flutter_flutter/packages/flutter/lib/src/material/input_border.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/// @docImport 'input_decorator.dart';
library;

import 'dart:math' as math;
import 'dart:ui' show lerpDouble;

import 'package:flutter/foundation.dart' show clampDouble;
import 'package:flutter/widgets.dart';

/// Defines the appearance of an [InputDecorator]'s border.
///
/// An input decorator's border is specified by [InputDecoration.border].
///
/// The border is drawn relative to the input decorator's "container" which
/// is the optionally filled area above the decorator's helper, error,
/// and counter.
///
/// Input border's are decorated with a line whose weight and color are defined
/// by [borderSide]. The input decorator's renderer animates the input border's
/// appearance in response to state changes, like gaining or losing the focus,
/// by creating new copies of its input border with [copyWith].
///
/// See also:
///
///  * [UnderlineInputBorder], the default [InputDecorator] border which
///    draws a horizontal line at the bottom of the input decorator's container.
///  * [OutlineInputBorder], an [InputDecorator] border which draws a
///    rounded rectangle around the input decorator's container.
///  * [InputDecoration], which is used to configure an [InputDecorator].
abstract class InputBorder extends ShapeBorder {
  /// Creates a border for an [InputDecorator].
  ///
  /// Applications typically do not specify a [borderSide] parameter because the
  /// [InputDecorator] substitutes its own, using [copyWith], based on the
  /// current theme and [InputDecorator.isFocused].
  const InputBorder({this.borderSide = BorderSide.none});

  /// No input border.
  ///
  /// Use this value with [InputDecoration.border] to specify that no border
  /// should be drawn. The [InputDecoration.collapsed] constructor sets
  /// its border to this value.
  static const InputBorder none = _NoInputBorder();

  /// Defines the border line's color and weight.
  ///
  /// The [InputDecorator] creates copies of its input border, using [copyWith],
  /// based on the current theme and [InputDecorator.isFocused].
  final BorderSide borderSide;

  /// Creates a copy of this input border with the specified `borderSide`.
  InputBorder copyWith({BorderSide? borderSide});

  /// True if this border will enclose the [InputDecorator]'s container.
  ///
  /// This property affects the alignment of container's contents. For example
  /// when an input decorator is configured with an [OutlineInputBorder] its
  /// label is centered with its container.
  bool get isOutline;

  /// Paint this input border on [canvas].
  ///
  /// The [rect] parameter bounds the [InputDecorator]'s container.
  ///
  /// The additional `gap` parameters reflect the state of the [InputDecorator]'s
  /// floating label. When an input decorator gains the focus, its label
  /// animates upwards, to make room for the input child. The [gapStart] and
  /// [gapExtent] parameters define a floating label width interval, and
  /// [gapPercentage] defines the animation's progress (0.0 to 1.0).
  @override
  void paint(
    Canvas canvas,
    Rect rect, {
    double? gapStart,
    double gapExtent = 0.0,
    double gapPercentage = 0.0,
    TextDirection? textDirection,
  });
}

// Used to create the InputBorder.none singleton.
class _NoInputBorder extends InputBorder {
  const _NoInputBorder() : super(borderSide: BorderSide.none);

  @override
  _NoInputBorder copyWith({BorderSide? borderSide}) => const _NoInputBorder();

  @override
  bool get isOutline => false;

  @override
  EdgeInsetsGeometry get dimensions => EdgeInsets.zero;

  @override
  _NoInputBorder scale(double t) => const _NoInputBorder();

  @override
  Path getInnerPath(Rect rect, {TextDirection? textDirection}) {
    return Path()..addRect(rect);
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection? textDirection}) {
    return Path()..addRect(rect);
  }

  @override
  void paintInterior(Canvas canvas, Rect rect, Paint paint, {TextDirection? textDirection}) {
    canvas.drawRect(rect, paint);
  }

  @override
  bool get preferPaintInterior => true;

  @override
  void paint(
    Canvas canvas,
    Rect rect, {
    double? gapStart,
    double gapExtent = 0.0,
    double gapPercentage = 0.0,
    TextDirection? textDirection,
  }) {
    // Do not paint.
  }
}

/// Draws a horizontal line at the bottom of an [InputDecorator]'s container and
/// defines the container's shape.
///
/// The input decorator's "container" is the optionally filled area above the
/// decorator's helper, error, and counter.
///
/// See also:
///
///  * [OutlineInputBorder], an [InputDecorator] border which draws a
///    rounded rectangle around the input decorator's container.
///  * [InputDecoration], which is used to configure an [InputDecorator].
class UnderlineInputBorder extends InputBorder {
  /// Creates an underline border for an [InputDecorator].
  ///
  /// The [borderSide] parameter defaults to [BorderSide.none] (it must not be
  /// null). Applications typically do not specify a [borderSide] parameter
  /// because the input decorator substitutes its own, using [copyWith], based
  /// on the current theme and [InputDecorator.isFocused].
  ///
  /// The [borderRadius] parameter defaults to a value where the top left
  /// and right corners have a circular radius of 4.0.
  const UnderlineInputBorder({
    super.borderSide = const BorderSide(),
    this.borderRadius = const BorderRadius.only(
      topLeft: Radius.circular(4.0),
      topRight: Radius.circular(4.0),
    ),
  });

  /// The radii of the border's rounded rectangle corners.
  ///
  /// When this border is used with a filled input decorator, see
  /// [InputDecoration.filled], the border radius defines the shape
  /// of the background fill as well as the bottom left and right
  /// edges of the underline itself.
  ///
  /// By default the top right and top left corners have a circular radius
  /// of 4.0.
  final BorderRadius borderRadius;

  @override
  bool get isOutline => false;

  @override
  UnderlineInputBorder copyWith({BorderSide? borderSide, BorderRadius? borderRadius}) {
    return UnderlineInputBorder(
      borderSide: borderSide ?? this.borderSide,
      borderRadius: borderRadius ?? this.borderRadius,
    );
  }

  @override
  EdgeInsetsGeometry get dimensions {
    return EdgeInsets.only(bottom: borderSide.width);
  }

  @override
  UnderlineInputBorder scale(double t) {
    return UnderlineInputBorder(borderSide: borderSide.scale(t));
  }

  @override
  Path getInnerPath(Rect rect, {TextDirection? textDirection}) {
    return Path()..addRect(
      Rect.fromLTWH(rect.left, rect.top, rect.width, math.max(0.0, rect.height - borderSide.width)),
    );
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection? textDirection}) {
    return Path()..addRRect(borderRadius.resolve(textDirection).toRRect(rect));
  }

  @override
  void paintInterior(Canvas canvas, Rect rect, Paint paint, {TextDirection? textDirection}) {
    canvas.drawRRect(borderRadius.resolve(textDirection).toRRect(rect), paint);
  }

  @override
  bool get preferPaintInterior => true;

  @override
  ShapeBorder? lerpFrom(ShapeBorder? a, double t) {
    if (a is UnderlineInputBorder) {
      return UnderlineInputBorder(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        borderRadius: BorderRadius.lerp(a.borderRadius, borderRadius, t)!,
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  ShapeBorder? lerpTo(ShapeBorder? b, double t) {
    if (b is UnderlineInputBorder) {
      return UnderlineInputBorder(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        borderRadius: BorderRadius.lerp(borderRadius, b.borderRadius, t)!,
      );
    }
    return super.lerpTo(b, t);
  }

  /// Draw a horizontal line at the bottom of [rect].
  ///
  /// The [borderSide] defines the line's color and weight. The `textDirection`
  /// `gap` and `textDirection` parameters are ignored.
  @override
  void paint(
    Canvas canvas,
    Rect rect, {
    double? gapStart,
    double gapExtent = 0.0,
    double gapPercentage = 0.0,
    TextDirection? textDirection,
  }) {
    if (borderSide.style == BorderStyle.none) {
      return;
    }

    if (borderRadius.bottomLeft != Radius.zero || borderRadius.bottomRight != Radius.zero) {
      // This prevents the border from leaking the color due to anti-aliasing rounding errors.
      final updatedBorderRadius = BorderRadius.only(
        bottomLeft: borderRadius.bottomLeft.clamp(maximum: Radius.circular(rect.height / 2)),
        bottomRight: borderRadius.bottomRight.clamp(maximum: Radius.circular(rect.height / 2)),
      );

      BoxBorder.paintNonUniformBorder(
        canvas,
        rect,
        textDirection: textDirection,
        borderRadius: updatedBorderRadius,
        bottom: borderSide.copyWith(strokeAlign: BorderSide.strokeAlignInside),
        color: borderSide.color,
      );
    } else {
      final alignInsideOffset = Offset(0, borderSide.width / 2);
      canvas.drawLine(
        rect.bottomLeft - alignInsideOffset,
        rect.bottomRight - alignInsideOffset,
        borderSide.toPaint(),
      );
    }
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is UnderlineInputBorder &&
        other.borderSide == borderSide &&
        other.borderRadius == borderRadius;
  }

  @override
  int get hashCode => Object.hash(borderSide, borderRadius);
}

/// Draws a rounded rectangle around an [InputDecorator]'s container.
///
/// When the input decorator's label is floating, for example because its
/// input child has the focus, the label appears in a gap in the border outline.
///
/// The input decorator's "container" is the optionally filled area above the
/// decorator's helper, error, and counter.
///
/// See also:
///
///  * [UnderlineInputBorder], the default [InputDecorator] border which
///    draws a horizontal line at the bottom of the input decorator's container.
///  * [ShapedInputBorder], an [InputDecorator] border which draws a custom
///    [ShapeBorder] around the input decorator's container.
///  * [InputDecoration], which is used to configure an [InputDecorator].
class OutlineInputBorder extends InputBorder {
  /// Creates a rounded rectangle outline border for an [InputDecorator].
  ///
  /// If the [borderSide] parameter is [BorderSide.none], it will not draw a
  /// border. However, it will still define a shape (which you can see if
  /// [InputDecoration.filled] is true).
  ///
  /// If an application does not specify a [borderSide] parameter of
  /// value [BorderSide.none], the input decorator substitutes its own, using
  /// [copyWith], based on the current theme and [InputDecorator.isFocused].
  ///
  /// The [borderRadius] parameter defaults to a value where all four corners
  /// have a circular radius of 4.0. The corner radii must be circular, i.e.
  /// their [Radius.x] and [Radius.y] values must be the same.
  ///
  /// See also:
  ///
  ///  * [InputDecoration.floatingLabelBehavior], which should be set to
  ///    [FloatingLabelBehavior.never] when the [borderSide] is
  ///    [BorderSide.none]. If left as [FloatingLabelBehavior.auto], the label
  ///    will extend beyond the container as if the border were still being
  ///    drawn.
  const OutlineInputBorder({
    super.borderSide = const BorderSide(),
    this.borderRadius = const BorderRadius.all(Radius.circular(4.0)),
    this.gapPadding = 4.0,
  }) : assert(gapPadding >= 0.0);

  // The label text's gap can extend into the corners (even both the top left
  // and the top right corner). To avoid the more complicated problem of finding
  // how far the gap penetrates into an elliptical corner, just require them
  // to be circular.
  //
  // This can't be checked by the constructor because const constructor.
  static bool _cornersAreCircular(BorderRadius borderRadius) {
    return borderRadius.topLeft.x == borderRadius.topLeft.y &&
        borderRadius.bottomLeft.x == borderRadius.bottomLeft.y &&
        borderRadius.topRight.x == borderRadius.topRight.y &&
        borderRadius.bottomRight.x == borderRadius.bottomRight.y;
  }

  /// Horizontal padding on either side of the border's
  /// [InputDecoration.labelText] width gap.
  ///
  /// This value is used by the [paint] method to compute the actual gap width.
  final double gapPadding;

  /// The radii of the border's rounded rectangle corners.
  ///
  /// The corner radii must be circular, i.e. their [Radius.x] and [Radius.y]
  /// values must be the same.
  final BorderRadius borderRadius;

  @override
  bool get isOutline => true;

  @override
  OutlineInputBorder copyWith({
    BorderSide? borderSide,
    BorderRadius? borderRadius,
    double? gapPadding,
  }) {
    return OutlineInputBorder(
      borderSide: borderSide ?? this.borderSide,
      borderRadius: borderRadius ?? this.borderRadius,
      gapPadding: gapPadding ?? this.gapPadding,
    );
  }

  @override
  EdgeInsetsGeometry get dimensions {
    return EdgeInsets.all(borderSide.width);
  }

  @override
  OutlineInputBorder scale(double t) {
    return OutlineInputBorder(
      borderSide: borderSide.scale(t),
      borderRadius: borderRadius * t,
      gapPadding: gapPadding * t,
    );
  }

  @override
  ShapeBorder? lerpFrom(ShapeBorder? a, double t) {
    if (a is OutlineInputBorder) {
      final OutlineInputBorder outline = a;
      return OutlineInputBorder(
        borderRadius: BorderRadius.lerp(outline.borderRadius, borderRadius, t)!,
        borderSide: BorderSide.lerp(outline.borderSide, borderSide, t),
        gapPadding: outline.gapPadding,
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  ShapeBorder? lerpTo(ShapeBorder? b, double t) {
    if (b is OutlineInputBorder) {
      final OutlineInputBorder outline = b;
      return OutlineInputBorder(
        borderRadius: BorderRadius.lerp(borderRadius, outline.borderRadius, t)!,
        borderSide: BorderSide.lerp(borderSide, outline.borderSide, t),
        gapPadding: outline.gapPadding,
      );
    }
    return super.lerpTo(b, t);
  }

  @override
  Path getInnerPath(Rect rect, {TextDirection? textDirection}) {
    return Path()
      ..addRRect(borderRadius.resolve(textDirection).toRRect(rect).deflate(borderSide.width));
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection? textDirection}) {
    return Path()..addRRect(borderRadius.resolve(textDirection).toRRect(rect));
  }

  @override
  void paintInterior(Canvas canvas, Rect rect, Paint paint, {TextDirection? textDirection}) {
    canvas.drawRRect(borderRadius.resolve(textDirection).toRRect(rect), paint);
  }

  @override
  bool get preferPaintInterior => true;

  Path _gapBorderPath(Canvas canvas, RRect center, double outerWidth, double start, double extent) {
    // When the corner radii on any side add up to be greater than the
    // given height, each radius has to be scaled to not exceed the
    // size of the width/height of the RRect.
    final RRect scaledRRect = center.scaleRadii();

    final tlCorner = Rect.fromLTWH(
      scaledRRect.left,
      scaledRRect.top,
      scaledRRect.tlRadiusX * 2.0,
      scaledRRect.tlRadiusY * 2.0,
    );
    final trCorner = Rect.fromLTWH(
      scaledRRect.right - scaledRRect.trRadiusX * 2.0,
      scaledRRect.top,
      scaledRRect.trRadiusX * 2.0,
      scaledRRect.trRadiusY * 2.0,
    );
    final brCorner = Rect.fromLTWH(
      scaledRRect.right - scaledRRect.brRadiusX * 2.0,
      scaledRRect.bottom - scaledRRect.brRadiusY * 2.0,
      scaledRRect.brRadiusX * 2.0,
      scaledRRect.brRadiusY * 2.0,
    );
    final blCorner = Rect.fromLTWH(
      scaledRRect.left,
      scaledRRect.bottom - scaledRRect.blRadiusY * 2.0,
      scaledRRect.blRadiusX * 2.0,
      scaledRRect.blRadiusY * 2.0,
    );

    // This assumes that the radius is circular (x and y radius are equal).
    // Currently, BorderRadius only supports circular radii.
    const double cornerArcSweep = math.pi / 2.0;
    final path = Path();

    // Top left corner
    if (scaledRRect.tlRadius != Radius.zero) {
      final double tlCornerArcSweep = math.acos(
        clampDouble(1 - start / scaledRRect.tlRadiusX, 0.0, 1.0),
      );
      path.addArc(tlCorner, math.pi, tlCornerArcSweep);
    } else {
      // Because the path is painted with Paint.strokeCap = StrokeCap.butt, horizontal coordinate is moved
      // to the left using borderSide.width / 2.
      path.moveTo(scaledRRect.left - borderSide.width / 2, scaledRRect.top);
    }

    // Draw top border from top left corner to gap start.
    if (start > scaledRRect.tlRadiusX) {
      path.lineTo(start, scaledRRect.top);
    }

    // Draw top border from gap end to top right corner and draw top right corner.
    const double trCornerArcStart = (3 * math.pi) / 2.0;
    const trCornerArcSweep = cornerArcSweep;
    if (start + extent < outerWidth - scaledRRect.trRadiusX) {
      path.moveTo(start + extent, scaledRRect.top);
      path.lineTo(scaledRRect.right - scaledRRect.trRadiusX, scaledRRect.top);
      if (scaledRRect.trRadius != Radius.zero) {
        path.addArc(trCorner, trCornerArcStart, trCornerArcSweep);
      }
    } else if (start + extent < outerWidth) {
      final double dx = outerWidth - (start + extent);
      final double sweep = math.asin(clampDouble(1 - dx / scaledRRect.trRadiusX, 0.0, 1.0));
      path.addArc(trCorner, trCornerArcStart + sweep, trCornerArcSweep - sweep);
    }

    // Draw right border and bottom right corner.
    if (scaledRRect.brRadius != Radius.zero) {
      path.moveTo(scaledRRect.right, scaledRRect.top + scaledRRect.trRadiusY);
    }
    path.lineTo(scaledRRect.right, scaledRRect.bottom - scaledRRect.brRadiusY);
    if (scaledRRect.brRadius != Radius.zero) {
      path.addArc(brCorner, 0.0, cornerArcSweep);
    }

    // Draw bottom border and bottom left corner.
    path.lineTo(scaledRRect.left + scaledRRect.blRadiusX, scaledRRect.bottom);
    if (scaledRRect.blRadius != Radius.zero) {
      path.addArc(blCorner, math.pi / 2.0, cornerArcSweep);
    }

    // Draw left border
    path.lineTo(scaledRRect.left, scaledRRect.top + scaledRRect.tlRadiusY);

    return path;
  }

  /// Draw a rounded rectangle around [rect] using [borderRadius].
  ///
  /// The [borderSide] defines the line's color and weight.
  ///
  /// The top side of the rounded rectangle may be interrupted by a single gap
  /// if [gapExtent] is non-null. In that case the gap begins at
  /// `gapStart - gapPadding` (assuming that the [textDirection] is [TextDirection.ltr]).
  /// The gap's width is `(gapPadding + gapExtent + gapPadding) * gapPercentage`.
  @override
  void paint(
    Canvas canvas,
    Rect rect, {
    double? gapStart,
    double gapExtent = 0.0,
    double gapPercentage = 0.0,
    TextDirection? textDirection,
  }) {
    assert(gapPercentage >= 0.0 && gapPercentage <= 1.0);
    assert(_cornersAreCircular(borderRadius));

    final Paint paint = borderSide.toPaint();
    final RRect outer = borderRadius.toRRect(rect);
    final RRect center = outer.deflate(borderSide.width / 2.0);
    if (gapStart == null || gapExtent <= 0.0 || gapPercentage == 0.0) {
      canvas.drawRRect(center, paint);
    } else {
      final double extent = lerpDouble(0.0, gapExtent + gapPadding * 2.0, gapPercentage)!;
      final double start = switch (textDirection!) {
        TextDirection.rtl => gapStart + gapPadding - extent,
        TextDirection.ltr => gapStart - gapPadding,
      };
      final Path path = _gapBorderPath(canvas, center, outer.width, math.max(0.0, start), extent);
      canvas.drawPath(path, paint);
    }
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is OutlineInputBorder &&
        other.borderSide == borderSide &&
        other.borderRadius == borderRadius &&
        other.gapPadding == gapPadding;
  }

  @override
  int get hashCode => Object.hash(borderSide, borderRadius, gapPadding);
}

/// Draws a custom shape around an [InputDecorator]'s container.
///
/// This border allows any [ShapeBorder] to be used as an input decorator border.
/// This provides maximum flexibility for custom border shapes while maintaining
/// the gap functionality for floating labels.
///
/// When the input decorator's label is floating, for example because its
/// input child has the focus, the label appears in a gap in the border outline.
///
/// The input decorator's "container" is the optionally filled area above the
/// decorator's helper, error, and counter.
///
/// {@tool dartpad}
/// This sample shows how to use [ShapedInputBorder] with different
/// [ShapeBorder] implementations.
///
/// ** See code in examples/api/lib/material/shaped_input_border/shaped_input_border.0.dart **
/// {@end-tool}
///
/// See also:
///
///  * [OutlineInputBorder], a traditional rounded rectangle border.
///  * [UnderlineInputBorder], the default [InputDecorator] border which
///    draws a horizontal line at the bottom of the input decorator's container.
///  * [RoundedSuperellipseBorder], which can be used with this border for iOS-style shapes.
///  * [InputDecoration], which is used to configure an [InputDecorator].
class ShapedInputBorder extends InputBorder {
  /// Creates a shaped outline border for an [InputDecorator].
  ///
  /// The [shape] parameter defines the custom border shape. It can be any
  /// [ShapeBorder] such as [RoundedSuperellipseBorder], [StadiumBorder],
  /// [BeveledRectangleBorder], or a custom shape.
  ///
  /// If the [borderSide] parameter is [BorderSide.none], it will not draw a
  /// border. However, it will still define a shape (which you can see if
  /// [InputDecoration.filled] is true).
  ///
  /// If an application does not specify a [borderSide] parameter of
  /// value [BorderSide.none], the input decorator substitutes its own, using
  /// [copyWith], based on the current theme and [InputDecorator.isFocused].
  ///
  /// See also:
  ///
  ///  * [InputDecoration.floatingLabelBehavior], which should be set to
  ///    [FloatingLabelBehavior.never] when the [borderSide] is
  ///    [BorderSide.none]. If left as [FloatingLabelBehavior.auto], the label
  ///    will extend beyond the container as if the border were still being
  ///    drawn.
  const ShapedInputBorder({
    super.borderSide = const BorderSide(),
    required this.shape,
    this.gapPadding = 4.0,
  }) : assert(gapPadding >= 0.0);

  /// Horizontal padding on either side of the border's
  /// [InputDecoration.labelText] width gap.
  ///
  /// This value is used by the [paint] method to compute the actual gap width.
  final double gapPadding;

  /// The shape of the border.
  final ShapeBorder shape;

  @override
  bool get isOutline => true;

  @override
  ShapedInputBorder copyWith({BorderSide? borderSide, ShapeBorder? shape, double? gapPadding}) {
    return ShapedInputBorder(
      borderSide: borderSide ?? this.borderSide,
      shape: shape ?? this.shape,
      gapPadding: gapPadding ?? this.gapPadding,
    );
  }

  @override
  EdgeInsetsGeometry get dimensions {
    return EdgeInsets.all(borderSide.width);
  }

  @override
  ShapedInputBorder scale(double t) {
    return ShapedInputBorder(
      borderSide: borderSide.scale(t),
      shape: shape.scale(t),
      gapPadding: gapPadding * t,
    );
  }

  @override
  ShapeBorder? lerpFrom(ShapeBorder? a, double t) {
    if (a is ShapedInputBorder) {
      return ShapedInputBorder(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        shape: ShapeBorder.lerp(a.shape, shape, t)!,
        gapPadding: a.gapPadding,
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  ShapeBorder? lerpTo(ShapeBorder? b, double t) {
    if (b is ShapedInputBorder) {
      return ShapedInputBorder(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        shape: ShapeBorder.lerp(shape, b.shape, t)!,
        gapPadding: b.gapPadding,
      );
    }
    return super.lerpTo(b, t);
  }

  @override
  Path getInnerPath(Rect rect, {TextDirection? textDirection}) {
    return shape.getInnerPath(rect.deflate(borderSide.width), textDirection: textDirection);
  }

  @override
  Path getOuterPath(Rect rect, {TextDirection? textDirection}) {
    return shape.getOuterPath(rect, textDirection: textDirection);
  }

  @override
  void paintInterior(Canvas canvas, Rect rect, Paint paint, {TextDirection? textDirection}) {
    if (shape is OutlinedBorder) {
      (shape as OutlinedBorder).paintInterior(canvas, rect, paint, textDirection: textDirection);
    } else {
      // Fallback for shapes that don't support paintInterior.
      canvas.drawPath(shape.getOuterPath(rect, textDirection: textDirection), paint);
    }
  }

  @override
  bool get preferPaintInterior => shape.preferPaintInterior;

  Path _gapBorderPath(Rect rect, double start, double extent, {TextDirection? textDirection}) {
    // Create a continuous path for the border with a gap in the top edge.
    final Path outerPath = shape.getOuterPath(rect, textDirection: textDirection);

    // If there's no meaningful gap, return the full outline.
    if (start <= 0 && extent <= 0) {
      return outerPath;
    }

    // Create a rectangle that represents the gap area.
    // The gap is on the top edge, so we create a rect that covers the gap region.
    final gapLeft = start;
    final double gapRight = start + extent;

    // Create a path that excludes the gap area by combining with a difference operation.
    // We'll subtract a small rectangle at the top where the gap should be.
    final gapRect = Path()
      ..addRect(
        Rect.fromLTRB(
          clampDouble(gapLeft, rect.left, rect.right),
          rect.top - 1.0, // Extend slightly beyond to ensure clean cut.
          clampDouble(gapRight, rect.left, rect.right),
          rect.top + 1.0, // Small height to only affect top edge.
        ),
      );

    return Path.combine(PathOperation.difference, outerPath, gapRect);
  }

  /// Draw the custom shape around [rect].
  ///
  /// The [borderSide] defines the line's color and weight.
  ///
  /// The top side of the border may be interrupted by a single gap
  /// if [gapExtent] is non-null. In that case the gap begins at
  /// `gapStart - gapPadding` (assuming that the [textDirection] is [TextDirection.ltr]).
  /// The gap's width is `(gapPadding + gapExtent + gapPadding) * gapPercentage`.
  @override
  void paint(
    Canvas canvas,
    Rect rect, {
    double? gapStart,
    double gapExtent = 0.0,
    double gapPercentage = 0.0,
    TextDirection? textDirection,
  }) {
    assert(gapPercentage >= 0.0 && gapPercentage <= 1.0);

    final Paint paint = borderSide.toPaint();
    final Rect deflatedRect = rect.deflate(borderSide.width / 2.0);

    if (gapStart == null || gapExtent <= 0.0 || gapPercentage == 0.0) {
      // Draw the shape without a gap.
      if (shape is OutlinedBorder) {
        final outlinedShape = shape as OutlinedBorder;
        // Create a copy with our border side.
        final OutlinedBorder shapedBorder = outlinedShape.copyWith(side: borderSide);
        shapedBorder.paint(canvas, deflatedRect, textDirection: textDirection);
      } else {
        canvas.drawPath(shape.getOuterPath(deflatedRect, textDirection: textDirection), paint);
      }
    } else {
      final double extent = lerpDouble(0.0, gapExtent + gapPadding * 2.0, gapPercentage)!;
      final double start = switch (textDirection!) {
        TextDirection.rtl => gapStart + gapPadding - extent,
        TextDirection.ltr => gapStart - gapPadding,
      };
      final Path path = _gapBorderPath(
        deflatedRect,
        math.max(0.0, start),
        extent,
        textDirection: textDirection,
      );
      canvas.drawPath(path, paint);
    }
  }

  @override
  bool operator ==(Object other) {
    if (identical(this, other)) {
      return true;
    }
    if (other.runtimeType != runtimeType) {
      return false;
    }
    return other is ShapedInputBorder &&
        other.borderSide == borderSide &&
        other.shape == shape &&
        other.gapPadding == gapPadding;
  }

  @override
  int get hashCode => Object.hash(borderSide, shape, gapPadding);
}