import 'package:flutter_test/flutter_test.dart';
import 'package:uto_manager/domain/services/doctrinal_templates.dart';
import 'package:uto_manager/domain/services/template_instantiator.dart';

void main() {
  // Use a deterministic counter-based ID generator for tests.
  var counter0 = 0;
  String nextId() => 'id-${counter0++}';

  late TemplateInstantiator instantiator;

  setUp(() {
    counter0 = 0;
    instantiator = TemplateInstantiator(idGenerator: nextId);
  });

  // ---------------------------------------------------------------------------
  // Basic instantiation
  // ---------------------------------------------------------------------------

  group('basic instantiation', () {
    test('instantiates a single root unit with no children or slots', () {
      const def = UnitDefinition(
        name: 'Test Brigade',
        echelon: 'brigade',
        branch: 'infantry',
      );

      final result = instantiator.instantiate(def);

      expect(result.units.length, 1);
      expect(result.slots, isEmpty);
      expect(result.units.first.name, 'Test Brigade');
      expect(result.units.first.parentUnitId, isNull);
    });

    test('root unit has no parent', () {
      const def = UnitDefinition(
        name: 'Root',
        echelon: 'brigade',
        branch: 'infantry',
      );

      final result = instantiator.instantiate(def);
      expect(result.units.first.isRoot, isTrue);
    });

    test('instantiates slots for root unit', () {
      const def = UnitDefinition(
        name: 'Test Platoon',
        echelon: 'platoon',
        branch: 'infantry',
        slots: [
          SlotDefinition(
            positionTitle: 'Platoon Leader',
            dutyMos: '11A',
            authorizedRank: 'o2',
            isKeyLeader: true,
          ),
          SlotDefinition(
            positionTitle: 'Platoon Sergeant',
            dutyMos: '11B',
            authorizedRank: 'e7',
            isKeyLeader: true,
          ),
        ],
      );

      final result = instantiator.instantiate(def);

      expect(result.units.length, 1);
      expect(result.slots.length, 2);
      expect(result.slots.first.positionTitle, 'Platoon Leader');
      expect(result.slots.first.isKeyLeader, isTrue);
      expect(result.slots.first.unitId, result.units.first.unitId);
    });

    test('all slots reference the correct unit ID', () {
      const def = UnitDefinition(
        name: 'Squad',
        echelon: 'squad',
        branch: 'infantry',
        slots: [
          SlotDefinition(
            positionTitle: 'Squad Leader',
            dutyMos: '11B',
            authorizedRank: 'e6',
          ),
          SlotDefinition(
            positionTitle: 'Rifleman',
            dutyMos: '11B',
            authorizedRank: 'e3',
          ),
        ],
      );

      final result = instantiator.instantiate(def);
      final unitId = result.units.first.unitId;

      for (final slot in result.slots) {
        expect(slot.unitId, unitId);
      }
    });
  });

  // ---------------------------------------------------------------------------
  // Parent-child relationships
  // ---------------------------------------------------------------------------

  group('parent-child relationships', () {
    test('child unit has correct parentUnitId', () {
      const def = UnitDefinition(
        name: 'Battalion',
        echelon: 'battalion',
        branch: 'infantry',
        children: [
          UnitDefinition(
            name: 'Alpha Company',
            echelon: 'company',
            branch: 'infantry',
          ),
        ],
      );

      final result = instantiator.instantiate(def);

      expect(result.units.length, 2);
      final parent = result.units.firstWhere((u) => u.name == 'Battalion');
      final child = result.units.firstWhere((u) => u.name == 'Alpha Company');
      expect(child.parentUnitId, parent.unitId);
    });

    test('deeply nested tree has correct parent chain', () {
      const def = UnitDefinition(
        name: 'Brigade',
        echelon: 'brigade',
        branch: 'infantry',
        children: [
          UnitDefinition(
            name: 'Battalion',
            echelon: 'battalion',
            branch: 'infantry',
            children: [
              UnitDefinition(
                name: 'Company',
                echelon: 'company',
                branch: 'infantry',
              ),
            ],
          ),
        ],
      );

      final result = instantiator.instantiate(def);

      expect(result.units.length, 3);
      final brigade = result.units.firstWhere((u) => u.name == 'Brigade');
      final battalion = result.units.firstWhere((u) => u.name == 'Battalion');
      final company = result.units.firstWhere((u) => u.name == 'Company');

      expect(battalion.parentUnitId, brigade.unitId);
      expect(company.parentUnitId, battalion.unitId);
    });

    test('all generated IDs are unique', () {
      // Use UUID-style generator to verify uniqueness.
      var counter = 0;
      final inst = TemplateInstantiator(idGenerator: () => 'uid-${counter++}');

      const def = UnitDefinition(
        name: 'Brigade',
        echelon: 'brigade',
        branch: 'infantry',
        slots: [
          SlotDefinition(
            positionTitle: 'Commander',
            dutyMos: '11A',
            authorizedRank: 'o6',
          ),
        ],
        children: [
          UnitDefinition(
            name: 'Battalion',
            echelon: 'battalion',
            branch: 'infantry',
          ),
        ],
      );

      final result = inst.instantiate(def);
      final allIds = [
        ...result.units.map((u) => u.unitId),
        ...result.slots.map((s) => s.slotId),
      ];

      expect(allIds.toSet().length, allIds.length);
    });
  });

  // ---------------------------------------------------------------------------
  // Doctrinal templates
  // ---------------------------------------------------------------------------

  group('doctrinal templates', () {
    test('MBCT instantiates with units and slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.mbct);

      expect(result.units, isNotEmpty);
      expect(result.slots, isNotEmpty);
      // MBCT has a brigade root
      expect(
        result.units.any((u) => u.name == 'Mobile Brigade Combat Team'),
        isTrue,
      );
    });

    test('MBCT root unit has no parent', () {
      final result = instantiator.instantiate(DoctrinalTemplates.mbct);
      final roots = result.units.where((u) => u.parentUnitId == null).toList();
      expect(roots.length, 1);
      expect(roots.first.name, 'Mobile Brigade Combat Team');
    });

    test('SBCT instantiates with units and slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.sbct);
      expect(result.units, isNotEmpty);
      expect(result.slots, isNotEmpty);
    });

    test('ABCT instantiates with units and slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.abct);
      expect(result.units, isNotEmpty);
      expect(result.slots, isNotEmpty);
    });

    test('CAB Heavy instantiates with units and slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.cabHeavy);
      expect(result.units, isNotEmpty);
      expect(result.slots, isNotEmpty);
    });

    test('CAB Light instantiates with units and slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.cabLight);
      expect(result.units, isNotEmpty);
      expect(result.slots, isNotEmpty);
    });

    test('all template units have valid parent references', () {
      for (final entry in DoctrinalTemplates.all.entries) {
        final result = instantiator.instantiate(entry.value);
        final unitIds = result.units.map((u) => u.unitId).toSet();

        for (final unit in result.units) {
          if (unit.parentUnitId != null) {
            expect(
              unitIds.contains(unit.parentUnitId),
              isTrue,
              reason: '${entry.key}: unit "${unit.name}" references unknown parent '
                  '${unit.parentUnitId}',
            );
          }
        }
      }
    });

    test('all template slots reference existing units', () {
      for (final entry in DoctrinalTemplates.all.entries) {
        final result = instantiator.instantiate(entry.value);
        final unitIds = result.units.map((u) => u.unitId).toSet();

        for (final slot in result.slots) {
          expect(
            unitIds.contains(slot.unitId),
            isTrue,
            reason: '${entry.key}: slot "${slot.positionTitle}" references unknown '
                'unit ${slot.unitId}',
          );
        }
      }
    });

    test('MBCT has key leader slots', () {
      final result = instantiator.instantiate(DoctrinalTemplates.mbct);
      expect(result.slots.any((s) => s.isKeyLeader), isTrue);
    });

    test('DoctrinalTemplates.all contains all five templates', () {
      expect(
          DoctrinalTemplates.all.keys,
          containsAll([
            'mbct',
            'sbct',
            'abct',
            'cab_heavy',
            'cab_light',
          ]),);
    });

    test('DoctrinalTemplates.displayName returns non-empty strings', () {
      for (final key in DoctrinalTemplates.all.keys) {
        expect(DoctrinalTemplates.displayName(key), isNotEmpty);
      }
    });
  });
}