import 'package:markdown/markdown.dart';
import 'dart:convert';

class LinebreakSyntax extends InlineSyntax {
  LinebreakSyntax() : super(r'\n');

  @override
  bool onMatch(InlineParser parser, Match match) {
    parser.addNode(Element.empty('br'));
    return true;
  }
}

class SpoilerSyntax extends TagSyntax {
  Map<String, String> reasonMap = <String, String>{};
  SpoilerSyntax() : super(
    r'\|\|(?:([^\|]+)\|(?!\|))?',
    requiresDelimiterRun: true,
    end: r'\|\|',
  );

  @override
  bool onMatch(InlineParser parser, Match match) {
    if (super.onMatch(parser, match)) {
      reasonMap[match.input] = match[1];
      return true;
    }
    return false;
  }

  @override
  bool onMatchEnd(InlineParser parser, Match match, TagState state) {
    final element = Element('span', state.children);
    element.attributes['data-mx-spoiler'] = htmlEscape.convert(reasonMap[match.input] ?? '');
    parser.addNode(element);
    return true;
  }
}

class EmoteSyntax extends InlineSyntax {
  final Map<String, Map<String, String>> emotePacks;
  EmoteSyntax(this.emotePacks) : super(r':(?:([-\w]+)~)?([-\w]+):');

  @override
  bool onMatch(InlineParser parser, Match match) {
    final pack = match[1] ?? '';
    final emote = ':${match[2]}:';
    String mxc;
    if (pack.isEmpty) {
      // search all packs
      for (final emotePack in emotePacks.values) {
        mxc = emotePack[emote];
        if (mxc != null) {
          break;
        }
      }
    } else {
      mxc = emotePacks[pack] != null ? emotePacks[pack][emote] : null;
    }
    if (mxc == null) {
      // emote not found. Insert the whole thing as plain text
      parser.addNode(Text(match[0]));
      return true;
    }
    final element = Element.empty('img');
    element.attributes['src'] = htmlEscape.convert(mxc);
    element.attributes['alt'] = htmlEscape.convert(emote);
    element.attributes['title'] = htmlEscape.convert(emote);
    element.attributes['height'] = '32';
    element.attributes['vertical-align'] = 'middle';
    parser.addNode(element);
    return true;
  }
}

class PillSyntax extends InlineSyntax {
  PillSyntax() : super(r'([@#!][^\s:]*:[^\s]+\.\w+)');

  @override
  bool onMatch(InlineParser parser, Match match) {
    final identifier = match[1];
    final element = Element.text('a', identifier);
    element.attributes['href'] = 'https://matrix.to/#/${identifier}';
    parser.addNode(element);
    return true;
  }
}

String markdown(String text, [Map<String, Map<String, String>> emotePacks]) {
  emotePacks ??= <String, Map<String, String>>{};
  var ret = markdownToHtml(text,
    extensionSet: ExtensionSet.commonMark,
    inlineSyntaxes: [StrikethroughSyntax(), LinebreakSyntax(), SpoilerSyntax(), EmoteSyntax(emotePacks), PillSyntax()],
  );
    
  var stripPTags = '<p>'.allMatches(ret).length <= 1;
  if (stripPTags) {
    final otherBlockTags = ['table', 'pre', 'ol', 'ul', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'blockquote'];
    for (final tag in otherBlockTags) {
      // we check for the close tag as the opening one might have attributes
      if (ret.contains('</${tag}>')) {
        stripPTags = false;
        break;
      }
    }
  }
  if (stripPTags) {
    ret = ret.replaceAll('<p>', '').replaceAll('</p>', '');
  }
  return ret.trim().replaceAll(RegExp(r'(<br />)+$'), '');
}