Parse a URL in bash without forking

parse-url.sh

#!/bin/bash

_SELF="${0##*/}"
_HERE="$(dirname $(realpath ${0}))"

function parse_url() {
  local url _url __url proto uphp user_pass host_port user pass host port path query_string

  url="${1}"

  proto="${url%://*}" # proto: everything up to the first '://'
  # There should definitely be a proto, neither empty nor equal to url
  if [ "${proto}" == "" -o "${proto}" == "$url" ]; then
    echo "Invalid url: ${url}" >&2
    return 1
  fi
  _url="${url:$((3 + ${#proto}))}" # _url: url minus "${proto}://"

  uphp="${_url%%/*}" # uphp (User-Password-Host-Port): everything up to the first '/' in _url
  __url="${_url:$((${#uphp} + 1))}" # __url: _url minus uphp
  user_pass="${uphp%%@*}"
  if [ "${user_pass}" == "${uphp}" ]; then
    user_pass=""
    host_port="${uphp}"
  else
    host_port="${uphp#*@}"
  fi

  user="${user_pass%%:*}" # user: everything up to the first ':' in user_pass
  if [ "${user}" == "${user_pass}" ]; then
    pass=""
  else
    pass="${user_pass#*:}" # pass: everything after the first ':' in user_pass, but only if there was a ':'
  fi

  host="${host_port%%:*}" # host: everything up to the first ':' in host_port
  if [ "${host}" == "${host_port}" ]; then
    port="80"
  else
    port="${host_port#*:}" # port: everything after the first ':' in host_port, but only if there was a ':'
  fi

  path="${__url%%\?*}" # path: everything up to the first '?' in __url
  if [ "${path}" == "${__url}" ]; then
    query_string=""
  else
    query_string="${__url%*\?}" # query_string: everything after the first '?' in __url, but only if there was a '?'
  fi

  echo "{"\
       "\"proto\": \"${proto}\","\
       "\"host\": \"${host}\","\
       "\"port\": ${port},"\
       "\"username\": \"${user}\","\
       "\"password\": \"${pass}\","\
       "\"path\": \"${path}\","\
       "\"query_string\": \"${query_string}\""\
       "}"
}

if [ "${_SELF}" = "parse-url.sh" ]; then
  set -eu
  parse_url "$@"
fi