class Rack::QueryParser

def self.make_default(param_depth_limit, **options)
  new(Params, param_depth_limit, **options)
end

def _normalize_params(params, name, v, depth)
ParamsTooDeepError if depth >= param_depth_limit
me
l name, treat same as empty string (required by tests)
after = ''
depth == 0
art of parsing, don't treat [] or [ at start of string specially
tart = name.index('[', 1)
Start of parameter nesting, use part before brackets as key
= name[0, start]
ter = name[start, name.length]

Plain parameter with no nesting
= name
ter = ''
name.start_with?('[]')
ray nesting
'[]'
r = name[2, name.length]
name.start_with?('[') && (start = name.index(']', 1))
sh nesting, use the part inside brackets as the key
name[1, start-1]
r = name[start+1, name.length]
obably malformed input, nested but not starting with [
eat full name as key for backwards compatibility.
name
r = ''
 if k.empty?
er == ''
 == '[]' && depth != 0
turn [v]

rams[k] = v
after == "["
ms[name] = v
after == "[]"
ms[k] ||= []
e ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
ms[k] << v
after.start_with?('[]')
cognize x[][y] (hash inside array) parameters
ss after[2] == '[' && after.end_with?(']') && (child_key = after[3, after.length-4]) && !child_key.empty? && !child_key.index('[') && !child_key.index(']')
Handle other nested array parameters
ild_key = after[2, after.length]
ms[k] ||= []
e ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
arams_hash_type?(params[k].last) && !params_hash_has_key?(params[k].last, child_key)
ormalize_params(params[k].last, child_key, v, depth + 1)

rams[k] << _normalize_params(make_params, child_key, v, depth + 1)
ms[k] ||= make_params
e ParameterTypeError, "expected Hash (got #{params[k].class.name}) for param `#{k}'" unless params_hash_type?(params[k])
ms[k] = _normalize_params(params[k], after, v, depth + 1)

def check_query_string(qs, sep)
  if qs
    if qs.bytesize > @bytesize_limit
      raise QueryLimitError, "total query size (#{qs.bytesize}) exceeds limit (#{@bytesize_limit})"
    end
    if (param_count = qs.count(sep.is_a?(String) ? sep : '&')) >= @params_limit
      raise QueryLimitError, "total number of query parameters (#{param_count+1}) exceeds limit (#{@params_limit})"
    end
    qs
  else
    ''
  end
end

def initialize(params_class, param_depth_limit, bytesize_limit: BYTESIZE_LIMIT, params_limit: PARAMS_LIMIT)
  @params_class = params_class
  @param_depth_limit = param_depth_limit
  @bytesize_limit = bytesize_limit
  @params_limit = params_limit
end

def make_params
  @params_class.new
end

def new_depth_limit(param_depth_limit)
  self.class.new @params_class, param_depth_limit
end

def normalize_params(params, name, v, _depth=nil)
  _normalize_params(params, name, v, 0)
end

def params_hash_has_key?(hash, key)
  return false if /\[\]/.match?(key)
  key.split(/[\[\]]+/).inject(hash) do |h, part|
    next h if part == ''
    return false unless params_hash_type?(h) && h.key?(part)
    h[part]
  end
  true
end

def params_hash_type?(obj)
  obj.kind_of?(@params_class)
end

def parse_nested_query(qs, separator = nil)
  params = make_params
  unless qs.nil? || qs.empty?
    check_query_string(qs, separator).split(separator ? (COMMON_SEP[separator] || /[#{separator}] */n) : DEFAULT_SEP).each do |p|
      k, v = p.split('=', 2).map! { |s| unescape(s) }
      _normalize_params(params, k, v, 0)
    end
  end
  return params.to_h
rescue ArgumentError => e
  raise InvalidParameterError, e.message, e.backtrace
end

def parse_query(qs, separator = nil, &unescaper)
  unescaper ||= method(:unescape)
  params = make_params
  check_query_string(qs, separator).split(separator ? (COMMON_SEP[separator] || /[#{separator}] */n) : DEFAULT_SEP).each do |p|
    next if p.empty?
    k, v = p.split('=', 2).map!(&unescaper)
    if cur = params[k]
      if cur.class == Array
        params[k] << v
      else
        params[k] = [cur, v]
      end
    else
      params[k] = v
    end
  end
  return params.to_h
end

def unescape(string, encoding = Encoding::UTF_8)
  URI.decode_www_form_component(string, encoding)
end