import 'package:vsc_quill_delta_to_html/vsc_quill_delta_to_html.dart';
import 'package:html/parser.dart' as html_parser;
import 'package:html/dom.dart' as dom;

/// Converts a Quill Delta (as JSON ops) into an HTML string that survives a
/// round-trip back through [HtmlToDelta] (see translation_input_container.dart).
///
/// Two issues in the underlying libraries are worked around here:
/// - flutter_quill stores colors as 8-digit ARGB hex (#AARRGGBB), which
///   vsc_quill_delta_to_html's sanitizer silently drops unless truncated to
///   #RRGGBB (colors picked in this editor are always opaque).
/// - vsc_quill_delta_to_html attaches a `style` attribute (color/background)
///   to whichever inline tag (e.g. <strong>) comes first, but
///   flutter_quill_delta_from_html only reads `style` off <span> elements.
///   Combined bold/italic + color would otherwise render fine everywhere
///   else but vanish when the editor reopens the HTML. Wrapping any styled
///   non-span element in a <span> fixes the round-trip.
String quillOpsToHtml(List<dynamic> ops) {
  final normalizedOps = _normalizeColors(ops);
  final html = QuillDeltaToHtmlConverter(
    List<Map<String, dynamic>>.from(normalizedOps),
    ConverterOptions(
      converterOptions: OpConverterOptions(inlineStylesFlag: true),
    ),
  ).convert();
  return _moveStyleToWrappingSpan(html);
}

List<Map<String, dynamic>> _normalizeColors(List<dynamic> ops) {
  return ops.map((op) {
    final copy = Map<String, dynamic>.from(op);
    final attrs = copy['attributes'];
    if (attrs is Map) {
      final attrsCopy = Map<String, dynamic>.from(attrs);
      for (final key in ['color', 'background']) {
        final value = attrsCopy[key];
        if (value is String && value.length == 9 && value.startsWith('#')) {
          attrsCopy[key] = '#${value.substring(3)}';
        }
      }
      copy['attributes'] = attrsCopy;
    }
    return copy;
  }).toList();
}

String _moveStyleToWrappingSpan(String htmlStr) {
  final fragment = html_parser.parseFragment(htmlStr);

  void visit(dom.Node node) {
    if (node is dom.Element) {
      if (node.localName != 'span' && node.attributes.containsKey('style')) {
        final style = node.attributes.remove('style');
        final span = dom.Element.tag('span')..attributes['style'] = style!;
        final parent = node.parent!;
        final index = parent.nodes.indexOf(node);
        parent.nodes
          ..removeAt(index)
          ..insert(index, span);
        span.nodes.add(node);
      }
      for (final child in List<dom.Node>.from(node.nodes)) {
        visit(child);
      }
    }
  }

  for (final child in List<dom.Node>.from(fragment.nodes)) {
    visit(child);
  }

  return fragment.outerHtml;
}