import { describe, expect, it } from 'vitest';
import { parseArgs } from '../src/roundtrip.js';

// R-Cfg-1: parseArgs is exported so the CLI flag parsing is unit-testable. The
// tricky bits are the --corpus lookahead (its directory arg is optional and must
// NOT swallow a following flag), the `argv[++i]` value consumption for
// --fixture/--page, and the empty-argv default.

describe('parseArgs', () => {
  it('returns an empty object for empty argv (no flags)', () => {
    expect(parseArgs([])).toEqual({});
  });

  it('reads the value after --fixture (argv[++i])', () => {
    expect(parseArgs(['--fixture', 'path/to/doc.json'])).toEqual({
      fixture: 'path/to/doc.json',
    });
  });

  it('reads the value after --page (argv[++i])', () => {
    expect(parseArgs(['--page', 'page-123'])).toEqual({ page: 'page-123' });
  });

  it('--corpus consumes the directory when the next token is not a flag', () => {
    expect(parseArgs(['--corpus', 'test/fixtures/corpus'])).toEqual({
      corpus: 'test/fixtures/corpus',
    });
  });

  it('--corpus uses the DEFAULT dir when followed by another flag (lookahead)', () => {
    // The lookahead must NOT consume "--fixture" as the corpus directory; corpus
    // falls back to its default and --fixture is still parsed on the next loop.
    const parsed = parseArgs(['--corpus', '--fixture', 'x']);
    expect(parsed.corpus).toBe('test/fixtures/corpus');
    expect(parsed.fixture).toBe('x');
  });

  it('--corpus uses the default dir when it is the LAST token (no lookahead value)', () => {
    expect(parseArgs(['--corpus'])).toEqual({ corpus: 'test/fixtures/corpus' });
  });

  it('a trailing --fixture with no value consumes undefined (off-by-one argv[++i])', () => {
    // `argv[++i]` reads past the end -> undefined; the loop then terminates.
    expect(parseArgs(['--fixture'])).toEqual({ fixture: undefined });
  });

  it('parses multiple flags together (page then a defaulted corpus)', () => {
    const parsed = parseArgs(['--page', 'p-1', '--corpus']);
    expect(parsed.page).toBe('p-1');
    expect(parsed.corpus).toBe('test/fixtures/corpus');
  });
});