import 'package:equatable/equatable.dart';

import 'package:uto_manager/domain/entities/doctrinal_branch.dart';
import 'package:uto_manager/domain/entities/echelon.dart';

/// Represents a single organizational unit node in the UTO hierarchy.
///
/// A [UnitNode] can represent any echelon from Brigade down to Team.
/// Nodes form a tree structure via [parentUnitId] references.
class UnitNode extends Equatable {
  const UnitNode({
    required this.unitId,
    required this.echelon,
    required this.branch,
    required this.name,
    required this.isKeyLeader,
    this.parentUnitId,
  });

  /// Unique identifier for this unit (UUID v4).
  final String unitId;

  /// The echelon level of this unit.
  final Echelon echelon;

  /// The functional branch/specialty of this unit.
  final DoctrinalBranch branch;

  /// The parent unit's ID, or null if this is a root node (Brigade HQ).
  final String? parentUnitId;

  /// The display name of this unit (e.g., "1st Platoon", "Alpha Company").
  final String name;

  /// Whether this node represents a key leader position.
  final bool isKeyLeader;

  /// Returns true if this unit has no parent (is a root/top-level unit).
  bool get isRoot => parentUnitId == null;

  /// Returns a copy of this [UnitNode] with the given fields replaced.
  UnitNode copyWith({
    String? unitId,
    Echelon? echelon,
    DoctrinalBranch? branch,
    String? parentUnitId,
    String? name,
    bool? isKeyLeader,
    bool clearParent = false,
  }) {
    return UnitNode(
      unitId: unitId ?? this.unitId,
      echelon: echelon ?? this.echelon,
      branch: branch ?? this.branch,
      parentUnitId: clearParent ? null : (parentUnitId ?? this.parentUnitId),
      name: name ?? this.name,
      isKeyLeader: isKeyLeader ?? this.isKeyLeader,
    );
  }

  /// Returns true if [potentialParent] is a doctrinally valid parent for
  /// this unit based on echelon hierarchy rules.
  bool isValidParentNode(UnitNode potentialParent) {
    return echelon.isValidParent(potentialParent.echelon);
  }

  @override
  List<Object?> get props => [unitId, echelon, branch, parentUnitId, name, isKeyLeader];

  @override
  String toString() => 'UnitNode(id: $unitId, name: $name, '
      'echelon: ${echelon.displayName}, branch: ${branch.displayName})';
}