'use strict';

// https://github.com/fastify/secure-json-parse
// https://github.com/hapijs/bourne
var suspectProtoRx = /"(?:_|\\u005[Ff])(?:_|\\u005[Ff])(?:p|\\u0070)(?:r|\\u0072)(?:o|\\u006[Ff])(?:t|\\u0074)(?:o|\\u006[Ff])(?:_|\\u005[Ff])(?:_|\\u005[Ff])"\s*:/;
var suspectConstructorRx = /"(?:c|\\u0063)(?:o|\\u006[Ff])(?:n|\\u006[Ee])(?:s|\\u0073)(?:t|\\u0074)(?:r|\\u0072)(?:u|\\u0075)(?:c|\\u0063)(?:t|\\u0074)(?:o|\\u006[Ff])(?:r|\\u0072)"\s*:/;
var JsonSigRx = /^["{[]|^-?[0-9][0-9.]*$/;

function jsonParseTransform(key, value) {
  if (key === '__proto__' || key === 'constructor') {
    return;
  }

  return value;
}

function destr(val) {
  if (typeof val !== 'string') {
    return val;
  }

  var _lval = val.toLowerCase();

  if (_lval === 'true') {
    return true;
  }

  if (_lval === 'false') {
    return false;
  }

  if (_lval === 'null') {
    return null;
  }

  if (_lval === 'nan') {
    return NaN;
  }

  if (_lval === 'infinity') {
    return Infinity;
  }

  if (_lval === 'undefined') {
    return undefined;
  }

  if (!JsonSigRx.test(val)) {
    return val;
  }

  try {
    if (suspectProtoRx.test(val) || suspectConstructorRx.test(val)) {
      return JSON.parse(val, jsonParseTransform);
    }

    return JSON.parse(val);
  } catch (_e) {
    return val;
  }
}

module.exports = destr;