// 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.

import 'package:flutter/widgets.dart';

import 'constants.dart';
import 'theme.dart';
import 'theme_data.dart';

// Examples can assume:
// String userAvatarUrl;

/// A circle that represents a user.
///
/// Typically used with a user's profile image, or, in the absence of
/// such an image, the user's initials. A given user's initials should
/// always be paired with the same background color, for consistency.
///
/// The [onBackgroundImageError] parameter must be null if the [backgroundImage]
/// is null.
///
/// {@tool snippet}
///
/// If the avatar is to have an image, the image should be specified in the
/// [backgroundImage] property:
///
/// ```dart
/// CircleAvatar(
///   backgroundImage: NetworkImage(userAvatarUrl),
/// )
/// ```
/// {@end-tool}
///
/// The image will be cropped to have a circle shape.
///
/// {@tool snippet}
///
/// If the avatar is to just have the user's initials, they are typically
/// provided using a [Text] widget as the [child] and a [backgroundColor]:
///
/// ```dart
/// CircleAvatar(
///   backgroundColor: Colors.brown.shade800,
///   child: Text('AH'),
/// )
/// ```
/// {@end-tool}
///
/// See also:
///
///  * [Chip], for representing users or concepts in long form.
///  * [ListTile], which can combine an icon (such as a [CircleAvatar]) with
///    some text for a fixed height list entry.
///  * <https://material.io/design/components/chips.html#input-chips>
class CircleAvatar extends StatelessWidget {
  /// Creates a circle that represents a user.
  const CircleAvatar({
    Key key,
    this.child,
    this.backgroundColor,
    this.backgroundImage,
    this.onBackgroundImageError,
    this.foregroundColor,
    this.radius,
    this.minRadius,
    this.maxRadius,
  }) : assert(radius == null || (minRadius == null && maxRadius == null)),
       assert(backgroundImage != null || onBackgroundImageError == null),
       super(key: key);

  /// The widget below this widget in the tree.
  ///
  /// Typically a [Text] widget. If the [CircleAvatar] is to have an image, use
  /// [backgroundImage] instead.
  final Widget child;

  /// The color with which to fill the circle. Changing the background
  /// color will cause the avatar to animate to the new color.
  ///
  /// If a [backgroundColor] is not specified, the theme's
  /// [ThemeData.primaryColorLight] is used with dark foreground colors, and
  /// [ThemeData.primaryColorDark] with light foreground colors.
  final Color backgroundColor;

  /// The default text color for text in the circle.
  ///
  /// Defaults to the primary text theme color if no [backgroundColor] is
  /// specified.
  ///
  /// Defaults to [ThemeData.primaryColorLight] for dark background colors, and
  /// [ThemeData.primaryColorDark] for light background colors.
  final Color foregroundColor;

  /// The background image of the circle. Changing the background
  /// image will cause the avatar to animate to the new image.
  ///
  /// If the [CircleAvatar] is to have the user's initials, use [child] instead.
  final ImageProvider backgroundImage;

  /// An optional error callback for errors emitted when loading
  /// [backgroundImage].
  final ImageErrorListener onBackgroundImageError;

  /// The size of the avatar, expressed as the radius (half the diameter).
  ///
  /// If [radius] is specified, then neither [minRadius] nor [maxRadius] may be
  /// specified. Specifying [radius] is equivalent to specifying a [minRadius]
  /// and [maxRadius], both with the value of [radius].
  ///
  /// If neither [minRadius] nor [maxRadius] are specified, defaults to 20
  /// logical pixels. This is the appropriate size for use with
  /// [ListTile.leading].
  ///
  /// Changes to the [radius] are animated (including changing from an explicit
  /// [radius] to a [minRadius]/[maxRadius] pair or vice versa).
  final double radius;

  /// The minimum size of the avatar, expressed as the radius (half the
  /// diameter).
  ///
  /// If [minRadius] is specified, then [radius] must not also be specified.
  ///
  /// Defaults to zero.
  ///
  /// Constraint changes are animated, but size changes due to the environment
  /// itself changing are not. For example, changing the [minRadius] from 10 to
  /// 20 when the [CircleAvatar] is in an unconstrained environment will cause
  /// the avatar to animate from a 20 pixel diameter to a 40 pixel diameter.
  /// However, if the [minRadius] is 40 and the [CircleAvatar] has a parent
  /// [SizedBox] whose size changes instantaneously from 20 pixels to 40 pixels,
  /// the size will snap to 40 pixels instantly.
  final double minRadius;

  /// The maximum size of the avatar, expressed as the radius (half the
  /// diameter).
  ///
  /// If [maxRadius] is specified, then [radius] must not also be specified.
  ///
  /// Defaults to [double.infinity].
  ///
  /// Constraint changes are animated, but size changes due to the environment
  /// itself changing are not. For example, changing the [maxRadius] from 10 to
  /// 20 when the [CircleAvatar] is in an unconstrained environment will cause
  /// the avatar to animate from a 20 pixel diameter to a 40 pixel diameter.
  /// However, if the [maxRadius] is 40 and the [CircleAvatar] has a parent
  /// [SizedBox] whose size changes instantaneously from 20 pixels to 40 pixels,
  /// the size will snap to 40 pixels instantly.
  final double maxRadius;

  // The default radius if nothing is specified.
  static const double _defaultRadius = 20.0;

  // The default min if only the max is specified.
  static const double _defaultMinRadius = 0.0;

  // The default max if only the min is specified.
  static const double _defaultMaxRadius = double.infinity;

  double get _minDiameter {
    if (radius == null && minRadius == null && maxRadius == null) {
      return _defaultRadius * 2.0;
    }
    return 2.0 * (radius ?? minRadius ?? _defaultMinRadius);
  }

  double get _maxDiameter {
    if (radius == null && minRadius == null && maxRadius == null) {
      return _defaultRadius * 2.0;
    }
    return 2.0 * (radius ?? maxRadius ?? _defaultMaxRadius);
  }

  @override
  Widget build(BuildContext context) {
    assert(debugCheckHasMediaQuery(context));
    final ThemeData theme = Theme.of(context);
    TextStyle textStyle = theme.primaryTextTheme.subtitle1.copyWith(color: foregroundColor);
    Color effectiveBackgroundColor = backgroundColor;
    if (effectiveBackgroundColor == null) {
      switch (ThemeData.estimateBrightnessForColor(textStyle.color)) {
        case Brightness.dark:
          effectiveBackgroundColor = theme.primaryColorLight;
          break;
        case Brightness.light:
          effectiveBackgroundColor = theme.primaryColorDark;
          break;
      }
    } else if (foregroundColor == null) {
      switch (ThemeData.estimateBrightnessForColor(backgroundColor)) {
        case Brightness.dark:
          textStyle = textStyle.copyWith(color: theme.primaryColorLight);
          break;
        case Brightness.light:
          textStyle = textStyle.copyWith(color: theme.primaryColorDark);
          break;
      }
    }
    final double minDiameter = _minDiameter;
    final double maxDiameter = _maxDiameter;
    return AnimatedContainer(
      constraints: BoxConstraints(
        minHeight: minDiameter,
        minWidth: minDiameter,
        maxWidth: maxDiameter,
        maxHeight: maxDiameter,
      ),
      duration: kThemeChangeDuration,
      decoration: BoxDecoration(
        color: effectiveBackgroundColor,
        image: backgroundImage != null
          ? DecorationImage(
              image: backgroundImage,
              onError: onBackgroundImageError,
              fit: BoxFit.cover,
            )
          : null,
        shape: BoxShape.circle,
      ),
      child: child == null
          ? null
          : Center(
              child: MediaQuery(
                // Need to ignore the ambient textScaleFactor here so that the
                // text doesn't escape the avatar when the textScaleFactor is large.
                data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
                child: IconTheme(
                  data: theme.iconTheme.copyWith(color: textStyle.color),
                  child: DefaultTextStyle(
                    style: textStyle,
                    child: child,
                  ),
                ),
              ),
            ),
    );
  }
}