git.scottworley.com Git - reliable-chat/blob - server/server.go

   1 package main
   2
   3 import "container/list"
   4 import "encoding/json"
   5 import "log"
   6 import "net/http"
   7 import "time"
   8
   9 type Message struct {
  10         Time time.Time
  11         Text string
  12 }
  13
  14 type StoreRequest struct {
  15         StartTime time.Time
  16         Messages  chan<- []Message
  17 }
  18
  19 type Store struct {
  20         Add chan *Message
  21         Get chan *StoreRequest
  22 }
  23
  24 // TODO: Monotonic clock
  25
  26 func manage_store(store Store) {
  27         messages := list.New()
  28         message_count := 0
  29         max_messages := 1000
  30         waiting := list.New()
  31 main:
  32         for {
  33                 select {
  34                 case new_message, ok := <-store.Add:
  35                         if !ok {
  36                                 break main
  37                         }
  38                         messages.PushBack(new_message)
  39                         for waiter := waiting.Front(); waiter != nil; waiter = waiter.Next() {
  40                                 waiter.Value.(*StoreRequest).Messages <- []Message{*new_message}
  41                                 close(waiter.Value.(*StoreRequest).Messages)
  42                         }
  43                         waiting.Init()
  44                         if message_count < max_messages {
  45                                 message_count++
  46                         } else {
  47                                 messages.Remove(messages.Front())
  48                         }
  49                 case request, ok := <-store.Get:
  50                         if !ok {
  51                                 break main
  52                         }
  53                         if messages.Back() == nil || !request.StartTime.Before(messages.Back().Value.(*Message).Time) {
  54                                 waiting.PushBack(request)
  55                         } else {
  56                                 start := messages.Back()
  57                                 response_size := 1
  58                                 if messages.Front().Value.(*Message).Time.After(request.StartTime) {
  59                                         start = messages.Front()
  60                                         response_size = message_count
  61                                 } else {
  62                                         for start.Prev().Value.(*Message).Time.After(request.StartTime) {
  63                                                 start = start.Prev()
  64                                                 response_size++
  65                                         }
  66                                 }
  67                                 response_messages := make([]Message, 0, response_size)
  68                                 for m := start; m != nil; m = m.Next() {
  69                                         response_messages = append(response_messages, *m.Value.(*Message))
  70                                 }
  71                                 request.Messages <- response_messages
  72                         }
  73                 }
  74         }
  75 }
  76
  77 func start_store() Store {
  78         store := Store{make(chan *Message, 20), make(chan *StoreRequest, 20)}
  79         go manage_store(store)
  80         return store
  81 }
  82
  83 func start_server(store Store) {
  84         http.HandleFunc("/fetch", func(w http.ResponseWriter, r *http.Request) {
  85                 var since time.Time
  86                 url_since := r.FormValue("since")
  87                 if url_since != "" {
  88                         err := json.Unmarshal([]byte(url_since), &since)
  89                         if err != nil {
  90                                 log.Print("fetch: parse since: ", err)
  91                                 w.WriteHeader(http.StatusBadRequest)
  92                                 w.Write([]byte("Could not parse since as date"))
  93                                 return
  94                         }
  95                 }
  96                 messages_from_store := make(chan []Message, 1)
  97                 store.Get <- &StoreRequest{since, messages_from_store}
  98
  99                 json_encoded, err := json.Marshal(<-messages_from_store)
 100                 if err != nil {
 101                         log.Print("json encode: ", err)
 102                         w.WriteHeader(http.StatusInternalServerError)
 103                         return
 104                 }
 105                 w.Header().Add("Content-Type", "application/json")
 106                 w.Write(json_encoded)
 107         })
 108
 109         http.HandleFunc("/speak", func(w http.ResponseWriter, r *http.Request) {
 110                 store.Add <- &Message{time.Now(), r.FormValue("text")}
 111         })
 112
 113         log.Fatal(http.ListenAndServe(":8080", nil))
 114 }
 115
 116 func main() {
 117         store := start_store()
 118         start_server(store)
 119 }