import 'dart:convert';

import 'package:relationship_saver/features/ai_digest/domain/ai_digest_models.dart';
import 'package:uuid/uuid.dart';

const Uuid _uuid = Uuid();

class AiDigestParseResult {
  const AiDigestParseResult({required this.drafts, this.error});

  final List<AiSuggestionDraft> drafts;
  final String? error;

  bool get success => error == null;
}

class AiDigestResponseParser {
  const AiDigestResponseParser({
    this.maxItems = 10,
    this.maxTitleChars = 90,
    this.maxDetailsChars = 420,
  });

  final int maxItems;
  final int maxTitleChars;
  final int maxDetailsChars;

  AiDigestParseResult parse({
    required String response,
    required Map<String, String> tokenToPersonId,
    required String sourceRunId,
    required DateTime suggestedAt,
  }) {
    try {
      final Object? decoded = jsonDecode(_extractJson(response));
      final List<dynamic> items = _extractItems(decoded);
      final List<AiSuggestionDraft> drafts = <AiSuggestionDraft>[];

      for (final dynamic item in items.take(maxItems)) {
        if (item is! Map<String, dynamic>) {
          continue;
        }
        final String? token = _string(item['personToken']);
        final String? personId = token == null ? null : tokenToPersonId[token];
        if (personId == null) {
          continue;
        }

        final AiSuggestionKind? kind = _kind(item['kind']);
        final String title = _trimAndCap(
          _string(item['title']) ?? '',
          maxTitleChars,
        );
        if (kind == null || title.isEmpty) {
          continue;
        }

        drafts.add(
          AiSuggestionDraft(
            id: 'ai-${_uuid.v4()}',
            personId: personId,
            kind: kind,
            title: title,
            details: _trimAndCap(
              _string(item['details']) ?? '',
              maxDetailsChars,
            ),
            suggestedAt: suggestedAt,
            suggestedFor:
                _dateOrNull(item['suggestedFor']) ??
                _dateOrNull(item['suggestedTiming']),
            eventEndsAt:
                _dateOrNull(item['eventEndsAt']) ??
                _dateOrNull(item['endsAt']) ??
                _dateOrNull(item['endTime']),
            eventLocation: _optionalTrimAndCap(
              _string(item['eventLocation']) ?? _string(item['location']),
              160,
            ),
            eventUrl: _urlOrNull(item['eventUrl']) ?? _urlOrNull(item['url']),
            sourceUrls: _sourceUrls(item['sourceUrls'] ?? item['sources']),
            confidence: _confidence(item['confidence']),
            status: AiSuggestionStatus.pending,
            sourceRunId: sourceRunId,
            reason: _trimAndCap(_string(item['reason']) ?? '', 240),
          ),
        );
      }

      if (drafts.isEmpty) {
        return const AiDigestParseResult(
          drafts: <AiSuggestionDraft>[],
          error: 'No valid digest suggestions returned.',
        );
      }

      return AiDigestParseResult(drafts: drafts);
    } catch (error) {
      return AiDigestParseResult(
        drafts: const <AiSuggestionDraft>[],
        error: 'Unable to parse digest response: $error',
      );
    }
  }

  String _extractJson(String response) {
    final String trimmed = response.trim();
    if (trimmed.startsWith('{') || trimmed.startsWith('[')) {
      return trimmed;
    }
    final int objectStart = trimmed.indexOf('{');
    final int arrayStart = trimmed.indexOf('[');
    final int start = objectStart == -1
        ? arrayStart
        : arrayStart == -1
        ? objectStart
        : objectStart < arrayStart
        ? objectStart
        : arrayStart;
    final int objectEnd = trimmed.lastIndexOf('}');
    final int arrayEnd = trimmed.lastIndexOf(']');
    final int end = objectEnd > arrayEnd ? objectEnd : arrayEnd;
    if (start < 0 || end < start) {
      throw const FormatException('No JSON object or array found.');
    }
    return trimmed.substring(start, end + 1);
  }

  List<dynamic> _extractItems(Object? decoded) {
    if (decoded is List<dynamic>) {
      return decoded;
    }
    if (decoded is Map<String, dynamic>) {
      final Object? suggestions = decoded['suggestions'] ?? decoded['items'];
      if (suggestions is List<dynamic>) {
        return suggestions;
      }
    }
    throw const FormatException('Digest response must be a JSON array.');
  }

  AiSuggestionKind? _kind(Object? raw) {
    final String? value = _string(raw);
    if (value == null) {
      return null;
    }
    for (final AiSuggestionKind kind in AiSuggestionKind.values) {
      if (kind.name == value) {
        return kind;
      }
    }
    return null;
  }

  String? _string(Object? raw) {
    if (raw == null) {
      return null;
    }
    final String value = '$raw'.trim();
    return value.isEmpty ? null : value;
  }

  DateTime? _dateOrNull(Object? raw) {
    final String? value = _string(raw);
    if (value == null) {
      return null;
    }
    return DateTime.tryParse(value)?.toLocal();
  }

  String? _urlOrNull(Object? raw) {
    final String? value = _string(raw);
    if (value == null) {
      return null;
    }
    final Uri? uri = Uri.tryParse(value);
    if (uri == null || !uri.hasScheme || uri.host.isEmpty) {
      return null;
    }
    return uri.toString();
  }

  List<String> _sourceUrls(Object? raw) {
    final List<Object?> values = raw is List<dynamic> ? raw : <Object?>[raw];
    final Set<String> urls = <String>{};
    for (final Object? value in values) {
      if (value is Map<String, dynamic>) {
        final String? url =
            _urlOrNull(value['url']) ??
            _urlOrNull(value['uri']) ??
            _urlOrNull(value['link']);
        if (url != null) {
          urls.add(url);
        }
        continue;
      }
      final String? url = _urlOrNull(value);
      if (url != null) {
        urls.add(url);
      }
    }
    return urls.take(5).toList(growable: false);
  }

  double _confidence(Object? raw) {
    if (raw is num) {
      return raw.toDouble().clamp(0.0, 1.0).toDouble();
    }
    return 0.5;
  }

  String _trimAndCap(String value, int maxChars) {
    final String trimmed = value.trim();
    if (trimmed.length <= maxChars) {
      return trimmed;
    }
    return trimmed.substring(0, maxChars).trim();
  }

  String? _optionalTrimAndCap(String? value, int maxChars) {
    if (value == null) {
      return null;
    }
    final String trimmed = _trimAndCap(value, maxChars);
    return trimmed.isEmpty ? null : trimmed;
  }
}