Hopefully prevent race conditions

microchat.go

@@ -1,11 +1,11 @@
 package main
 
 import (
-  "net/http"
-  "log"
-  "time"
-  "strconv"
 	"encoding/json"
+	"log"
+	"net/http"
+	"strconv"
+	"time"
 )
 
 type Message struct {
@@ -17,14 +17,33 @@ type Message struct {
 type Forum struct {
 	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,
+		SendQ: make(chan Message, 10),
+		LogQ:  make(chan []Message, 10),
 	}
+	go f.HandleSends()
+	go f.HandleReads()
+
 	foraByName[name] = f
 	return f
 }
@@ -35,13 +54,12 @@ func sayHandler(w http.ResponseWriter, r *http.Request) {
 		Who:  r.FormValue("who"),
 		Text: r.FormValue("text"),
 	}
-  log.Println(message)
 	forumName := r.FormValue("forum")
-  forum, ok := foraByName[forumName]
+	f, ok := foraByName[forumName]
 	if !ok {
-    forum = newForum(forumName)
+		f = newForum(forumName)
 	}
-  forum.Log = append(forum.Log, message)
+	f.SendQ <- message
 
 	w.WriteHeader(http.StatusOK)
 }
@@ -66,13 +84,15 @@ func readHandler(w http.ResponseWriter, r *http.Request) {
 		entries = 500
 	}
 
-  forum, ok := foraByName[forumName]
+	f, ok := foraByName[forumName]
 	if !ok {
 		http.NotFound(w, r)
 		return
 	}
 
-  pos := len(forum.Log) - entries
+	log := <-f.LogQ
+
+	pos := len(log) - entries
 	if pos < 0 {
 		pos = 0
 	}
@@ -81,7 +101,7 @@ func readHandler(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusOK)
 
 	e := json.NewEncoder(w)
-  e.Encode(forum.Log[pos:])
+	e.Encode(f.Log[pos:])
 }
 
 func main() {

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) {