class ContractSuccessor {
  final int id;
  final String title;
  const ContractSuccessor({required this.id, required this.title});
  factory ContractSuccessor.fromJson(Map<String, dynamic> j) =>
      ContractSuccessor(id: j['id'], title: j['title'] ?? '');
}

class Contract {
  final int id;
  final String title;
  final int? companyId;
  final int? vendorId;
  final String? companyName;
  final String? vendorName;
  final List<ContractSuccessor> predecessors;
  final List<ContractSuccessor> successors;
  final DateTime? periodStart;
  final DateTime? periodEnd;
  final String? body;
  final String? filePath;
  final int? createdBy;
  final DateTime createdAt;

  const Contract({
    required this.id, required this.title, this.companyId, this.vendorId,
    this.companyName, this.vendorName,
    this.predecessors = const [], this.successors = const [],
    this.periodStart, this.periodEnd, this.body, this.filePath,
    this.createdBy, required this.createdAt,
  });

  factory Contract.fromJson(Map<String, dynamic> j) => Contract(
    id: j['id'],
    title: j['title'] ?? '',
    companyId: j['company_id'],
    vendorId: j['vendor_id'],
    companyName: j['company_name'],
    vendorName: j['vendor_name'],
    predecessors: (j['predecessors'] as List? ?? [])
        .map((e) => ContractSuccessor.fromJson(e))
        .toList(),
    successors: (j['successors'] as List? ?? [])
        .map((e) => ContractSuccessor.fromJson(e))
        .toList(),
    periodStart: j['period_start'] != null ? DateTime.tryParse(j['period_start']) : null,
    periodEnd: j['period_end'] != null ? DateTime.tryParse(j['period_end']) : null,
    body: j['body'],
    filePath: j['file_path'],
    createdBy: j['created_by'],
    createdAt: DateTime.parse(j['created_at']),
  );

  String get status {
    if (successors.isNotEmpty) return 'Replaced';
    final today = DateTime.now();
    if (periodEnd != null && periodEnd!.isBefore(today)) return 'Expired';
    if (periodStart != null && periodStart!.isAfter(today)) return 'Upcoming';
    return 'Active';
  }

  bool get isExpiringSoon {
    if (periodEnd == null) return false;
    final diff = periodEnd!.difference(DateTime.now()).inDays;
    return diff >= 0 && diff <= 90;
  }

  int? get daysUntilExpiry {
    if (periodEnd == null) return null;
    return periodEnd!.difference(DateTime.now()).inDays;
  }
}

class ContractAnalysis {
  final String title;
  final String summary;
  final String? periodStart;
  final String? periodEnd;

  const ContractAnalysis({
    required this.title, required this.summary,
    this.periodStart, this.periodEnd,
  });

  factory ContractAnalysis.fromJson(Map<String, dynamic> j) => ContractAnalysis(
    title: j['title'] ?? '',
    summary: j['summary'] ?? '',
    periodStart: j['period_start'],
    periodEnd: j['period_end'],
  );
}

class PagedContracts {
  final List<Contract> items;
  final int total;
  final int page;
  final int limit;
  const PagedContracts({required this.items, required this.total, required this.page, required this.limit});
  factory PagedContracts.fromJson(Map<String, dynamic> j) => PagedContracts(
    items: (j['items'] as List).map((e) => Contract.fromJson(e)).toList(),
    total: j['total'], page: j['page'], limit: j['limit'],
  );
}