Avoid overwriting others work (fix #107)

handlers.go

@@ -356,6 +356,7 @@ func handlePageRequest(c *gin.Context) {
 		"Debounce":           debounceTime,
 		"DiaryMode":          diaryMode,
 		"Date":               time.Now().Format("2006-01-02"),
+		"UnixTime":           time.Now().Unix(),
 	})
 }
 
@@ -415,6 +416,7 @@ func handlePageUpdate(c *gin.Context) {
 	type QueryJSON struct {
 		Page        string `json:"page"`
 		NewText     string `json:"new_text"`
+		FetchedAt   int64  `json:"fetched_at"`
 		IsEncrypted bool   `json:"is_encrypted"`
 		IsPrimed    bool   `json:"is_primed"`
 		Meta        string `json:"meta"`
@@ -442,6 +444,8 @@ func handlePageUpdate(c *gin.Context) {
 		message = "Locked, must unlock first"
 	} else if p.IsEncrypted {
 		message = "Encrypted, must decrypt first"
+	} else if json.FetchedAt > 0 && p.LastEditUnixTime() > json.FetchedAt {
+		message = "Refusing to overwrite others work"
 	} else {
 		p.Meta = json.Meta
 		p.Update(json.NewText)
@@ -455,7 +459,7 @@ func handlePageUpdate(c *gin.Context) {
 		message = "Saved"
 		success = true
 	}
-	c.JSON(http.StatusOK, gin.H{"success": success, "message": message})
+	c.JSON(http.StatusOK, gin.H{"success": success, "message": message, "unix_time": time.Now().Unix()})
 }
 
 func handlePrime(c *gin.Context) {

page.go

@@ -27,6 +27,14 @@ type Page struct {
 	IsPublished             bool
 }
 
+func (p Page) LastEditTime() time.Time {
+	return time.Unix(p.LastEditUnixTime(), 0)
+}
+
+func (p Page) LastEditUnixTime() int64 {
+	return p.Text.LastEditTime() / 1000000000
+}
+
 func Open(name string) (p *Page) {
 	p = new(Page)
 	p.Name = name

templates/index.tmpl

@@ -182,18 +182,21 @@ body#pad textarea {
                     upload();
                 }, {{ .Debounce }}));
 
+                var lastFetch = {{ .UnixTime }};
                 function upload() {
                     $.ajax({
                         type: 'POST',
                         url: '/update',
                         data: JSON.stringify({
                             new_text: $('#userInput').val(),
-                            page: "{{ .Page }}"
+                            page: "{{ .Page }}",
+                            fetched_at: lastFetch,
                         }),
                         success: function(data) {
                             $('#saveEditButton').removeClass()
                             if (data.success == true) {
                                 $('#saveEditButton').addClass("success");
+                                lastFetch = data.unix_time;
                             } else {
                                 $('#saveEditButton').addClass("failure");
                             }