class Rack::Lint::Wrapper

def check_environment(env)
  ## The environment must be an unfrozen instance of Hash that includes
  ## CGI-like headers. The Rack application is free to modify the
  ## environment.
  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?
  ##
  ## The environment is required to include these variables
  ## (adopted from {PEP 333}[https://peps.python.org/pep-0333/]), except when they'd be empty, but see
  ## below.
  ## <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.
  ## <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.
  ## <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.
  ## <tt>QUERY_STRING</tt>:: The portion of the request URL that
  ##                         follows the <tt>?</tt>, if any. May be
  ##                         empty, but is always required!
  ## <tt>SERVER_NAME</tt>:: When combined with <tt>SCRIPT_NAME</tt> and
  ##                        <tt>PATH_INFO</tt>, these variables can be
  ##                        used to complete the 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.
  ##                        <tt>SERVER_NAME</tt> can never be an empty
  ##                        string, and so is always required.
  ## <tt>SERVER_PORT</tt>:: An optional +Integer+ which is the port the
  ##                        server is running on. Should be specified if
  ##                        the server is running on a non-standard port.
  ## <tt>SERVER_PROTOCOL</tt>:: A string representing the HTTP version used
  ##                            for the request.
  ## <tt>HTTP_</tt> Variables:: Variables corresponding to the
  ##                            client-supplied HTTP request
  ##                            headers (i.e., variables whose
  ##                            names begin 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. See
  ##                            {RFC3875 section 4.1.18}[https://tools.ietf.org/html/rfc3875#section-4.1.18]
  ##                            for specific behavior.
  ## In addition to this, the Rack environment must include these
  ## Rack-specific variables:
  ## <tt>rack.url_scheme</tt>:: +http+ or +https+, depending on the
  ##                            request URL.
  ## <tt>rack.input</tt>:: See below, the input stream.
  ## <tt>rack.errors</tt>:: See below, the error stream.
  ## <tt>rack.hijack?</tt>:: See below, if present and true, indicates
  ##                         that the server supports partial hijacking.
  ## <tt>rack.hijack</tt>:: See below, if present, an object responding
  ##                        to +call+ that is used to perform a full
  ##                        hijack.
  ## <tt>rack.protocol</tt>:: An optional +Array+ of +String+, containing
  ##                          the protocols advertised by the client in
  ##                          the +upgrade+ header (HTTP/1) or the
  ##                          +:protocol+ 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
  ## Additional environment specifications have approved to
  ## standardized middleware APIs. None of these are required to
  ## be implemented by the server.
  ## <tt>rack.session</tt>:: A hash-like interface for storing
  ##                         request session data.
  ##                         The store must implement:
  if session = env[RACK_SESSION]
    ##                         store(key, value)         (aliased as []=);
    unless session.respond_to?(:store) && session.respond_to?(:[]=)
      raise LintError, "session #{session.inspect} must respond to store and []="
    end
    ##                         fetch(key, default = nil) (aliased as []);
    unless session.respond_to?(:fetch) && session.respond_to?(:[])
      raise LintError, "session #{session.inspect} must respond to fetch and []"
    end
    ##                         delete(key);
    unless session.respond_to?(:delete)
      raise LintError, "session #{session.inspect} must respond to delete"
    end
    ##                         clear;
    unless session.respond_to?(:clear)
      raise LintError, "session #{session.inspect} must respond to clear"
    end
    ##                         to_hash (returning unfrozen Hash instance);
    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>:: A common object interface for logging messages.
  ##                        The object must implement:
  if logger = env[RACK_LOGGER]
    ##                         info(message, &block)
    unless logger.respond_to?(:info)
      raise LintError, "logger #{logger.inspect} must respond to info"
    end
    ##                         debug(message, &block)
    unless logger.respond_to?(:debug)
      raise LintError, "logger #{logger.inspect} must respond to debug"
    end
    ##                         warn(message, &block)
    unless logger.respond_to?(:warn)
      raise LintError, "logger #{logger.inspect} must respond to warn"
    end
    ##                         error(message, &block)
    unless logger.respond_to?(:error)
      raise LintError, "logger #{logger.inspect} must respond to error"
    end
    ##                         fatal(message, &block)
    unless logger.respond_to?(:fatal)
      raise LintError, "logger #{logger.inspect} must respond to fatal"
    end
  end
  ## <tt>rack.multipart.buffer_size</tt>:: An Integer hint to the multipart parser as to what chunk size to use for reads and writes.
  if bufsize = env[RACK_MULTIPART_BUFFER_SIZE]
    unless bufsize.is_a?(Integer) && bufsize > 0
      raise LintError, "rack.multipart.buffer_size must be an Integer > 0 if specified"
    end
  end
  ## <tt>rack.multipart.tempfile_factory</tt>:: An object responding to #call with two arguments, the filename and content_type given for the multipart form field, and returning an IO-like object that responds to #<< and optionally #rewind. This factory will be used to instantiate the tempfile for each multipart form file upload field, rather than the default class of Tempfile.
  if tempfile_factory = env[RACK_MULTIPART_TEMPFILE_FACTORY]
    raise LintError, "rack.multipart.tempfile_factory must respond to #call" unless tempfile_factory.respond_to?(:call)
    env[RACK_MULTIPART_TEMPFILE_FACTORY] = lambda do |filename, content_type|
      io = tempfile_factory.call(filename, content_type)
      raise LintError, "rack.multipart.tempfile_factory return value must respond to #<<" unless io.respond_to?(:<<)
      io
    end
  end
  ## The server or the 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 core distribution and other
  ## accepted specifications and must not be used otherwise.
  ##
  %w[REQUEST_METHOD SERVER_NAME QUERY_STRING SERVER_PROTOCOL rack.errors].each do |header|
    raise LintError, "env missing required key #{header}" unless env.include? header
  end
  ## The <tt>SERVER_PORT</tt> must be an Integer if set.
  server_port = env["SERVER_PORT"]
  unless server_port.nil? || (Integer(server_port) rescue false)
    raise LintError, "env[SERVER_PORT] is not an Integer"
  end
  ## The <tt>SERVER_NAME</tt> must be a valid authority as defined by RFC7540.
  unless (URI.parse("http://#{env[SERVER_NAME]}/") rescue false)
    raise LintError, "#{env[SERVER_NAME]} must be a valid authority"
  end
  ## The <tt>HTTP_HOST</tt> must be a valid authority as defined by RFC7540.
  unless (URI.parse("http://#{env[HTTP_HOST]}/") rescue false)
    raise LintError, "#{env[HTTP_HOST]} must be a valid authority"
  end
  ## The <tt>SERVER_PROTOCOL</tt> must match the regexp <tt>HTTP/\d(\.\d)?</tt>.
  server_protocol = env['SERVER_PROTOCOL']
  unless %r{HTTP/\d(\.\d)?}.match?(server_protocol)
    raise LintError, "env[SERVER_PROTOCOL] does not match HTTP/\\d(\\.\\d)?"
  end
  ## The environment must not contain the keys
  ## <tt>HTTP_CONTENT_TYPE</tt> or <tt>HTTP_CONTENT_LENGTH</tt>
  ## (use the versions without <tt>HTTP_</tt>).
  %w[HTTP_CONTENT_TYPE HTTP_CONTENT_LENGTH].each { |header|
    if env.include? header
      raise LintError, "env contains #{header}, must use #{header[5..-1]}"
    end
  }
  ## The CGI keys (named without a period) must have String values.
  ## If the string values for CGI keys contain non-ASCII characters,
  ## they should use ASCII-8BIT encoding.
  env.each { |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
  }
  ## There are the following restrictions:
  ## * <tt>rack.url_scheme</tt> must either be +http+ or +https+.
  unless %w[http https].include?(env[RACK_URL_SCHEME])
    raise LintError, "rack.url_scheme unknown: #{env[RACK_URL_SCHEME].inspect}"
  end
  ## * There may be a valid input stream in <tt>rack.input</tt>.
  if rack_input = env[RACK_INPUT]
    check_input_stream(rack_input)
    @env[RACK_INPUT] = InputWrapper.new(rack_input)
  end
  ## * There must be a valid error stream in <tt>rack.errors</tt>.
  rack_errors = env[RACK_ERRORS]
  check_error_stream(rack_errors)
  @env[RACK_ERRORS] = ErrorWrapper.new(rack_errors)
  ## * There may be a valid hijack callback in <tt>rack.hijack</tt>
  check_hijack env
  ## * There may be a valid early hints callback in <tt>rack.early_hints</tt>
  check_early_hints env
  ## * The <tt>REQUEST_METHOD</tt> must be a valid token.
  unless env[REQUEST_METHOD] =~ /\A[0-9A-Za-z!\#$%&'*+.^_`|~-]+\z/
    raise LintError, "REQUEST_METHOD unknown: #{env[REQUEST_METHOD].dump}"
  end
  ## * The <tt>SCRIPT_NAME</tt>, if non-empty, must start with <tt>/</tt>
  if env.include?(SCRIPT_NAME) && env[SCRIPT_NAME] != "" && env[SCRIPT_NAME] !~ /\A\//
    raise LintError, "SCRIPT_NAME must start with /"
  end
  ## * The <tt>PATH_INFO</tt>, if provided, must be a valid request target or an empty string.
  if env.include?(PATH_INFO)
    case env[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 env[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 env[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 env[REQUEST_METHOD] == CONNECT || env[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 '#' (origin-form).
    when ""
      # Empty string is okay.
    else
      raise LintError, "PATH_INFO must start with a '/' and must not include a fragment part starting with '#' (origin-form)"
    end
  end
  ## * The <tt>CONTENT_LENGTH</tt>, if given, must consist of digits only.
  if env.include?("CONTENT_LENGTH") && env["CONTENT_LENGTH"] !~ /\A\d+\z/
    raise LintError, "Invalid CONTENT_LENGTH: #{env["CONTENT_LENGTH"]}"
  end
  ## * One of <tt>SCRIPT_NAME</tt> or <tt>PATH_INFO</tt> must be
  ##   set. <tt>PATH_INFO</tt> should be <tt>/</tt> if
  ##   <tt>SCRIPT_NAME</tt> is empty.
  unless env[SCRIPT_NAME] || env[PATH_INFO]
    raise LintError, "One of SCRIPT_NAME or PATH_INFO must be set (make PATH_INFO '/' if SCRIPT_NAME is empty)"
  end
  ##   <tt>SCRIPT_NAME</tt> never should be <tt>/</tt>, but instead be empty.
  unless env[SCRIPT_NAME] != "/"
    raise LintError, "SCRIPT_NAME cannot be '/', make it '' and PATH_INFO '/'"
  end
  ## <tt>rack.response_finished</tt>:: An array of callables run by the server after the response has been
  ## processed. This would typically be invoked after sending the response to the client, but it could also be
  ## invoked if an error occurs while generating the response or sending the response; in that case, the error
  ## argument will be a subclass of +Exception+.
  ## The callables are invoked with +env, status, headers, error+ arguments and should not raise any
  ## exceptions. They should be invoked in reverse order of registration.
  if callables = env[RACK_RESPONSE_FINISHED]
    raise LintError, "rack.response_finished must be an array of callable objects" unless callables.is_a?(Array)
    callables.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