import 'package:equatable/equatable.dart';

import 'package:uto_manager/domain/entities/authorized_rank.dart';
import 'package:uto_manager/domain/value_objects/duty_mos.dart';

/// Represents an authorized duty position slot within a unit.
///
/// A [PositionSlot] defines a specific billet in the unit's MTOE,
/// including the required MOS, authorized rank, and whether it is
/// a key leader position. A slot may or may not have an assigned soldier.
class PositionSlot extends Equatable {
  const PositionSlot({
    required this.slotId,
    required this.unitId,
    required this.positionTitle,
    required this.dutyMos,
    required this.authorizedRank,
    required this.isKeyLeader,
    this.assignedPersonnelId,
  });

  /// Unique identifier for this position slot (UUID v4).
  final String slotId;

  /// The unit this slot belongs to.
  final String unitId;

  /// The official position title (e.g., "Platoon Leader", "Squad Leader").
  final String positionTitle;

  /// The authorized duty MOS for this position.
  final DutyMos dutyMos;

  /// The authorized pay grade for this position.
  final AuthorizedRank authorizedRank;

  /// Whether this is a key leader position (PL, PSG, SL, CO CDR, etc.).
  final bool isKeyLeader;

  /// The ID of the assigned soldier, or null if the slot is vacant.
  final String? assignedPersonnelId;

  /// Returns true if this slot has no assigned soldier.
  bool get isVacant => assignedPersonnelId == null;

  /// Returns true if this slot is filled.
  bool get isFilled => assignedPersonnelId != null;

  /// Returns a copy of this [PositionSlot] with the given fields replaced.
  PositionSlot copyWith({
    String? slotId,
    String? unitId,
    String? positionTitle,
    DutyMos? dutyMos,
    AuthorizedRank? authorizedRank,
    bool? isKeyLeader,
    String? assignedPersonnelId,
    bool clearAssignment = false,
  }) {
    return PositionSlot(
      slotId: slotId ?? this.slotId,
      unitId: unitId ?? this.unitId,
      positionTitle: positionTitle ?? this.positionTitle,
      dutyMos: dutyMos ?? this.dutyMos,
      authorizedRank: authorizedRank ?? this.authorizedRank,
      isKeyLeader: isKeyLeader ?? this.isKeyLeader,
      assignedPersonnelId:
          clearAssignment ? null : (assignedPersonnelId ?? this.assignedPersonnelId),
    );
  }

  @override
  List<Object?> get props => [
        slotId,
        unitId,
        positionTitle,
        dutyMos,
        authorizedRank,
        isKeyLeader,
        assignedPersonnelId,
      ];

  @override
  String toString() => 'PositionSlot(id: $slotId, title: $positionTitle, '
      'mos: ${dutyMos.code}, rank: ${authorizedRank.payGrade}, '
      'vacant: $isVacant)';
}