episodecache.go

   1 package anidb
   2
   3 import (
   4         "encoding/gob"
   5         "strconv"
   6         "strings"
   7         "time"
   8 )
   9
  10 func init() {
  11         gob.RegisterName("*github.com/Kovensky/go-anidb.Episode", &Episode{})
  12 }
  13
  14 func (e *Episode) Touch() {
  15         e.Cached = time.Now()
  16 }
  17
  18 func (e *Episode) IsStale() bool {
  19         if e == nil {
  20                 return true
  21         }
  22         return time.Now().Sub(e.Cached) > EpisodeCacheDuration
  23 }
  24
  25 // Unique Episode IDentifier.
  26 type EID int
  27
  28 // Retrieves the Episode corresponding to this EID from the cache.
  29 func (eid EID) Episode() *Episode {
  30         var e Episode
  31         if cache.Get(&e, "eid", eid) == nil {
  32                 return &e
  33         }
  34         return nil
  35 }
  36
  37 func cacheEpisode(ep *Episode) {
  38         cache.Set(ep.AID, "aid", "by-eid", ep.EID)
  39         cache.Set(ep, "eid", ep.EID)
  40 }
  41
  42 // Retrieves the Episode from the cache if possible.
  43 //
  44 // If the result is stale, then queries the UDP API to
  45 // know which AID owns this EID, then gets the episode
  46 // from the Anime.
  47 func (adb *AniDB) EpisodeByID(eid EID) <-chan *Episode {
  48         keys := []cacheKey{"eid", eid}
  49         ch := make(chan *Episode, 1)
  50
  51         ic := make(chan Cacheable, 1)
  52         go func() { ch <- (<-ic).(*Episode); close(ch) }()
  53         if intentMap.Intent(ic, keys...) {
  54                 return ch
  55         }
  56
  57         if !cache.CheckValid(keys...) {
  58                 intentMap.Notify((*Episode)(nil), keys...)
  59                 return ch
  60         }
  61
  62         if e := eid.Episode(); !e.IsStale() {
  63                 intentMap.Notify(e, keys...)
  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                 aid := AID(0)
  72                 ok := cache.Get(&aid, "aid", "by-eid", eid) == nil
  73
  74                 udpDone := false
  75
  76                 var e *Episode
  77                 for i := 0; i < 2; i++ {
  78                         if !ok && udpDone {
  79                                 // couldn't get anime and we already ran the EPISODE query
  80                                 break
  81                         }
  82
  83                         if !ok {
  84                                 // We don't know what the AID is yet.
  85                                 reply := <-adb.udp.SendRecv("EPISODE", paramMap{"eid": eid})
  86
  87                                 if reply.Error() == nil {
  88                                         parts := strings.Split(reply.Lines()[1], "|")
  89
  90                                         if id, err := strconv.ParseInt(parts[1], 10, 32); err == nil {
  91                                                 ok = true
  92                                                 aid = AID(id)
  93                                         }
  94                                 } else if reply.Code() == 340 {
  95                                         cache.MarkInvalid(keys...)
  96                                 } else {
  97                                         break
  98                                 }
  99                                 udpDone = true
 100                         }
 101                         <-adb.AnimeByID(AID(aid)) // this caches episodes...
 102                         e = eid.Episode()         // ...so this is now a cache hit
 103
 104                         if e != nil {
 105                                 break
 106                         } else {
 107                                 // if this is somehow still a miss, then the EID<->AID map broke
 108                                 cache.Delete("aid", "by-eid", eid)
 109                                 ok = false
 110                         }
 111                 }
 112                 intentMap.Notify(e, keys...)
 113         }()
 114         return ch
 115 }