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

/* System */
#include <poll.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

/* Opentracker */
#include "ot_accesslist.h"
#include "ot_clean.h"
#include "ot_mutex.h"
#include "ot_stats.h"
#include "ot_vector.h"
#include "trackerlogic.h"

/* Returns amount of removed peers */
static ssize_t clean_single_bucket(ot_peer *peers, size_t peer_count, size_t peer_size, time_t timedout, size_t *removed_seeders) {
  ot_peer *last_peer = peers + peer_count * peer_size, *insert_point;

  /* Two scan modes: unless there is one peer removed, just increase ot_peertime */
  while (peers < last_peer) {
    time_t timediff = timedout + OT_PEERTIME(peers, peer_size);
    if (timediff >= OT_PEER_TIMEOUT)
      break;
    OT_PEERTIME(peers, peer_size)  = timediff;
    peers += peer_size;
  }

  /* If we at least remove one peer, we have to copy */
  for (insert_point = peers; peers < last_peer; peers += peer_size) {
    time_t timediff = timedout + OT_PEERTIME(peers, peer_size);

    if (timediff < OT_PEER_TIMEOUT) {
      OT_PEERTIME(peers, peer_size) = timediff;
      memcpy(insert_point, peers, peer_size);
      insert_point += peer_size;
    } else if (OT_PEERFLAG_D(peers, peer_size) & PEER_FLAG_SEEDING)
      (*removed_seeders)++;
  }

  return (peers - insert_point) / peer_size;
}

int clean_single_peer_list(ot_peerlist *peer_list, size_t peer_size) {
  ot_vector *peer_vector = &peer_list->peers;
  ot_time    timedout    = time_since_minutes(peer_list->base);
  size_t     num_buckets = 1, removed_seeders = 0;

  /* No need to clean empty torrent */
  if (!timedout)
    return 0;

  /* Torrent has idled out */
  if (timedout > OT_TORRENT_TIMEOUT)
    return 1;

  /* Nothing to be cleaned here? Test if torrent is worth keeping */
  if (timedout > OT_PEER_TIMEOUT) {
    if (!peer_list->peer_count)
      return peer_list->down_count ? 0 : 1;
    timedout = OT_PEER_TIMEOUT;
  }

  if (OT_PEERLIST_HASBUCKETS(peer_list)) {
    num_buckets = peer_vector->size;
    peer_vector = (ot_vector *)peer_vector->data;
  }

  while (num_buckets--) {
    size_t removed_peers   = clean_single_bucket(peer_vector->data, peer_vector->size, peer_size, timedout, &removed_seeders);
    peer_list->peer_count -= removed_peers;
    peer_vector->size     -= removed_peers;
    if (removed_peers)
      vector_fixup_peers(peer_vector, peer_size);

    /* Skip to next bucket, a vector containing peers */
    ++peer_vector;
  }

  peer_list->seed_count -= removed_seeders;

  /* See if we need to convert a torrent from simple vector to bucket list */
  if ((peer_list->peer_count > OT_PEER_BUCKET_MINCOUNT) || OT_PEERLIST_HASBUCKETS(peer_list))
    vector_redistribute_buckets(peer_list, peer_size);

  if (peer_list->peer_count)
    peer_list->base = time_now_minutes();
  else {
    /* When we got here, the last time that torrent
     has been touched is OT_PEER_TIMEOUT Minutes before */
    peer_list->base = time_now_minutes() - OT_PEER_TIMEOUT;
  }
  return 0;
}

/* Clean a single torrent
   return 1 if torrent timed out
*/
int clean_single_torrent(ot_torrent *torrent) {
  return clean_single_peer_list(torrent->peer_list6, OT_PEER_SIZE6) * clean_single_peer_list(torrent->peer_list4, OT_PEER_SIZE4);
}

/* Written to once, by clean_deinit, and never read: the byte stays in and
   every sleep after it returns at once */
static int g_clean_pipe[2] = {-1, -1};

static void clean_sleep(void) {
  struct pollfd pfd;

  pfd.fd      = g_clean_pipe[0];
  pfd.events  = POLLIN;
  pfd.revents = 0;

  poll(&pfd, 1, OT_CLEAN_SLEEP / 1000);
}

/* Clean up all peers in one bucket, remove timedout pools and torrents */
static void clean_bucket(size_t bucket) {
  ot_vector *torrents_list = mutex_bucket_lock((int)bucket);
  size_t     toffs;
  int        delta_torrentcount = 0;

  for (toffs = 0; toffs < torrents_list->size; ++toffs) {
    ot_torrent *torrent = ((ot_torrent *)(torrents_list->data)) + toffs;
    if (clean_single_torrent(torrent)) {
      vector_remove_torrent(torrents_list, torrent);
      --delta_torrentcount;
      --toffs;
    }
  }
  mutex_bucket_unlock((int)bucket, delta_torrentcount);
}

static void *clean_worker(void *args) {
  (void)args;
  while (1) {
    size_t bucket = OT_BUCKET_COUNT;
    while (bucket) {
      size_t todo = bucket < OT_CLEAN_BUCKETS_PER_WAKE ? bucket : OT_CLEAN_BUCKETS_PER_WAKE;

      /* One bucket is locked at a time, however many a wake gets through */
      while (todo--)
        clean_bucket(--bucket);

      if (!g_opentracker_running)
        return NULL;
      clean_sleep();
    }
    stats_cleanup();
#ifdef WANT_ACCESSLIST
    accesslist_cleanup();
#endif
  }
  return NULL;
}

static pthread_t thread_id;
void clean_init(void) {
  if (pipe(g_clean_pipe) == -1)
    fprintf(stderr, "Warning: the cleaner has no pipe to be woken through and will take up to one sleep interval to stop.\n");
  pthread_create(&thread_id, NULL, clean_worker, NULL);
}

void clean_deinit(void) {
  const char byte = 0;

  (void)!write(g_clean_pipe[1], &byte, 1);
  pthread_join(thread_id, NULL);

  close(g_clean_pipe[0]);
  close(g_clean_pipe[1]);
}