using System;
using System.Collections.Generic;
using RSG;
using Unity.UIWidgets.animation;
using Unity.UIWidgets.async;
using Unity.UIWidgets.foundation;
using Unity.UIWidgets.gestures;
using Unity.UIWidgets.material;
using Unity.UIWidgets.painting;
using Unity.UIWidgets.rendering;
using Unity.UIWidgets.scheduler;
using Unity.UIWidgets.service;
using Unity.UIWidgets.ui;
using UnityEngine;
using Color = Unity.UIWidgets.ui.Color;
using Rect = Unity.UIWidgets.ui.Rect;
using TextStyle = Unity.UIWidgets.painting.TextStyle;

namespace Unity.UIWidgets.widgets {
    public delegate void SelectionChangedCallback(TextSelection selection, SelectionChangedCause cause);

    public class TextEditingController : ValueNotifier<TextEditingValue> {
        public TextEditingController(string text = null) : base(text == null
            ? TextEditingValue.empty
            : new TextEditingValue(text)) {
        }

        TextEditingController(TextEditingValue value) : base(value ?? TextEditingValue.empty) {
        }

        public static TextEditingController fromValue(TextEditingValue value) {
            return new TextEditingController(value);
        }

        public string text {
            get { return value.text; }

            set {
                this.value = this.value.copyWith(
                    text: value,
                    selection: TextSelection.collapsed(-1),
                    composing: TextRange.empty);
            }
        }

        public TextSelection selection {
            get { return value.selection; }

            set {
                if (value.start > text.Length || value.end > text.Length) {
                    throw new UIWidgetsError($"invalid text selection: {value}");
                }

                this.value = this.value.copyWith(selection: value, composing: TextRange.empty);
            }
        }

        public void clear() {
            value = TextEditingValue.empty;
        }

        public void clearComposing() {
            value = value.copyWith(composing: TextRange.empty);
        }
    }

    public class EditableText : StatefulWidget {
        public EditableText(
            TextEditingController controller = null,
            FocusNode focusNode = null, TextStyle style = null,
            StrutStyle strutStyle = null,
            Color cursorColor = null,
            Color backgroundCursorColor = null,
            bool obscureText = false,
            bool autocorrect = false,
            TextAlign textAlign = TextAlign.left,
            TextDirection? textDirection = null,
            float? textScaleFactor = null,
            int? maxLines = 1,
            int? minLines = null,
            bool expands = false,
            bool autofocus = false,
            Color selectionColor = null,
            TextSelectionControls selectionControls = null,
            TextInputType keyboardType = null,
            TextInputAction? textInputAction = null,
            TextCapitalization textCapitalization = TextCapitalization.none,
            ValueChanged<string> onChanged = null,
            VoidCallback onEditingComplete = null,
            ValueChanged<string> onSubmitted = null,
            SelectionChangedCallback onSelectionChanged = null,
            List<TextInputFormatter> inputFormatters = null,
            bool rendererIgnoresPointer = false,
            EdgeInsets scrollPadding = null,
            bool unityTouchKeyboard = false,
            Key key = null,
            float? cursorWidth = 2.0f,
            Radius cursorRadius = null,
            bool cursorOpacityAnimates = false,
            Offset cursorOffset = null,
            bool paintCursorAboveText = false,
            Brightness? keyboardAppearance = Brightness.light,
            DragStartBehavior dragStartBehavior = DragStartBehavior.down,
            bool? enableInteractiveSelection = null,
            ScrollPhysics scrollPhysics = null,
            GlobalKeyEventHandlerDelegate globalKeyEventHandler = null
        ) : base(key) {
            D.assert(controller != null);
            D.assert(focusNode != null);
            D.assert(style != null);
            D.assert(cursorColor != null);
            D.assert(maxLines == null || maxLines > 0);
            D.assert(minLines == null || minLines > 0);
            D.assert((maxLines == null) || (minLines == null) || (maxLines >= minLines),
                () => "minLines can't be greater than maxLines");
            D.assert(!expands || (maxLines == null && minLines == null),
                () => "minLines and maxLines must be null when expands is true.");
            // D.assert(backgroundCursorColor != null); // TODO: remove comment
            this.keyboardType = keyboardType ?? (maxLines == 1 ? TextInputType.text : TextInputType.multiline);

            this.scrollPadding = scrollPadding ?? EdgeInsets.all(20.0f);
            this.controller = controller;
            this.focusNode = focusNode;
            this.obscureText = obscureText;
            this.autocorrect = autocorrect;
            this.style = style;
            _strutStyle = strutStyle;
            this.textAlign = textAlign;
            this.textDirection = textDirection;
            this.textScaleFactor = textScaleFactor;
            this.textInputAction = textInputAction;
            this.textCapitalization = textCapitalization;
            this.cursorColor = cursorColor;
            this.backgroundCursorColor = backgroundCursorColor ?? Colors.grey; // TODO: remove ??
            this.maxLines = maxLines;
            this.minLines = minLines;
            this.expands = expands;
            this.autofocus = autofocus;
            this.selectionColor = selectionColor;
            this.onChanged = onChanged;
            this.onSubmitted = onSubmitted;
            this.onSelectionChanged = onSelectionChanged;
            this.onEditingComplete = onEditingComplete;
            this.rendererIgnoresPointer = rendererIgnoresPointer;
            this.selectionControls = selectionControls;
            this.unityTouchKeyboard = unityTouchKeyboard;
            if (maxLines == 1) {
                this.inputFormatters = new List<TextInputFormatter>();
                this.inputFormatters.Add(BlacklistingTextInputFormatter.singleLineFormatter);
                if (inputFormatters != null) {
                    this.inputFormatters.AddRange(inputFormatters);
                }
            }
            else {
                this.inputFormatters = inputFormatters;
            }

            this.cursorWidth = cursorWidth;
            this.cursorRadius = cursorRadius;
            this.cursorOpacityAnimates = cursorOpacityAnimates;
            this.cursorOffset = cursorOffset;
            this.paintCursorAboveText = paintCursorAboveText;
            this.keyboardAppearance = keyboardAppearance;
            this.enableInteractiveSelection = enableInteractiveSelection;
            this.dragStartBehavior = dragStartBehavior;
            this.scrollPhysics = scrollPhysics;
            this.globalKeyEventHandler = globalKeyEventHandler;
        }

        public readonly TextEditingController controller;
        public readonly FocusNode focusNode;
        public readonly bool obscureText;
        public readonly bool autocorrect;
        public readonly TextStyle style;
        public StrutStyle strutStyle {
            get {
                if (_strutStyle == null) {
                    return style != null
                        ? StrutStyle.fromTextStyle(style, forceStrutHeight: true)
                        : StrutStyle.disabled;
                }

                return _strutStyle.inheritFromTextStyle(style);
            }
        }

        readonly StrutStyle _strutStyle;
        public readonly TextAlign textAlign;
        public readonly TextDirection? textDirection;
        public readonly TextCapitalization textCapitalization;
        public readonly float? textScaleFactor;
        public readonly Color cursorColor;
        public readonly Color backgroundCursorColor;
        public readonly int? maxLines;
        public readonly int? minLines;
        public readonly bool expands;
        public readonly bool autofocus;
        public readonly Color selectionColor;
        public readonly TextSelectionControls selectionControls;
        public readonly TextInputType keyboardType;
        public readonly TextInputAction? textInputAction;
        public readonly ValueChanged<string> onChanged;
        public readonly VoidCallback onEditingComplete;
        public readonly ValueChanged<string> onSubmitted;
        public readonly SelectionChangedCallback onSelectionChanged;
        public readonly List<TextInputFormatter> inputFormatters;
        public readonly bool rendererIgnoresPointer;
        public readonly bool unityTouchKeyboard;
        public readonly float? cursorWidth;
        public readonly Radius cursorRadius;
        public readonly bool cursorOpacityAnimates;
        public readonly Offset cursorOffset;
        public readonly bool paintCursorAboveText;
        public readonly Brightness? keyboardAppearance;
        public readonly EdgeInsets scrollPadding;
        public readonly DragStartBehavior dragStartBehavior;
        public readonly bool? enableInteractiveSelection;
        public readonly ScrollPhysics scrollPhysics;
        public readonly GlobalKeyEventHandlerDelegate globalKeyEventHandler;

        public bool selectionEnabled {
            get { return enableInteractiveSelection ?? !obscureText; }
        }

        public override State createState() {
            return new EditableTextState();
        }

        public static bool debugDeterministicCursor = false;

        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
            base.debugFillProperties(properties);
            properties.add(new DiagnosticsProperty<TextEditingController>("controller", controller));
            properties.add(new DiagnosticsProperty<FocusNode>("focusNode", focusNode));
            properties.add(new DiagnosticsProperty<bool>("obscureText", obscureText, defaultValue: false));
            properties.add(new DiagnosticsProperty<bool>("autocorrect", autocorrect, defaultValue: true));
            if (style != null) {
                style.debugFillProperties(properties);
            }

            properties.add(new EnumProperty<TextAlign>("textAlign", textAlign,
                defaultValue: foundation_.kNullDefaultValue));
            properties.add(new EnumProperty<TextDirection?>("textDirection", textDirection,
                defaultValue: foundation_.kNullDefaultValue));
            properties.add(new DiagnosticsProperty<float?>("textScaleFactor", textScaleFactor,
                defaultValue: foundation_.kNullDefaultValue));
            properties.add(new DiagnosticsProperty<int?>("maxLines", maxLines, defaultValue: 1));
            properties.add(new DiagnosticsProperty<int?>("minLines", minLines,
                defaultValue: foundation_.kNullDefaultValue));
            properties.add(new DiagnosticsProperty<bool>("expands", expands, defaultValue: false));
            properties.add(new DiagnosticsProperty<bool>("autofocus", autofocus, defaultValue: false));
            properties.add(
                new DiagnosticsProperty<TextInputType>("keyboardType", keyboardType, defaultValue: null));
            properties.add(new DiagnosticsProperty<ScrollPhysics>("scrollPhysics", scrollPhysics,
                defaultValue: foundation_.kNullDefaultValue));
        }
    }

    public class EditableTextState : AutomaticKeepAliveClientWithTickerProviderStateMixin<EditableText>,
        WidgetsBindingObserver, TextInputClient,
        TextSelectionDelegate {
        const int _kObscureShowLatestCharCursorTicks = 3;
        static TimeSpan _kCursorBlinkHalfPeriod = TimeSpan.FromMilliseconds(500);
        static TimeSpan _kCursorBlinkWaitForStart = TimeSpan.FromMilliseconds(150);

        Timer _cursorTimer;
        bool _targetCursorVisibility = false;
        ValueNotifier<bool> _cursorVisibilityNotifier = new ValueNotifier<bool>(false);
        GlobalKey _editableKey = GlobalKey.key();

        TextInputConnection _textInputConnection;
        TextSelectionOverlay _selectionOverlay;

        public ScrollController _scrollController = new ScrollController();
        AnimationController _cursorBlinkOpacityController;

        LayerLink _layerLink = new LayerLink();
        bool _didAutoFocus = false;

        static readonly TimeSpan _fadeDuration = TimeSpan.FromMilliseconds(250);

        static readonly TimeSpan _floatingCursorResetTime = TimeSpan.FromMilliseconds(125);

        AnimationController _floatingCursorResetController;

        protected override bool wantKeepAlive {
            get { return widget.focusNode.hasFocus; }
        }


        Color _cursorColor {
            get { return widget.cursorColor.withOpacity(_cursorBlinkOpacityController.value); }
        }

        public override void initState() {
            base.initState();
            widget.controller.addListener(_didChangeTextEditingValue);
            widget.focusNode.addListener(_handleFocusChanged);
            _scrollController.addListener(() => { _selectionOverlay?.updateForScroll(); });
            _cursorBlinkOpacityController = new AnimationController(vsync: this, duration: _fadeDuration);
            _cursorBlinkOpacityController.addListener(_onCursorColorTick);
            _floatingCursorResetController = new AnimationController(vsync: this);
            _floatingCursorResetController.addListener(_onFloatingCursorResetTick);
        }

        public override void didChangeDependencies() {
            base.didChangeDependencies();
            if (!_didAutoFocus && widget.autofocus) {
                FocusScope.of(context).autofocus(widget.focusNode);
                _didAutoFocus = true;
            }
        }

        public override void didUpdateWidget(StatefulWidget old) {
            EditableText oldWidget = (EditableText) old;
            base.didUpdateWidget(oldWidget);
            if (widget.controller != oldWidget.controller) {
                oldWidget.controller.removeListener(_didChangeTextEditingValue);
                widget.controller.addListener(_didChangeTextEditingValue);
                _updateRemoteEditingValueIfNeeded();
                _updateImePosIfNeed();
            }

            if (widget.focusNode != oldWidget.focusNode) {
                oldWidget.focusNode.removeListener(_handleFocusChanged);
                widget.focusNode.addListener(_handleFocusChanged);
                updateKeepAlive();
            }
        }

        public override void dispose() {
            widget.controller.removeListener(_didChangeTextEditingValue);
            _cursorBlinkOpacityController.removeListener(_onCursorColorTick);
            _floatingCursorResetController.removeListener(_onFloatingCursorResetTick);
            _closeInputConnectionIfNeeded();
            D.assert(!_hasInputConnection);
            _stopCursorTimer();
            D.assert(_cursorTimer == null);
            _selectionOverlay?.dispose();
            _selectionOverlay = null;
            widget.focusNode.removeListener(_handleFocusChanged);
            base.dispose();
        }

        TextEditingValue _lastKnownRemoteTextEditingValue;

        public void updateEditingValue(TextEditingValue value, bool isIMEInput) {
            if (value.text != _value.text) {
                _hideSelectionOverlayIfNeeded();
                _showCaretOnScreen();
                if (widget.obscureText && value.text.Length == _value.text.Length + 1) {
                    _obscureShowCharTicksPending = !_unityKeyboard() ? _kObscureShowLatestCharCursorTicks : 0;
                    _obscureLatestCharIndex = _value.selection.baseOffset;
                }
            }

            _lastKnownRemoteTextEditingValue = value;
            _formatAndSetValue(value, isIMEInput);

            _stopCursorTimer(resetCharTicks: false);
            _startCursorTimer();
        }

        public void performAction(TextInputAction action) {
            switch (action) {
                case TextInputAction.newline:
                    if (!_isMultiline) {
                        _finalizeEditing(true);
                    }

                    break;
                case TextInputAction.done:
                case TextInputAction.go:
                case TextInputAction.send:
                case TextInputAction.search:
                    _finalizeEditing(true);
                    break;
                default:
                    _finalizeEditing(false);
                    break;
            }
        }

        Rect _startCaretRect;

        TextPosition _lastTextPosition;

        Offset _pointOffsetOrigin;

        Offset _lastBoundedOffset;

        Offset _floatingCursorOffset {
            get { return new Offset(0, renderEditable.preferredLineHeight / 2); }
        }

        public void updateFloatingCursor(RawFloatingCursorPoint point) {
            switch (point.state) {
                case FloatingCursorDragState.Start:
                    if (_floatingCursorResetController.isAnimating) {
                        _floatingCursorResetController.stop();
                        _onFloatingCursorResetTick();
                    }
                    TextPosition currentTextPosition =
                        new TextPosition(offset: renderEditable.selection.baseOffset);
                    _startCaretRect = renderEditable.getLocalRectForCaret(currentTextPosition);
                    renderEditable.setFloatingCursor(point.state,
                        _startCaretRect.center - _floatingCursorOffset, currentTextPosition);
                    break;
                case FloatingCursorDragState.Update:
                    // We want to send in points that are centered around a (0,0) origin, so we cache the
                    // position on the first update call.
                    if (_pointOffsetOrigin != null) {
                        Offset centeredPoint = point.offset - _pointOffsetOrigin;
                        Offset rawCursorOffset =
                            _startCaretRect.center + centeredPoint - _floatingCursorOffset;
                        _lastBoundedOffset =
                            renderEditable.calculateBoundedFloatingCursorOffset(rawCursorOffset);
                        _lastTextPosition = renderEditable.getPositionForPoint(
                            renderEditable.localToGlobal(_lastBoundedOffset + _floatingCursorOffset));
                        renderEditable.setFloatingCursor(point.state, _lastBoundedOffset,
                            _lastTextPosition);
                    }
                    else {
                        _pointOffsetOrigin = point.offset;
                    }

                    break;
                case FloatingCursorDragState.End:
                    _floatingCursorResetController.setValue(0.0f);
                    _floatingCursorResetController.animateTo(1.0f, duration: _floatingCursorResetTime,
                        curve: Curves.decelerate);
                    break;
            }
        }

        public RawInputKeyResponse globalInputKeyHandler(RawKeyEvent evt) {
            return widget.globalKeyEventHandler?.Invoke(evt, true) ?? RawInputKeyResponse.convert(evt);
        }

        void _onFloatingCursorResetTick() {
            Offset finalPosition = renderEditable.getLocalRectForCaret(_lastTextPosition).centerLeft -
                                   _floatingCursorOffset;
            if (_floatingCursorResetController.isCompleted) {
                renderEditable.setFloatingCursor(FloatingCursorDragState.End, finalPosition,
                    _lastTextPosition);
                if (_lastTextPosition.offset != renderEditable.selection.baseOffset) {
                    _handleSelectionChanged(TextSelection.collapsed(offset: _lastTextPosition.offset),
                        renderEditable, SelectionChangedCause.forcePress);
                }

                _startCaretRect = null;
                _lastTextPosition = null;
                _pointOffsetOrigin = null;
                _lastBoundedOffset = null;
            }
            else {
                float lerpValue = _floatingCursorResetController.value;
                float lerpX = MathUtils.lerpFloat(_lastBoundedOffset.dx, finalPosition.dx, lerpValue);
                float lerpY = MathUtils.lerpFloat(_lastBoundedOffset.dy, finalPosition.dy, lerpValue);

                renderEditable.setFloatingCursor(FloatingCursorDragState.Update, new Offset(lerpX, lerpY),
                    _lastTextPosition, resetLerpValue: lerpValue);
            }
        }

        void _finalizeEditing(bool shouldUnfocus) {
            if (widget.onEditingComplete != null) {
                widget.onEditingComplete();
            }
            else {
                widget.controller.clearComposing();
                if (shouldUnfocus) {
                    widget.focusNode.unfocus();
                }
            }

            if (widget.onSubmitted != null) {
                widget.onSubmitted(_value.text);
            }
        }

        void _updateRemoteEditingValueIfNeeded() {
            if (!_hasInputConnection) {
                return;
            }

            var localValue = _value;
            if (localValue == _lastKnownRemoteTextEditingValue) {
                return;
            }

            _lastKnownRemoteTextEditingValue = localValue;
            _textInputConnection.setEditingState(localValue);
        }

        TextEditingValue _value {
            get { return widget.controller.value; }
            set { widget.controller.value = value; }
        }

        bool _hasFocus {
            get { return widget.focusNode.hasFocus; }
        }

        bool _isMultiline {
            get { return widget.maxLines != 1; }
        }

        // Calculate the new scroll offset so the cursor remains visible.
        float _getScrollOffsetForCaret(Rect caretRect) {
            float caretStart;
            float caretEnd;
            if (_isMultiline) {
                // The caret is vertically centered within the line. Expand the caret's
                // height so that it spans the line because we're going to ensure that the entire
                // expanded caret is scrolled into view.
                float lineHeight = renderEditable.preferredLineHeight;
                float caretOffset = (lineHeight - caretRect.height) / 2;
                caretStart = caretRect.top - caretOffset;
                caretEnd = caretRect.bottom + caretOffset;
            }
            else {
                caretStart = caretRect.left;
                caretEnd = caretRect.right;
            }

            float scrollOffset = _scrollController.offset;
            float viewportExtent = _scrollController.position.viewportDimension;
            if (caretStart < 0.0) {
                scrollOffset += caretStart;
            }
            else if (caretEnd >= viewportExtent) {
                scrollOffset += caretEnd - viewportExtent;
            }

            return scrollOffset;
        }

        // Calculates where the `caretRect` would be if `_scrollController.offset` is set to `scrollOffset`.
        Rect _getCaretRectAtScrollOffset(Rect caretRect, float scrollOffset) {
            float offsetDiff = _scrollController.offset - scrollOffset;
            return _isMultiline ? caretRect.translate(0.0f, offsetDiff) : caretRect.translate(offsetDiff, 0.0f);
        }

        bool _hasInputConnection {
            get { return _textInputConnection != null && _textInputConnection.attached; }
        }

        void _openInputConnection() {
            if (!_hasInputConnection) {
                TextEditingValue localValue = _value;
                _lastKnownRemoteTextEditingValue = localValue;
                _textInputConnection = TextInput.attach(this, new TextInputConfiguration(
                    inputType: widget.keyboardType,
                    obscureText: widget.obscureText,
                    autocorrect: widget.autocorrect,
                    inputAction: widget.textInputAction ?? ((widget.keyboardType == TextInputType.multiline)
                                     ? TextInputAction.newline
                                     : TextInputAction.done),
                    textCapitalization: widget.textCapitalization,
                    keyboardAppearance: widget.keyboardAppearance ?? Brightness.light,
                    unityTouchKeyboard: widget.unityTouchKeyboard
                ));
                _textInputConnection.setEditingState(localValue);
                _updateImePosIfNeed();
            }

            _textInputConnection.show();
        }

        void _closeInputConnectionIfNeeded() {
            if (_hasInputConnection) {
                _textInputConnection.close();
                _textInputConnection = null;
                _lastKnownRemoteTextEditingValue = null;
            }
        }

        void _openOrCloseInputConnectionIfNeeded() {
            if (_hasFocus && widget.focusNode.consumeKeyboardToken()) {
                _openInputConnection();
            }
            else if (!_hasFocus) {
                _closeInputConnectionIfNeeded();
                widget.controller.clearComposing();
            }
        }

        public void requestKeyboard() {
            if (_hasFocus) {
                _openInputConnection();
            }
            else {
                List<FocusScopeNode> ancestorScopes = FocusScope.ancestorsOf(context);
                for (int i = ancestorScopes.Count - 1; i >= 1; i -= 1) {
                    ancestorScopes[i].setFirstFocus(ancestorScopes[i - 1]);
                }

                FocusScope.of(context).requestFocus(widget.focusNode);
            }
        }

        void _hideSelectionOverlayIfNeeded() {
            _selectionOverlay?.hide();
            _selectionOverlay = null;
        }

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


        void _handleSelectionChanged(TextSelection selection, RenderEditable renderObject,
            SelectionChangedCause cause) {
            widget.controller.selection = selection;
            requestKeyboard();

            _hideSelectionOverlayIfNeeded();

            if (widget.selectionControls != null && Application.isMobilePlatform && !_unityKeyboard()) {
                _selectionOverlay = new TextSelectionOverlay(
                    context: context,
                    value: _value,
                    debugRequiredFor: widget,
                    layerLink: _layerLink,
                    renderObject: renderObject,
                    selectionControls: widget.selectionControls,
                    selectionDelegate: this,
                    dragStartBehavior: widget.dragStartBehavior
                );
                bool longPress = cause == SelectionChangedCause.longPress;
                if (cause != SelectionChangedCause.keyboard && (_value.text.isNotEmpty() || longPress)) {
                    _selectionOverlay.showHandles();
                }

                if (longPress || cause == SelectionChangedCause.doubleTap) {
                    _selectionOverlay.showToolbar();
                }
            }

            if (widget.onSelectionChanged != null) {
                widget.onSelectionChanged(selection, cause);
            }
        }

        bool _textChangedSinceLastCaretUpdate = false;
        Rect _currentCaretRect;

        void _handleCaretChanged(Rect caretRect) {
            _currentCaretRect = caretRect;
            // If the caret location has changed due to an update to the text or
            // selection, then scroll the caret into view.
            if (_textChangedSinceLastCaretUpdate) {
                _textChangedSinceLastCaretUpdate = false;
                _showCaretOnScreen();
            }
        }

        // Animation configuration for scrolling the caret back on screen.
        static readonly TimeSpan _caretAnimationDuration = TimeSpan.FromMilliseconds(100);
        static readonly Curve _caretAnimationCurve = Curves.fastOutSlowIn;
        bool _showCaretOnScreenScheduled = false;

        void _showCaretOnScreen() {
            if (_showCaretOnScreenScheduled) {
                return;
            }

            _showCaretOnScreenScheduled = true;
            SchedulerBinding.instance.addPostFrameCallback(_ => {
                _showCaretOnScreenScheduled = false;
                if (_currentCaretRect == null || !_scrollController.hasClients) {
                    return;
                }

                float scrollOffsetForCaret = _getScrollOffsetForCaret(_currentCaretRect);
                _scrollController.animateTo(scrollOffsetForCaret,
                    duration: _caretAnimationDuration,
                    curve: _caretAnimationCurve);

                Rect newCaretRect = _getCaretRectAtScrollOffset(_currentCaretRect, scrollOffsetForCaret);
                // Enlarge newCaretRect by scrollPadding to ensure that caret is not positioned directly at the edge after scrolling.
                Rect inflatedRect = Rect.fromLTRB(
                    newCaretRect.left - widget.scrollPadding.left,
                    newCaretRect.top - widget.scrollPadding.top,
                    newCaretRect.right + widget.scrollPadding.right,
                    newCaretRect.bottom + widget.scrollPadding.bottom
                );
                _editableKey.currentContext.findRenderObject().showOnScreen(
                    rect: inflatedRect,
                    duration: _caretAnimationDuration,
                    curve: _caretAnimationCurve
                );
            });
        }


        double _lastBottomViewInset;

        public void didChangeMetrics() {
            if (_lastBottomViewInset < Window.instance.viewInsets.bottom) {
                _showCaretOnScreen();
            }

            _lastBottomViewInset = Window.instance.viewInsets.bottom;
        }

        public void didChangeTextScaleFactor() {
        }

        public void didChangePlatformBrightness() {
        }

        public void didChangeLocales(List<Locale> locale) {
        }

        public IPromise<bool> didPopRoute() {
            return Promise<bool>.Resolved(false);
        }

        public IPromise<bool> didPushRoute(string route) {
            return Promise<bool>.Resolved(false);
        }

        void _formatAndSetValue(TextEditingValue value, bool isIMEInput = false) {
            var textChanged = _value?.text != value?.text || isIMEInput;
            if (textChanged && widget.inputFormatters != null && widget.inputFormatters.isNotEmpty()) {
                foreach (var formatter in widget.inputFormatters) {
                    value = formatter.formatEditUpdate(_value, value);
                }

                _value = value;
                _updateRemoteEditingValueIfNeeded();
                _updateImePosIfNeed();
            }
            else {
                _value = value;
            }

            if (textChanged && widget.onChanged != null) {
                widget.onChanged(value.text);
            }
        }

        void _onCursorColorTick() {
            renderEditable.cursorColor =
                widget.cursorColor.withOpacity(_cursorBlinkOpacityController.value);
            _cursorVisibilityNotifier.value = _cursorBlinkOpacityController.value > 0;
        }

        public bool cursorCurrentlyVisible {
            get { return _cursorBlinkOpacityController.value > 0; }
        }

        public TimeSpan cursorBlinkInterval {
            get { return _kCursorBlinkHalfPeriod; }
        }

        public TextSelectionOverlay selectionOverlay {
            get { return _selectionOverlay; }
        }

        int _obscureShowCharTicksPending = 0;
        int _obscureLatestCharIndex;

        void _cursorTick() {
            _targetCursorVisibility = !_unityKeyboard() && !_targetCursorVisibility;
            float targetOpacity = _targetCursorVisibility ? 1.0f : 0.0f;
            if (widget.cursorOpacityAnimates) {
                _cursorBlinkOpacityController.animateTo(targetOpacity, curve: Curves.easeOut);
            }
            else {
                _cursorBlinkOpacityController.setValue(targetOpacity);
            }

            if (_obscureShowCharTicksPending > 0) {
                setState(() => { _obscureShowCharTicksPending--; });
            }
        }

        void _cursorWaitForStart() {
            D.assert(_kCursorBlinkHalfPeriod > _fadeDuration);
            _cursorTimer?.cancel();
            _cursorTimer = Window.instance.run(_kCursorBlinkHalfPeriod, _cursorTick, periodic: true);
        }

        void _startCursorTimer() {
            _targetCursorVisibility = true;
            _cursorBlinkOpacityController.setValue(1.0f);
            if (EditableText.debugDeterministicCursor) {
                return;
            }

            if (widget.cursorOpacityAnimates) {
                _cursorTimer =
                    Window.instance.run(_kCursorBlinkWaitForStart, _cursorWaitForStart, periodic: true);
            }
            else {
                _cursorTimer = Window.instance.run(_kCursorBlinkHalfPeriod, _cursorTick, periodic: true);
            }
        }

        void _stopCursorTimer(bool resetCharTicks = true) {
            _cursorTimer?.cancel();
            _cursorTimer = null;
            _targetCursorVisibility = false;
            _cursorBlinkOpacityController.setValue(0.0f);
            if (EditableText.debugDeterministicCursor) {
                return;
            }

            if (resetCharTicks) {
                _obscureShowCharTicksPending = 0;
            }

            if (widget.cursorOpacityAnimates) {
                _cursorBlinkOpacityController.stop();
                _cursorBlinkOpacityController.setValue(0.0f);
            }
        }

        void _startOrStopCursorTimerIfNeeded() {
            if (_cursorTimer == null && _hasFocus && _value.selection.isCollapsed) {
                _startCursorTimer();
            }
            else if (_cursorTimer != null && (!_hasFocus || !_value.selection.isCollapsed)) {
                _stopCursorTimer();
            }
        }


        void _didChangeTextEditingValue() {
            _updateRemoteEditingValueIfNeeded();
            _updateImePosIfNeed();
            _startOrStopCursorTimerIfNeeded();
            _updateOrDisposeSelectionOverlayIfNeeded();
            _textChangedSinceLastCaretUpdate = true;
            setState(() => { });
        }

        void _handleFocusChanged() {
            _openOrCloseInputConnectionIfNeeded();
            _startOrStopCursorTimerIfNeeded();
            _updateOrDisposeSelectionOverlayIfNeeded();
            if (_hasFocus) {
                WidgetsBinding.instance.addObserver(this);
                _lastBottomViewInset = Window.instance.viewInsets.bottom;
                _showCaretOnScreen();
                if (!_value.selection.isValid) {
                    widget.controller.selection = TextSelection.collapsed(offset: _value.text.Length);
                }
            }
            else {
                WidgetsBinding.instance.removeObserver(this);
                _value = new TextEditingValue(text: _value.text);
            }

            updateKeepAlive();
        }


        TextDirection? _textDirection {
            get {
                TextDirection? result = widget.textDirection ?? Directionality.of(context);
                D.assert(result != null,
                    () =>
                        $"{GetType().FullName} created without a textDirection and with no ambient Directionality.");
                return result;
            }
        }

        public RenderEditable renderEditable {
            get { return (RenderEditable) _editableKey.currentContext.findRenderObject(); }
        }

        public TextEditingValue textEditingValue {
            get { return _value; }
            set {
                _selectionOverlay?.update(value);
                _formatAndSetValue(value);
            }
        }

        float _devicePixelRatio {
            get { return MediaQuery.of(context).devicePixelRatio; }
        }

        public void bringIntoView(TextPosition position) {
            _scrollController.jumpTo(
                _getScrollOffsetForCaret(renderEditable.getLocalRectForCaret(position)));
        }

        public bool showToolbar() {
            if (_selectionOverlay == null) {
                return false;
            }

            _selectionOverlay.showToolbar();
            return true;
        }

        public void hideToolbar() {
            _selectionOverlay?.hide();
        }

        public override Widget build(BuildContext context) {
            D.assert(WidgetsD.debugCheckHasMediaQuery(context));
            FocusScope.of(context).reparentIfNeeded(widget.focusNode);
            base.build(context); // See AutomaticKeepAliveClientMixin.

            return new Scrollable(
                axisDirection: _isMultiline ? AxisDirection.down : AxisDirection.right,
                controller: _scrollController,
                physics: widget.scrollPhysics,
                dragStartBehavior: widget.dragStartBehavior,
                viewportBuilder: (BuildContext _context, ViewportOffset offset) =>
                    new CompositedTransformTarget(
                        link: _layerLink,
                        child: new _Editable(
                            key: _editableKey,
                            textSpan: buildTextSpan(),
                            value: _value,
                            cursorColor: _cursorColor,
                            backgroundCursorColor: widget.backgroundCursorColor,
                            showCursor: EditableText.debugDeterministicCursor
                                ? new ValueNotifier<bool>(true)
                                : _cursorVisibilityNotifier,
                            hasFocus: _hasFocus,
                            maxLines: widget.maxLines,
                            minLines: widget.minLines,
                            expands: widget.expands,
                            strutStyle: widget.strutStyle,
                            selectionColor: widget.selectionColor,
                            textScaleFactor: widget.textScaleFactor ?? MediaQuery.textScaleFactorOf(context),
                            textAlign: widget.textAlign,
                            textDirection: _textDirection,
                            obscureText: widget.obscureText,
                            autocorrect: widget.autocorrect,
                            offset: offset,
                            onSelectionChanged: _handleSelectionChanged,
                            onCaretChanged: _handleCaretChanged,
                            rendererIgnoresPointer: widget.rendererIgnoresPointer,
                            cursorWidth: widget.cursorWidth,
                            cursorRadius: widget.cursorRadius,
                            cursorOffset: widget.cursorOffset,
                            paintCursorAboveText: widget.paintCursorAboveText,
                            enableInteractiveSelection: widget.enableInteractiveSelection == true,
                            textSelectionDelegate: this,
                            devicePixelRatio: _devicePixelRatio,
                            globalKeyEventHandler : widget.globalKeyEventHandler
                        )
                    )
            );
        }

        public TextSpan buildTextSpan() {
            if (!widget.obscureText && _value.composing.isValid) {
                TextStyle composingStyle = widget.style.merge(
                    new TextStyle(decoration: TextDecoration.underline)
                );

                return new TextSpan(
                    style: widget.style,
                    children: new List<TextSpan> {
                        new TextSpan(text: _value.composing.textBefore(_value.text)),
                        new TextSpan(
                            style: composingStyle,
                            text: _value.composing.textInside(_value.text)
                        ),
                        new TextSpan(text: _value.composing.textAfter(_value.text)),
                    });
            }

            var text = _value.text;
            if (widget.obscureText) {
                text = new string(RenderEditable.obscuringCharacter, text.Length);
                int o = _obscureShowCharTicksPending > 0 ? _obscureLatestCharIndex : -1;
                if (o >= 0 && o < text.Length) {
                    text = text.Substring(0, o) + _value.text.Substring(o, 1) + text.Substring(o + 1);
                }
            }

            return new TextSpan(style: widget.style, text: text);
        }

        // unity keyboard has a preview view with editing function, text selection & cursor function of this widget is disable
        // in the case
        bool _unityKeyboard() {
            return TouchScreenKeyboard.isSupported && widget.unityTouchKeyboard;
        }

        Offset _getImePos() {
            if (_hasInputConnection && _textInputConnection.imeRequired()) {
                var localPos = renderEditable.getLocalRectForCaret(_value.selection.basePos).bottomLeft;
                return renderEditable.localToGlobal(localPos);
            }

            return null;
        }

        bool _imePosUpdateScheduled = false;

        void _updateImePosIfNeed() {
            if (!_hasInputConnection || !_textInputConnection.imeRequired()) {
                return;
            }

            if (_imePosUpdateScheduled) {
                return;
            }

            _imePosUpdateScheduled = true;
            SchedulerBinding.instance.addPostFrameCallback(_ => {
                _imePosUpdateScheduled = false;
                if (!_hasInputConnection) {
                    return;
                }

                _textInputConnection.setIMEPos(_getImePos());
            });
        }
    }

    class _Editable : LeafRenderObjectWidget {
        public readonly TextSpan textSpan;
        public readonly TextEditingValue value;
        public readonly Color cursorColor;
        public readonly Color backgroundCursorColor;
        public readonly ValueNotifier<bool> showCursor;
        public readonly bool hasFocus;
        public readonly int? maxLines;
        public readonly int? minLines;
        public readonly bool expands;
        public readonly StrutStyle strutStyle;
        public readonly Color selectionColor;
        public readonly float textScaleFactor;
        public readonly TextAlign textAlign;
        public readonly TextDirection? textDirection;
        public readonly bool obscureText;
        public readonly bool autocorrect;
        public readonly ViewportOffset offset;
        public readonly SelectionChangedHandler onSelectionChanged;
        public readonly CaretChangedHandler onCaretChanged;
        public readonly bool rendererIgnoresPointer;
        public readonly float? cursorWidth;
        public readonly Radius cursorRadius;
        public readonly Offset cursorOffset;
        public readonly bool enableInteractiveSelection;
        public readonly TextSelectionDelegate textSelectionDelegate;
        public readonly bool? paintCursorAboveText;
        public readonly float? devicePixelRatio;
        public readonly GlobalKeyEventHandlerDelegate globalKeyEventHandler;

        public _Editable(TextSpan textSpan = null,
            TextEditingValue value = null,
            Color cursorColor = null,
            Color backgroundCursorColor = null,
            ValueNotifier<bool> showCursor = null,
            bool hasFocus = false,
            int? maxLines = null,
            int? minLines = null,
            bool expands = false,
            StrutStyle strutStyle = null,
            Color selectionColor = null,
            float textScaleFactor = 1.0f,
            TextDirection? textDirection = null,
            bool obscureText = false,
            TextAlign textAlign = TextAlign.left,
            bool autocorrect = false,
            ViewportOffset offset = null,
            SelectionChangedHandler onSelectionChanged = null,
            CaretChangedHandler onCaretChanged = null,
            bool rendererIgnoresPointer = false,
            Key key = null,
            TextSelectionDelegate textSelectionDelegate = null,
            float? cursorWidth = null,
            Radius cursorRadius = null,
            Offset cursorOffset = null,
            bool enableInteractiveSelection = true,
            bool? paintCursorAboveText = null,
            float? devicePixelRatio = null,
            GlobalKeyEventHandlerDelegate globalKeyEventHandler = null) : base(key) {
            this.textSpan = textSpan;
            this.value = value;
            this.cursorColor = cursorColor;
            this.backgroundCursorColor = backgroundCursorColor;
            this.showCursor = showCursor;
            this.hasFocus = hasFocus;
            this.maxLines = maxLines;
            this.minLines = minLines;
            this.expands = expands;
            this.strutStyle = strutStyle;
            this.selectionColor = selectionColor;
            this.textScaleFactor = textScaleFactor;
            this.textAlign = textAlign;
            this.textDirection = textDirection;
            this.obscureText = obscureText;
            this.autocorrect = autocorrect;
            this.offset = offset;
            this.onSelectionChanged = onSelectionChanged;
            this.onCaretChanged = onCaretChanged;
            this.rendererIgnoresPointer = rendererIgnoresPointer;
            this.textSelectionDelegate = textSelectionDelegate;
            this.cursorWidth = cursorWidth;
            this.cursorRadius = cursorRadius;
            this.cursorOffset = cursorOffset;
            this.enableInteractiveSelection = enableInteractiveSelection;
            this.paintCursorAboveText = paintCursorAboveText;
            this.devicePixelRatio = devicePixelRatio;
            this.globalKeyEventHandler = globalKeyEventHandler;
        }

        public override RenderObject createRenderObject(BuildContext context) {
            return new RenderEditable(
                text: textSpan,
                textDirection: textDirection ?? TextDirection.ltr,
                offset: offset,
                showCursor: showCursor,
                cursorColor: cursorColor,
                backgroundCursorColor: backgroundCursorColor,
                hasFocus: hasFocus,
                maxLines: maxLines,
                minLines: minLines,
                expands: expands,
                strutStyle: strutStyle,
                selectionColor: selectionColor,
                textScaleFactor: textScaleFactor,
                textAlign: textAlign,
                selection: value.selection,
                obscureText: obscureText,
                onSelectionChanged: onSelectionChanged,
                onCaretChanged: onCaretChanged,
                ignorePointer: rendererIgnoresPointer,
                cursorWidth: cursorWidth ?? 1.0f,
                cursorRadius: cursorRadius,
                cursorOffset: cursorOffset,
                enableInteractiveSelection: enableInteractiveSelection,
                textSelectionDelegate: textSelectionDelegate,
                paintCursorAboveText: paintCursorAboveText == true,
                devicePixelRatio: devicePixelRatio ?? 1.0f,
                globalKeyEventHandler : globalKeyEventHandler
            );
        }

        public override void updateRenderObject(BuildContext context, RenderObject renderObject) {
            var edit = (RenderEditable) renderObject;
            edit.text = textSpan;
            edit.cursorColor = cursorColor;
            edit.backgroundCursorColor = backgroundCursorColor;
            edit.showCursor = showCursor;
            edit.hasFocus = hasFocus;
            edit.maxLines = maxLines;
            edit.strutStyle = strutStyle;
            edit.selectionColor = selectionColor;
            edit.textScaleFactor = textScaleFactor;
            edit.textAlign = textAlign;
            edit.textDirection = textDirection;
            edit.selection = value.selection;
            edit.offset = offset;
            edit.onSelectionChanged = onSelectionChanged;
            edit.onCaretChanged = onCaretChanged;
            edit.ignorePointer = rendererIgnoresPointer;
            edit.obscureText = obscureText;
            edit.textSelectionDelegate = textSelectionDelegate;
            edit.cursorWidth = cursorWidth ?? 1.0f;
            edit.cursorRadius = cursorRadius;
            edit.cursorOffset = cursorOffset;
            edit.enableInteractiveSelection = enableInteractiveSelection;
            edit.paintCursorAboveText = paintCursorAboveText == true;
            edit.devicePixelRatio = devicePixelRatio ?? 1.0f;
            edit.globalKeyEventHandler = globalKeyEventHandler;
        }
    }
}