/**
 * CLI argument parsing — no external deps, uses Node's parseArgs.
 */
import { parseArgs as nodeParseArgs } from 'util';

const HELP = `
Usage: delta-backup [options] <command>

Commands:
  run       Full backup run (clear PEND, rsync, delta, commit, promote)
  status    Show current state

Options:
  --source <path>      SOURCE directory (required)
  --base <path>        Sets --prev, --pend, --deltas as subdirs of base path
  --prev <path>        PREV directory (default: <base>/previous)
  --pend <path>        PEND directory (default: <base>/pending)
  --deltas <path>      DELTAS directory (default: <base>/deltas)
  --backend <name>     Delta backend: zstd (default), xdelta3
  --config <file>      Load options from JSON config file (flags override)
  --dry-run            Print what would happen, execute nothing
  --help               Show this help
`.trim();

export function parseArgs(argv) {
  const { values, positionals } = nodeParseArgs({
    args: argv,
    options: {
      source:    { type: 'string' },
      base:      { type: 'string' },
      prev:      { type: 'string' },
      pend:      { type: 'string' },
      deltas:    { type: 'string' },
      backend:   { type: 'string' },
      config:    { type: 'string' },
      'dry-run': { type: 'boolean', default: false },
      help:      { type: 'boolean', default: false },
    },
    allowPositionals: true,
  });

  if (values.help) {
    console.log(HELP);
    process.exit(0);
  }

  const command = positionals[0];
  if (!command) {
    console.error('Error: command required (run, status)\n');
    console.error(HELP);
    process.exit(1);
  }

  return { ...values, command, dryRun: values['dry-run'] };
}