action_sheet: Add "Quote and reply" button

Fixes: zulip#116

lib/widgets/action_sheet.dart

@@ -1,30 +1,50 @@
 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 = MessageListPage.composeBoxControllerOf(context) != null;
   showDraggableScrollableModalBottomSheet(
     context: context,
     builder: (BuildContext innerContext) {
       return Column(children: [
-        ShareButton(message: message),
+        ShareButton(message: message, messageListContext: context),
+        if (isComposeBoxOffered) QuoteAndReplyButton(
+          message: message,
+          messageListContext: context,
+        ),
       ]);
     });
 }
 
 abstract class MessageActionSheetMenuItemButton extends StatelessWidget {
-  const MessageActionSheetMenuItemButton({
+  MessageActionSheetMenuItemButton({
     super.key,
     required this.message,
-  });
+    required this.messageListContext,
+  }) : assert(messageListContext.findAncestorWidgetOfExactType<MessageListPage>() != null);
 
   IconData get icon;
   String get label;
   void Function(BuildContext) get onPressed;
 
   final Message message;
+  final BuildContext messageListContext;
 
   @override
   Widget build(BuildContext context) {
@@ -36,9 +56,10 @@ abstract class MessageActionSheetMenuItemButton extends StatelessWidget {
 }
 
 class ShareButton extends MessageActionSheetMenuItemButton {
-  const ShareButton({
+  ShareButton({
     super.key,
     required super.message,
+    required super.messageListContext,
   });
 
   @override get icon => Icons.adaptive.share;
@@ -65,3 +86,91 @@ class ShareButton extends MessageActionSheetMenuItemButton {
     await Share.shareWithResult(message.content);
   };
 }
+
+class QuoteAndReplyButton extends MessageActionSheetMenuItemButton {
+  QuoteAndReplyButton({
+    super.key,
+    required super.message,
+    required super.messageListContext,
+  });
+
+  @override get icon => Icons.format_quote_outlined;
+
+  @override get label => 'Quote and reply';
+
+  @override get onPressed => (BuildContext bottomSheetContext) 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 =
+      MessageListPage.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;
+        // TODO specific messages for common errors, like network errors
+        //   (support with reusable code)
+        default:
+          errorMessage = 'Could not fetch message source.';
+      }
+    }
+
+    if (!messageListContext.mounted) return;
+
+    if (fetchedMessage == null) {
+      assert(errorMessage != null);
+      // 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 = MessageListPage.composeBoxControllerOf(messageListContext)!;
+    composeBoxController.contentController
+      .registerQuoteAndReplyEnd(PerAccountStoreWidget.of(messageListContext), tag,
+        message: message,
+        rawContent: fetchedMessage?.content,
+      );
+    if (!composeBoxController.contentFocusNode.hasFocus) {
+      composeBoxController.contentFocusNode.requestFocus();
+    }
+  };
+}

test/widgets/action_sheet_test.dart

@@ -0,0 +1,94 @@
+import 'package:checks/checks.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:zulip/api/route/messages.dart';
+import 'package:zulip/model/compose.dart';
+import 'package:zulip/model/narrow.dart';
+import 'package:zulip/widgets/compose_box.dart';
+import 'package:zulip/widgets/content.dart';
+import 'package:zulip/widgets/message_list.dart';
+import 'package:zulip/widgets/store.dart';
+import '../api/fake_api.dart';
+
+import '../example_data.dart' as eg;
+import '../model/binding.dart';
+import '../model/test_store.dart';
+
+void main() {
+  group('QuoteAndReplyButton', () {
+    TestDataBinding.ensureInitialized();
+
+    testWidgets('happy path', (WidgetTester tester) async {
+      addTearDown(TestDataBinding.instance.reset);
+
+      final sender = eg.user();
+      final stream = eg.stream();
+      final message = eg.streamMessage(sender: sender, stream: stream);
+      await TestDataBinding.instance.globalStore.add(eg.selfAccount, eg.initialSnapshot);
+      final store = await TestDataBinding.instance.globalStore.perAccount(eg.selfAccount.id);
+      store.addUser(sender);
+      store.addStream(stream);
+      final connection = store.connection as FakeApiConnection;
+
+      // prepare message list data
+      connection.prepare(json: GetMessagesResult(
+        anchor: message.id,
+        foundNewest: true,
+        foundOldest: true,
+        foundAnchor: true,
+        historyLimited: false,
+        messages: [message],
+      ).toJson());
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: GlobalStoreWidget(
+            child: PerAccountStoreWidget(
+              accountId: eg.selfAccount.id,
+              child: MessageListPage(
+                narrow: StreamNarrow(message.streamId))))));
+
+      // global store, per-account store, and message list get loaded
+      await tester.pumpAndSettle();
+
+      // request the message action sheet
+      final messageContent = tester.widget<MessageContent>(
+        find.byWidgetPredicate((Widget widget) => widget is MessageContent && widget.message.id == message.id));
+      await tester.longPress(find.byWidget(messageContent));
+      await tester.pumpAndSettle(); // sheet appears onscreen
+
+      // Prepare fetch-raw-Markdown response
+      // TODO: Message should really only differ from `message`
+      //   in its content / content_type, not in `id` or anything else.
+      connection.prepare(json:
+        GetMessageResult(message: eg.streamMessage(contentMarkdown: 'Hello world')).toJson());
+
+      // compose box exists because this is a stream narrow
+      final composeBox = tester.widget<ComposeBox>(find.byType(ComposeBox));
+      final composeBoxController = composeBox.controllerKey!.currentState!;
+      final contentController = composeBoxController.contentController;
+
+      // the "Quote and reply" button, which exists because the compose box exists
+      await tester.tap(find.byIcon(Icons.format_quote_outlined));
+
+      final expectedPlaceholder = quoteAndReplyPlaceholder(store, message: message);
+      // expect newline from [ComposeContentController.insertPadded]
+      String expectedText = '$expectedPlaceholder\n';
+      check(contentController.value).equals(TextEditingValue(
+        text: expectedText,
+        // compose input not yet focused, so there is no selection
+        selection: const TextSelection.collapsed(offset: -1)));
+
+      // message is fetched; compose box updates
+      await tester.pumpAndSettle();
+
+      final expectedQuoteAndReplyText = quoteAndReply(store, message: message, rawContent: 'Hello world');
+      // expect newline from [ComposeContentController.insertPadded]
+      expectedText = '$expectedQuoteAndReplyText\n';
+      check(contentController.value).equals(TextEditingValue(
+        text: expectedText,
+        // compose input focused, so there is a selection
+        selection: TextSelection.collapsed(offset: expectedText.length)));
+    });
+  });
+}