import 'dart:math';

import 'package:flutter/material.dart';

import '../../bloc/theme/theme_bloc.dart';
import '../../settings.dart';

// TODO: Check that it looks right in
// - saved

/// The ratio is defined as 'the amount of space the text should take'
/// divided by 'the amount of space the padding should take'.
///
/// So if the KanjiBox should span 50 pixels, and you wanted 10 of those pixels
/// to be used for padding (5 on each side), and 40 to be used for the text,
/// you could write:
///
/// ```dart
/// KanjiBox.withRatioAndFontSize({
///   kanji: '例',
///   ratio: 4 / 1,
///   fontSize: 40,
/// })
/// ```
///
class KanjiBox extends StatelessWidget {
  final String kanji;
  final double? fontSize;
  final double? padding;
  final Color? foreground;
  final Color? background;
  final double? contentPaddingRatio;
  final double borderRadius;

  static const double defaultRatio = 3 / 1;
  static const double defaultBorderRadius = 10;

  double get ratio => contentPaddingRatio ?? fontSize! / padding!;
  double get fontSizeFactor => ratio / (ratio + 1);
  double get paddingSizeFactor => 1 / (ratio + 1);

  bool get isExpanded => contentPaddingRatio != null;
  double? get size => isExpanded ? null : fontSize! + (2 * padding!);
  double? get oneSidePadding => padding != null ? padding! / 2 : null;

  const KanjiBox._({
    Key? key,
    required this.kanji,
    this.fontSize,
    this.padding,
    this.contentPaddingRatio,
    this.foreground,
    this.background,
    this.borderRadius = defaultBorderRadius,
  })  : assert(
          kanji.length == 1,
          'KanjiBox can not show more than one character at a time',
        ),
        assert(
          contentPaddingRatio != null || (fontSize != null && padding != null),
          'Either contentPaddingRatio or both the fontSize and padding need to be '
          'explicitly defined in order for the box to be able to render correctly',
        ),
        super(key: key);

  const factory KanjiBox.withFontSizeAndPadding({
    required String kanji,
    required double fontSize,
    required double padding,
    Color? foreground,
    Color? background,
    double borderRadius,
  }) = KanjiBox._;

  factory KanjiBox.withFontSize({
    required String kanji,
    required double fontSize,
    double ratio = defaultRatio,
    Color? foreground,
    Color? background,
    double borderRadius = defaultBorderRadius,
  }) =>
      KanjiBox._(
        kanji: kanji,
        fontSize: fontSize,
        padding: pow(ratio * (1 / fontSize), -1).toDouble(),
        foreground: foreground,
        background: background,
        borderRadius: borderRadius,
      );

  factory KanjiBox.withPadding({
    required String kanji,
    double ratio = defaultRatio,
    required double padding,
    Color? foreground,
    Color? background,
    double borderRadius = defaultBorderRadius,
  }) =>
      KanjiBox._(
        kanji: kanji,
        fontSize: ratio * padding,
        padding: padding,
        foreground: foreground,
        background: background,
        borderRadius: borderRadius,
      );

  factory KanjiBox.expanded({
    required String kanji,
    double ratio = defaultRatio,
    Color? foreground,
    Color? background,
    double borderRadius = defaultBorderRadius,
  }) =>
      KanjiBox._(
        kanji: kanji,
        contentPaddingRatio: ratio,
        foreground: foreground,
        background: background,
        borderRadius: borderRadius,
      );

  /// A shortcut
  factory KanjiBox.headline4({
    required BuildContext context,
    required String kanji,
    double ratio = defaultRatio,
    Color? foreground,
    Color? background,
    double borderRadius = defaultBorderRadius,
  }) =>
      KanjiBox.withFontSize(
        kanji: kanji,
        fontSize: Theme.of(context).textTheme.headline4!.fontSize!,
        ratio: ratio,
        foreground: foreground,
        background: background,
        borderRadius: borderRadius,
      );

  @override
  Widget build(BuildContext context) {
    return BlocBuilder<ThemeBloc, ThemeState>(
      builder: (context, state) {
        final calculatedForeground =
            foreground ?? state.theme.menuGreyLight.foreground;
        final calculatedBackground =
            background ?? state.theme.menuGreyLight.background;
        return LayoutBuilder(
          builder: (context, constraints) {
            final sizeConstraint =
                min(constraints.maxHeight, constraints.maxWidth);
            final calculatedFontSize =
                fontSize ?? sizeConstraint * fontSizeFactor;
            final calculatedPadding =
                oneSidePadding ?? (sizeConstraint * paddingSizeFactor) / 2;

            return Container(
              padding: EdgeInsets.all(calculatedPadding),
              alignment: Alignment.center,
              width: size,
              height: size,
              decoration: BoxDecoration(
                color: calculatedBackground,
                borderRadius: BorderRadius.circular(borderRadius),
              ),
              child: FittedBox(
                child: Text(
                  kanji,
                  textScaleFactor: 1,
                  style: TextStyle(
                    color: calculatedForeground,
                    fontSize: calculatedFontSize,
                  ).merge(japaneseFont.textStyle),
                ),
              ),
            );
          },
        );
      },
    );
  }
}