const scan = (
  string: string,
  pattern: RegExp,
  callback: (match: RegExpMatchArray) => void,
) => {
  let result = "";

  while (string.length > 0) {
    const match = string.match(pattern);

    if (match && match.index != null && match[0] != null) {
      result += string.slice(0, match.index);
      result += callback(match);
      string = string.slice(match.index + match[0].length);
    } else {
      result += string;
      string = "";
    }
  }

  return result;
};

/**
 * Splits a string into an array of tokens in the same way the UNIX Bourne shell does.
 *
 * @param line A string to split.
 * @returns An array of the split tokens.
 */
export const split = (line = "") => {
  const words = [];
  let field = "";
  scan(
    line,
    /\s*(?:([^\s\\'"]+)|'((?:[^'\\]|\\.)*)'|"((?:[^"\\]|\\.)*)"|(\\.?)|(\S))(\s|$)?/,
    (match) => {
      const [_raw, word, sq, dq, escape, garbage, separator] = match;

      if (garbage != null) {
        throw new Error(`Unmatched quote: ${line}`);
      }

      if (word) {
        field += word;
      } else {
        let addition;

        if (sq) {
          addition = sq;
        } else if (dq) {
          addition = dq;
        } else if (escape) {
          addition = escape;
        }

        if (addition) {
          field += addition.replace(/\\(?=.)/, "");
        }
      }

      if (separator != null) {
        words.push(field);
        field = "";
      }
    },
  );

  if (field) {
    words.push(field);
  }

  return words;
};

/**
 * Escapes a string so that it can be safely used in a Bourne shell command line.
 *
 * @param str A string to escape.
 * @returns The escaped string.
 */
export const escape = (str = "") => {
  return str
    .replace(/([^A-Za-z0-9_\-.,:/@\n])/g, "\\$1")
    .replace(/\n/g, "'\n'");
};

/**
 * Builds a command line string from an argument list.
 *
 * @param array An array of string arguments.
 * @returns The command line string.
 */
export const join = (array: string[]) =>
  array.map((element) => escape(element)).join(" ");