// 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'

const defaultErrorMessages = {
  missingRequiredOption: (optionName) => `Missing required option '${optionName}'`,
  missingRequiredArgument: (optionName) => `Missing argument for option ${optionName}`,
  tooManyArguments: (optionName) => `Too many arguments for option ${optionName}`,
}

// TODO figure out how to avoid having to use '<options>.opts to access the output of this'

module.exports = class Opts {
  constructor(argv) {
    this.opts = get(argv);
    this.synonyms = [];
  }

  // TODO equip prototype with ability to print directly through `console.log(opts)`

  /**
   * Declare multiple option flags to be synonymous.
   * Use this if you have short and long names for the same flag
   * eg: '-d' and '--debug'
   * 
   * @param {Array<string>} namesWithDashes
   * @returns {void}
   **/
  synonymize(...namesWithDashes) {
    const names = namesWithDashes.map(n => stripDashes(n));
    names.forEach((n) => {
      const others = names.filter(x => x != n)
      this.synonyms[n] = others;
    });
  }

  /**
   * Verify the presence of a required option
   * @param {string} nameWithDashes
   * @param {string} [errorMessage]
   * @returns {Boolean} **True** indicates that the option is present
   **/
  requireOption(nameWithDashes, errorMessage=null) {
    const name = stripDashes(nameWithDashes);
    if (name in this.opts) return true;
    if (name in this.synonyms) {
      const syns = this.synonyms[name];
      const hits = syns.filter(s => s in this.opts ).length;
      if (hits > 0) { return true; }
    }
    throw new Error(errorMessage || defaultErrorMessages.missingRequiredOption(nameWithDashes));
  }

  /**
   * Verify the presence of arguments for an option that requires them,
   * if that option is present
   * @param {string} nameWithDashes
   * @param {number} [minRequired]
   * @param {number} [maxRequired]
   * @param {string} [tooFewMessage] Error message if there are too few arguments provided
   * @param {string} [tooManyMessage] Error message if there are too many arguments provided
   * @returns {Boolean} **True** indicates that the arguments are present, or that the option is *not* present
   **/
  requireOptionArgument(nameWithDashes, minRequired=1, maxRequired=1, tooFewMessage=null, tooManyMessage=null) {
    let name = stripDashes(nameWithDashes);

    const checkArgs = (name) => {
      if (typeof this.opts[name] === 'boolean') {
        throw new Error(tooFewMessage || defaultErrorMessages.missingRequiredArgument(nameWithDashes));
      } else if (this.opts[name].length < minRequired) {
        throw new Error(tooFewMessage || defaultErrorMessages.missingRequiredArgument(nameWithDashes));
      } else if (this.opts[name].length > maxRequired) {
        throw new Error(tooManyMessage || defaultErrorMessages.tooManyArguments(nameWithDashes));
      }
    }

    if (name in this.opts) {
      checkArgs(name);
    }
    if (name in this.synonyms) {
      const syn = this.synonyms[name].filter(s => s in this.opts )[0];
      checkArgs(syn);
    }
    return true;
  }

  contains(nameWithDashes) {
    const name = stripDashes(nameWithDashes);
    if (name in this.opts) return true;
    if (name in this.synonyms) {
      const syns = this.synonyms[name];
      const hits = syns.filter(s => s in this.opts).length;
      if (hits > 0) { return true; }
    }
    return false;
  }
}

/**
 * @returns [ string: (boolean | string[]) ]
 **/
function get(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);
      out[a[0].arg] = next_shortened;
      grouped.splice(i, 1);
    } else {
      let pair = {};
      pair[a[0].arg] = true;
      a.forEach((b) => {
        out[b.arg] = true;
      });
    }
  });
  return out;
}

function stripDashes(optionName) {
  if (optionName.startsWith('--')) return optionName.substring(2);
  if (optionName.startsWith('-')) return optionName.substring(1);
  return optionName;
}