MM-10249 Adding plugin ability to intercept posts before they reach the DB. (#8791)

* Adding plugin ability to intercept posts before they reach the DB.

* s/envoked/invoked/

plugin/pluginenv/environment.go

@@ -306,6 +306,65 @@ func (h *MultiPluginHooks) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	http.NotFound(w, r)
 }
 
+// MessageWillBePosted invokes the MessageWillBePosted hook for all plugins. Ordering
+// is not guaranteed and the next plugin will get the previous one's modifications.
+// if a plugin rejects a post, the rest of the plugins will not know that an attempt was made.
+// Returns the final result post, or nil if the post was rejected and a string with a reason
+// for the user the message was rejected.
+func (h *MultiPluginHooks) MessageWillBePosted(post *model.Post) (*model.Post, string) {
+	h.env.mutex.RLock()
+	defer h.env.mutex.RUnlock()
+
+	for _, activePlugin := range h.env.activePlugins {
+		if activePlugin.Supervisor == nil {
+			continue
+		}
+		var rejectionReason string
+		post, rejectionReason = activePlugin.Supervisor.Hooks().MessageWillBePosted(post)
+		if post == nil {
+			return nil, rejectionReason
+		}
+	}
+	return post, ""
+}
+
+// MessageWillBeUpdated invokes the MessageWillBeUpdated hook for all plugins. Ordering
+// is not guaranteed and the next plugin will get the previous one's modifications.
+// if a plugin rejects a post, the rest of the plugins will not know that an attempt was made.
+// Returns the final result post, or nil if the post was rejected and a string with a reason
+// for the user the message was rejected.
+func (h *MultiPluginHooks) MessageWillBeUpdated(newPost, oldPost *model.Post) (*model.Post, string) {
+	h.env.mutex.RLock()
+	defer h.env.mutex.RUnlock()
+
+	post := newPost
+	for _, activePlugin := range h.env.activePlugins {
+		if activePlugin.Supervisor == nil {
+			continue
+		}
+		var rejectionReason string
+		post, rejectionReason = activePlugin.Supervisor.Hooks().MessageWillBeUpdated(post, oldPost)
+		if post == nil {
+			return nil, rejectionReason
+		}
+	}
+	return post, ""
+}
+
+func (h *MultiPluginHooks) MessageHasBeenPosted(post *model.Post) {
+	h.invoke(func(hooks plugin.Hooks) error {
+		hooks.MessageHasBeenPosted(post)
+		return nil
+	})
+}
+
+func (h *MultiPluginHooks) MessageHasBeenUpdated(newPost, oldPost *model.Post) {
+	h.invoke(func(hooks plugin.Hooks) error {
+		hooks.MessageHasBeenUpdated(newPost, oldPost)
+		return nil
+	})
+}
+
 func (h *SinglePluginHooks) invoke(f func(plugin.Hooks) error) error {
 	h.env.mutex.RLock()
 	defer h.env.mutex.RUnlock()