import 'package:superport_v2/core/common/models/paginated_result.dart';
import 'package:superport_v2/core/common/utils/json_utils.dart';

import '../../domain/entities/approval.dart';

/// 결재 API 응답을 표현하는 DTO.
///
/// - 원본 JSON 형식을 유지하면서 도메인 엔티티 변환을 제공한다.
/// - 일부 필드는 누락 가능성을 고려하여 기본값을 지정한다.
class ApprovalDto {
  ApprovalDto({
    this.id,
    required this.approvalNo,
    this.transactionNo,
    required this.status,
    this.currentStep,
    required this.requester,
    required this.requestedAt,
    this.decidedAt,
    this.note,
    this.isActive = true,
    this.isDeleted = false,
    this.steps = const [],
    this.histories = const [],
    this.createdAt,
    this.updatedAt,
  });

  final int? id;
  final String approvalNo;
  final String? transactionNo;
  final ApprovalStatusDto status;
  final ApprovalStepDto? currentStep;
  final ApprovalRequesterDto requester;
  final DateTime requestedAt;
  final DateTime? decidedAt;
  final String? note;
  final bool isActive;
  final bool isDeleted;
  final List<ApprovalStepDto> steps;
  final List<ApprovalHistoryDto> histories;
  final DateTime? createdAt;
  final DateTime? updatedAt;

  /// API 응답 JSON을 [ApprovalDto]로 변환한다.
  factory ApprovalDto.fromJson(Map<String, dynamic> json) {
    final approvalEnvelope = _mapOrEmpty(json['approval']);
    final statusMap = _firstNonEmptyMap([
      json['status'],
      json['approval_status'],
      approvalEnvelope['status'],
      approvalEnvelope['approval_status'],
    ]);
    final requesterMap = _firstNonEmptyMap([
      json['requester'],
      json['requested_by'],
      approvalEnvelope['requester'],
      approvalEnvelope['requested_by'],
    ]);
    final currentStepMap = _firstNonEmptyMap([
      json['current_step'],
      json['currentStep'],
      approvalEnvelope['current_step'],
    ]);
    final transactionMap = _mapOrEmpty(json['transaction']);
    final envelopeTransactionMap = _mapOrEmpty(approvalEnvelope['transaction']);
    var stepsSource = _asListOfMap(json['steps']);
    if (stepsSource.isEmpty) {
      stepsSource = _asListOfMap(approvalEnvelope['steps']);
    }
    var historiesSource = _asListOfMap(json['histories']);
    if (historiesSource.isEmpty) {
      historiesSource = _asListOfMap(approvalEnvelope['histories']);
    }
    final currentStepDto = currentStepMap.isEmpty
        ? null
        : ApprovalStepDto.fromJson(currentStepMap);

    final approvalNo =
        _pickString(
          [json, approvalEnvelope],
          const ['approval_no', 'approvalNo'],
        ) ??
        '-';
    final transactionNo = _pickString(
      [json, transactionMap, approvalEnvelope, envelopeTransactionMap],
      const ['transaction_no', 'transactionNo'],
    );

    return ApprovalDto(
      id: json['id'] as int? ?? approvalEnvelope['id'] as int?,
      approvalNo: approvalNo,
      transactionNo: transactionNo,
      status: ApprovalStatusDto.fromJson(statusMap),
      currentStep: currentStepDto,
      requester: ApprovalRequesterDto.fromJson(requesterMap),
      requestedAt:
          _parseDate(
            json['requested_at'] ?? approvalEnvelope['requested_at'],
          ) ??
          DateTime.now(),
      decidedAt: _parseDate(
        json['decided_at'] ?? approvalEnvelope['decided_at'],
      ),
      note: json['note'] as String? ?? approvalEnvelope['note'] as String?,
      isActive:
          (json['is_active'] as bool?) ??
          (approvalEnvelope['is_active'] as bool?) ??
          true,
      isDeleted:
          (json['is_deleted'] as bool?) ??
          (approvalEnvelope['is_deleted'] as bool?) ??
          false,
      steps: stepsSource.map(ApprovalStepDto.fromJson).toList(growable: false),
      histories: historiesSource
          .map(ApprovalHistoryDto.fromJson)
          .toList(growable: false),
      createdAt: _parseDate(
        json['created_at'] ?? approvalEnvelope['created_at'],
      ),
      updatedAt: _parseDate(
        json['updated_at'] ?? approvalEnvelope['updated_at'],
      ),
    );
  }

  /// DTO를 도메인 [Approval] 엔티티로 변환한다.
  Approval toEntity() => Approval(
    id: id,
    approvalNo: approvalNo,
    transactionNo: transactionNo ?? '-',
    status: status.toEntity(),
    currentStep: currentStep?.toEntity(),
    requester: requester.toEntity(),
    requestedAt: requestedAt,
    decidedAt: decidedAt,
    note: note,
    isActive: isActive,
    isDeleted: isDeleted,
    steps: steps.map((e) => e.toEntity()).toList(),
    histories: histories.map((e) => e.toEntity()).toList(),
    createdAt: createdAt,
    updatedAt: updatedAt,
  );

  /// 페이징 응답을 파싱해 [PaginatedResult]로 변환한다.
  static PaginatedResult<Approval> parsePaginated(Map<String, dynamic>? json) {
    final rawItems = JsonUtils.extractList(json, keys: const ['items']);
    final items = rawItems
        .map(ApprovalDto.fromJson)
        .map((dto) => dto.toEntity())
        .toList(growable: false);
    return PaginatedResult<Approval>(
      items: items,
      page: JsonUtils.readInt(json, 'page', fallback: 1),
      pageSize: JsonUtils.readInt(json, 'page_size', fallback: items.length),
      total: JsonUtils.readInt(json, 'total', fallback: items.length),
    );
  }
}

/// 결재 상태(Status) DTO.
class ApprovalStatusDto {
  ApprovalStatusDto({required this.id, required this.name, this.color});

  final int id;
  final String name;
  final String? color;

  factory ApprovalStatusDto.fromJson(Map<String, dynamic> json) {
    if (json['status'] is Map<String, dynamic>) {
      return ApprovalStatusDto.fromJson(json['status'] as Map<String, dynamic>);
    }
    return ApprovalStatusDto(
      id:
          json['id'] as int? ??
          json['status_id'] as int? ??
          json['approval_status_id'] as int? ??
          0,
      name:
          json['name'] as String? ??
          json['status_name'] as String? ??
          json['approval_status_name'] as String? ??
          (json['status'] as String?) ??
          '-',
      color: json['color'] as String?,
    );
  }

  /// DTO를 [ApprovalStatus]로 변환한다.
  ApprovalStatus toEntity() => ApprovalStatus(id: id, name: name, color: color);
}

/// 결재 요청자 DTO.
class ApprovalRequesterDto {
  ApprovalRequesterDto({
    required this.id,
    required this.employeeNo,
    required this.name,
  });

  final int id;
  final String employeeNo;
  final String name;

  factory ApprovalRequesterDto.fromJson(Map<String, dynamic> json) {
    return ApprovalRequesterDto(
      id: json['id'] as int? ?? json['employee_id'] as int? ?? 0,
      employeeNo: json['employee_no'] as String? ?? '-',
      name: json['name'] as String? ?? json['employee_name'] as String? ?? '-',
    );
  }

  /// DTO를 [ApprovalRequester]로 변환한다.
  ApprovalRequester toEntity() =>
      ApprovalRequester(id: id, employeeNo: employeeNo, name: name);
}

/// 결재 승인자 DTO.
class ApprovalApproverDto {
  ApprovalApproverDto({
    required this.id,
    required this.employeeNo,
    required this.name,
  });

  final int id;
  final String employeeNo;
  final String name;

  factory ApprovalApproverDto.fromJson(Map<String, dynamic> json) {
    return ApprovalApproverDto(
      id: json['id'] as int? ?? json['approver_id'] as int? ?? 0,
      employeeNo: json['employee_no'] as String? ?? '-',
      name: json['name'] as String? ?? json['employee_name'] as String? ?? '-',
    );
  }

  /// DTO를 [ApprovalApprover]로 변환한다.
  ApprovalApprover toEntity() =>
      ApprovalApprover(id: id, employeeNo: employeeNo, name: name);
}

/// 결재 단계 DTO.
class ApprovalStepDto {
  ApprovalStepDto({
    this.id,
    required this.stepOrder,
    required this.approver,
    required this.status,
    required this.assignedAt,
    this.decidedAt,
    this.note,
    this.isDeleted = false,
  });

  final int? id;
  final int stepOrder;
  final ApprovalApproverDto approver;
  final ApprovalStatusDto status;
  final DateTime assignedAt;
  final DateTime? decidedAt;
  final String? note;
  final bool isDeleted;

  factory ApprovalStepDto.fromJson(Map<String, dynamic> json) {
    return ApprovalStepDto(
      id: json['id'] as int?,
      stepOrder: json['step_order'] as int? ?? 0,
      approver: ApprovalApproverDto.fromJson(
        (json['approver'] as Map<String, dynamic>? ?? const {}),
      ),
      status: ApprovalStatusDto.fromJson(
        (json['status'] as Map<String, dynamic>? ??
            json['step_status'] as Map<String, dynamic>? ??
            json['approval_status'] as Map<String, dynamic>? ??
            const {}),
      ),
      assignedAt: _parseDate(json['assigned_at']) ?? DateTime.now(),
      decidedAt: _parseDate(json['decided_at']),
      note: json['note'] as String?,
      isDeleted:
          json['is_deleted'] as bool? ??
          (json['deleted_at'] != null ||
              (json['is_active'] is bool && !(json['is_active'] as bool))),
    );
  }

  /// DTO를 [ApprovalStep]으로 변환한다.
  ApprovalStep toEntity() => ApprovalStep(
    id: id,
    stepOrder: stepOrder,
    approver: approver.toEntity(),
    status: status.toEntity(),
    assignedAt: assignedAt,
    decidedAt: decidedAt,
    note: note,
    isDeleted: isDeleted,
  );
}

/// 결재 이력 DTO.
class ApprovalHistoryDto {
  ApprovalHistoryDto({
    this.id,
    required this.action,
    this.fromStatus,
    required this.toStatus,
    required this.approver,
    required this.actionAt,
    this.note,
  });

  final int? id;
  final ApprovalActionDto action;
  final ApprovalStatusDto? fromStatus;
  final ApprovalStatusDto toStatus;
  final ApprovalApproverDto approver;
  final DateTime actionAt;
  final String? note;

  factory ApprovalHistoryDto.fromJson(Map<String, dynamic> json) {
    final actionMap = _firstNonEmptyMap([
      json['action'],
      json['approval_action'],
      json['step_action'],
    ]);
    final fromStatusMap = _firstNonEmptyMap([
      json['from_status'],
      json['fromStatus'],
    ]);
    final toStatusMap = _firstNonEmptyMap([
      json['to_status'],
      json['toStatus'],
    ]);
    final approverMap = _firstNonEmptyMap([json['approver'], json['employee']]);
    final fallbackAction = {
      'id': json['approval_action_id'] ?? json['action_id'],
      'name':
          json['approval_action_name'] ??
          json['action_name'] ??
          (json['action'] as String?) ??
          '-',
    };

    return ApprovalHistoryDto(
      id: json['id'] as int?,
      action: ApprovalActionDto.fromJson(
        actionMap.isEmpty ? fallbackAction : actionMap,
      ),
      fromStatus: fromStatusMap.isEmpty
          ? null
          : ApprovalStatusDto.fromJson(fromStatusMap),
      toStatus: ApprovalStatusDto.fromJson(toStatusMap),
      approver: ApprovalApproverDto.fromJson(approverMap),
      actionAt:
          _parseDate(json['action_at'] ?? json['actionAt']) ?? DateTime.now(),
      note: json['note'] as String?,
    );
  }

  /// DTO를 [ApprovalHistory]로 변환한다.
  ApprovalHistory toEntity() => ApprovalHistory(
    id: id,
    action: action.toEntity(),
    fromStatus: fromStatus?.toEntity(),
    toStatus: toStatus.toEntity(),
    approver: approver.toEntity(),
    actionAt: actionAt,
    note: note,
  );
}

/// 결재 행위(Action) DTO.
class ApprovalActionDto {
  ApprovalActionDto({required this.id, required this.name});

  final int id;
  final String name;

  factory ApprovalActionDto.fromJson(Map<String, dynamic> json) {
    if (json['action'] is Map<String, dynamic>) {
      return ApprovalActionDto.fromJson(json['action'] as Map<String, dynamic>);
    }
    return ApprovalActionDto(
      id:
          json['id'] as int? ??
          json['action_id'] as int? ??
          json['approval_action_id'] as int? ??
          0,
      name:
          json['name'] as String? ??
          json['action_name'] as String? ??
          json['approval_action_name'] as String? ??
          (json['action'] as String?) ??
          '-',
    );
  }

  /// DTO를 [ApprovalAction]으로 변환한다.
  ApprovalAction toEntity() => ApprovalAction(id: id, name: name);
}

List<Map<String, dynamic>> _asListOfMap(dynamic value) {
  if (value is List) {
    return value.whereType<Map<String, dynamic>>().toList(growable: false);
  }
  return const [];
}

Map<String, dynamic> _mapOrEmpty(dynamic value) =>
    value is Map<String, dynamic> ? value : const {};

Map<String, dynamic> _firstNonEmptyMap(List<dynamic> candidates) {
  for (final candidate in candidates) {
    if (candidate is Map<String, dynamic> && candidate.isNotEmpty) {
      return candidate;
    }
  }
  return const {};
}

String? _pickString(List<dynamic> sources, List<String> keys) {
  for (final source in sources) {
    if (source is Map<String, dynamic>) {
      for (final key in keys) {
        final value = source[key];
        if (value is String && value.isNotEmpty) {
          return value;
        }
      }
    }
  }
  return null;
}

/// 문자열/DateTime 입력을 DateTime으로 변환한다.
DateTime? _parseDate(Object? value) {
  if (value == null) return null;
  if (value is DateTime) return value;
  if (value is String) return DateTime.tryParse(value);
  return null;
}