Hopefully prevent race conditions

microchat.go

@@ -1,105 +1,125 @@
 package main
 
 import (
-  "net/http"
-  "log"
-  "time"
-  "strconv"
-  "encoding/json"
+	"encoding/json"
+	"log"
+	"net/http"
+	"strconv"
+	"time"
 )
 
 type Message struct {
-  When int64
-  Who string
-  Text string
+	When int64
+	Who  string
+	Text string
 }
 
 type Forum struct {
-  Name string
-  Log []Message
+	Name  string
+	Log   []Message
+	SendQ chan Message
+	LogQ  chan []Message
 }
 
 var foraByName map[string]*Forum
 
+func (f *Forum) HandleSends() {
+	for m := range f.SendQ {
+		f.Log = append(f.Log, m)
+	}
+}
+
+func (f *Forum) HandleReads() {
+	for {
+		f.LogQ <- f.Log
+	}
+}
+
 func newForum(name string) *Forum {
-  f := &Forum{
-    Name: name,
-  }
-  foraByName[name] = f
-  return f
+	f := &Forum{
+		Name:  name,
+		SendQ: make(chan Message, 10),
+		LogQ:  make(chan []Message, 10),
+	}
+	go f.HandleSends()
+	go f.HandleReads()
+
+	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)
+	message := Message{
+		When: time.Now().Unix(),
+		Who:  r.FormValue("who"),
+		Text: r.FormValue("text"),
+	}
+	forumName := r.FormValue("forum")
+	f, ok := foraByName[forumName]
+	if !ok {
+		f = newForum(forumName)
+	}
+	f.SendQ <- 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
-  }
+	r.ParseForm()
 
-  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:])
+	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
+	}
+
+	f, ok := foraByName[forumName]
+	if !ok {
+		http.NotFound(w, r)
+		return
+	}
+
+	log := <-f.LogQ
+
+	pos := len(log) - entries
+	if pos < 0 {
+		pos = 0
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+
+	e := json.NewEncoder(w)
+	e.Encode(f.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))
+	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))
 }

static/microchat.css

@@ -11,6 +11,10 @@ body {
 input[name="who"] {
   width: 6em;
 }
+input[name="text"] {
+  min-width: 30em;
+  width: calc(90% - 6em);
+}
 
 .when {
   color: #888;

static/microchat.js

@@ -18,7 +18,6 @@ function μchatInit(initEvent) {
     let form = event.target
     let inp = form.elements.text
     let body = new FormData(form)
-    console.log(form, body)
     fetch("say", {
       method: "POST",
       body: body,
@@ -86,6 +85,9 @@ function μchatInit(initEvent) {
         .then(updateLog)
       }
     })
+    .catch(err => {
+      toast("Server error: " + err)
+    })
   }
 
   for (let f of document.forms) {