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         for {
  32                 select {
  33                 case new_message := <-store.Add:
  34                         messages.PushBack(new_message)
  35                         for waiter := waiting.Front(); waiter != nil; waiter = waiter.Next() {
  36                                 waiter.Value.(StoreRequest).Messages <- []Message{new_message}
  37                                 close(waiter.Value.(StoreRequest).Messages)
  38                         }
  39                         waiting.Init()
  40                         if message_count < max_messages {
  41                                 message_count++
  42                         } else {
  43                                 messages.Remove(messages.Front())
  44                         }
  45                 case request := <-store.Get:
  46                         if messages.Back() == nil || !request.StartTime.Before(messages.Back().Value.(Message).Time) {
  47                                 waiting.PushBack(request)
  48                         } else {
  49                                 start := messages.Back()
  50                                 response_size := 1
  51                                 if messages.Front().Value.(Message).Time.After(request.StartTime) {
  52                                         start = messages.Front()
  53                                         response_size = message_count
  54                                 } else {
  55                                         for start.Prev().Value.(Message).Time.After(request.StartTime) {
  56                                                 start = start.Prev()
  57                                                 response_size++
  58                                         }
  59                                 }
  60                                 response_messages := make([]Message, 0, response_size)
  61                                 for m := start; m != nil; m = m.Next() {
  62                                         response_messages = append(response_messages, m.Value.(Message))
  63                                 }
  64                                 request.Messages <- response_messages
  65                         }
  66                 }
  67         }
  68 }
  69
  70 func start_store() Store {
  71         store := Store{make(chan Message, 20), make(chan StoreRequest, 20)}
  72         go manage_store(store)
  73         return store
  74 }
  75
  76 func start_server(store Store) {
  77         http.HandleFunc("/fetch", func(w http.ResponseWriter, r *http.Request) {
  78                 var since time.Time
  79                 url_since := r.FormValue("since")
  80                 if url_since != "" {
  81                         err := json.Unmarshal([]byte(url_since), &since)
  82                         if err != nil {
  83                                 log.Print("fetch: parse since: ", err)
  84                                 w.WriteHeader(http.StatusBadRequest)
  85                                 w.Write([]byte("Could not parse since as date"))
  86                                 return
  87                         }
  88                 }
  89                 messages_from_store := make(chan []Message, 1)
  90                 store.Get <- StoreRequest{since, messages_from_store}
  91
  92                 json_encoded, err := json.Marshal(<-messages_from_store)
  93                 if err != nil {
  94                         log.Print("json encode: ", err)
  95                         w.WriteHeader(http.StatusInternalServerError)
  96                         return
  97                 }
  98                 w.Header().Add("Content-Type", "application/json")
  99                 w.Write(json_encoded)
 100         })
 101
 102         http.HandleFunc("/speak", func(w http.ResponseWriter, r *http.Request) {
 103                 store.Add <- Message{time.Now(), r.FormValue("text")}
 104         })
 105
 106         log.Fatal(http.ListenAndServe(":8080", nil))
 107 }
 108
 109 func main() {
 110         store := start_store()
 111         start_server(store)
 112 }