episodecache.go

   1 package anidb
   2
   3 import (
   4         "encoding/gob"
   5         "strconv"
   6         "strings"
   7         "sync"
   8         "time"
   9 )
  10
  11 func init() {
  12         gob.RegisterName("*github.com/Kovensky/go-anidb.Episode", &Episode{})
  13 }
  14
  15 func (e *Episode) Touch() {
  16         e.Cached = time.Now()
  17 }
  18
  19 func (e *Episode) IsStale() bool {
  20         if e == nil {
  21                 return true
  22         }
  23         return time.Now().Sub(e.Cached) > EpisodeCacheDuration
  24 }
  25
  26 var eidAidMap = map[EID]AID{}
  27 var eidAidLock = sync.RWMutex{}
  28
  29 // Unique Episode IDentifier.
  30 type EID int
  31
  32 // Retrieves the Episode corresponding to this EID from the cache.
  33 func (eid EID) Episode() *Episode {
  34         e, _ := caches.Get(episodeCache).Get(int(eid)).(*Episode)
  35         return e
  36 }
  37
  38 func cacheEpisode(ep *Episode) {
  39         eidAidLock.Lock()
  40         defer eidAidLock.Unlock()
  41
  42         eidAidMap[ep.EID] = ep.AID
  43         caches.Get(episodeCache).Set(int(ep.EID), ep)
  44 }
  45
  46 // Retrieves the Episode from the cache if possible.
  47 //
  48 // If the result is stale, then queries the UDP API to
  49 // know which AID owns this EID, then gets the episodes
  50 // from the Anime.
  51 func (adb *AniDB) EpisodeByID(eid EID) <-chan *Episode {
  52         ch := make(chan *Episode, 1)
  53
  54         if e := eid.Episode(); e != nil && !e.IsStale() {
  55                 ch <- e
  56                 close(ch)
  57                 return ch
  58         }
  59
  60         ec := caches.Get(episodeCache)
  61         ic := make(chan Cacheable, 1)
  62         go func() { ch <- (<-ic).(*Episode); close(ch) }()
  63         if ec.Intent(int(eid), ic) {
  64                 return ch
  65         }
  66
  67         go func() {
  68                 // The UDP API data is worse than the HTTP API anime data,
  69                 // try and get from the corresponding Anime
  70
  71                 eidAidLock.RLock()
  72                 aid, ok := eidAidMap[eid]
  73                 eidAidLock.RUnlock()
  74
  75                 udpDone := false
  76
  77                 var e *Episode
  78                 for i := 0; i < 2; i++ {
  79                         if !ok && udpDone {
  80                                 // couldn't get anime and we already ran the EPISODE query
  81                                 break
  82                         }
  83
  84                         if !ok {
  85                                 // We don't know what the AID is yet.
  86                                 reply := <-adb.udp.SendRecv("EPISODE", paramMap{"eid": eid})
  87
  88                                 if reply.Error() == nil {
  89                                         parts := strings.Split(reply.Lines()[1], "|")
  90
  91                                         if id, err := strconv.ParseInt(parts[1], 10, 32); err == nil {
  92                                                 ok = true
  93                                                 aid = AID(id)
  94                                         }
  95                                 } else {
  96                                         break
  97                                 }
  98                                 udpDone = true
  99                         }
 100                         <-adb.AnimeByID(AID(aid)) // this caches episodes...
 101                         e = eid.Episode()         // ...so this is now a cache hit
 102
 103                         if e != nil {
 104                                 break
 105                         } else {
 106                                 // if this is somehow still a miss, then the EID<->AID map broke
 107                                 eidAidLock.Lock()
 108                                 delete(eidAidMap, eid)
 109                                 eidAidLock.Unlock()
 110
 111                                 ok = false
 112                         }
 113                 }
 114                 // Caching (and channel broadcasting) done by AnimeByID
 115         }()
 116         return ch
 117 }