content: // Copyright (c) 2012, 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.
  
  /// Parses text in a markdown-like format and renders to HTML.
  library markdown;
  
  // TODO(rnystrom): Use "package:" URL (#4968).
  part 'src/markdown/ast.dart';
  part 'src/markdown/block_parser.dart';
  part 'src/markdown/html_renderer.dart';
  part 'src/markdown/inline_parser.dart';
  
  typedef Node Resolver(String name);
  
  /// Converts the given string of markdown to HTML.
  String markdownToHtml(String markdown, {inlineSyntaxes, linkResolver}) {
    final document = new Document(inlineSyntaxes: inlineSyntaxes,
        linkResolver: linkResolver);
  
    // Replace windows line endings with unix line endings, and split.
    final lines = markdown.replaceAll('\r\n','\n').split('\n');
    document.parseRefLinks(lines);
    final blocks = document.parseLines(lines);
    return renderToHtml(blocks);
  }
  
  /// Replaces `<`, `&`, and `>`, with their HTML entity equivalents.
  String escapeHtml(String html) {
    return html.replaceAll('&', '&amp;')
               .replaceAll('<', '&lt;')
               .replaceAll('>', '&gt;');
  }
  
  /// Maintains the context needed to parse a markdown document.
  class Document {
    final Map<String, Link> refLinks;
    List<InlineSyntax> inlineSyntaxes;
    Resolver linkResolver;
  
    Document({this.inlineSyntaxes, this.linkResolver})
      : refLinks = <String, Link>{};
  
    parseRefLinks(List<String> lines) {
      // This is a hideous regex. It matches:
      // [id]: http:foo.com "some title"
      // Where there may whitespace in there, and where the title may be in
      // single quotes, double quotes, or parentheses.
      final indent = r'^[ ]{0,3}'; // Leading indentation.
      final id = r'\[([^\]]+)\]';  // Reference id in [brackets].
      final quote = r'"[^"]+"';    // Title in "double quotes".
      final apos = r"'[^']+'";     // Title in 'single quotes'.
      final paren = r"\([^)]+\)";  // Title in (parentheses).
      final pattern = new RegExp(
          '$indent$id:\\s+(\\S+)\\s*($quote|$apos|$paren|)\\s*\$');
  
      for (int i = 0; i < lines.length; i++) {
        final match = pattern.firstMatch(lines[i]);
        if (match != null) {
          // Parse the link.
          var id = match[1];
          var url = match[2];
          var title = match[3];
  
          if (title == '') {
            // No title.
            title = null;
          } else {
            // Remove "", '', or ().
            title = title.substring(1, title.length - 1);
          }
  
          // References are case-insensitive.
          id = id.toLowerCase();
  
          refLinks[id] = new Link(id, url, title);
  
          // Remove it from the output. We replace it with a blank line which will
          // get consumed by later processing.
          lines[i] = '';
        }
      }
    }
  
    /// Parse the given [lines] of markdown to a series of AST nodes.
    List<Node> parseLines(List<String> lines) {
      final parser = new BlockParser(lines, this);
  
      final blocks = [];
      while (!parser.isDone) {
        for (final syntax in BlockSyntax.syntaxes) {
          if (syntax.canParse(parser)) {
            final block = syntax.parse(parser);
            if (block != null) blocks.add(block);
            break;
          }
        }
      }
  
      return blocks;
    }
  
    /// Takes a string of raw text and processes all inline markdown tags,
    /// returning a list of AST nodes. For example, given ``"*this **is** a*
    /// `markdown`"``, returns:
    /// `<em>this <strong>is</strong> a</em> <code>markdown</code>`.
    List<Node> parseInline(String text) => new InlineParser(text, this).parse();
  }
  
  class Link {
    final String id;
    final String url;
    final String title;
    Link(this.id, this.url, this.title);
  }
  