import 'dart:async';
import 'dart:convert';

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/services.dart';
import 'package:flutter_keyboard_visibility/flutter_keyboard_visibility.dart';
import 'package:tuple/tuple.dart';

import '../models/documents/attribute.dart';
import '../models/documents/document.dart';
import '../models/documents/nodes/block.dart';
import '../models/documents/nodes/line.dart';
import 'controller.dart';
import 'cursor.dart';
import 'default_styles.dart';
import 'delegate.dart';
import 'editor.dart';
import 'keyboard_listener.dart';
import 'proxy.dart';
import 'raw_editor/raw_editor_state_keyboard_mixin.dart';
import 'raw_editor/raw_editor_state_text_input_client_mixin.dart';
import 'text_block.dart';
import 'text_line.dart';
import 'text_selection.dart';

class RawEditor extends StatefulWidget {
  const RawEditor(
    Key key,
    this.controller,
    this.focusNode,
    this.scrollController,
    this.scrollable,
    this.scrollBottomInset,
    this.padding,
    this.readOnly,
    this.placeholder,
    this.onLaunchUrl,
    this.toolbarOptions,
    this.showSelectionHandles,
    bool? showCursor,
    this.cursorStyle,
    this.textCapitalization,
    this.maxHeight,
    this.minHeight,
    this.customStyles,
    this.expands,
    this.autoFocus,
    this.selectionColor,
    this.selectionCtrls,
    this.keyboardAppearance,
    this.enableInteractiveSelection,
    this.scrollPhysics,
    this.embedBuilder,
  )   : assert(maxHeight == null || maxHeight > 0, 'maxHeight cannot be null'),
        assert(minHeight == null || minHeight >= 0, 'minHeight cannot be null'),
        assert(maxHeight == null || minHeight == null || maxHeight >= minHeight,
            'maxHeight cannot be null'),
        showCursor = showCursor ?? true,
        super(key: key);

  final QuillController controller;
  final FocusNode focusNode;
  final ScrollController scrollController;
  final bool scrollable;
  final double scrollBottomInset;
  final EdgeInsetsGeometry padding;
  final bool readOnly;
  final String? placeholder;
  final ValueChanged<String>? onLaunchUrl;
  final ToolbarOptions toolbarOptions;
  final bool showSelectionHandles;
  final bool showCursor;
  final CursorStyle cursorStyle;
  final TextCapitalization textCapitalization;
  final double? maxHeight;
  final double? minHeight;
  final DefaultStyles? customStyles;
  final bool expands;
  final bool autoFocus;
  final Color selectionColor;
  final TextSelectionControls selectionCtrls;
  final Brightness keyboardAppearance;
  final bool enableInteractiveSelection;
  final ScrollPhysics? scrollPhysics;
  final EmbedBuilder embedBuilder;

  @override
  State<StatefulWidget> createState() {
    return RawEditorState();
  }
}

class RawEditorState extends EditorState
    with
        AutomaticKeepAliveClientMixin<RawEditor>,
        WidgetsBindingObserver,
        TickerProviderStateMixin<RawEditor>,
        RawEditorStateKeyboardMixin,
        RawEditorStateTextInputClientMixin
    implements TextSelectionDelegate, TextInputClient {
  final GlobalKey _editorKey = GlobalKey();
  EditorTextSelectionOverlay? _selectionOverlay;
  FocusAttachment? _focusAttachment;
  late CursorCont _cursorCont;
  ScrollController? _scrollController;
  KeyboardVisibilityController? _keyboardVisibilityController;
  StreamSubscription<bool>? _keyboardVisibilitySubscription;
  late KeyboardListener _keyboardListener;
  bool _didAutoFocus = false;
  bool _keyboardVisible = false;
  DefaultStyles? _styles;
  final ClipboardStatusNotifier? _clipboardStatus =
      kIsWeb ? null : ClipboardStatusNotifier();
  final LayerLink _toolbarLayerLink = LayerLink();
  final LayerLink _startHandleLayerLink = LayerLink();
  final LayerLink _endHandleLayerLink = LayerLink();

  bool get _hasFocus => widget.focusNode.hasFocus;

  TextDirection get _textDirection {
    final result = Directionality.of(context);
    return result;
  }

  @override
  TextEditingValue get textEditingValue {
    return getTextEditingValue();
  }

  @override
  set textEditingValue(TextEditingValue value) {
    setTextEditingValue(value);
  }

  @override
  void bringIntoView(TextPosition position) {}

  @override
  Widget build(BuildContext context) {
    assert(debugCheckHasMediaQuery(context));
    _focusAttachment!.reparent();
    super.build(context);

    var _doc = widget.controller.document;
    if (_doc.isEmpty() &&
        !widget.focusNode.hasFocus &&
        widget.placeholder != null) {
      _doc = Document.fromJson(jsonDecode(
          '[{"attributes":{"placeholder":true},"insert":"${widget.placeholder}\\n"}]'));
    }

    Widget child = CompositedTransformTarget(
      link: _toolbarLayerLink,
      child: Semantics(
        child: _Editor(
          key: _editorKey,
          document: _doc,
          selection: widget.controller.selection,
          hasFocus: _hasFocus,
          textDirection: _textDirection,
          startHandleLayerLink: _startHandleLayerLink,
          endHandleLayerLink: _endHandleLayerLink,
          onSelectionChanged: _handleSelectionChanged,
          scrollBottomInset: widget.scrollBottomInset,
          padding: widget.padding,
          children: _buildChildren(_doc, context),
        ),
      ),
    );

    if (widget.scrollable) {
      final baselinePadding =
          EdgeInsets.only(top: _styles!.paragraph!.verticalSpacing.item1);
      child = BaselineProxy(
        textStyle: _styles!.paragraph!.style,
        padding: baselinePadding,
        child: SingleChildScrollView(
          controller: _scrollController,
          physics: widget.scrollPhysics,
          child: child,
        ),
      );
    }

    final constraints = widget.expands
        ? const BoxConstraints.expand()
        : BoxConstraints(
            minHeight: widget.minHeight ?? 0.0,
            maxHeight: widget.maxHeight ?? double.infinity);

    return QuillStyles(
      data: _styles!,
      child: MouseRegion(
        cursor: SystemMouseCursors.text,
        child: Container(
          constraints: constraints,
          child: child,
        ),
      ),
    );
  }

  void _handleSelectionChanged(
      TextSelection selection, SelectionChangedCause cause) {
    widget.controller.updateSelection(selection, ChangeSource.LOCAL);

    _selectionOverlay?.handlesVisible = _shouldShowSelectionHandles();

    if (!_keyboardVisible) {
      requestKeyboard();
    }
  }

  /// Updates the checkbox positioned at [offset] in document
  /// by changing its attribute according to [value].
  void _handleCheckboxTap(int offset, bool value) {
    if (!widget.readOnly) {
      if (value) {
        widget.controller.formatText(offset, 0, Attribute.checked);
      } else {
        widget.controller.formatText(offset, 0, Attribute.unchecked);
      }
    }
  }

  List<Widget> _buildChildren(Document doc, BuildContext context) {
    final result = <Widget>[];
    final indentLevelCounts = <int, int>{};
    for (final node in doc.root.children) {
      if (node is Line) {
        final editableTextLine = _getEditableTextLineFromNode(node, context);
        result.add(editableTextLine);
      } else if (node is Block) {
        final attrs = node.style.attributes;
        final editableTextBlock = EditableTextBlock(
          node,
          _textDirection,
          widget.scrollBottomInset,
          _getVerticalSpacingForBlock(node, _styles),
          widget.controller.selection,
          widget.selectionColor,
          _styles,
          widget.enableInteractiveSelection,
          _hasFocus,
          attrs.containsKey(Attribute.codeBlock.key)
              ? const EdgeInsets.all(16)
              : null,
          widget.embedBuilder,
          _cursorCont,
          indentLevelCounts,
          _handleCheckboxTap,
        );
        result.add(editableTextBlock);
      } else {
        throw StateError('Unreachable.');
      }
    }
    return result;
  }

  EditableTextLine _getEditableTextLineFromNode(
      Line node, BuildContext context) {
    final textLine = TextLine(
      line: node,
      textDirection: _textDirection,
      embedBuilder: widget.embedBuilder,
      styles: _styles!,
    );
    final editableTextLine = EditableTextLine(
        node,
        null,
        textLine,
        0,
        _getVerticalSpacingForLine(node, _styles),
        _textDirection,
        widget.controller.selection,
        widget.selectionColor,
        widget.enableInteractiveSelection,
        _hasFocus,
        MediaQuery.of(context).devicePixelRatio,
        _cursorCont);
    return editableTextLine;
  }

  Tuple2<double, double> _getVerticalSpacingForLine(
      Line line, DefaultStyles? defaultStyles) {
    final attrs = line.style.attributes;
    if (attrs.containsKey(Attribute.header.key)) {
      final int? level = attrs[Attribute.header.key]!.value;
      switch (level) {
        case 1:
          return defaultStyles!.h1!.verticalSpacing;
        case 2:
          return defaultStyles!.h2!.verticalSpacing;
        case 3:
          return defaultStyles!.h3!.verticalSpacing;
        default:
          throw 'Invalid level $level';
      }
    }

    return defaultStyles!.paragraph!.verticalSpacing;
  }

  Tuple2<double, double> _getVerticalSpacingForBlock(
      Block node, DefaultStyles? defaultStyles) {
    final attrs = node.style.attributes;
    if (attrs.containsKey(Attribute.blockQuote.key)) {
      return defaultStyles!.quote!.verticalSpacing;
    } else if (attrs.containsKey(Attribute.codeBlock.key)) {
      return defaultStyles!.code!.verticalSpacing;
    } else if (attrs.containsKey(Attribute.indent.key)) {
      return defaultStyles!.indent!.verticalSpacing;
    }
    return defaultStyles!.lists!.verticalSpacing;
  }

  @override
  void initState() {
    super.initState();

    _clipboardStatus?.addListener(_onChangedClipboardStatus);

    widget.controller.addListener(() {
      _didChangeTextEditingValue(widget.controller.ignoreFocusOnTextChange);
    });

    _scrollController = widget.scrollController;
    _scrollController!.addListener(_updateSelectionOverlayForScroll);

    _cursorCont = CursorCont(
      show: ValueNotifier<bool>(widget.showCursor),
      style: widget.cursorStyle,
      tickerProvider: this,
    );

    _keyboardListener = KeyboardListener(
      handleCursorMovement,
      handleShortcut,
      handleDelete,
    );

    if (defaultTargetPlatform == TargetPlatform.windows ||
        defaultTargetPlatform == TargetPlatform.macOS ||
        defaultTargetPlatform == TargetPlatform.linux ||
        defaultTargetPlatform == TargetPlatform.fuchsia) {
      _keyboardVisible = true;
    } else {
      _keyboardVisibilityController = KeyboardVisibilityController();
      _keyboardVisible = _keyboardVisibilityController!.isVisible;
      _keyboardVisibilitySubscription =
          _keyboardVisibilityController?.onChange.listen((visible) {
        _keyboardVisible = visible;
        if (visible) {
          _onChangeTextEditingValue();
        }
      });
    }

    _focusAttachment = widget.focusNode.attach(context,
        onKey: (node, event) => _keyboardListener.handleRawKeyEvent(event));
    widget.focusNode.addListener(_handleFocusChanged);
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    final parentStyles = QuillStyles.getStyles(context, true);
    final defaultStyles = DefaultStyles.getInstance(context);
    _styles = (parentStyles != null)
        ? defaultStyles.merge(parentStyles)
        : defaultStyles;

    if (widget.customStyles != null) {
      _styles = _styles!.merge(widget.customStyles!);
    }

    if (!_didAutoFocus && widget.autoFocus) {
      FocusScope.of(context).autofocus(widget.focusNode);
      _didAutoFocus = true;
    }
  }

  @override
  void didUpdateWidget(RawEditor oldWidget) {
    super.didUpdateWidget(oldWidget);

    _cursorCont.show.value = widget.showCursor;
    _cursorCont.style = widget.cursorStyle;

    if (widget.controller != oldWidget.controller) {
      oldWidget.controller.removeListener(_didChangeTextEditingValue);
      widget.controller.addListener(_didChangeTextEditingValue);
      updateRemoteValueIfNeeded();
    }

    if (widget.scrollController != _scrollController) {
      _scrollController!.removeListener(_updateSelectionOverlayForScroll);
      _scrollController = widget.scrollController;
      _scrollController!.addListener(_updateSelectionOverlayForScroll);
    }

    if (widget.focusNode != oldWidget.focusNode) {
      oldWidget.focusNode.removeListener(_handleFocusChanged);
      _focusAttachment?.detach();
      _focusAttachment = widget.focusNode.attach(context,
          onKey: (node, event) => _keyboardListener.handleRawKeyEvent(event));
      widget.focusNode.addListener(_handleFocusChanged);
      updateKeepAlive();
    }

    if (widget.controller.selection != oldWidget.controller.selection) {
      _selectionOverlay?.update(textEditingValue);
    }

    _selectionOverlay?.handlesVisible = _shouldShowSelectionHandles();
    if (!shouldCreateInputConnection) {
      closeConnectionIfNeeded();
    } else {
      if (oldWidget.readOnly && _hasFocus) {
        openConnectionIfNeeded();
      }
    }
  }

  bool _shouldShowSelectionHandles() {
    return widget.showSelectionHandles &&
        !widget.controller.selection.isCollapsed;
  }

  @override
  void dispose() {
    closeConnectionIfNeeded();
    _keyboardVisibilitySubscription?.cancel();
    assert(!hasConnection);
    _selectionOverlay?.dispose();
    _selectionOverlay = null;
    widget.controller.removeListener(_didChangeTextEditingValue);
    widget.focusNode.removeListener(_handleFocusChanged);
    _focusAttachment!.detach();
    _cursorCont.dispose();
    _clipboardStatus?.removeListener(_onChangedClipboardStatus);
    _clipboardStatus?.dispose();
    super.dispose();
  }

  void _updateSelectionOverlayForScroll() {
    _selectionOverlay?.markNeedsBuild();
  }

  void _didChangeTextEditingValue([bool ignoreFocus = false]) {
    if (kIsWeb) {
      _onChangeTextEditingValue(ignoreFocus);
      if (!ignoreFocus) {
        requestKeyboard();
      }
      return;
    }

    if (ignoreFocus || _keyboardVisible) {
      _onChangeTextEditingValue(ignoreFocus);
    } else {
      requestKeyboard();
      if (mounted) {
        setState(() {
          // Use widget.controller.value in build()
          // Trigger build and updateChildren
        });
      }
    }
  }

  void _onChangeTextEditingValue([bool ignoreCaret = false]) {
    updateRemoteValueIfNeeded();
    if (ignoreCaret) {
      return;
    }
    _showCaretOnScreen();
    _cursorCont.startOrStopCursorTimerIfNeeded(
        _hasFocus, widget.controller.selection);
    if (hasConnection) {
      _cursorCont
        ..stopCursorTimer(resetCharTicks: false)
        ..startCursorTimer();
    }

    SchedulerBinding.instance!.addPostFrameCallback(
        (_) => _updateOrDisposeSelectionOverlayIfNeeded());
    if (mounted) {
      setState(() {
        // Use widget.controller.value in build()
        // Trigger build and updateChildren
      });
    }
  }

  void _updateOrDisposeSelectionOverlayIfNeeded() {
    if (_selectionOverlay != null) {
      if (_hasFocus) {
        _selectionOverlay!.update(textEditingValue);
      } else {
        _selectionOverlay!.dispose();
        _selectionOverlay = null;
      }
    } else if (_hasFocus) {
      _selectionOverlay?.hide();
      _selectionOverlay = null;

      _selectionOverlay = EditorTextSelectionOverlay(
        textEditingValue,
        false,
        context,
        widget,
        _toolbarLayerLink,
        _startHandleLayerLink,
        _endHandleLayerLink,
        getRenderEditor(),
        widget.selectionCtrls,
        this,
        DragStartBehavior.start,
        null,
        _clipboardStatus!,
      );
      _selectionOverlay!.handlesVisible = _shouldShowSelectionHandles();
      _selectionOverlay!.showHandles();
    }
  }

  void _handleFocusChanged() {
    openOrCloseConnection();
    _cursorCont.startOrStopCursorTimerIfNeeded(
        _hasFocus, widget.controller.selection);
    _updateOrDisposeSelectionOverlayIfNeeded();
    if (_hasFocus) {
      WidgetsBinding.instance!.addObserver(this);
      _showCaretOnScreen();
    } else {
      WidgetsBinding.instance!.removeObserver(this);
    }
    updateKeepAlive();
  }

  void _onChangedClipboardStatus() {
    if (!mounted) return;
    setState(() {
      // Inform the widget that the value of clipboardStatus has changed.
      // Trigger build and updateChildren
    });
  }

  bool _showCaretOnScreenScheduled = false;

  void _showCaretOnScreen() {
    if (!widget.showCursor || _showCaretOnScreenScheduled) {
      return;
    }

    _showCaretOnScreenScheduled = true;
    SchedulerBinding.instance!.addPostFrameCallback((_) {
      if (widget.scrollable) {
        _showCaretOnScreenScheduled = false;

        final viewport = RenderAbstractViewport.of(getRenderEditor());

        final editorOffset = getRenderEditor()!
            .localToGlobal(const Offset(0, 0), ancestor: viewport);
        final offsetInViewport = _scrollController!.offset + editorOffset.dy;

        final offset = getRenderEditor()!.getOffsetToRevealCursor(
          _scrollController!.position.viewportDimension,
          _scrollController!.offset,
          offsetInViewport,
        );

        if (offset != null) {
          _scrollController!.animateTo(
            offset,
            duration: const Duration(milliseconds: 100),
            curve: Curves.fastOutSlowIn,
          );
        }
      }
    });
  }

  @override
  RenderEditor? getRenderEditor() {
    return _editorKey.currentContext!.findRenderObject() as RenderEditor?;
  }

  @override
  EditorTextSelectionOverlay? getSelectionOverlay() {
    return _selectionOverlay;
  }

  @override
  TextEditingValue getTextEditingValue() {
    return widget.controller.plainTextEditingValue;
  }

  @override
  void hideToolbar([bool hideHandles = true]) {
    if (getSelectionOverlay()?.toolbar != null) {
      getSelectionOverlay()?.hideToolbar();
    }
  }

  @override
  bool get cutEnabled => widget.toolbarOptions.cut && !widget.readOnly;

  @override
  bool get copyEnabled => widget.toolbarOptions.copy;

  @override
  bool get pasteEnabled => widget.toolbarOptions.paste && !widget.readOnly;

  @override
  bool get selectAllEnabled => widget.toolbarOptions.selectAll;

  @override
  void requestKeyboard() {
    if (_hasFocus) {
      openConnectionIfNeeded();
    } else {
      widget.focusNode.requestFocus();
    }
  }

  @override
  void setTextEditingValue(TextEditingValue value) {
    if (value.text == textEditingValue.text) {
      widget.controller.updateSelection(value.selection, ChangeSource.LOCAL);
    } else {
      __setEditingValue(value);
    }
  }

  Future<void> __setEditingValue(TextEditingValue value) async {
    if (await __isItCut(value)) {
      widget.controller.replaceText(
        textEditingValue.selection.start,
        textEditingValue.text.length - value.text.length,
        '',
        value.selection,
      );
    } else {
      final value = textEditingValue;
      final data = await Clipboard.getData(Clipboard.kTextPlain);
      if (data != null) {
        final length =
            textEditingValue.selection.end - textEditingValue.selection.start;
        widget.controller.replaceText(
          value.selection.start,
          length,
          data.text,
          value.selection,
        );
        // move cursor to the end of pasted text selection
        widget.controller.updateSelection(
            TextSelection.collapsed(
                offset: value.selection.start + data.text!.length),
            ChangeSource.LOCAL);
      }
    }
  }

  Future<bool> __isItCut(TextEditingValue value) async {
    final data = await Clipboard.getData(Clipboard.kTextPlain);
    if (data == null) {
      return false;
    }
    return textEditingValue.text.length - value.text.length ==
        data.text!.length;
  }

  @override
  bool showToolbar() {
    // Web is using native dom elements to enable clipboard functionality of the
    // toolbar: copy, paste, select, cut. It might also provide additional
    // functionality depending on the browser (such as translate). Due to this
    // we should not show a Flutter toolbar for the editable text elements.
    if (kIsWeb) {
      return false;
    }
    if (_selectionOverlay == null || _selectionOverlay!.toolbar != null) {
      return false;
    }

    _selectionOverlay!.update(textEditingValue);
    _selectionOverlay!.showToolbar();
    return true;
  }

  @override
  bool get wantKeepAlive => widget.focusNode.hasFocus;

  @override
  void userUpdateTextEditingValue(
      TextEditingValue value, SelectionChangedCause cause) {
    // TODO: implement userUpdateTextEditingValue
  }
}

class _Editor extends MultiChildRenderObjectWidget {
  _Editor({
    required Key key,
    required List<Widget> children,
    required this.document,
    required this.textDirection,
    required this.hasFocus,
    required this.selection,
    required this.startHandleLayerLink,
    required this.endHandleLayerLink,
    required this.onSelectionChanged,
    required this.scrollBottomInset,
    this.padding = EdgeInsets.zero,
  }) : super(key: key, children: children);

  final Document document;
  final TextDirection textDirection;
  final bool hasFocus;
  final TextSelection selection;
  final LayerLink startHandleLayerLink;
  final LayerLink endHandleLayerLink;
  final TextSelectionChangedHandler onSelectionChanged;
  final double scrollBottomInset;
  final EdgeInsetsGeometry padding;

  @override
  RenderEditor createRenderObject(BuildContext context) {
    return RenderEditor(
      null,
      textDirection,
      scrollBottomInset,
      padding,
      document,
      selection,
      hasFocus,
      onSelectionChanged,
      startHandleLayerLink,
      endHandleLayerLink,
      const EdgeInsets.fromLTRB(4, 4, 4, 5),
    );
  }

  @override
  void updateRenderObject(
      BuildContext context, covariant RenderEditor renderObject) {
    renderObject
      ..document = document
      ..setContainer(document.root)
      ..textDirection = textDirection
      ..setHasFocus(hasFocus)
      ..setSelection(selection)
      ..setStartHandleLayerLink(startHandleLayerLink)
      ..setEndHandleLayerLink(endHandleLayerLink)
      ..onSelectionChanged = onSelectionChanged
      ..setScrollBottomInset(scrollBottomInset)
      ..setPadding(padding);
  }
}