apidash/lib/widgets/code_highlighter.dart

import 'package:flutter/material.dart';
import 'package:highlighter/highlighter.dart' show highlight, Node;
import 'package:flutter_highlighter/themes/xcode.dart';

class CodeHighlight extends StatelessWidget {
  late final String source;

  /// [All available languages](https://github.com/predatorx7/highlight/tree/master/highlight/lib/languages)
  final String? language;

  /// [All available themes](https://github.com/predatorx7/highlight/blob/master/flutter_highlighter/lib/themes)
  final Map<String, TextStyle> theme;

  /// Padding
  final EdgeInsetsGeometry padding;

  /// Specify text styles such as font family and font size
  final TextStyle? textStyle;

  CodeHighlight({
    super.key,
    required String input,
    this.language,
    this.textStyle,
    this.padding = const EdgeInsets.all(12),
    this.theme = xcodeTheme,
    int tabSize = 4, // TODO: https://github.com/flutter/flutter/issues/50087
  }) {
    if (input.startsWith("\t")) {
      source = input.replaceAll('\t', ' ' * tabSize);
    } else {
      source = input;
    }
  }

  List<TextSpan> _convert(List<Node> nodes) {
    List<TextSpan> spans = [];
    var currentSpans = spans;
    List<List<TextSpan>> stack = [];

    _traverse(Node node) {
      if (node.value != null) {
        currentSpans.add(node.className == null
            ? TextSpan(text: node.value)
            : TextSpan(text: node.value, style: theme[node.className!]));
      } else if (node.children != null) {
        List<TextSpan> tmp = [];
        currentSpans
            .add(TextSpan(children: tmp, style: theme[node.className!]));
        stack.add(currentSpans);
        currentSpans = tmp;

        node.children!.forEach((n) {
          _traverse(n);
          if (n == node.children!.last) {
            currentSpans = stack.isEmpty ? spans : stack.removeLast();
          }
        });
      }
    }

    for (var node in nodes) {
      _traverse(node);
    }

    return spans;
  }

  static const _rootKey = 'root';
  static const _defaultFontColor = Color(0xff000000);
  static const _defaultBackgroundColor = Color(0xffffffff);

  // TODO: dart:io is not available at web platform currently
  // See: https://github.com/flutter/flutter/issues/39998
  // So we just use monospace here for now
  static const _defaultFontFamily = 'monospace';

  @override
  Widget build(BuildContext context) {
    var _textStyle = TextStyle(
      fontFamily: _defaultFontFamily,
      color: theme[_rootKey]?.color ?? _defaultFontColor,
    );
    if (textStyle != null) {
      _textStyle = _textStyle.merge(textStyle);
    }

    return Padding(
      //color: theme[_rootKey]?.backgroundColor ?? _defaultBackgroundColor,
      padding: padding,
      child: SelectableText.rich(
        TextSpan(
          style: _textStyle,
          children:
              _convert(highlight.parse(source, language: language).nodes!),
        ),
      ),
    );
  }
}

/*
CodeHighlight(
              input: encoder.convert(requestHeaders),
              language: 'json',
              textStyle: kCodeStyle,
            )
*/

const code =
    '''// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. 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/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '\$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}
''';

const code2 = '''void main() {
  for (var i = 0; i < 4; i++) {
    print('hello \$i');
  }
}
''';