udp/comm.go

   1 // Low-level AniDB UDP API client library
   2 //
   3 // Implements the commands essential to setting up and tearing down an API connection,
   4 // as well as an asynchronous layer. Throttles sends internally according to API spec.
   5 //
   6 // This library doesn't implement caching; beware since aggressive caching is an
   7 // implementation requirement. Not doing so can get you banned.
   8 package udp
   9
  10 import (
  11         "bytes"
  12         "compress/zlib"
  13         "crypto/aes"
  14         "crypto/cipher"
  15         "crypto/md5"
  16         "fmt"
  17         "io"
  18         "io/ioutil"
  19         "log"
  20         "net"
  21         "sort"
  22         "strings"
  23         "sync"
  24         "time"
  25 )
  26
  27 const (
  28         AniDBUDPServer = "api.anidb.net"
  29         AniDBUDPPort   = 9000
  30 )
  31
  32 type AniDBUDP struct {
  33         KeepAliveInterval time.Duration // Interval between keep-alive packets; only sent when PUSH notifications are enabled (default: 20 minutes)
  34         Timeout           time.Duration // The time to wait before a packet is considered lost (default: 45 seconds)
  35         Notifications     chan APIReply // Channel where PUSH notifications are sent to
  36
  37         session string
  38
  39         conn *net.UDPConn
  40         ecb  *ecbState
  41
  42         counter uint16
  43         ctrLock sync.Mutex
  44
  45         tagRouter  map[string]chan APIReply
  46         routerLock sync.RWMutex
  47
  48         sendCh chan packet
  49
  50         breakRecv chan bool
  51         breakSend chan bool
  52
  53         // notifyState *notifyState
  54         pingTimer *time.Timer
  55 }
  56
  57 // Creates and initializes the AniDBUDP struct
  58 func NewAniDBUDP() *AniDBUDP {
  59         c := &AniDBUDP{
  60                 KeepAliveInterval: 20 * time.Minute,
  61                 Timeout:           45 * time.Second,
  62                 Notifications:     make(chan APIReply, 5),
  63                 tagRouter:         make(map[string]chan APIReply),
  64         }
  65         return c
  66 }
  67
  68 // Key-value list of parameters.
  69 type ParamMap map[string]interface{}
  70
  71 // Returns a query-like string representation of the ParamMap
  72 func (m ParamMap) String() string {
  73         keys := make([]string, 0, len(m))
  74         for k, _ := range m {
  75                 keys = append(keys, k)
  76         }
  77         sort.Strings(keys)
  78
  79         parts := make([]string, 0, len(m))
  80         for _, k := range keys {
  81                 parts = append(parts, strings.Join([]string{k, fmt.Sprint((m)[k])}, "="))
  82         }
  83         return strings.Join(parts, "&")
  84 }
  85
  86 // Sends the requested query to the AniDB UDP API server.
  87 //
  88 // Returns a channel through which the eventual reply is sent.
  89 //
  90 // See http://wiki.anidb.net/w/UDP_API_Definition for the defined commands.
  91 func (a *AniDBUDP) SendRecv(command string, args ParamMap) <-chan APIReply {
  92         a.ctrLock.Lock()
  93         tag := fmt.Sprintf("T%d", a.counter)
  94         a.counter++
  95         a.ctrLock.Unlock()
  96
  97         args["tag"] = tag
  98         if a.session != "" {
  99                 args["s"] = a.session
 100         }
 101
 102         if err := a.dial(); err != nil {
 103                 ch <- newErrorWrapper(err)
 104                 close(ch)
 105                 return ch
 106         }
 107
 108         ch := make(chan APIReply, 1)
 109
 110         a.routerLock.Lock()
 111         a.tagRouter[tag] = ch
 112         a.routerLock.Unlock()
 113
 114         reply := make(chan APIReply, 1)
 115         go func() {
 116                 <-a.send(command, args)
 117                 timeout := time.After(a.Timeout)
 118
 119                 select {
 120                 case <-timeout:
 121                         a.routerLock.Lock()
 122                         delete(a.tagRouter, tag)
 123                         a.routerLock.Unlock()
 124                         close(ch)
 125
 126                         reply <- TimeoutError
 127                         close(reply)
 128
 129                         log.Println("!!! Timeout")
 130                 case r := <-ch:
 131                         a.routerLock.Lock()
 132                         delete(a.tagRouter, tag)
 133                         a.routerLock.Unlock()
 134                         close(ch)
 135
 136                         reply <- r
 137                         close(reply)
 138                 }
 139         }()
 140         return reply
 141 }
 142
 143 var laddr, _ = net.ResolveUDPAddr("udp4", "0.0.0.0:0")
 144
 145 func (a *AniDBUDP) dial() (err error) {
 146         if a.conn != nil {
 147                 return nil
 148         }
 149
 150         srv := fmt.Sprintf("%s:%d", AniDBUDPServer, AniDBUDPPort)
 151         if raddr, err := net.ResolveUDPAddr("udp4", srv); err != nil {
 152                 return err
 153         } else {
 154                 a.conn, err = net.DialUDP("udp4", laddr, raddr)
 155
 156                 if a.breakSend != nil {
 157                         a.breakSend <- true
 158                         <-a.breakSend
 159                 } else {
 160                         a.breakSend = make(chan bool)
 161                 }
 162                 a.sendCh = make(chan packet, 10)
 163                 go a.sendLoop()
 164
 165                 if a.breakRecv != nil {
 166                         a.breakRecv <- true
 167                         <-a.breakRecv
 168                 } else {
 169                         a.breakRecv = make(chan bool)
 170                 }
 171                 go a.recvLoop()
 172         }
 173         return err
 174 }
 175
 176 func (a *AniDBUDP) send(command string, args ParamMap) chan bool {
 177         str := command
 178         arg := args.String()
 179         if len(arg) > 0 {
 180                 str = strings.Join([]string{command, arg}, " ")
 181         }
 182         log.Println(">>>", str)
 183
 184         p := makePacket([]byte(str), a.ecb)
 185
 186         sendPacket(p, a.sendCh)
 187 }
 188
 189 type packet struct {
 190         b    []byte
 191         err  error
 192         sent chan bool
 193 }
 194
 195 func (a *AniDBUDP) sendLoop() {
 196         for {
 197                 select {
 198                 case <-a.breakSend:
 199                         a.breakSend <- true
 200                         return
 201                 case pkt := <-a.sendCh:
 202                         a.conn.Write(pkt.b)
 203
 204                         // send twice: once for confirming with the queue,
 205                         // again for timeout calculations
 206                         for i := 0; i < 2; i++ {
 207                                 pkt.sent <- true
 208                         }
 209                 }
 210         }
 211 }
 212
 213 func (a *AniDBUDP) recvLoop() {
 214         pkt := make(chan packet, 1)
 215         brk := make(chan bool)
 216         go func() {
 217                 for {
 218                         select {
 219                         case <-brk:
 220                                 brk <- true
 221                                 return
 222                         default:
 223                                 b, err := getPacket(a.conn, a.ecb)
 224                                 pkt <- packet{b: b, err: err}
 225                         }
 226                 }
 227         }()
 228
 229         var pingTimer <-chan time.Time
 230
 231         for {
 232                 if a.pingTimer != nil {
 233                         pingTimer = a.pingTimer.C
 234                 }
 235
 236                 select {
 237                 case <-a.breakRecv:
 238                         brk <- true
 239                         <-brk
 240                         a.breakRecv <- true
 241                         return
 242                 case <-pingTimer:
 243                         go func() {
 244                                 if a.KeepAliveInterval >= 30*time.Minute {
 245                                         if (<-a.Uptime()).Error() != nil {
 246                                                 return
 247                                         }
 248                                 } else if (<-a.Ping()).Error() != nil {
 249                                         return
 250                                 }
 251                                 a.pingTimer.Reset(a.KeepAliveInterval)
 252                         }()
 253                 case p := <-pkt:
 254                         b, err := p.b, p.err
 255
 256                         if err != nil && err != io.EOF && err != zlib.ErrChecksum {
 257                                 // can UDP recv even raise other errors?
 258                                 panic("UDP recv: " + err.Error())
 259                         }
 260
 261                         if r := newGenericReply(b); r != nil {
 262                                 if a.pingTimer != nil {
 263                                         a.pingTimer.Reset(a.KeepAliveInterval)
 264                                 }
 265
 266                                 if err == zlib.ErrChecksum {
 267                                         r.truncated = true
 268                                 }
 269
 270                                 a.routerLock.RLock()
 271                                 if ch, ok := a.tagRouter[r.Tag()]; ok {
 272
 273                                         log.Println("<<<", string(b))
 274                                         ch <- r
 275                                 } else {
 276                                         c := r.Code()
 277                                         if c >= 720 && c < 799 {
 278                                                 // notices that need PUSHACK
 279                                                 id := strings.Fields(r.Text())[0]
 280                                                 a.send("PUSHACK", paramMap{"nid": id})
 281
 282                                                 a.Notifications <- r
 283                                         } else if c == 799 {
 284                                                 // notice that doesn't need PUSHACK
 285                                                 a.Notifications <- r
 286                                         } else if c == 270 {
 287                                                 // PUSH enabled
 288                                                 if a.pingTimer == nil {
 289                                                         a.pingTimer = time.NewTimer(a.KeepAliveInterval)
 290                                                 }
 291                                         } else if c == 370 {
 292                                                 // PUSH disabled
 293                                                 a.pingTimer = nil
 294                                         } else if c == 701 || c == 702 {
 295                                                 // PUSHACK ACK, no need to route
 296                                         } else if c == 281 || c == 282 || c == 381 || c == 382 {
 297                                                 // NOTIFYACK reply, ignore
 298                                         } else {
 299                                                 // untagged error, broadcast to all
 300                                                 log.Println("<!<", string(b))
 301                                                 for _, ch := range a.tagRouter {
 302                                                         ch <- r
 303                                                 }
 304                                         }
 305                                 }
 306                                 a.routerLock.RUnlock()
 307                         }
 308                 }
 309         }
 310 }