, j;
  int    i, k;
  char  *r;
  time_t time_now = NOW;

  for( i=0; i<256; ++i ) {
    ot_vector *torrents_list = &all_torrents[i];
    torrent_count += torrents_list->size;
  }

  if( !( r = *reply = malloc( 128*torrent_count ) ) ) return 0;

  memmove( r, "d5:filesd", 9 ); r += 9;
  for( i=0; i<256; ++i ) {
    ot_vector *torrents_list = &all_torrents[i];
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      ot_hash     *hash      =&( ((ot_torrent*)(torrents_list->data))[j] ).hash;
      size_t       peers = 0, seeds = 0;
      clean_peerlist( time_now, peer_list );
      for( k=0; k<OT_POOLS_COUNT; ++k ) {
        peers += peer_list->peers[k].size;
        seeds += peer_list->seed_count[k];
      }
      memmove( r, "20:", 3 ); r+=3;
      memmove( r, hash, 20 ); r+=20;
      r += sprintf( r, "d8:completei%zde10:downloadedi%zde10:incompletei%zdee", seeds, peer_list->downloaded, peers-seeds );
    }
  }

  *r++='e'; *r++='e';
  return r - *reply;
}

size_t return_memstat_for_tracker( char **reply ) {
  size_t torrent_count = 0, j;
  int    i, k;
  char  *r;
  time_t time_now = NOW;

  for( i=0; i<256; ++i ) {
    ot_vector *torrents_list = &all_torrents[i];
    torrent_count += torrents_list->size;
  }

  if( !( r = *reply = malloc( 256*32 + (43+OT_POOLS_COUNT*32)*torrent_count ) ) ) return 0;

  for( i=0; i<256; ++i )
    r += sprintf( r, "%02X: %08X %08X\n", i, (unsigned int)all_torrents[i].size, (unsigned int)all_torrents[i].space );

  for( i=0; i<256; ++i ) {
    ot_vector *torrents_list = &all_torrents[i];
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      ot_hash     *hash      =&( ((ot_torrent*)(torrents_list->data))[j] ).hash;
      r += sprintf( r, "\n%s:\n", to_hex( (ot_byte*)hash ) );
      clean_peerlist( time_now, peer_list );
      for( k=0; k<OT_POOLS_COUNT; ++k )
        r += sprintf( r, "\t%04X %04X\n", ((unsigned int)peer_list->peers[k].size), (unsigned int)peer_list->peers[k].space );
    }
  }

  return r - *reply;
}

/* Fetches scrape info for a specific torrent */
size_t return_scrape_for_torrent( ot_hash *hash, char *reply ) {
  char        *r = reply;
  int          exactmatch, i;
  size_t       peers = 0, seeds = 0;
  ot_vector   *torrents_list = &all_torrents[*hash[0]];
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

  if( !exactmatch ) return sprintf( r, "d5:filesdee" );
  clean_peerlist( NOW, torrent->peer_list );

  for( i=0; i<OT_POOLS_COUNT; ++i ) {
    peers += torrent->peer_list->peers[i].size;
    seeds += torrent->peer_list->seed_count[i];
  }

  memmove( r, "d5:filesd20:", 12 ); memmove( r+12, hash, 20 );
  r += sprintf( r+32, "d8:completei%zde10:downloadedi%zde10:incompletei%zdeeee", seeds, torrent->peer_list->downloaded, peers-seeds ) + 32;

  return r - reply;
}

size_t return_sync_for_torrent( ot_hash *hash, char **reply ) {
  int         exactmatch;
  size_t      peers = 0;
  char       *r;
  ot_vector  *torrents_list = &all_torrents[*hash[0]];
  ot_torrent *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

  if( exactmatch ) {
    clean_peerlist( NOW, torrent->peer_list );
    peers = torrent->peer_list->peers[0].size;
  }

  if( !( r = *reply = malloc( 10 + peers * sizeof( ot_peer ) ) ) ) return 0;

  memmove( r, "d4:sync", 7 );
  r += 7;
  r += sprintf( r, "%zd:", peers * sizeof( ot_peer ) );
  if( peers ) {
    memmove( r, torrent->peer_list->peers[0].data, peers * sizeof( ot_peer ) );
    r += peers * sizeof( ot_peer );
  }
  *r++ = 'e';
  return r - *reply;
}

typedef struct { int val; ot_torrent * torrent; } ot_record;

/* Fetches stats from tracker */
size_t return_stats_for_tracker( char *reply, int mode ) {
  time_t    time_now = NOW;
  size_t    torrent_count = 0, peer_count = 0, seed_count = 0, j;
  ot_record top5s[5], top5c[5];
  char     *r  = reply;
  int       i,k;

  byte_zero( top5s, sizeof( top5s ) );
  byte_zero( top5c, sizeof( top5c ) );

  for( i=0; i<256; ++i ) {
    ot_vector *torrents_list = &all_torrents[i];
    torrent_count += torrents_list->size;
    for( j=0; j<torrents_list->size; ++j ) {
      ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[j] ).peer_list;
      size_t local_peers = 0, local_seeds = 0;

      if( clean_peerlist( time_now, peer_list ) ) {
        ot_hash *hash =&( ((ot_torrent*)(torrents_list->data))[j] ).hash;
        vector_remove_torrent( torrents_list, hash );
        --j;
        continue;
      }
      for( k=0; k<OT_POOLS_COUNT; ++k ) {
        local_peers += peer_list->peers[k].size;
        local_seeds += peer_list->seed_count[k];
      }
      if( mode == STATS_TOP5 ) {
        int idx = 4; while( (idx >= 0) && ( local_peers > top5c[idx].val ) ) --idx;
        if ( idx++ != 4 ) {
          memmove( top5c + idx + 1, top5c + idx, ( 4 - idx ) * sizeof( ot_record ) );
          top5c[idx].val = local_peers;
          top5c[idx].torrent = (ot_torrent*)(torrents_list->data) + j;
        }
        idx = 4; while( (idx >= 0) && ( local_seeds > top5s[idx].val ) ) --idx;
        if ( idx++ != 4 ) {
          memmove( top5s + idx + 1, top5s + idx, ( 4 - idx ) * sizeof( ot_record ) );
          top5s[idx].val = local_seeds;
          top5s[idx].torrent = (ot_torrent*)(torrents_list->data) + j;
        }
      }
      peer_count += local_peers; seed_count += local_seeds;
    }
  }
  if( mode == STATS_TOP5 ) {
    int idx;
    r += sprintf( r, "Top5 torrents by peers:\n" );
    for( idx=0; idx<5; ++idx )
      if( top5c[idx].torrent )
        r += sprintf( r, "\t%i\t%s\n", top5c[idx].val, to_hex(top5c[idx].torrent->hash) );
    r += sprintf( r, "Top5 torrents by seeds:\n" );
    for( idx=0; idx<5; ++idx )
      if( top5s[idx].torrent )
        r += sprintf( r, "\t%i\t%s\n", top5s[idx].val, to_hex(top5s[idx].torrent->hash) );
  } else {
    r += sprintf( r, "%zd\n%zd\nopentracker serving %zd torrents\nopentracker", peer_count, seed_count, torrent_count );
  }

  return r - reply;
}

void remove_peer_from_torrent( ot_hash *hash, ot_peer *peer ) {
  int          exactmatch, i;
  ot_vector   *torrents_list = &all_torrents[*hash[0]];
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

  if( !exactmatch ) return;

  /* Maybe this does the job */
  if( clean_peerlist( NOW, torrent->peer_list ) ) {
    vector_remove_torrent( torrents_list, hash );
    return;
  }

  for( i=0; i<OT_POOLS_COUNT; ++i )
    switch( vector_remove_peer( &torrent->peer_list->peers[i], peer, i == 0 ) ) {
      case 0: continue;
      case 2: torrent->peer_list->seed_count[i]--;
      case 1: default: return;
    }
}

int init_logic( const char * const serverdir ) {
  if( serverdir && chdir( serverdir ) ) {
    fprintf( stderr, "Could not chdir() to %s\n", serverdir );
    return -1;
  }

  srandom( time(NULL) );

  /* Initialize control structures */
  byte_zero( all_torrents, sizeof (all_torrents) );

  return 0;
}

void deinit_logic( void ) {
  int i;
  size_t j;

  /* Free all torrents... */
  for(i=0; i<256; ++i ) {
    if( all_torrents[i].size ) {
      ot_torrent *torrents_list = (ot_torrent*)all_torrents[i].data;
      for( j=0; j<all_torrents[i].size; ++j )
        free_peerlist( torrents_list[j].peer_list );
      free( all_torrents[i].data );
    }
  }
  byte_zero( all_torrents, sizeof (all_torrents));
}