compose_box: Add video chat service button

Author: MritunjayTiwari14

lib/widgets/compose_box.dart

@@ -1031,6 +1031,66 @@ Future<void> _uploadFiles({
   }
 }
 
+class _AttachVideoChatUrlButton extends StatelessWidget {
+  const _AttachVideoChatUrlButton({
+    required this.controller,
+    required this.enabled,
+  });
+
+  final ComposeBoxController controller;
+  final bool enabled;
+
+  static const int jitsi = 1;
+  static const int zoom = 2;
+  static const int googleMeet = 5;
+
+  String _generateJitsiUrl(String serverUrl, String linkText) {
+    final id = List.generate(15, (_) => Random.secure().nextInt(10)).join();
+    return '[$linkText]($serverUrl/$id#config.startWithVideoMuted=false)\n';
+  }
+
+  String? _getMeetingUrl(BuildContext context, int? provider, String? jitsiServerUrl) {
+    if (jitsiServerUrl == null) return null;
+
+    final linkText = ZulipLocalizations.of(context).composeBoxAttachFromVideoCallTooltip;
+
+    switch (provider) {
+      case jitsi: return _generateJitsiUrl(jitsiServerUrl, linkText);
+      case zoom: return 'https://zoom.us/start/meeting';
+      case googleMeet: return 'https://meet.google.com/new';
+      default: return null;
+    }
+  }
+
+  void _handlePress(BuildContext context) {
+    final store = PerAccountStoreWidget.of(context);
+    final url = _getMeetingUrl(context, store.realmVideoChatProvider, store.realmJitsiServerUrl);
+
+    if (url == null) return;
+
+    final text = controller.content.text;
+    final selection = controller.content.selection;
+
+    controller
+      ..content.text = text.replaceRange(selection.start, selection.end, url)
+      ..content.selection = TextSelection.collapsed(
+        offset: selection.start + url.length);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final designVariables = DesignVariables.of(context);
+    final zulipLocalizations = ZulipLocalizations.of(context);
+
+    return SizedBox(
+      width: _composeButtonSize,
+      child: IconButton(
+        icon: Icon(ZulipIcons.video, color: designVariables.foreground.withFadedAlpha(0.5)),
+        tooltip: zulipLocalizations.composeBoxAttachFromVideoCallTooltip,
+        onPressed: enabled ? () => _handlePress(context) : null));
+  }
+}
+
 abstract class _AttachUploadsButton extends StatelessWidget {
   const _AttachUploadsButton({required this.controller, required this.enabled});
 
@@ -1469,6 +1529,7 @@ abstract class _ComposeBoxBody extends StatelessWidget {
       _AttachFileButton(controller: controller, enabled: composeButtonsEnabled),
       _AttachMediaButton(controller: controller, enabled: composeButtonsEnabled),
       _AttachFromCameraButton(controller: controller, enabled: composeButtonsEnabled),
+      _AttachVideoChatUrlButton(controller: controller, enabled: composeButtonsEnabled),
     ];
 
     final topicInput = buildTopicInput();