class Rack::QueryParser

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

def check_query_string(qs, sep)
  if qs
    if qs.bytesize > @bytesize_limit
      raise QueryLimitError, "total query size 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, key_space_limit, param_depth_limit, bytesize_limit: BYTESIZE_LIMIT, params_limit: PARAMS_LIMIT)
  @params_class = params_class
  @key_space_limit = key_space_limit
  @param_depth_limit = param_depth_limit
  @bytesize_limit = bytesize_limit
  @params_limit = params_limit
end

def make_params
  @params_class.new @key_space_limit
end

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

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

def normalize_params(params, name, v, depth)
  raise ParamsTooDeepError if depth <= 0
  name =~ %r(\A[\[\]]*([^\[\]]+)\]*)
  k = $1 || ''
  after = $' || ''
  if k.empty?
    if !v.nil? && name == "[]"
      return Array(v)
    else
      return
    end
  end
  if after == ''
    params[k] = v
  elsif after == "["
    params[name] = v
  elsif after == "[]"
    params[k] ||= []
    raise ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
    params[k] << v
  elsif after =~ %r(^\[\]\[([^\[\]]+)\]$) || after =~ %r(^\[\](.+)$)
    child_key = $1
    params[k] ||= []
    raise ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
    if params_hash_type?(params[k].last) && !params_hash_has_key?(params[k].last, child_key)
      normalize_params(params[k].last, child_key, v, depth - 1)
    else
      params[k] << normalize_params(make_params, child_key, v, depth - 1)
    end
  else
    params[k] ||= make_params
    raise ParameterTypeError, "expected Hash (got #{params[k].class.name}) for param `#{k}'" unless params_hash_type?(params[k])
    params[k] = normalize_params(params[k], after, v, depth - 1)
  end
  params
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, d = nil)
  params = make_params
  unless qs.nil? || qs.empty?
    check_query_string(qs, d).split(d ? (COMMON_SEP[d] || /[#{d}] */n) : DEFAULT_SEP).each do |p|
      k, v = p.split('=', 2).map! { |s| unescape(s) }
      normalize_params(params, k, v, param_depth_limit)
    end
  end
  return params.to_h
rescue ArgumentError => e
  raise InvalidParameterError, e.message, e.backtrace
end

def parse_query(qs, d = nil, &unescaper)
  unescaper ||= method(:unescape)
  params = make_params
  check_query_string(qs, d).split(d ? (COMMON_SEP[d] || /[#{d}] */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)
  Utils.unescape(string)
end