// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

import 'feedback.dart';
import 'input_decorator.dart';
import 'material.dart';
import 'text_selection.dart';
import 'theme.dart';

export 'package:flutter/services.dart' show TextInputType;

/// A material design text field.
///
/// A text field lets the user enter text, either with hardware keyboard or with
/// an onscreen keyboard.
///
/// The text field calls the [onChanged] callback whenever the user changes the
/// text in the field. If the user indicates that they are done typing in the
/// field (e.g., by pressing a button on the soft keyboard), the text field
/// calls the [onSubmitted] callback.
///
/// To control the text that is displayed in the text field, use the
/// [controller]. For example, to set the initial value of the text field, use
/// a [controller] that already contains some text. The [controller] can also
/// control the selection and composing region (and to observe changes to the
/// text, selection, and composing region).
///
/// By default, a text field has a [decoration] that draws a divider below the
/// text field. You can use the [decoration] property to control the decoration,
/// for example by adding a label or an icon. If you set the [decoration]
/// property to null, the decoration will be removed entirely, including the
/// extra padding introduced by the decoration to save space for the labels.
///
/// If [decoration] is non-null (which is the default), the text field requires
/// one of its ancestors to be a [Material] widget.
///
/// To integrate the [TextField] into a [Form] with other [FormField] widgets,
/// consider using [TextFormField].
///
/// See also:
///
///  * <https://material.google.com/components/text-fields.html>
///  * [TextFormField], which integrates with the [Form] widget.
///  * [InputDecorator], which shows the labels and other visual elements that
///    surround the actual text editing widget.
///  * [EditableText], which is the raw text editing control at the heart of a
///    [TextField]. (The [EditableText] widget is rarely used directly unless
///    you are implementing an entirely different design language, such as
///    Cupertino.)
class TextField extends StatefulWidget {
  /// Creates a Material Design text field.
  ///
  /// If [decoration] is non-null (which is the default), the text field requires
  /// one of its ancestors to be a [Material] widget.
  ///
  /// To remove the decoration entirely (including the extra padding introduced
  /// by the decoration to save space for the labels), set the [decoration] to
  /// null.
  ///
  /// The [maxLines] property can be set to null to remove the restriction on
  /// the number of lines. By default, it is one, meaning this is a single-line
  /// text field. [maxLines] must not be zero. If [maxLines] is not one, then
  /// [keyboardType] is ignored, and the [TextInputType.multiline] keyboard
  /// type is used.
  ///
  /// The [maxLength] property is set to null by default, which means the
  /// number of characters allowed in the text field is not restricted. If
  /// [maxLength] is set, a character counter will be displayed below the
  /// field, showing how many characters have been entered and how many are
  /// allowed. After [maxLength] characters have been input, additional input
  /// is ignored, unless [maxLengthEnforced] is set to false. The TextField
  /// enforces the length with a [LengthLimitingTextInputFormatter], which is
  /// evaluated after the supplied [inputFormatters], if any. The [maxLength]
  /// value must be either null or greater than zero.
  ///
  /// If [maxLengthEnforced] is set to false, then more than [maxLength]
  /// characters may be entered, and the error counter and divider will
  /// switch to the [decoration.errorStyle] when the limit is exceeded.
  ///
  /// The [keyboardType], [textAlign], [autofocus], [obscureText], and
  /// [autocorrect] arguments must not be null.
  ///
  /// See also:
  ///
  ///  * [maxLength], which discusses the precise meaning of "number of
  ///    characters" and how it may differ from the intuitive meaning.
  const TextField({
    Key key,
    this.controller,
    this.focusNode,
    this.decoration: const InputDecoration(),
    TextInputType keyboardType: TextInputType.text,
    this.style,
    this.textAlign: TextAlign.start,
    this.autofocus: false,
    this.obscureText: false,
    this.autocorrect: true,
    this.maxLines: 1,
    this.maxLength,
    this.maxLengthEnforced: true,
    this.onChanged,
    this.onSubmitted,
    this.inputFormatters,
  }) : assert(keyboardType != null),
       assert(textAlign != null),
       assert(autofocus != null),
       assert(obscureText != null),
       assert(autocorrect != null),
       assert(maxLengthEnforced != null),
       assert(maxLines == null || maxLines > 0),
       assert(maxLength == null || maxLength > 0),
       keyboardType = maxLines == 1 ? keyboardType : TextInputType.multiline,
       super(key: key);

  /// Controls the text being edited.
  ///
  /// If null, this widget will create its own [TextEditingController].
  final TextEditingController controller;

  /// Controls whether this widget has keyboard focus.
  ///
  /// If null, this widget will create its own [FocusNode].
  final FocusNode focusNode;

  /// The decoration to show around the text field.
  ///
  /// By default, draws a horizontal line under the text field but can be
  /// configured to show an icon, label, hint text, and error text.
  ///
  /// Set this field to null to remove the decoration entirely (including the
  /// extra padding introduced by the decoration to save space for the labels).
  final InputDecoration decoration;

  /// The type of keyboard to use for editing the text.
  ///
  /// Defaults to [TextInputType.text]. Must not be null. If
  /// [maxLines] is not one, then [keyboardType] is ignored, and the
  /// [TextInputType.multiline] keyboard type is used.
  final TextInputType keyboardType;

  /// The style to use for the text being edited.
  ///
  /// This text style is also used as the base style for the [decoration].
  ///
  /// If null, defaults to the `subhead` text style from the current [Theme].
  final TextStyle style;

  /// How the text being edited should be aligned horizontally.
  ///
  /// Defaults to [TextAlign.start].
  final TextAlign textAlign;

  /// Whether this text field should focus itself if nothing else is already
  /// focused.
  ///
  /// If true, the keyboard will open as soon as this text field obtains focus.
  /// Otherwise, the keyboard is only shown after the user taps the text field.
  ///
  /// Defaults to false. Cannot be null.
  // See https://github.com/flutter/flutter/issues/7035 for the rationale for this
  // keyboard behavior.
  final bool autofocus;

  /// Whether to hide the text being edited (e.g., for passwords).
  ///
  /// When this is set to true, all the characters in the text field are
  /// replaced by U+2022 BULLET characters (•).
  ///
  /// Defaults to false. Cannot be null.
  final bool obscureText;

  /// Whether to enable autocorrection.
  ///
  /// Defaults to true. Cannot be null.
  final bool autocorrect;

  /// The maximum number of lines for the text to span, wrapping if necessary.
  ///
  /// If this is 1 (the default), the text will not wrap, but will scroll
  /// horizontally instead.
  ///
  /// If this is null, there is no limit to the number of lines. If it is not
  /// null, the value must be greater than zero.
  final int maxLines;

  /// The maximum number of characters (Unicode scalar values) to allow in the
  /// text field.
  ///
  /// If set, a character counter will be displayed below the
  /// field, showing how many characters have been entered and how many are
  /// allowed. After [maxLength] characters have been input, additional input
  /// is ignored, unless [maxLengthEnforced] is set to false. The TextField
  /// enforces the length with a [LengthLimitingTextInputFormatter], which is
  /// evaluated after the supplied [inputFormatters], if any.
  ///
  /// This value must be either null or greater than zero. If set to null
  /// (the default), there is no limit to the number of characters allowed.
  ///
  /// Whitespace characters (e.g. newline, space, tab) are included in the
  /// character count.
  ///
  /// If [maxLengthEnforced] is set to false, then more than [maxLength]
  /// characters may be entered, but the error counter and divider will
  /// switch to the [decoration.errorStyle] when the limit is exceeded.
  ///
  /// The TextField does not currently count Unicode grapheme clusters (i.e.
  /// characters visible to the user), it counts Unicode scalar values, which
  /// leaves out a number of useful possible characters (like many emoji and
  /// composed characters), so this will be inaccurate in the presence of those
  /// characters. If you expect to encounter these kinds of characters, be
  /// generous in the maxLength used.
  ///
  /// For instance, the character "ö" can be represented as '\u{006F}\u{0308}',
  /// which is the letter "o" followed by a composed diaeresis "¨", or it can
  /// be represented as '\u{00F6}', which is the Unicode scalar value "LATIN
  /// SMALL LETTER O WITH DIAERESIS".  In the first case, the text field will
  /// count two characters, and the second case will be counted as one
  /// character, even though the user can see no difference in the input.
  ///
  /// Similarly, some emoji are represented by multiple scalar values. The
  /// Unicode "THUMBS UP SIGN + MEDIUM SKIN TONE MODIFIER", "👍🏽", should be
  /// counted as a single character, but because it is a combination of two
  /// Unicode scalar values, '\u{1F44D}\u{1F3FD}', it is counted as two
  /// characters.
  ///
  /// See also:
  ///
  ///  * [LengthLimitingTextInputFormatter] for more information on how it
  ///    counts characters, and how it may differ from the intuitive meaning.
  final int maxLength;

  /// If true, prevents the field from allowing more than [maxLength]
  /// characters.
  ///
  /// If [maxLength] is set, [maxLengthEnforced] indicates whether or not to
  /// enforce the limit, or merely provide a character counter and warning when
  /// [maxLength] is exceeded.
  final bool maxLengthEnforced;

  /// Called when the text being edited changes.
  final ValueChanged<String> onChanged;

  /// Called when the user indicates that they are done editing the text in the
  /// field.
  final ValueChanged<String> onSubmitted;

  /// Optional input validation and formatting overrides.
  ///
  /// Formatters are run in the provided order when the text input changes.
  final List<TextInputFormatter> inputFormatters;

  @override
  _TextFieldState createState() => new _TextFieldState();

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder description) {
    super.debugFillProperties(description);
    description.add(new DiagnosticsProperty<TextEditingController>('controller', controller, defaultValue: null));
    description.add(new DiagnosticsProperty<FocusNode>('focusNode', focusNode, defaultValue: null));
    description.add(new DiagnosticsProperty<InputDecoration>('decoration', decoration));
    description.add(new EnumProperty<TextInputType>('keyboardType', keyboardType, defaultValue: TextInputType.text));
    description.add(new DiagnosticsProperty<TextStyle>('style', style, defaultValue: null));
    description.add(new DiagnosticsProperty<bool>('autofocus', autofocus, defaultValue: false));
    description.add(new DiagnosticsProperty<bool>('obscureText', obscureText, defaultValue: false));
    description.add(new DiagnosticsProperty<bool>('autocorrect', autocorrect, defaultValue: false));
    description.add(new IntProperty('maxLines', maxLines, defaultValue: 1));
    description.add(new IntProperty('maxLength', maxLength, defaultValue: null));
    description.add(new FlagProperty('maxLengthEnforced', value: maxLengthEnforced, ifTrue: 'max length enforced'));
  }
}

class _TextFieldState extends State<TextField> {
  final GlobalKey<EditableTextState> _editableTextKey = new GlobalKey<EditableTextState>();

  TextEditingController _controller;
  TextEditingController get _effectiveController => widget.controller ?? _controller;

  FocusNode _focusNode;
  FocusNode get _effectiveFocusNode => widget.focusNode ?? (_focusNode ??= new FocusNode());

  bool get needsCounter => widget.maxLength != null
    && widget.decoration != null
    && widget.decoration.counterText == null;

  InputDecoration _getEffectiveDecoration() {
    if (!needsCounter)
      return widget.decoration;

    final InputDecoration effectiveDecoration = widget?.decoration ?? const InputDecoration();
    final String counterText = '${_effectiveController.value.text.runes.length} / ${widget.maxLength}';
    if (_effectiveController.value.text.runes.length > widget.maxLength) {
      final ThemeData themeData = Theme.of(context);
      return effectiveDecoration.copyWith(
        errorText: effectiveDecoration.errorText ?? '',
        counterStyle: effectiveDecoration.errorStyle
          ?? themeData.textTheme.caption.copyWith(color: themeData.errorColor),
        counterText: counterText,
      );
    }
    return effectiveDecoration.copyWith(counterText: counterText);
  }

  @override
  void initState() {
    super.initState();
    if (widget.controller == null)
      _controller = new TextEditingController();
  }

  @override
  void didUpdateWidget(TextField oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.controller == null && oldWidget.controller != null)
      _controller = new TextEditingController.fromValue(oldWidget.controller.value);
    else if (widget.controller != null && oldWidget.controller == null)
      _controller = null;
  }

  @override
  void dispose() {
    _focusNode?.dispose();
    super.dispose();
  }

  void _requestKeyboard() {
    _editableTextKey.currentState?.requestKeyboard();
  }

  void _onSelectionChanged(BuildContext context, SelectionChangedCause cause) {
    if (cause == SelectionChangedCause.longPress)
      Feedback.forLongPress(context);
  }

  @override
  Widget build(BuildContext context) {
    final ThemeData themeData = Theme.of(context);
    final TextStyle style = widget.style ?? themeData.textTheme.subhead;
    final TextEditingController controller = _effectiveController;
    final FocusNode focusNode = _effectiveFocusNode;
    final List<TextInputFormatter> formatters = widget.inputFormatters ?? <TextInputFormatter>[];
    if (widget.maxLength != null && widget.maxLengthEnforced)
      formatters.add(new LengthLimitingTextInputFormatter(widget.maxLength));

    Widget child = new RepaintBoundary(
      child: new EditableText(
        key: _editableTextKey,
        controller: controller,
        focusNode: focusNode,
        keyboardType: widget.keyboardType,
        style: style,
        textAlign: widget.textAlign,
        autofocus: widget.autofocus,
        obscureText: widget.obscureText,
        autocorrect: widget.autocorrect,
        maxLines: widget.maxLines,
        cursorColor: themeData.textSelectionColor,
        selectionColor: themeData.textSelectionColor,
        selectionControls: themeData.platform == TargetPlatform.iOS
            ? cupertinoTextSelectionControls
            : materialTextSelectionControls,
        onChanged: widget.onChanged,
        onSubmitted: widget.onSubmitted,
        onSelectionChanged: (TextSelection _, SelectionChangedCause cause) => _onSelectionChanged(context, cause),
        inputFormatters: formatters,
      ),
    );

    if (widget.decoration != null) {
      child = new AnimatedBuilder(
        animation: new Listenable.merge(<Listenable>[ focusNode, controller ]),
        builder: (BuildContext context, Widget child) {
          return new InputDecorator(
            decoration: _getEffectiveDecoration(),
            baseStyle: widget.style,
            textAlign: widget.textAlign,
            isFocused: focusNode.hasFocus,
            isEmpty: controller.value.text.isEmpty,
            child: child,
          );
        },
        child: child,
      );
    }

    return new Semantics(
      onTap: () {
        if (!_controller.selection.isValid)
          _controller.selection = new TextSelection.collapsed(offset: _controller.text.length);
        _requestKeyboard();
      },
      child: new GestureDetector(
        behavior: HitTestBehavior.opaque,
        onTap: _requestKeyboard,
        child: child,
        excludeFromSemantics: true,
      ),
    );
  }
}