action_sheet: Add "Quote and reply" button

Fixes: zulip#116

Author: chrisbobbe

lib/widgets/action_sheet.dart

@@ -1,15 +1,34 @@
 import 'package:flutter/material.dart';
 import 'package:share_plus/share_plus.dart';
 
+import '../api/exception.dart';
 import '../api/model/model.dart';
+import '../api/route/messages.dart';
+import 'compose_box.dart';
+import 'dialog.dart';
 import 'draggable_scrollable_modal_bottom_sheet.dart';
+import 'message_list.dart';
+import 'store.dart';
 
+/// Show a sheet of actions you can take on a message in the message list.
+///
+/// Must have a [MessageListPage] ancestor.
 void showMessageActionSheet({required BuildContext context, required Message message}) {
+  // The UI that's conditioned on this won't live-update during this appearance
+  // of the action sheet (we avoid calling composeBoxControllerOf in a build
+  // method; see its doc). But currently it will be constant through the life of
+  // any message list, so that's fine.
+  final isComposeBoxOffered = MessageListPageState.composeBoxControllerOf(context) != null;
   showDraggableScrollableModalBottomSheet(
     context: context,
     builder: (BuildContext innerContext) {
       return Column(children: [
-        ShareButton(message: message, bottomSheetContext: innerContext),
+        ShareButton(message: message, bottomSheetContext: innerContext, messageListContext: context),
+        if (isComposeBoxOffered) QuoteAndReplyButton(
+          message: message,
+          bottomSheetContext: innerContext,
+          messageListContext: context,
+        ),
       ]);
     });
 }
@@ -19,14 +38,17 @@ abstract class MessageActionSheetMenuItemButton extends StatelessWidget {
     super.key,
     required this.message,
     required this.bottomSheetContext,
-  }) : assert(bottomSheetContext.findAncestorWidgetOfExactType<BottomSheet>() != null);
+    required this.messageListContext,
+  }) : assert(bottomSheetContext.findAncestorWidgetOfExactType<BottomSheet>() != null),
+       assert(messageListContext.findAncestorWidgetOfExactType<MessageListPage>() != null);
 
   IconData get icon;
   String get label;
   VoidCallback get onPressed;
 
   final Message message;
   final BuildContext bottomSheetContext;
+  final BuildContext messageListContext;
 
   @override
   Widget build(BuildContext context) {
@@ -42,6 +64,7 @@ class ShareButton extends MessageActionSheetMenuItemButton {
     super.key,
     required super.message,
     required super.bottomSheetContext,
+    required super.messageListContext,
   });
 
   @override IconData get icon => Icons.adaptive.share;
@@ -68,3 +91,92 @@ class ShareButton extends MessageActionSheetMenuItemButton {
     await Share.shareWithResult(message.content);
   };
 }
+
+class QuoteAndReplyButton extends MessageActionSheetMenuItemButton {
+  QuoteAndReplyButton({
+    super.key,
+    required super.message,
+    required super.bottomSheetContext,
+    required super.messageListContext,
+  });
+
+  @override IconData get icon => Icons.format_quote_outlined;
+
+  @override String get label => 'Quote and reply';
+
+  @override VoidCallback get onPressed => () async {
+    // Close the message action sheet. We'll show the request progress
+    // in the compose-box content input with a "[Quoting…]" placeholder.
+    Navigator.of(bottomSheetContext).pop();
+
+    // This will be null only if the compose box disappeared after the
+    // message action sheet opened, and before "Quote and reply" was pressed.
+    // Currently a compose box can't ever disappear, so this is impossible.
+    ComposeBoxController? composeBoxController = MessageListPageState.composeBoxControllerOf(messageListContext);
+    final topicController = composeBoxController!.topicController;
+    if (
+      topicController != null
+      && topicController.textNormalized == kNoTopicTopic
+      && message is StreamMessage
+    ) {
+      topicController.value = TextEditingValue(text: message.subject);
+    }
+    final tag = composeBoxController.contentController
+      .registerQuoteAndReplyStart(PerAccountStoreWidget.of(messageListContext),
+        message: message,
+      );
+
+    Message? fetchedMessage;
+    String? errorMessage;
+    // TODO, supported by reusable code:
+    // - (?) Retry with backoff on plausibly transient errors.
+    // - If request(s) take(s) a long time, show snackbar with cancel
+    //   button, like "Still working on quote-and-reply…".
+    //   On final failure or success, auto-dismiss the snackbar.
+    try {
+      fetchedMessage = await getMessageCompat(PerAccountStoreWidget.of(messageListContext).connection,
+        messageId: message.id,
+        applyMarkdown: false,
+      );
+      if (fetchedMessage == null) {
+        errorMessage = 'That message does not seem to exist.';
+      }
+    } catch (e) {
+      switch (e) {
+        case ZulipApiException():
+          errorMessage = e.message;
+      }
+    }
+
+    if (fetchedMessage == null && errorMessage == null) {
+      errorMessage = 'Could not fetch message source.';
+    }
+
+    if (!messageListContext.mounted) return;
+
+    if (fetchedMessage == null) {
+      // TODO specific messages for common errors, like network errors
+      //   (support with reusable code)
+      // TODO(?) give no feedback on error conditions we expect to
+      //   flag centrally in event polling, like invalid auth,
+      //   user/realm deactivated. (Support with reusable code.)
+      await showErrorDialog(context: messageListContext,
+        title: 'Quotation failed', message: errorMessage);
+    }
+
+    if (!messageListContext.mounted) return;
+
+    // This will be null only if the compose box disappeared during the
+    // quotation request. Currently a compose box can't ever disappear,
+    // so this is impossible.
+    composeBoxController = MessageListPageState.composeBoxControllerOf(messageListContext);
+    composeBoxController!.contentController
+      .registerQuoteAndReplyEnd(PerAccountStoreWidget.of(messageListContext), tag,
+        message: message,
+        rawContent: fetchedMessage?.content,
+      );
+    if (!composeBoxController.contentFocusNode.hasFocus) {
+      composeBoxController.contentFocusNode.requestFocus();
+    }
+  };
+}