import 'package:flutter_test/flutter_test.dart';
import 'package:own_ledger/src/services/balance_calculator.dart';

void main() {
  group('computeBalance', () {
    test('happy path with realistic month data', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 0,
          paychecks: [
            PaycheckSnapshot(
              label: 'Paycheck',
              amountCents: 324000,
              items: [
                const ItemSnapshot(label: 'Gas', amountCents: 8500),
                const ItemSnapshot(label: 'Groceries', amountCents: 14230),
                const ItemSnapshot(label: 'Other', amountCents: 4300),
              ],
            ),
          ],
          priorityPayouts: [
            const ItemSnapshot(label: 'Owed to friend', amountCents: 4500),
          ],
          bills: [
            const BillSnapshot(id: 1, label: 'Rent', defaultAmountCents: 185000),
            const BillSnapshot(id: 2, label: 'Electric', defaultAmountCents: 12743),
            const BillSnapshot(id: 3, label: 'Internet', defaultAmountCents: 7499),
            const BillSnapshot(id: 4, label: 'Phone', defaultAmountCents: 8500),
            const BillSnapshot(id: 5, label: 'Car Insurance', defaultAmountCents: 16400),
            const BillSnapshot(id: 6, label: 'Student Loan', defaultAmountCents: 31250),
            const BillSnapshot(id: 10, label: 'CC Chase', defaultAmountCents: 32537),
            const BillSnapshot(id: 11, label: 'CC Discover', defaultAmountCents: 7500),
          ],
          notablePayouts: [
            const ItemSnapshot(label: 'Concert tickets', amountCents: 8900),
          ],
        ),
      );

      // opening = 0
      // + Paycheck 324000 → 324000
      // - Gas 8500 → 315500
      // - Groceries 14230 → 301270
      // - Other 4300 → 296970
      // - Owed to friend 4500 → 292470
      // - Rent 185000 → 107470
      // - Electric 12743 → 94727
      // - Internet 7499 → 87228
      // - Phone 8500 → 78728
      // - Car Insurance 16400 → 62328
      // - Student Loan 31250 → 31078
      // - CC Chase 32537 → -1459
      // - CC Discover 7500 → -8959  ← balanceBeforeCc (after all bills)
      // - Concert 8900 → -17859

      expect(result.balanceBeforeCcCents, -8959);
      expect(result.remainingCents, -17859);
      expect(result.entries.length, 15); // opening + 14 items
    });

    test('empty month — returns opening balance', () {
      final result = computeBalance(
        month: const MonthSnapshot(openingBalanceCents: 50000),
      );

      expect(result.remainingCents, 50000);
      expect(result.balanceBeforeCcCents, 50000);
      expect(result.entries.length, 1);
      expect(result.entries.first.runningBalanceCents, 50000);
    });

    test('single paycheck, no bills', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 0,
          paychecks: [
            const PaycheckSnapshot(label: 'Pay', amountCents: 300000, items: []),
          ],
        ),
      );

      expect(result.remainingCents, 300000);
      expect(result.balanceBeforeCcCents, 300000);
    });

    test('negative balance — bills exceed income', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 0,
          paychecks: [
            const PaycheckSnapshot(label: 'Pay', amountCents: 100000, items: []),
          ],
          bills: [
            const BillSnapshot(id: 1, label: 'Rent', defaultAmountCents: 185000),
          ],
        ),
      );

      expect(result.remainingCents, -85000);
    });

    test('zero opening balance is default', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 0,
          bills: [
            const BillSnapshot(id: 1, label: 'Phone', defaultAmountCents: 8500),
          ],
        ),
      );

      expect(result.remainingCents, -8500);
      expect(result.entries.first.runningBalanceCents, 0);
    });

    test('bill with amount override uses override', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 100000,
          bills: [
            const BillSnapshot(
              id: 1,
              label: 'Electric',
              defaultAmountCents: 12000,
              amountOverrideCents: 15000,
            ),
          ],
        ),
      );

      expect(result.remainingCents, 85000);
    });

    test('all bills deducted uniformly', () {
      final result = computeBalance(
        month: MonthSnapshot(
          openingBalanceCents: 100000,
          bills: [
            const BillSnapshot(id: 1, label: 'Rent', defaultAmountCents: 50000),
            const BillSnapshot(id: 2, label: 'CC', defaultAmountCents: 20000),
          ],
        ),
      );

      // 100000 - 50000 - 20000 = 30000
      expect(result.remainingCents, 30000);
    });
  });
}