module.exports = parse;

// https://unix.stackexchange.com/questions/364383/confusion-about-changing-meaning-of-arguments-and-options-is-there-an-official
// https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/basedefs/V1_chap12.html#tag_12_01

// 'options' are --foo, -f
//
// 'option-arguments' are (non-option) things that follow an option, and that the option expects
//     eg. 'filename.txt' in './example --input filename.txt'
//
// 'operands' are (non-option) things that follow an option, but aren't option-arguments
//    eg 'filename.txt' in './example --verbose filename.txt'


/**
 * @returns [ { string: boolean } | { string: string[] } ]
 **/
function parse(argv) {
  argv = process.argv.slice(2);

  // Label everything in argv as either
  // an 'option' or an 'arg_or_operand'
  let mapped = argv.flatMap((a) => {
    // A single long option
    if (a.startsWith('--')) {
      return { arg: a.substring(2), type: 'option' }
    }

    // A single short option
    if (a.startsWith('-') && (a.length === 2)) {
      return { arg: a.substring(1), type: 'option' }
    }

    // Multiple short options
    if (a.startsWith('-')) {
      let splitGroup = a.substring(1).split('');
      return splitGroup.map((sg) => { return {arg: sg, type: 'option'} });
    }

    // An option-argument or operand
    return { arg: a, type: 'arg_or_operand' };
  });

  // Group consecutive option-args/operands
  let wrapped = mapped.map((a) => [a]);
  let grouped = [];
  wrapped.forEach((a, i) => {
    if (i === 0 || a[0].type === 'option') {
      grouped.push(a);
      return;
    }
    let prev = grouped.pop();
    if (prev[0].type === 'option') {
      grouped.push(prev);
      grouped.push(a);
      return;
    }
    grouped.push(prev.concat(a));
    return;
  });

  let out = []
  grouped.forEach((a, i) => {
    let next = grouped[i+1];

    if ((a[0].type === 'option')
      && next
      && (next[0].type === 'arg_or_operand')) {
      let next_shortened = next.map(n => n.arg);
      let o = {};
      o[a[0].arg] = next_shortened;
      out.push(o);
      grouped.splice(i, 1);
    } else {
      let pair = {};
      pair[a[0].arg] = true;
      a.forEach((b) => {
        let o = {};
        o[b.arg] = true;
        out.push(o);
      });
    }
  });
  return out;
}