module.exports = function http_build_query(formdata, numericPrefix, argSeparator, encType) {
  //  discuss at: https://locutus.io/php/http_build_query/
  // original by: Kevin van Zonneveld (https://kvz.io)
  // improved by: Legaev Andrey
  // improved by: Michael White (https://getsprink.com)
  // improved by: Kevin van Zonneveld (https://kvz.io)
  // improved by: Brett Zamir (https://brett-zamir.me)
  //  revised by: stag019
  //    input by: Dreamer
  // bugfixed by: Brett Zamir (https://brett-zamir.me)
  // bugfixed by: MIO_KODUKI (https://mio-koduki.blogspot.com/)
  // improved by: Will Rowe
  //      note 1: If the value is null, key and value are skipped in the
  //      note 1: http_build_query of PHP while in locutus they are not.
  //   example 1: http_build_query({foo: 'bar', php: 'hypertext processor', baz: 'boom', cow: 'milk'}, '', '&')
  //   returns 1: 'foo=bar&php=hypertext+processor&baz=boom&cow=milk'
  //   example 2: http_build_query({'php': 'hypertext processor', 0: 'foo', 1: 'bar', 2: 'baz', 3: 'boom', 'cow': 'milk'}, 'myvar_')
  //   returns 2: 'myvar_0=foo&myvar_1=bar&myvar_2=baz&myvar_3=boom&php=hypertext+processor&cow=milk'
  //   example 3: http_build_query({foo: 'bar', php: 'hypertext processor', baz: 'boom', cow: 'milk'}, '', '&', 'PHP_QUERY_RFC3986')
  //   returns 3: 'foo=bar&php=hypertext%20processor&baz=boom&cow=milk'

  let encodeFunc

  switch (encType) {
    case 'PHP_QUERY_RFC3986':
      encodeFunc = require('../url/rawurlencode')
      break

    case 'PHP_QUERY_RFC1738':
    default:
      encodeFunc = require('../url/urlencode')
      break
  }

  let value
  let key
  const tmp = []

  const _httpBuildQueryHelper = function (key, val, argSeparator) {
    let k
    const tmp = []
    if (val === true) {
      val = '1'
    } else if (val === false) {
      val = '0'
    }
    if (val !== null) {
      if (typeof val === 'object') {
        for (k in val) {
          if (val[k] !== null) {
            tmp.push(_httpBuildQueryHelper(key + '[' + k + ']', val[k], argSeparator))
          }
        }
        return tmp.join(argSeparator)
      } else if (typeof val !== 'function') {
        return encodeFunc(key) + '=' + encodeFunc(val)
      } else {
        throw new Error('There was an error processing for http_build_query().')
      }
    } else {
      return ''
    }
  }

  if (!argSeparator) {
    argSeparator = '&'
  }
  for (key in formdata) {
    value = formdata[key]
    if (numericPrefix && !isNaN(key)) {
      key = String(numericPrefix) + key
    }
    const query = _httpBuildQueryHelper(key, value, argSeparator)
    if (query !== '') {
      tmp.push(query)
    }
  }

  return tmp.join(argSeparator)
}