import 'dart:convert';

import 'package:archive/archive.dart';
import 'package:miaoji_zhang/shared/services/local_database.dart';
import 'package:miaoji_zhang/shared/services/session_store.dart';

class LocalExportService {
  const LocalExportService._();

  static List<int> buildZip() {
    final snapshot = LocalDatabase.instance.exportSnapshot();
    final session = SessionStore.instance;
    return buildZipFromSnapshot(
      snapshot,
      profile: {
        'mode': session.isGuest ? 'guest' : 'account',
        'userId': session.userId,
        'username': session.username,
        'nickname': session.nickname,
      },
    );
  }

  static List<int> buildZipFromSnapshot(
    Map<String, dynamic> snapshot, {
    Map<String, dynamic> profile = const {},
  }) {
    final document = <String, dynamic>{...snapshot, 'profile': profile};
    final ledgers = _indexById(snapshot['ledgers'] as List<dynamic>);
    final categories = _indexById(snapshot['categories'] as List<dynamic>);
    final transactions = (snapshot['transactions'] as List<dynamic>)
        .cast<Map<String, dynamic>>();
    final budgets = (snapshot['budgets'] as List<dynamic>)
        .cast<Map<String, dynamic>>();

    final archive = Archive();
    archive.addFile(
      ArchiveFile.bytes(
        'transactions.csv',
        _utf8Bom(
          _csv([
            const [
              'id',
              'ledger',
              'type',
              'amount',
              'category',
              'note',
              'payment_method',
              'source',
              'occurred_at',
              'is_deleted',
              'updated_at',
            ],
            for (final item in transactions)
              [
                item['id'],
                ledgers[item['ledgerId']]?['name'],
                item['type'],
                (item['amount'] as num).toStringAsFixed(2),
                item['categoryName'],
                item['note'],
                item['paymentMethod'],
                item['source'],
                item['occurredAt'],
                item['isDeleted'],
                item['updatedAt'],
              ],
          ]),
        ),
      ),
    );
    archive.addFile(
      ArchiveFile.bytes(
        'budgets.csv',
        _utf8Bom(
          _csv([
            const [
              'ledger',
              'period',
              'category',
              'amount',
              'recurring',
              'updated_at',
            ],
            for (final item in budgets)
              [
                ledgers[item['ledgerId']]?['name'],
                item['period'],
                item['categoryId'] == null
                    ? 'total'
                    : categories[item['categoryId']]?['name'],
                (item['amount'] as num).toStringAsFixed(2),
                item['recurring'],
                item['updatedAt'],
              ],
          ]),
        ),
      ),
    );
    archive.addFile(
      ArchiveFile.string(
        'jizhi-backup.json',
        const JsonEncoder.withIndent('  ').convert(document),
      ),
    );
    return ZipEncoder().encode(archive);
  }

  static Map<int, Map<String, dynamic>> _indexById(List<dynamic> items) => {
    for (final item in items.cast<Map<String, dynamic>>())
      item['id'] as int: item,
  };

  static List<int> _utf8Bom(String value) => [
    0xef,
    0xbb,
    0xbf,
    ...utf8.encode(value),
  ];

  static String _csv(List<List<Object?>> rows) =>
      rows.map((row) => row.map(_csvCell).join(',')).join('\r\n');

  static String _csvCell(Object? value) {
    final text = value?.toString() ?? '';
    if (!text.contains(RegExp('[,"\r\n]'))) return text;
    return '"${text.replaceAll('"', '""')}"';
  }
}