IRCClient: Implement the "part from channel" action.

Also make sure the action is disabled while we're not in a window that
corresponds to an open channel. :^)

Fixes #277.

Applications/IRCClient/IRCAppWindow.cpp

@@ -1,4 +1,5 @@
 #include "IRCAppWindow.h"
+#include "IRCChannel.h"
 #include "IRCWindow.h"
 #include "IRCWindowListModel.h"
 #include <LibGUI/GAction.h>
@@ -48,6 +49,9 @@ void IRCAppWindow::setup_client()
     m_client.on_nickname_changed = [this](const String&) {
         update_title();
     };
+    m_client.on_part_from_channel = [this](auto&) {
+        update_part_action();
+    };
 
     if (m_client.hostname().is_empty()) {
         GInputBox input_box("Enter server:", "Connect to server", this);
@@ -70,8 +74,13 @@ void IRCAppWindow::setup_actions()
             m_client.handle_join_action(input_box.text_value());
     });
 
-    m_part_action = GAction::create("Part from channel", GraphicsBitmap::load_from_file("/res/icons/16x16/irc-part.png"), [](auto&) {
+    m_part_action = GAction::create("Part from channel", GraphicsBitmap::load_from_file("/res/icons/16x16/irc-part.png"), [this](auto&) {
-        printf("FIXME: Implement part action\n");
+        auto* window = m_client.current_window();
+        if (!window || window->type() != IRCWindow::Type::Channel) {
+            // FIXME: Perhaps this action should have been disabled instead of allowing us to activate it.
+            return;
+        }
+        m_client.handle_part_action(window->channel().name());
     });
 
     m_whois_action = GAction::create("Whois user", GraphicsBitmap::load_from_file("/res/icons/16x16/irc-whois.png"), [&](auto&) {
@@ -163,10 +172,20 @@ void IRCAppWindow::setup_widgets()
     };
 
     m_container = new GStackWidget(horizontal_container);
+    m_container->on_active_widget_change = [this](auto*) {
+        update_part_action();
+    };
 
     create_window(&m_client, IRCWindow::Server, "Server");
 }
 
+void IRCAppWindow::update_part_action()
+{
+    auto* window = static_cast<IRCWindow*>(m_container->active_widget());
+    bool is_open_channel = window && window->type() == IRCWindow::Type::Channel && window->channel().is_open();
+    m_part_action->set_enabled(is_open_channel);
+}
+
 IRCWindow& IRCAppWindow::create_window(void* owner, IRCWindow::Type type, const String& name)
 {
     return *new IRCWindow(m_client, owner, type, name, m_container);

Applications/IRCClient/IRCAppWindow.h

@@ -19,6 +19,7 @@ private:
     void setup_menus();
     void setup_widgets();
     void update_title();
+    void update_part_action();
 
     IRCWindow& create_window(void* owner, IRCWindow::Type, const String& name);
     IRCClient m_client;

Applications/IRCClient/IRCChannel.cpp

@@ -78,6 +78,7 @@ void IRCChannel::handle_part(const String& nick, const String& hostmask)
     if (nick == m_client.nickname()) {
         m_open = false;
         m_members.clear();
+        m_client.did_part_from_channel({}, *this);
     } else {
         remove_member(nick);
     }

Applications/IRCClient/IRCClient.cpp

@@ -647,3 +647,9 @@ void IRCClient::handle_part_action(const String& channel)
 {
     part_channel(channel);
 }
+
+void IRCClient::did_part_from_channel(IRCChannel& channel)
+{
+    if (on_part_from_channel)
+        on_part_from_channel(channel);
+}

Applications/IRCClient/IRCClient.h

@@ -44,6 +44,7 @@ public:
     Function<void()> on_disconnect;
     Function<void()> on_server_message;
     Function<void(const String&)> on_nickname_changed;
+    Function<void(IRCChannel&)> on_part_from_channel;
 
     Function<IRCWindow*(void*, IRCWindow::Type, const String&)> aid_create_window;
     Function<IRCWindow*()> aid_get_active_window;
@@ -59,6 +60,8 @@ public:
     const IRCWindow& window_at(int index) const { return *m_windows.at(index); }
     IRCWindow& window_at(int index) { return *m_windows.at(index); }
 
+    void did_part_from_channel(Badge<IRCChannel>, IRCChannel&);
+
     void handle_user_input_in_channel(const String& channel_name, const String&);
     void handle_user_input_in_query(const String& query_name, const String&);
     void handle_user_input_in_server(const String&);