import { DateTime } from './date-time';
import { InvalidDateTimeError } from './invalid-date-time.error';

describe('DateTime', () => {
  const originalTimezone = process.env.DEFAULT_TIMEZONE;

  afterEach(() => {
    if (originalTimezone === undefined) {
      delete process.env.DEFAULT_TIMEZONE;
    } else {
      process.env.DEFAULT_TIMEZONE = originalTimezone;
    }
  });

  describe('create', () => {
    it('parses ISO with +07:00 offset into UTC unix milliseconds', () => {
      const dt = DateTime.create('2026-08-20T17:00:00+07:00');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('parses ISO with Z into the same instant as an equivalent offset', () => {
      const withOffset = DateTime.create('2026-08-20T17:00:00+07:00');
      const withZ = DateTime.create('2026-08-20T10:00:00.000Z');

      expect(withZ.value).toBe(withOffset.value);
      expect(withZ.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('parses compact offset without colon', () => {
      const dt = DateTime.create('2026-08-20T17:00:00.123+0700');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 123));
    });

    it('parses hour-only ISO offset', () => {
      const dt = DateTime.create('2026-08-20T17:00:00+07');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('accepts lowercase z designator', () => {
      const dt = DateTime.create('2026-08-20T10:00:00z');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('truncates fractional seconds beyond milliseconds', () => {
      const dt = DateTime.create('2026-08-20T10:00:00.123456Z');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 123));
    });

    it('trims surrounding whitespace', () => {
      const dt = DateTime.create('  2026-08-20T10:00:00Z  ');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('interprets naive ISO as wall clock in DEFAULT_TIMEZONE (GMT+7)', () => {
      delete process.env.DEFAULT_TIMEZONE;

      const dt = DateTime.create('2026-08-20T17:00:00');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('interprets naive ISO with fractional seconds using env timezone', () => {
      process.env.DEFAULT_TIMEZONE = 'GMT+7';

      const dt = DateTime.create('2026-08-20T17:00:00.500');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 500));
    });

    it('uses a custom DEFAULT_TIMEZONE for naive ISO parse', () => {
      process.env.DEFAULT_TIMEZONE = 'UTC+0';

      const dt = DateTime.create('2026-08-20T17:00:00');

      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 17, 0, 0, 0));
    });

    it('does not change value of offset-aware instant when DEFAULT_TIMEZONE changes', () => {
      process.env.DEFAULT_TIMEZONE = 'GMT+7';
      const dt = DateTime.create('2026-08-20T10:00:00Z');
      const valueBefore = dt.value;

      process.env.DEFAULT_TIMEZONE = 'UTC-5';

      expect(dt.value).toBe(valueBefore);
      expect(dt.value).toBe(Date.UTC(2026, 7, 20, 10, 0, 0, 0));
    });

    it('rejects date-only strings', () => {
      expect(() => DateTime.create('2026-08-20')).toThrow(InvalidDateTimeError);
    });

    it('rejects empty string', () => {
      expect(() => DateTime.create('')).toThrow(InvalidDateTimeError);
    });

    it('rejects whitespace-only input', () => {
      expect(() => DateTime.create('   ')).toThrow(InvalidDateTimeError);
    });

    it('rejects non-string input', () => {
      expect(() => DateTime.create(null as unknown as string)).toThrow(
        InvalidDateTimeError,
      );
      expect(() => DateTime.create(123 as unknown as string)).toThrow(
        InvalidDateTimeError,
      );
    });

    it('rejects junk', () => {
      expect(() => DateTime.create('not-a-date')).toThrow(InvalidDateTimeError);
    });

    it('rejects overflow calendar dates', () => {
      expect(() => DateTime.create('2026-02-30T10:00:00Z')).toThrow(
        InvalidDateTimeError,
      );
    });

    it('rejects out-of-range ISO offsets', () => {
      expect(() => DateTime.create('2026-08-20T10:00:00+15:00')).toThrow(
        InvalidDateTimeError,
      );
      expect(() => DateTime.create('2026-08-20T10:00:00+14:30')).toThrow(
        InvalidDateTimeError,
      );
      expect(() => DateTime.create('2026-08-20T10:00:00-12:30')).toThrow(
        InvalidDateTimeError,
      );
    });

    it('rejects invalid DEFAULT_TIMEZONE when parsing naive ISO', () => {
      process.env.DEFAULT_TIMEZONE = 'Asia/Jakarta';

      expect(() => DateTime.create('2026-08-20T17:00:00')).toThrow(
        InvalidDateTimeError,
      );
    });

    it('throws a generic message that does not echo the input', () => {
      expect(() => DateTime.create('not-a-date')).toThrow('Invalid date time');
    });
  });

  describe('fromUnixMs', () => {
    it('reconstructs from a unix millisecond timestamp', () => {
      const ms = Date.UTC(2026, 7, 20, 10, 0, 0, 0);
      const dt = DateTime.fromUnixMs(ms);

      expect(dt.value).toBe(ms);
    });

    it('round-trips with create', () => {
      const created = DateTime.create('2026-08-20T17:00:00+07:00');
      const restored = DateTime.fromUnixMs(created.value);

      expect(restored.equals(created)).toBe(true);
    });

    it('rejects non-finite numbers', () => {
      expect(() => DateTime.fromUnixMs(Number.NaN)).toThrow(
        InvalidDateTimeError,
      );
      expect(() => DateTime.fromUnixMs(Number.POSITIVE_INFINITY)).toThrow(
        InvalidDateTimeError,
      );
    });

    it('rejects non-safe integers', () => {
      expect(() => DateTime.fromUnixMs(1.5)).toThrow(InvalidDateTimeError);
      expect(() => DateTime.fromUnixMs(Number.MAX_SAFE_INTEGER + 2)).toThrow(
        InvalidDateTimeError,
      );
    });

    it('rejects values outside the Date time-value range', () => {
      expect(() => DateTime.fromUnixMs(8_640_000_000_000_001)).toThrow(
        InvalidDateTimeError,
      );
      expect(() => DateTime.fromUnixMs(-8_640_000_000_000_001)).toThrow(
        InvalidDateTimeError,
      );
    });

    it('accepts pre-1970 negative timestamps', () => {
      const ms = Date.UTC(1969, 11, 31, 23, 59, 59, 0);
      const dt = DateTime.fromUnixMs(ms);

      expect(dt.value).toBe(ms);
      expect(dt.format('UTC')).toBe('1969-12-31T23:59:59.000+00:00');
    });

    it('rejects non-number input', () => {
      expect(() =>
        DateTime.fromUnixMs('1724150000000' as unknown as number),
      ).toThrow(InvalidDateTimeError);
    });
  });

  describe('format / toString', () => {
    it('formats in DEFAULT_TIMEZONE (GMT+7) by default', () => {
      delete process.env.DEFAULT_TIMEZONE;
      const dt = DateTime.fromUnixMs(Date.UTC(2026, 7, 20, 10, 0, 0, 0));

      expect(dt.format()).toBe('2026-08-20T17:00:00.000+07:00');
      expect(dt.toString()).toBe('2026-08-20T17:00:00.000+07:00');
    });

    it('formats in an explicit timezone override', () => {
      const dt = DateTime.fromUnixMs(Date.UTC(2026, 7, 20, 10, 0, 0, 0));

      expect(dt.format('UTC')).toBe('2026-08-20T10:00:00.000+00:00');
      expect(dt.format('Z')).toBe('2026-08-20T10:00:00.000+00:00');
      expect(dt.format('+00:00')).toBe('2026-08-20T10:00:00.000+00:00');
    });

    it('changes render output when DEFAULT_TIMEZONE changes', () => {
      const dt = DateTime.fromUnixMs(Date.UTC(2026, 7, 20, 10, 0, 0, 0));

      process.env.DEFAULT_TIMEZONE = 'GMT+7';
      expect(dt.format()).toBe('2026-08-20T17:00:00.000+07:00');

      process.env.DEFAULT_TIMEZONE = 'UTC-5';
      expect(dt.format()).toBe('2026-08-20T05:00:00.000-05:00');
    });

    it('rejects invalid timezone override', () => {
      const dt = DateTime.fromUnixMs(Date.UTC(2026, 7, 20, 10, 0, 0, 0));

      expect(() => dt.format('Asia/Jakarta')).toThrow(InvalidDateTimeError);
    });

    it('rejects out-of-range timezone override', () => {
      const dt = DateTime.fromUnixMs(Date.UTC(2026, 7, 20, 10, 0, 0, 0));

      expect(() => dt.format('+15:00')).toThrow(InvalidDateTimeError);
      expect(() => dt.format('GMT-13')).toThrow(InvalidDateTimeError);
    });

    it('rejects formatting when offset shift overflows Date range', () => {
      const dt = DateTime.fromUnixMs(8_640_000_000_000_000);

      expect(() => dt.format('GMT+7')).toThrow(InvalidDateTimeError);
    });
  });

  describe('equals', () => {
    it('returns true for the same instant from different inputs', () => {
      const a = DateTime.create('2026-08-20T17:00:00+07:00');
      const b = DateTime.create('2026-08-20T10:00:00Z');

      expect(a.equals(b)).toBe(true);
    });

    it('returns false for different instants', () => {
      const a = DateTime.create('2026-08-20T10:00:00Z');
      const b = DateTime.create('2026-08-20T11:00:00Z');

      expect(a.equals(b)).toBe(false);
    });

    it('returns false for null or undefined', () => {
      const dt = DateTime.create('2026-08-20T10:00:00Z');

      expect(dt.equals(null as unknown as DateTime)).toBe(false);
      expect(dt.equals(undefined as unknown as DateTime)).toBe(false);
    });
  });

  describe('serialization', () => {
    it('toJSON returns unix milliseconds', () => {
      const ms = Date.UTC(2026, 7, 20, 10, 0, 0, 0);
      const dt = DateTime.fromUnixMs(ms);

      expect(dt.toJSON()).toBe(ms);
      expect(JSON.stringify({ at: dt })).toBe(`{"at":${ms}}`);
    });
  });

  describe('immutability', () => {
    it('is frozen after creation', () => {
      const dt = DateTime.create('2026-08-20T10:00:00Z');

      expect(Object.isFrozen(dt)).toBe(true);
    });

    it('cannot be constructed with new from outside', () => {
      expect(
        () =>
          new (DateTime as unknown as new (value: number) => DateTime)(
            Date.UTC(2026, 7, 20, 10, 0, 0, 0),
          ),
      ).toThrow();
    });
  });
});