import { describe, it, expect, afterEach } from 'vitest';
import {
  AMBIENT_TZ_ENV,
  ambientTz,
  formatAmbientNow,
  ambientContextLine,
  formatCurrentTimeResult,
} from '@mcpctl/shared';

const SUMMER = new Date('2026-07-01T09:30:00Z'); // London = BST, +01:00
const WINTER = new Date('2026-01-15T09:30:00Z'); // London = GMT, +00:00

afterEach(() => {
  delete process.env[AMBIENT_TZ_ENV];
});

describe('ambientTz', () => {
  it('returns undefined when unset', () => {
    delete process.env[AMBIENT_TZ_ENV];
    expect(ambientTz()).toBeUndefined();
  });

  it('returns a valid IANA name', () => {
    process.env[AMBIENT_TZ_ENV] = 'Europe/London';
    expect(ambientTz()).toBe('Europe/London');
  });

  it('falls back to undefined on an invalid name without throwing', () => {
    process.env[AMBIENT_TZ_ENV] = 'Not/AZone';
    expect(ambientTz()).toBeUndefined();
  });
});

describe('formatAmbientNow', () => {
  it('renders UTC-only when no tz', () => {
    expect(formatAmbientNow(SUMMER, undefined)).toBe('Wed 2026-07-01 09:30 UTC');
  });

  it('renders local + UTC in summer (BST +01:00)', () => {
    expect(formatAmbientNow(SUMMER, 'Europe/London'))
      .toBe('Wed 2026-07-01 10:30 +01:00 Europe/London (09:30 UTC)');
  });

  it('renders local + UTC in winter (GMT +00:00)', () => {
    expect(formatAmbientNow(WINTER, 'Europe/London'))
      .toBe('Thu 2026-01-15 09:30 +00:00 Europe/London (09:30 UTC)');
  });

  it('stays short (~15 tokens)', () => {
    expect(formatAmbientNow(SUMMER, 'Europe/London').length).toBeLessThan(70);
  });
});

describe('ambientContextLine', () => {
  it('prefixes with [context] now:', () => {
    delete process.env[AMBIENT_TZ_ENV];
    expect(ambientContextLine(SUMMER)).toBe('[context] now: Wed 2026-07-01 09:30 UTC');
  });
});

describe('formatCurrentTimeResult', () => {
  it('includes UTC ISO and epoch, no local line when tz unset', () => {
    delete process.env[AMBIENT_TZ_ENV];
    const text = formatCurrentTimeResult(SUMMER);
    expect(text).toContain('UTC: 2026-07-01T09:30:00.000Z');
    expect(text).toContain(`Unix epoch seconds: ${Math.floor(SUMMER.getTime() / 1000)}`);
    expect(text).not.toContain('Europe/London');
  });

  it('includes the local rendering when tz set', () => {
    process.env[AMBIENT_TZ_ENV] = 'Europe/London';
    const text = formatCurrentTimeResult(SUMMER);
    expect(text).toContain('Europe/London: Wed 2026-07-01 10:30 +01:00 Europe/London (09:30 UTC)');
  });
});