import '../models/chat_model.dart';
import 'protocol_helper.dart';

class MessageProcessor {
  /// Processes raw SMS data into ChatModel objects in a background-friendly way.
  /// This is intended to be called via compute() or Isolate.run().
  static List<ChatModel> processSmsList(
      List<Map<String, dynamic>> rawSmsList, String targetAddress) {
    // 1. Sort by date
    final allSms = List<Map<String, dynamic>>.from(rawSmsList)
      ..sort((a, b) {
        final dateComp =
            (a['date'] as int? ?? 0).compareTo(b['date'] as int? ?? 0);
        if (dateComp != 0) return dateComp;
        final smsIdComp =
            (a['sms_id'] as int? ?? 0).compareTo(b['sms_id'] as int? ?? 0);
        if (smsIdComp != 0) return smsIdComp;
        return (a['id'] as int? ?? 0).compareTo(b['id'] as int? ?? 0);
      });

    final convertedMessages = <ChatModel>[];
    final processedPacketIds = <String>{};
    final packetLeaders = <String, int>{}; // packetKey -> newest SMS ID
    final packetFragments = <String, List<Map<String, dynamic>>>{};
    final packetTotals = <String, int>{};
    final allDecryptedBodies = <String>{};

    // PASS 1: Identify all packets and their status
    for (final sms in allSms) {
      final bodyText = (sms['body'] as String).trim();
      final parsed = ProtocolHelper.parseMessage(bodyText);
      final type = parsed['type'] as String;
      final bool dbIsSecure = (sms['is_secure'] as int? ?? 0) == 1;

      final packetId = parsed['packetId'] as String?;
      final packetMode = (type == 'asym' || type == 'afrag') ? 'AE' : 'SYM';
      final packetKey = (packetId == null || packetId.isEmpty)
          ? null
          : '$packetMode::$packetId';

      if (type == 'sym' || type == 'asym') {
        if (packetKey != null) {
          processedPacketIds.add(packetKey);
        }
      }

      if (dbIsSecure && type == 'plain') {
        allDecryptedBodies.add(bodyText);
      }

      if (type == 'key_init' || type == 'key_reply' || type == 'norm') continue;

      if ((type == 'sfra' || type == 'afrag') && packetKey != null) {
        packetLeaders[packetKey] = sms['sms_id'] as int? ?? 0;
        packetFragments.putIfAbsent(packetKey, () => []).add(sms);
        packetTotals[packetKey] = parsed['totalParts'] as int? ?? 1;
      }
    }

    // PASS 2: Convert to ChatModel with linked deduplication
    for (final sms in allSms) {
      final isMe = (sms['is_me'] as int? ?? 0) == 1;
      final smsId = sms['sms_id'] as int?;
      final cacheRowId = sms['id'] as int?;
      final rawBody = (sms['body'] as String);
      final bool dbIsSecure = (sms['is_secure'] as int? ?? 0) == 1;

      final parsed = ProtocolHelper.parseMessage(rawBody);
      final type = parsed['type'] as String;

      // Deduplication Rule: If this is a plain message but its content is a known decrypted version of a secure message, skip.
      if (type == 'plain' &&
          !dbIsSecure &&
          allDecryptedBodies.contains(rawBody.trim())) {
        continue;
      }

      if (type == 'key_init' || type == 'key_reply' || type == 'norm') continue;

      final String? dbPacketId = sms['packet_id'] as String?;
      final String? dbPacketMode = sms['packet_mode'] as String?;
      final packetId = dbPacketId ?? parsed['packetId'] as String?;
      final bool isAsymmetric = type == 'afrag' || type == 'asym';
      final String packetMode = dbPacketMode ?? (isAsymmetric ? 'AE' : 'SYM');
      final packetKey = (packetId == null || packetId.isEmpty)
          ? null
          : '$packetMode::$packetId';
      final isFragment = type == 'sfra' || type == 'afrag';

      // Deduplication: If we already have a decrypted/complete version of this packet, skip the fragments.
      if (packetKey != null &&
          processedPacketIds.contains(packetKey) &&
          !dbIsSecure &&
          (isFragment || type == 'sym' || type == 'asym')) {
        continue;
      }

      String bodyText = rawBody;
      String? encryptedPayload;
      bool isSecureMessage = dbIsSecure || type != 'plain';
      bool isAssembled = false;

      if (isFragment && packetKey != null) {
        if (packetLeaders[packetKey] != sms['sms_id']) continue;

        final fragments = packetFragments[packetKey] ?? [];
        final totalPartsCount = packetTotals[packetKey] ?? 1;
        final receivedPartsCount = fragments.length;

        if (receivedPartsCount == totalPartsCount) {
          fragments.sort((a, b) {
            final pA =
                ProtocolHelper.parseMessage(a['body'] as String)['partNo']
                        as int? ??
                    0;
            final pB =
                ProtocolHelper.parseMessage(b['body'] as String)['partNo']
                        as int? ??
                    0;
            return pA.compareTo(pB);
          });
          final payload = fragments
              .map((f) =>
                  ProtocolHelper.parseMessage(f['body'] as String)['chunk']
                      as String? ??
                  '')
              .join();
          final isGroup = parsed['isGroup'] == true;
          bodyText = (type == 'sfra')
              ? (isGroup
                  ? '${ProtocolHelper.gPrefix}${ProtocolHelper.typeSym}|$payload'
                  : ProtocolHelper.buildSymmetricMsg(payload))
              : ProtocolHelper.buildAsymmetricMsg(payload);
          encryptedPayload = payload;
          isAssembled = true;
          processedPacketIds.add(packetKey);
        } else {
          bodyText =
              'در حال ${isMe ? "ارسال" : "دریافت"} قطعات... ($receivedPartsCount/$totalPartsCount)';
        }
      } else if (type != 'plain') {
        if (type == 'sym' || type == 'asym') {
          encryptedPayload = parsed['payload'] as String?;
          if (packetKey != null) processedPacketIds.add(packetKey);
        }
      }

      convertedMessages.add(ChatModel(
        id: smsId,
        localId: cacheRowId != null ? 'cache::$cacheRowId' : null,
        body: bodyText,
        rawBody: rawBody,
        encryptedPayload: encryptedPayload,
        packetId: packetId,
        packetMode: (packetId != null) ? packetMode : null,
        date: sms['date'] as int? ?? 0,
        isMe: isMe,
        status: isMe ? MessageStatus.sent : MessageStatus.received,
        isSecure: isSecureMessage,
        isPendingMultipart: isFragment && !isAssembled,
        statusLabel:
            (isFragment && !isAssembled) ? 'در حال دریافت قطعات...' : null,
      ));
    }

    return convertedMessages.reversed.toList();
  }
}