class Rack::Lint::Wrapper

def assert_required(key)
LintError, "env missing required key #{key}" unless @env.include?(key)
 @env[key]

def call(stream)
  ## The Streaming Body must respond to +call+, \
  raise LintError, "Streaming Body must respond to call" unless @body.respond_to?(:call)
  ## which must only be called once, \
  raise LintError, "Response body must only be called once (#{@consumed})" unless @consumed.nil?
  ## must not be called after being closed, \
  raise LintError, "Response body is already closed" if @closed
  @consumed = :call
  ## and accept a +stream+ argument.
  ##
  ## The +stream+ argument must respond to: +read+, +write+, <tt><<</tt>, +flush+, +close+, +close_read+, +close_write+, and +closed?+. \
  @body.call(StreamWrapper.new(stream))
end

def check_content_length_header(status, headers)
  headers.each do |key, value|
    if key == 'content-length'
      ## There must not be a <tt>content-length</tt> header key when the status is <tt>1xx</tt>, <tt>204</tt>, or <tt>304</tt>.
      if Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.key? status.to_i
        raise LintError, "content-length header found in #{status} response, not allowed"
      end
      @content_length = value
    end
  end
end

def check_content_type_header(status, headers)
  headers.each do |key, value|
    ## There must not be a <tt>content-type</tt> header key when the status is <tt>1xx</tt>, <tt>204</tt>, or <tt>304</tt>.
    if key == "content-type"
      if Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.key? status.to_i
        raise LintError, "content-type header found in #{status} response, not allowed"
      end
      return
    end
  end
end

def check_early_hints(env)
  if env[RACK_EARLY_HINTS]
    ##
    ## If <tt>rack.early_hints</tt> is present, it must respond to +call+.
    unless env[RACK_EARLY_HINTS].respond_to?(:call)
      raise LintError, "rack.early_hints must respond to call"
    end
    original_callback = env[RACK_EARLY_HINTS]
    env[RACK_EARLY_HINTS] = lambda do |headers|
      ## If <tt>rack.early_hints</tt> is called, it must be called with valid Rack response headers.
      check_headers(headers)
      original_callback.call(headers)
    end
  end
end

def check_environment(env)
  ## The environment must be an unfrozen +Hash+. The Rack application is free to modify the environment, but the modified environment should also comply with this specification. \
  raise LintError, "env #{env.inspect} is not a Hash, but #{env.class}" unless env.kind_of? Hash
  raise LintError, "env should not be frozen, but is" if env.frozen?
  ## All environment keys must be strings.
  keys = env.keys
  keys.reject!{|key| String === key}
  unless keys.empty?
    raise LintError, "env contains non-string keys: #{keys.inspect}"
  end
  ##
  ## === CGI Variables
  ##
  ## The environment is required to include these variables, adopted from {The Common Gateway Interface}[https://datatracker.ietf.org/doc/html/rfc3875] (CGI), except when they'd be empty, but see below.
  ##
  ## The CGI keys (named without a period) must have +String+ values and are reserved for the Rack specification. If the values for CGI keys contain non-ASCII characters, they should use <tt>ASCII-8BIT</tt> encoding.
  env.each do |key, value|
    next if key.include?(".") # Skip extensions
    
    unless value.kind_of? String
      raise LintError, "env variable #{key} has non-string value #{value.inspect}"
    end
    next if value.encoding == Encoding::ASCII_8BIT
    unless value.b !~ /[\x80-\xff]/n
      raise LintError, "env variable #{key} has value containing non-ASCII characters and has non-ASCII-8BIT encoding #{value.inspect} encoding: #{value.encoding}"
    end
  end
  ##
  ## The server and application can store their own data in the environment, too. The keys must contain at least one dot, and should be prefixed uniquely. The prefix <tt>rack.</tt> is reserved for use with the Rack specification and the classes that ship with Rack.
  ##
  ## ==== <tt>REQUEST_METHOD</tt>
  ##
  ## The HTTP request method, such as "GET" or "POST". This cannot ever be an empty string, and so is always required.
  request_method = assert_required(REQUEST_METHOD)
  unless request_method =~ /\A[0-9A-Za-z!\#$%&'*+.^_`|~-]+\z/
    raise LintError, "REQUEST_METHOD unknown: #{request_method.inspect}"
  end
  ##
  ## ==== <tt>SCRIPT_NAME</tt>
  ##
  ## The initial portion of the request URL's path that corresponds to the application object, so that the application knows its virtual location. This may be an empty string, if the application corresponds to the root of the server. If non-empty, the string must start with <tt>/</tt>, but should not end with <tt>/</tt>.
  if script_name = env[SCRIPT_NAME]
    if script_name != "" && script_name !~ /\A\//
      raise LintError, "SCRIPT_NAME must start with /"
    end
    ##
    ## In addition, <tt>SCRIPT_NAME</tt> MUST not be <tt>/</tt>, but instead be empty, \
    if script_name == "/"
      raise LintError, "SCRIPT_NAME cannot be '/', make it '' and PATH_INFO '/'"
    end
  end
  ## and one of <tt>SCRIPT_NAME</tt> or <tt>PATH_INFO</tt> must be set, e.g. <tt>PATH_INFO</tt> can be <tt>/</tt> if <tt>SCRIPT_NAME</tt> is empty.
  path_info = env[PATH_INFO]
  if (script_name.nil? || script_name.empty?) && (path_info.nil? || path_info.empty?)
    raise LintError, "One of SCRIPT_NAME or PATH_INFO must be set (make PATH_INFO '/' if SCRIPT_NAME is empty)"
  end
  ##
  ## ==== <tt>PATH_INFO</tt>
  ##
  ## The remainder of the request URL's "path", designating the virtual "location" of the request's target within the application. This may be an empty string, if the request URL targets the application root and does not have a trailing slash. This value may be percent-encoded when originating from a URL.
  ##
  ## The <tt>PATH_INFO</tt>, if provided, must be a valid request target or an empty string, as defined by {RFC9110}[https://datatracker.ietf.org/doc/html/rfc9110#target.resource].
  case path_info
  when REQUEST_PATH_ASTERISK_FORM
    ## * Only <tt>OPTIONS</tt> requests may have <tt>PATH_INFO</tt> set to <tt>*</tt> (asterisk-form).
    unless request_method == OPTIONS
      raise LintError, "Only OPTIONS requests may have PATH_INFO set to '*' (asterisk-form)"
    end
  when REQUEST_PATH_AUTHORITY_FORM
    ## * Only <tt>CONNECT</tt> requests may have <tt>PATH_INFO</tt> set to an authority (authority-form). Note that in HTTP/2+, the authority-form is not a valid request target.
    unless request_method == CONNECT
      raise LintError, "Only CONNECT requests may have PATH_INFO set to an authority (authority-form)"
    end
  when REQUEST_PATH_ABSOLUTE_FORM
    ## * <tt>CONNECT</tt> and <tt>OPTIONS</tt> requests must not have <tt>PATH_INFO</tt> set to a URI (absolute-form).
    if request_method == CONNECT || request_method == OPTIONS
      raise LintError, "CONNECT and OPTIONS requests must not have PATH_INFO set to a URI (absolute-form)"
    end
  when REQUEST_PATH_ORIGIN_FORM
    ## * Otherwise, <tt>PATH_INFO</tt> must start with a <tt>/</tt> and must not include a fragment part starting with <tt>#</tt> (origin-form).
  when "", nil
    # Empty string or nil is okay.
  else
    raise LintError, "PATH_INFO must start with a '/' and must not include a fragment part starting with '#' (origin-form)"
  end
  ##
  ## ==== <tt>QUERY_STRING</tt>
  ##
  ## The portion of the request URL that follows the <tt>?</tt>, if any. May be empty, but is always required!
  assert_required(QUERY_STRING)
  ##
  ## ==== <tt>SERVER_NAME</tt>
  ##
  ## Must be a valid host, as defined by {RFC3986}[https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2].
  ##
  ## When combined with <tt>SCRIPT_NAME</tt>, <tt>PATH_INFO</tt>, and <tt>QUERY_STRING</tt>, these variables can be used to reconstruct the original the request URL. Note, however, that <tt>HTTP_HOST</tt>, if present, should be used in preference to <tt>SERVER_NAME</tt> for reconstructing the request URL.
  server_name = assert_required(SERVER_NAME)
  unless server_name.match?(SERVER_NAME_PATTERN)
    raise LintError, "env[SERVER_NAME] must be a valid host"
  end
  ##
  ## ==== <tt>SERVER_PROTOCOL</tt>
  ##
  ## The HTTP version used for the request. It must match the regular expression <tt>HTTP\/\d(\.\d)?</tt>.
  server_protocol = assert_required(SERVER_PROTOCOL)
  unless %r{HTTP/\d(\.\d)?}.match?(server_protocol)
    raise LintError, "env[SERVER_PROTOCOL] does not match HTTP/\\d(\\.\\d)?"
  end
  ##
  ## ==== <tt>SERVER_PORT</tt>
  ##
  ## The port the server is running on, if the server is running on a non-standard port. It must consist of digits only.
  ##
  ## The standard ports are:
  ## * 80 for HTTP
  ## * 443 for HTTPS
  if server_port = env[SERVER_PORT]
    unless server_port =~ /\A\d+\z/
      raise LintError, "env[SERVER_PORT] is not an Integer"
    end
  end
  ##
  ## ==== <tt>CONTENT_TYPE</tt>
  ##
  ## The optional MIME type of the request body, if any.
  # N.B. We do not validate this field as it is considered user-provided data.
  ##
  ## ==== <tt>CONTENT_LENGTH</tt>
  ##
  ## The length of the request body, if any. It must consist of digits only.
  if content_length = env["CONTENT_LENGTH"]
    if content_length !~ /\A\d+\z/
      raise LintError, "Invalid CONTENT_LENGTH: #{content_length.inspect}"
    end
  end
  ##
  ## ==== <tt>HTTP_HOST</tt>
  ##
  ## An optional HTTP authority, as defined by {RFC9110}[https://datatracker.ietf.org/doc/html/rfc9110#name-host-and-authority].
  if http_host = env[HTTP_HOST]
    unless http_host.match?(HTTP_HOST_PATTERN)
      raise LintError, "env[HTTP_HOST] must be a valid authority"
    end
  end
  ##
  ## ==== <tt>HTTP_</tt> Headers
  ##
  ## Unless specified above, the environment can contain any number of additional headers, each starting with <tt>HTTP_</tt>. The presence or absence of these variables should correspond with the presence or absence of the appropriate HTTP header in the request, and those headers have no specific interpretation or validation by the Rack specification. However, there are many standard HTTP headers that have a specific meaning in the context of a request; see {RFC3875 section 4.1.18}[https://tools.ietf.org/html/rfc3875#section-4.1.18] for more details.
  ##
  ## For compatibility with the CGI specifiction, the environment must not contain the keys <tt>HTTP_CONTENT_TYPE</tt> or <tt>HTTP_CONTENT_LENGTH</tt>. Instead, the keys <tt>CONTENT_TYPE</tt> and <tt>CONTENT_LENGTH</tt> must be used.
  %w[HTTP_CONTENT_TYPE HTTP_CONTENT_LENGTH].each do |header|
    if env.include?(header)
      raise LintError, "env contains #{header}, must use #{header[5..-1]}"
    end
  end
  ##
  ## === Rack-Specific Variables
  ##
  ## In addition to CGI variables, the Rack environment includes Rack-specific variables. These variables are prefixed with <tt>rack.</tt> and are reserved for use by the Rack specification, or by the classes that ship with Rack.
  ##
  ## ==== <tt>rack.url_scheme</tt>
  ##
  ## The URL scheme, which must be one of <tt>http</tt>, <tt>https</tt>, <tt>ws</tt> or <tt>wss</tt>. This can never be an empty string, and so is always required. The scheme should be set according to the last hop. For example, if a client makes a request to a reverse proxy over HTTPS, but the connection between the reverse proxy and the server is over plain HTTP, the reverse proxy should set <tt>rack.url_scheme</tt> to <tt>http</tt>.
  rack_url_scheme = assert_required(RACK_URL_SCHEME)
  unless ALLOWED_SCHEMES.include?(rack_url_scheme)
    raise LintError, "rack.url_scheme unknown: #{rack_url_scheme.inspect}"
  end
  ##
  ## ==== <tt>rack.protocol</tt>
  ##
  ## An optional +Array+ of +String+ values, containing the protocols advertised by the client in the <tt>upgrade</tt> header (HTTP/1) or the <tt>:protocol</tt> pseudo-header (HTTP/2+).
  if protocols = env[RACK_PROTOCOL]
    unless protocols.is_a?(Array) && protocols.all?{|protocol| protocol.is_a?(String)}
      raise LintError, "rack.protocol must be an Array of Strings"
    end
  end
  ##
  ## ==== <tt>rack.session</tt>
  ##
  ## An optional +Hash+-like interface for storing request session data. The store must implement:
  if session = env[RACK_SESSION]
    ## * <tt>store(key, value)</tt> (aliased as <tt>[]=</tt>) to set a value for a key,
    unless session.respond_to?(:store) && session.respond_to?(:[]=)
      raise LintError, "session #{session.inspect} must respond to store and []="
    end
    ## * <tt>fetch(key, default = nil)</tt> (aliased as <tt>[]</tt>) to retrieve a value for a key,
    unless session.respond_to?(:fetch) && session.respond_to?(:[])
      raise LintError, "session #{session.inspect} must respond to fetch and []"
    end
    ## * <tt>delete(key)</tt> to delete a key,
    unless session.respond_to?(:delete)
      raise LintError, "session #{session.inspect} must respond to delete"
    end
    ## * <tt>clear</tt> to clear the session,
    unless session.respond_to?(:clear)
      raise LintError, "session #{session.inspect} must respond to clear"
    end
    ## * <tt>to_hash</tt> (optional) to retrieve the session as a Hash.
    unless session.respond_to?(:to_hash) && session.to_hash.kind_of?(Hash) && !session.to_hash.frozen?
      raise LintError, "session #{session.inspect} must respond to to_hash and return unfrozen Hash instance"
    end
  end
  ##
  ## ==== <tt>rack.logger</tt>
  ##
  ## An optional +Logger+-like interface for logging messages. The logger must implement:
  if logger = env[RACK_LOGGER]
    ## * <tt>info(message, &block)</tt>,
    unless logger.respond_to?(:info)
      raise LintError, "logger #{logger.inspect} must respond to info"
    end
    ## * <tt>debug(message, &block)</tt>,
    unless logger.respond_to?(:debug)
      raise LintError, "logger #{logger.inspect} must respond to debug"
    end
    ## * <tt>warn(message, &block)</tt>,
    unless logger.respond_to?(:warn)
      raise LintError, "logger #{logger.inspect} must respond to warn"
    end
    ## * <tt>error(message, &block)</tt>,
    unless logger.respond_to?(:error)
      raise LintError, "logger #{logger.inspect} must respond to error"
    end
    ## * <tt>fatal(message, &block)</tt>.
    unless logger.respond_to?(:fatal)
      raise LintError, "logger #{logger.inspect} must respond to fatal"
    end
  end
  ##
  ## ==== <tt>rack.multipart.buffer_size</tt>
  ##
  ## An optional +Integer+ hint to the multipart parser as to what chunk size to use for reads and writes.
  if rack_multipart_buffer_size = env[RACK_MULTIPART_BUFFER_SIZE]
    unless rack_multipart_buffer_size.is_a?(Integer) && rack_multipart_buffer_size > 0
      raise LintError, "rack.multipart.buffer_size must be an Integer > 0 if specified"
    end
  end
  ##
  ## ==== <tt>rack.multipart.tempfile_factory</tt>
  ##
  ## An optional object for constructing temporary files for multipart form data. The factory must implement:
  if rack_multipart_tempfile_factory = env[RACK_MULTIPART_TEMPFILE_FACTORY]
    ## * <tt>call(filename, content_type)</tt> to create a temporary file for a multipart form field.
    unless rack_multipart_tempfile_factory.respond_to?(:call)
      raise LintError, "rack.multipart.tempfile_factory must respond to #call"
    end
    ## The factory must return an +IO+-like object that responds to <tt><<</tt> and optionally <tt>rewind</tt>.
    env[RACK_MULTIPART_TEMPFILE_FACTORY] = lambda do |filename, content_type|
      io = rack_multipart_tempfile_factory.call(filename, content_type)
      unless io.respond_to?(:<<)
        raise LintError, "rack.multipart.tempfile_factory return value must respond to #<<"
      end
      io
    end
  end
  ##
  ## ==== <tt>rack.hijack?</tt>
  ##
  ## If present and truthy, indicates that the server supports partial hijacking. See the section below on hijacking for more information.
  #
  # N.B. There is no specific validation here. If the user provides a partial hijack response, we will confirm this value is truthy in `check_hijack_response`.
  ##
  ## ==== <tt>rack.hijack</tt>
  ##
  ## If present, an object responding to +call+ that is used to perform a full hijack. See the section below on hijacking for more information.
  check_hijack(env)
  ##
  ## ==== <tt>rack.early_hints</tt>
  ##
  ## If present, an object responding to +call+ that is used to send early hints. See the section below on early hints for more information.
  check_early_hints env
  ##
  ## ==== <tt>rack.input</tt>
  ##
  ## If present, the input stream. See the section below on the input stream for more information.
  if rack_input = env[RACK_INPUT]
    check_input_stream(rack_input)
    @env[RACK_INPUT] = InputWrapper.new(rack_input)
  end
  ##
  ## ==== <tt>rack.errors</tt>
  ##
  ## The error stream. See the section below on the error stream for more information.
  rack_errors = assert_required(RACK_ERRORS)
  check_error_stream(rack_errors)
  @env[RACK_ERRORS] = ErrorWrapper.new(rack_errors)
  ##
  ## ==== <tt>rack.response_finished</tt>
  ##
  ## If present, an array of callables that will be run by the server after the response has been processed. The callables are called with <tt>environment, status, headers, error</tt> arguments and should not raise any exceptions. The callables would typically be called after sending the response to the client, but it could also be called if an error occurs while generating the response or sending the response (in that case, the +error+ argument will be a kind of +Exception+). The callables will be called in reverse order.
  if rack_response_finished = env[RACK_RESPONSE_FINISHED]
    raise LintError, "rack.response_finished must be an array of callable objects" unless rack_response_finished.is_a?(Array)
    rack_response_finished.each do |callable|
      raise LintError, "rack.response_finished values must respond to call(env, status, headers, error)" unless callable.respond_to?(:call)
    end
  end
end

def check_error_stream(error)
  ## The error stream must respond to +puts+, +write+ and +flush+:
  [:puts, :write, :flush].each do |method|
    unless error.respond_to? method
      raise LintError, "rack.error #{error} does not respond to ##{method}"
    end
  end
end

def check_header_value(key, value)
  ## such that each +String+ must not contain <tt>NUL</tt> (<tt>\0</tt>), <tt>CR</tt> (<tt>\r</tt>), or <tt>LF</tt> (<tt>\n</tt>).
  if value.match?(/[\x00\x0A\x0D]/)
    raise LintError, "invalid header value #{key}: #{value.inspect}"
  end
end

def check_headers(headers)
  ## The headers must be an unfrozen +Hash+. \
  unless headers.kind_of?(Hash)
    raise LintError, "headers object should be a hash, but isn't (got #{headers.class} as headers)"
  end
  if headers.frozen?
    raise LintError, "headers object should not be frozen, but is"
  end
  headers.each do |key, value|
    ## The header keys must be +String+ values. \
    unless key.kind_of? String
      raise LintError, "header key must be a string, was #{key.class}"
    end
    ## Special headers starting <tt>rack.</tt> are for communicating with the server, and must not be sent back to the client.
    next if key.start_with?("rack.")
    ##
    ## * The headers must not contain a <tt>"status"</tt> key.
    raise LintError, "headers must not contain status" if key == "status"
    ## * Header keys must conform to {RFC7230}[https://tools.ietf.org/html/rfc7230] token specification, i.e. cannot contain non-printable ASCII, <tt>DQUOTE</tt> or <tt>(),/:;<=>?@[\]{}</tt>.
    raise LintError, "invalid header name: #{key}" if key =~ /[\(\),\/:;<=>\?@\[\\\]{}[:cntrl:]]/
    ## * Header keys must not contain uppercase ASCII characters (A-Z).
    raise LintError, "uppercase character in header name: #{key}" if key =~ /[A-Z]/
    ## * Header values must be either a +String+, \
    if value.kind_of?(String)
      check_header_value(key, value)
    elsif value.kind_of?(Array)
      ## or an +Array+ of +String+ values, \
      value.each{|value| check_header_value(key, value)}
    else
      raise LintError, "a header value must be a String or Array of Strings, but the value of '#{key}' is a #{value.class}"
    end
  end
end

def check_hijack(env)
  ## If <tt>rack.hijack</tt> is present in +env+, it must respond to +call+ \
  if original_hijack = env[RACK_HIJACK]
    raise LintError, "rack.hijack must respond to call" unless original_hijack.respond_to?(:call)
    env[RACK_HIJACK] = proc do
      io = original_hijack.call
      ## and return an +IO+ object which can be used to read and write to the underlying connection using HTTP/1 semantics and formatting.
      raise LintError, "rack.hijack must return an IO instance" unless io.is_a?(IO)
      io
    end
  end
end

def check_hijack_response(headers, env)
  ## If <tt>rack.hijack?</tt> is present in +env+ and truthy, \
  if env[RACK_IS_HIJACK]
    ## an application may set the special response header <tt>rack.hijack</tt> \
    if original_hijack = headers[RACK_HIJACK]
      ## to an object that responds to +call+, \
      unless original_hijack.respond_to?(:call)
        raise LintError, 'rack.hijack header must respond to #call'
      end
      ## accepting a +stream+ argument.
      return proc do |io|
        original_hijack.call StreamWrapper.new(io)
      end
    end
    ##
    ## After the response status and headers have been sent, this hijack callback will be called with a +stream+ argument which follows the same interface as outlined in "Streaming Body". Servers must ignore the +body+ part of the response tuple when the <tt>rack.hijack</tt> response header is present. Using an empty +Array+ is recommended.
  else
    ##
    ## If <tt>rack.hijack?</tt> is not present and truthy, the special response header <tt>rack.hijack</tt> must not be present in the response headers.
    if headers.key?(RACK_HIJACK)
      raise LintError, 'rack.hijack header must not be present if server does not support hijacking'
    end
  end
  nil
end

def check_input_stream(input)
  ## When applicable, its external encoding must be <tt>ASCII-8BIT</tt> and it must be opened in binary mode. \
  if input.respond_to?(:external_encoding) && input.external_encoding != Encoding::ASCII_8BIT
    raise LintError, "rack.input #{input} does not have ASCII-8BIT as its external encoding"
  end
  if input.respond_to?(:binmode?) && !input.binmode?
    raise LintError, "rack.input #{input} is not opened in binary mode"
  end
  ## The input stream must respond to +gets+, +each+, and +read+:
  [:gets, :each, :read].each do |method|
    unless input.respond_to? method
      raise LintError, "rack.input #{input} does not respond to ##{method}"
    end
  end
end

def check_rack_protocol_header(status, headers)
  ## If the <tt>rack.protocol</tt> header is present, it must be a +String+, and must be one of the values from the <tt>rack.protocol</tt> array from the environment.
  protocol = headers['rack.protocol']
  if protocol
    request_protocols = @env['rack.protocol']
    if request_protocols.nil?
      raise LintError, "rack.protocol header is #{protocol.inspect}, but rack.protocol was not set in request!"
    elsif !request_protocols.include?(protocol)
      raise LintError, "rack.protocol header is #{protocol.inspect}, but should be one of #{request_protocols.inspect} from the request!"
    end
  end
end

def check_status(status)
  ## This is an HTTP status. It must be an Integer greater than or equal to 100.
  unless status.is_a?(Integer) && status >= 100
    raise LintError, "Status must be an Integer >=100"
  end
end

def close
  ##
  ## After calling +close+, the Body is considered closed and should not be consumed again. \
  @closed = true
  ## If the original Body is replaced by a new Body, the new Body must also consume the original Body by calling +close+ if possible.
  @body.close if @body.respond_to?(:close)
  index = @lint.index(self)
  unless @env['rack.lint'][0..index].all? {|lint| lint.instance_variable_get(:@closed)}
    raise LintError, "Body has not been closed"
  end
end

def each
  ## The Enumerable Body must respond to +each+, \
  raise LintError, "Enumerable Body must respond to each" unless @body.respond_to?(:each)
  ## which must only be called once, \
  raise LintError, "Response body must only be called once (#{@consumed})" unless @consumed.nil?
  ## must not be called after being closed, \
  raise LintError, "Response body is already closed" if @closed
  @consumed = :each
  @body.each do |chunk|
    ## and must only yield +String+ values.
    unless chunk.kind_of? String
      raise LintError, "Body yielded non-string value #{chunk.inspect}"
    end
    ##
    ## Middleware must not call +each+ directly on the Body. Instead, middleware can return a new Body that calls +each+ on the original Body, yielding at least once per iteration.
    if @lint[0] == self
      @env['rack.lint.body_iteration'] += 1
    else
      if (@env['rack.lint.body_iteration'] -= 1) > 0
        raise LintError, "New body must yield at least once per iteration of old body"
      end
    end
    @size += chunk.bytesize
    yield chunk
  end
  verify_content_length(@size)
  verify_to_path
end

def initialize(app, env)
  @app = app
  @env = env
  @response = nil
  @head_request = false
  @status = nil
  @headers = nil
  @body = nil
  @consumed = nil
  @content_length = nil
  @closed = false
  @size = 0
end

def respond_to?(name, *)
  if BODY_METHODS.key?(name)
    @body.respond_to?(name)
  else
    super
  end
end

def response
  ## It takes exactly one argument, the +environment+ (representing an HTTP request) \
  raise LintError, "No env given" unless @env
  check_environment(@env)
  ## and returns a non-frozen +Array+ of exactly three elements: \
  @response = @app.call(@env)
  raise LintError, "response is not an Array, but #{@response.class}" unless @response.kind_of? Array
  raise LintError, "response is frozen" if @response.frozen?
  raise LintError, "response array has #{@response.size} elements instead of 3" unless @response.size == 3
  @status, @headers, @body = @response
  ## the +status+, \
  check_status(@status)
  ## the +headers+, \
  check_headers(@headers)
  hijack_proc = check_hijack_response(@headers, @env)
  if hijack_proc
    @headers[RACK_HIJACK] = hijack_proc
  end
  ## and the +body+ (representing an HTTP response).
  check_content_type_header(@status, @headers)
  check_content_length_header(@status, @headers)
  check_rack_protocol_header(@status, @headers)
  @head_request = @env[REQUEST_METHOD] == HEAD
  @lint = (@env['rack.lint'] ||= []) << self
  if (@env['rack.lint.body_iteration'] ||= 0) > 0
    raise LintError, "Middleware must not call #each directly"
  end
  return [@status, @headers, self]
end

def to_ary
  @body.to_ary.tap do |content|
    unless content == @body.enum_for.to_a
      raise LintError, "#to_ary not identical to contents produced by calling #each"
    end
  end
ensure
  close
end

def to_path
  @body.to_path
end

def verify_content_length(size)
  if @head_request
    unless size == 0
      raise LintError, "Response body was given for HEAD request, but should be empty"
    end
  elsif @content_length
    unless @content_length == size.to_s
      raise LintError, "content-length header was #{@content_length}, but should be #{size}"
    end
  end
end

def verify_to_path
  ##
  ## If the Body responds to +to_path+, it must return either +nil+ or a +String+. If a +String+ is returned, it must be a path for the local file system whose contents are identical to that produced by calling +each+; this may be used by the server as an alternative, possibly more efficient way to transport the response. The +to_path+ method does not consume the body.
  if @body.respond_to?(:to_path)
    optional_path = @body.to_path
    if optional_path != nil
      unless optional_path.is_a?(String) && ::File.exist?(optional_path)
        raise LintError, "body.to_path must be nil or a path to an existing file"
      end
    end
  end
end