import 'package:flutter/material.dart';
import 'package:stream_chat/stream_chat.dart';
import 'package:stream_chat_flutter/src/back_button.dart';
import 'package:stream_chat_flutter/src/channel_info.dart';
import 'package:stream_chat_flutter/src/channel_name.dart';
import 'package:stream_chat_flutter/src/stream_chat_theme.dart';

import './channel_name.dart';
import 'channel_image.dart';
import 'stream_channel.dart';

/// ![screenshot](https://raw.githubusercontent.com/GetStream/stream-chat-flutter/master/screenshots/channel_header.png)
/// ![screenshot](https://raw.githubusercontent.com/GetStream/stream-chat-flutter/master/screenshots/channel_header_paint.png)
///
/// It shows the current [Channel] information.
///
/// ```dart
/// class MyApp extends StatelessWidget {
///   final Client client;
///   final Channel channel;
///
///   MyApp(this.client, this.channel);
///
///   @override
///   Widget build(BuildContext context) {
///     return MaterialApp(
///       home: StreamChat(
///         client: client,
///         child: StreamChannel(
///           channel: channel,
///           child: Scaffold(
///             appBar: ChannelHeader(),
///           ),
///         ),
///       ),
///     );
///   }
/// }
/// ```
///
/// Usually you would use this widget as an [AppBar] inside a [Scaffold].
/// However you can also use it as a normal widget.
///
/// Make sure to have a [StreamChannel] ancestor in order to provide the information about the channel.
/// Every part of the widget uses a [StreamBuilder] to render the channel information as soon as it updates.
///
/// By default the widget shows a backButton that calls [Navigator.pop].
/// You can disable this button using the [showBackButton] property of just override the behaviour
/// with [onBackPressed].
///
/// The widget components render the ui based on the first ancestor of type [StreamChatTheme] and on its [ChannelTheme.channelHeaderTheme] property.
/// Modify it to change the widget appearance.
class ChannelHeader extends StatelessWidget implements PreferredSizeWidget {
  /// True if this header shows the leading back button
  final bool showBackButton;

  /// Callback to call when pressing the back button.
  /// By default it calls [Navigator.pop]
  final VoidCallback onBackPressed;

  /// Callback to call when the header is tapped.
  final VoidCallback onTitleTap;

  /// Callback to call when the image is tapped.
  final VoidCallback onImageTap;

  /// Creates a channel header
  ChannelHeader({
    Key key,
    this.showBackButton = true,
    this.onBackPressed,
    this.onTitleTap,
    this.onImageTap,
  })  : preferredSize = Size.fromHeight(kToolbarHeight),
        super(key: key);

  @override
  Widget build(BuildContext context) {
    final channel = StreamChannel.of(context).channel;
    return AppBar(
      brightness: Theme.of(context).brightness,
      elevation: 1,
      leading: showBackButton
          ? StreamBackButton(
              onPressed: onBackPressed,
              showUnreads: true,
            )
          : SizedBox(),
      backgroundColor:
          StreamChatTheme.of(context).channelTheme.channelHeaderTheme.color,
      actions: <Widget>[
        Padding(
          padding: const EdgeInsets.only(right: 10.0),
          child: Center(
            child: ChannelImage(
              onTap: onImageTap,
            ),
          ),
        ),
      ],
      centerTitle: true,
      title: InkWell(
        onTap: onTitleTap,
        child: Container(
          height: preferredSize.height,
          width: preferredSize.width,
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ChannelName(
                textStyle: StreamChatTheme.of(context)
                    .channelTheme
                    .channelHeaderTheme
                    .title,
              ),
              ChannelInfo(
                channel: channel,
                textStyle:
                    StreamChatTheme.of(context).channelPreviewTheme.subtitle,
              ),
            ],
          ),
        ),
      ),
    );
  }

  @override
  final Size preferredSize;
}