package main

import (
  "net/http"
  "log"
  "time"
  "strconv"
  "encoding/json"
)

type Message struct {
  When int64
  Who string
  Text string
}

type Forum struct {
  Name string
  Log []Message
}

var foraByName map[string]*Forum

func newForum(name string) *Forum {
  f := &Forum{
    Name: name,
  }
  foraByName[name] = f
  return f
}

func sayHandler(w http.ResponseWriter, r *http.Request) {
  message := Message{
    When: time.Now().Unix(),
    Who: r.FormValue("who"),
    Text: r.FormValue("text"),
  }
  log.Println(message)
  forumName := r.FormValue("forum")
  forum, ok := foraByName[forumName]
  if !ok {
    forum = newForum(forumName)
  }
  forum.Log = append(forum.Log, message)
  
  w.WriteHeader(http.StatusOK)
}

func readHandler(w http.ResponseWriter, r *http.Request) {
  r.ParseForm()
  
  forumName := r.FormValue("forum")
  entriesStr := r.FormValue("entries")
  
  if entriesStr == "" {
    entriesStr = "0"
  }
  entries, err := strconv.Atoi(entriesStr)
  if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
    return
  }
  if entries <= 0 {
    entries = 20
  } else if entries > 500 {
    entries = 500
  }
  
  forum, ok := foraByName[forumName]
  if !ok {
    http.NotFound(w, r)
    return
  }

  pos := len(forum.Log) - entries
  if pos < 0 {
    pos = 0
  }
  
  w.Header().Set("Content-Type", "application/json")
  w.WriteHeader(http.StatusOK)
  
  e := json.NewEncoder(w)
  e.Encode(forum.Log[pos:])
}

func main() {
  http.HandleFunc("/say", sayHandler)
  http.HandleFunc("/read", readHandler)
  http.Handle("/", http.FileServer(http.Dir("static/")))
  
  foraByName = map[string]*Forum{}
  f := newForum("")
  f.Log = []Message{
    {
      When: time.Now().Unix(),
      Who: "(system)",
      Text: "Welcome to μChat",
    },
  }
  
  bind := ":8080"
  log.Printf("Listening on %s", bind)
  log.Fatal(http.ListenAndServe(bind, nil))
}