flutter_flutter/dev/tools/gen_defaults/lib/template.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.

import 'dart:io';

import 'token_logger.dart';

/// Base class for code generation templates.
abstract class TokenTemplate {
  const TokenTemplate(
    this.blockName,
    this.fileName,
    this._tokens, {
    this.colorSchemePrefix = 'Theme.of(context).colorScheme.',
    this.textThemePrefix = 'Theme.of(context).textTheme.',
  });

  /// Name of the code block that this template will generate.
  ///
  /// Used to identify an existing block when updating it.
  final String blockName;

  /// Name of the file that will be updated with the generated code.
  final String fileName;

  /// Map of token data extracted from the Material Design token database.
  final Map<String, dynamic> _tokens;

  /// Optional prefix prepended to color definitions.
  ///
  /// Defaults to 'Theme.of(context).colorScheme.'
  final String colorSchemePrefix;

  /// Optional prefix prepended to text style definitions.
  ///
  /// Defaults to 'Theme.of(context).textTheme.'
  final String textThemePrefix;

  /// Check if a token is available.
  bool tokenAvailable(String tokenName) => _tokens.containsKey(tokenName);

  /// Resolve a token while logging its usage.
  /// There will be no log if [optional] is true and the token doesn't exist.
  dynamic getToken(String tokenName, {bool optional = false}) {
    if (optional && !tokenAvailable(tokenName)) {
      return null;
    }
    tokenLogger.log(tokenName);
    return _tokens[tokenName];
  }

  static const String beginGeneratedComment = '''

// BEGIN GENERATED TOKEN PROPERTIES''';

  static const String headerComment = '''

// Do not edit by hand. The code between the "BEGIN GENERATED" and
// "END GENERATED" comments are generated from data in the Material
// Design token database by the script:
//   dev/tools/gen_defaults/bin/gen_defaults.dart.

// dart format off
''';

  // TODO(goderbauer): Update the script to output auto-formatted code and remove
  //  "dart format off/on" from headerComment and footerComment.
  static const String footerComment = '''
// dart format on
''';

  static const String endGeneratedComment = '''

// END GENERATED TOKEN PROPERTIES''';

  /// Replace or append the contents of the file with the text from [generate].
  ///
  /// If the file already contains a generated text block matching the
  /// [blockName], it will be replaced by the [generate] output. Otherwise
  /// the content will just be appended to the end of the file.
  void updateFile() {
    final String contents = File(fileName).readAsStringSync();
    final beginComment = '$beginGeneratedComment - $blockName\n';
    final endComment = '$endGeneratedComment - $blockName\n';
    final int beginPreviousBlock = contents.indexOf(beginComment);
    final int endPreviousBlock = contents.indexOf(endComment);
    late String contentBeforeBlock;
    late String contentAfterBlock;
    if (beginPreviousBlock != -1) {
      if (endPreviousBlock < beginPreviousBlock) {
        print('Unable to find block named $blockName in $fileName, skipping code generation.');
        return;
      }
      // Found a valid block matching the name, so record the content before and after.
      contentBeforeBlock = contents.substring(0, beginPreviousBlock);
      contentAfterBlock = contents.substring(endPreviousBlock + endComment.length);
    } else {
      // Just append to the bottom.
      contentBeforeBlock = contents;
      contentAfterBlock = '';
    }

    final buffer = StringBuffer(contentBeforeBlock);
    buffer.write(beginComment);
    buffer.write(headerComment);
    buffer.write(generate());
    buffer.write(footerComment);
    buffer.write(endComment);
    buffer.write(contentAfterBlock);
    File(fileName).writeAsStringSync(buffer.toString());
  }

  /// Provide the generated content for the template.
  ///
  /// This abstract method needs to be implemented by subclasses
  /// to provide the content that [updateFile] will append to the
  /// bottom of the file.
  String generate();

  /// Generate a [ColorScheme] color name for the given token.
  ///
  /// If there is a value for the given token, this will return
  /// the value prepended with [colorSchemePrefix].
  ///
  /// Otherwise it will return [defaultValue] if provided or 'null' if not.
  ///
  /// If a [defaultValue] is not provided and the token doesn't exist, the token
  /// lookup is logged and a warning will be shown at the end of the process.
  ///
  /// See also:
  ///   * [componentColor], that provides support for an optional opacity.
  String color(String colorToken, [String? defaultValue]) {
    final String effectiveDefault = defaultValue ?? 'null';
    final dynamic tokenVal = getToken(colorToken, optional: defaultValue != null);
    return tokenVal == null ? effectiveDefault : '$colorSchemePrefix$tokenVal';
  }

  /// Generate a [ColorScheme] color name for the given token or a transparent
  /// color if there is no value for the token.
  ///
  /// If there is a value for the given token, this will return
  /// the value prepended with [colorSchemePrefix].
  ///
  /// Otherwise it will return 'Colors.transparent'.
  ///
  /// See also:
  ///   * [componentColor], that provides support for an optional opacity.
  String? colorOrTransparent(String token) => color(token, 'Colors.transparent');

  /// Generate a [ColorScheme] color name for the given component's color
  /// with opacity if available.
  ///
  /// If there is a value for the given component's color, this will return
  /// the value prepended with [colorSchemePrefix]. If there is also
  /// an opacity specified for the component, then the returned value
  /// will include this opacity calculation.
  ///
  /// If there is no value for the component's color, 'null' will be returned.
  ///
  /// See also:
  ///   * [color], that provides support for looking up a raw color token.
  String componentColor(String componentToken) {
    final colorToken = '$componentToken.color';
    if (!tokenAvailable(colorToken)) {
      return 'null';
    }
    String value = color(colorToken);
    final opacityToken = '$componentToken.opacity';
    if (tokenAvailable(opacityToken)) {
      value += '.withOpacity(${opacity(opacityToken)})';
    }
    return value;
  }

  /// Generate the opacity value for the given token.
  String? opacity(String token) {
    tokenLogger.log(token);
    return _numToString(getToken(token));
  }

  String? _numToString(Object? value, [int? digits]) {
    return switch (value) {
      null => null,
      double.infinity => 'double.infinity',
      num() when digits == null => value.toString(),
      num() => value.toStringAsFixed(digits!),
      _ => getToken(value as String).toString(),
    };
  }

  /// Generate an elevation value for the given component token.
  String elevation(String componentToken) {
    return getToken(getToken('$componentToken.elevation')! as String)!.toString();
  }

  /// Generate a size value for the given component token.
  ///
  /// Non-square sizes are specified as width and height.
  String size(String componentToken) {
    final sizeToken = '$componentToken.size';
    if (!tokenAvailable(sizeToken)) {
      final widthToken = '$componentToken.width';
      final heightToken = '$componentToken.height';
      if (!tokenAvailable(widthToken) && !tokenAvailable(heightToken)) {
        throw Exception('Unable to find width, height, or size tokens for $componentToken');
      }
      final String? width = _numToString(
        tokenAvailable(widthToken) ? getToken(widthToken)! as num : double.infinity,
        0,
      );
      final String? height = _numToString(
        tokenAvailable(heightToken) ? getToken(heightToken)! as num : double.infinity,
        0,
      );
      return 'const Size($width, $height)';
    }
    return 'const Size.square(${_numToString(getToken(sizeToken))})';
  }

  /// Generate a shape constant for the given component token.
  ///
  /// Currently supports family:
  ///   - "SHAPE_FAMILY_ROUNDED_CORNERS" which maps to [RoundedRectangleBorder].
  ///   - "SHAPE_FAMILY_CIRCULAR" which maps to a [StadiumBorder].
  String shape(String componentToken, [String prefix = 'const ']) {
    final shape = getToken(getToken('$componentToken.shape') as String) as Map<String, dynamic>;
    switch (shape['family']) {
      case 'SHAPE_FAMILY_ROUNDED_CORNERS':
        final topLeft = shape['topLeft'] as double;
        final topRight = shape['topRight'] as double;
        final bottomLeft = shape['bottomLeft'] as double;
        final bottomRight = shape['bottomRight'] as double;
        if (topLeft == topRight && topLeft == bottomLeft && topLeft == bottomRight) {
          if (topLeft == 0) {
            return '${prefix}RoundedRectangleBorder()';
          }
          return '${prefix}RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular($topLeft)))';
        }
        if (topLeft == topRight && bottomLeft == bottomRight) {
          return '${prefix}RoundedRectangleBorder(borderRadius: BorderRadius.vertical('
              '${topLeft > 0 ? 'top: Radius.circular($topLeft)' : ''}'
              '${topLeft > 0 && bottomLeft > 0 ? ',' : ''}'
              '${bottomLeft > 0 ? 'bottom: Radius.circular($bottomLeft)' : ''}'
              '))';
        }
        return '${prefix}RoundedRectangleBorder(borderRadius: '
            'BorderRadius.only('
            'topLeft: Radius.circular(${shape['topLeft']}), '
            'topRight: Radius.circular(${shape['topRight']}), '
            'bottomLeft: Radius.circular(${shape['bottomLeft']}), '
            'bottomRight: Radius.circular(${shape['bottomRight']})))';
      case 'SHAPE_FAMILY_CIRCULAR':
        return '${prefix}StadiumBorder()';
    }
    print('Unsupported shape family type: ${shape['family']} for $componentToken');
    return '';
  }

  /// Generate a [BorderSide] for the given component.
  String border(String componentToken) {
    if (!tokenAvailable('$componentToken.color')) {
      return 'null';
    }
    final String borderColor = componentColor(componentToken);
    final width =
        (getToken('$componentToken.width', optional: true) ??
                getToken('$componentToken.height', optional: true) ??
                1.0)
            as double;
    return 'BorderSide(color: $borderColor${width != 1.0 ? ", width: $width" : ""})';
  }

  /// Generate a [TextTheme] text style name for the given component token.
  String textStyle(String componentToken) {
    return '$textThemePrefix${getToken("$componentToken.text-style")}';
  }

  String textStyleWithColor(String componentToken) {
    if (!tokenAvailable('$componentToken.text-style')) {
      return 'null';
    }
    String style = textStyle(componentToken);
    if (tokenAvailable('$componentToken.color')) {
      style = '$style?.copyWith(color: ${componentColor(componentToken)})';
    }
    return style;
  }
}