text: # -*- test-case-name: twisted.web.test.test_web -*-
  # Copyright (c) Twisted Matrix Laboratories.
  # See LICENSE for details.
  
  """
  Implementation of the lowest-level Resource class.
  """
  
  
  __all__ = [
      "IResource",
      "getChildForRequest",
      "Resource",
      "ErrorPage",
      "NoResource",
      "ForbiddenResource",
      "EncodingResourceWrapper",
  ]
  
  import warnings
  
  from zope.interface import Attribute, Interface, implementer
  
  from twisted.python.compat import nativeString
  from twisted.python.reflect import prefixedMethodNames
  from twisted.python.components import proxyForInterface
  
  from twisted.web._responses import FORBIDDEN, NOT_FOUND
  from twisted.web.error import UnsupportedMethod
  
  
  class IResource(Interface):
      """
      A web resource.
      """
  
      isLeaf = Attribute(
          """
          Signal if this IResource implementor is a "leaf node" or not. If True,
          getChildWithDefault will not be called on this Resource.
          """
      )
  
      def getChildWithDefault(name, request):
          """
          Return a child with the given name for the given request.
          This is the external interface used by the Resource publishing
          machinery. If implementing IResource without subclassing
          Resource, it must be provided. However, if subclassing Resource,
          getChild overridden instead.
  
          @param name: A single path component from a requested URL.  For example,
              a request for I{http://example.com/foo/bar} will result in calls to
              this method with C{b"foo"} and C{b"bar"} as values for this
              argument.
          @type name: C{bytes}
  
          @param request: A representation of all of the information about the
              request that is being made for this child.
          @type request: L{twisted.web.server.Request}
          """
  
      def putChild(path, child):
          """
          Put a child IResource implementor at the given path.
  
          @param path: A single path component, to be interpreted relative to the
              path this resource is found at, at which to put the given child.
              For example, if resource A can be found at I{http://example.com/foo}
              then a call like C{A.putChild(b"bar", B)} will make resource B
              available at I{http://example.com/foo/bar}.
          @type path: C{bytes}
          """
  
      def render(request):
          """
          Render a request. This is called on the leaf resource for a request.
  
          @return: Either C{server.NOT_DONE_YET} to indicate an asynchronous or a
              C{bytes} instance to write as the response to the request.  If
              C{NOT_DONE_YET} is returned, at some point later (for example, in a
              Deferred callback) call C{request.write(b"<html>")} to write data to
              the request, and C{request.finish()} to send the data to the
              browser.
  
          @raise twisted.web.error.UnsupportedMethod: If the HTTP verb
              requested is not supported by this resource.
          """
  
  
  def getChildForRequest(resource, request):
      """
      Traverse resource tree to find who will handle the request.
      """
      while request.postpath and not resource.isLeaf:
          pathElement = request.postpath.pop(0)
          request.prepath.append(pathElement)
          resource = resource.getChildWithDefault(pathElement, request)
      return resource
  
  
  @implementer(IResource)
  class Resource:
      """
      Define a web-accessible resource.
  
      This serves 2 main purposes; one is to provide a standard representation
      for what HTTP specification calls an 'entity', and the other is to provide
      an abstract directory structure for URL retrieval.
      """
  
      entityType = IResource
  
      server = None
  
      def __init__(self):
          """
          Initialize.
          """
          self.children = {}
  
      isLeaf = 0
  
      ### Abstract Collection Interface
  
      def listStaticNames(self):
          return list(self.children.keys())
  
      def listStaticEntities(self):
          return list(self.children.items())
  
      def listNames(self):
          return list(self.listStaticNames()) + self.listDynamicNames()
  
      def listEntities(self):
          return list(self.listStaticEntities()) + self.listDynamicEntities()
  
      def listDynamicNames(self):
          return []
  
      def listDynamicEntities(self, request=None):
          return []
  
      def getStaticEntity(self, name):
          return self.children.get(name)
  
      def getDynamicEntity(self, name, request):
          if name not in self.children:
              return self.getChild(name, request)
          else:
              return None
  
      def delEntity(self, name):
          del self.children[name]
  
      def reallyPutEntity(self, name, entity):
          self.children[name] = entity
  
      # Concrete HTTP interface
  
      def getChild(self, path, request):
          """
          Retrieve a 'child' resource from me.
  
          Implement this to create dynamic resource generation -- resources which
          are always available may be registered with self.putChild().
  
          This will not be called if the class-level variable 'isLeaf' is set in
          your subclass; instead, the 'postpath' attribute of the request will be
          left as a list of the remaining path elements.
  
          For example, the URL /foo/bar/baz will normally be::
  
            | site.resource.getChild('foo').getChild('bar').getChild('baz').
  
          However, if the resource returned by 'bar' has isLeaf set to true, then
          the getChild call will never be made on it.
  
          Parameters and return value have the same meaning and requirements as
          those defined by L{IResource.getChildWithDefault}.
          """
          return NoResource("No such child resource.")
  
      def getChildWithDefault(self, path, request):
          """
          Retrieve a static or dynamically generated child resource from me.
  
          First checks if a resource was added manually by putChild, and then
          call getChild to check for dynamic resources. Only override if you want
          to affect behaviour of all child lookups, rather than just dynamic
          ones.
  
          This will check to see if I have a pre-registered child resource of the
          given name, and call getChild if I do not.
  
          @see: L{IResource.getChildWithDefault}
          """
          if path in self.children:
              return self.children[path]
          return self.getChild(path, request)
  
      def getChildForRequest(self, request):
          warnings.warn(
              "Please use module level getChildForRequest.", DeprecationWarning, 2
          )
          return getChildForRequest(self, request)
  
      def putChild(self, path, child):
          """
          Register a static child.
  
          You almost certainly don't want '/' in your path. If you
          intended to have the root of a folder, e.g. /foo/, you want
          path to be ''.
  
          @param path: A single path component.
          @type path: L{bytes}
  
          @param child: The child resource to register.
          @type child: L{IResource}
  
          @see: L{IResource.putChild}
          """
          if not isinstance(path, bytes):
              warnings.warn(
                  "Path segment must be bytes; "
                  "passing {} has never worked, and "
                  "will raise an exception in the future.".format(type(path)),
                  category=DeprecationWarning,
                  stacklevel=2,
              )
  
          self.children[path] = child
          child.server = self.server
  
      def render(self, request):
          """
          Render a given resource. See L{IResource}'s render method.
  
          I delegate to methods of self with the form 'render_METHOD'
          where METHOD is the HTTP that was used to make the
          request. Examples: render_GET, render_HEAD, render_POST, and
          so on. Generally you should implement those methods instead of
          overriding this one.
  
          render_METHOD methods are expected to return a byte string which will be
          the rendered page, unless the return value is C{server.NOT_DONE_YET}, in
          which case it is this class's responsibility to write the results using
          C{request.write(data)} and then call C{request.finish()}.
  
          Old code that overrides render() directly is likewise expected
          to return a byte string or NOT_DONE_YET.
  
          @see: L{IResource.render}
          """
          m = getattr(self, "render_" + nativeString(request.method), None)
          if not m:
              try:
                  allowedMethods = self.allowedMethods
              except AttributeError:
                  allowedMethods = _computeAllowedMethods(self)
              raise UnsupportedMethod(allowedMethods)
          return m(request)
  
      def render_HEAD(self, request):
          """
          Default handling of HEAD method.
  
          I just return self.render_GET(request). When method is HEAD,
          the framework will handle this correctly.
          """
          return self.render_GET(request)
  
  
  def _computeAllowedMethods(resource):
      """
      Compute the allowed methods on a C{Resource} based on defined render_FOO
      methods. Used when raising C{UnsupportedMethod} but C{Resource} does
      not define C{allowedMethods} attribute.
      """
      allowedMethods = []
      for name in prefixedMethodNames(resource.__class__, "render_"):
          # Potentially there should be an API for encode('ascii') in this
          # situation - an API for taking a Python native string (bytes on Python
          # 2, text on Python 3) and returning a socket-compatible string type.
          allowedMethods.append(name.encode("ascii"))
      return allowedMethods
  
  
  class ErrorPage(Resource):
      """
      L{ErrorPage} is a resource which responds with a particular
      (parameterized) status and a body consisting of HTML containing some
      descriptive text.  This is useful for rendering simple error pages.
  
      @ivar template: A native string which will have a dictionary interpolated
          into it to generate the response body.  The dictionary has the following
          keys:
  
            - C{"code"}: The status code passed to L{ErrorPage.__init__}.
            - C{"brief"}: The brief description passed to L{ErrorPage.__init__}.
            - C{"detail"}: The detailed description passed to
              L{ErrorPage.__init__}.
  
      @ivar code: An integer status code which will be used for the response.
      @type code: C{int}
  
      @ivar brief: A short string which will be included in the response body as
          the page title.
      @type brief: C{str}
  
      @ivar detail: A longer string which will be included in the response body.
      @type detail: C{str}
      """
  
      template = """
  <html>
    <head><title>%(code)s - %(brief)s</title></head>
    <body>
      <h1>%(brief)s</h1>
      <p>%(detail)s</p>
    </body>
  </html>
  """
  
      def __init__(self, status, brief, detail):
          Resource.__init__(self)
          self.code = status
          self.brief = brief
          self.detail = detail
  
      def render(self, request):
          request.setResponseCode(self.code)
          request.setHeader(b"content-type", b"text/html; charset=utf-8")
          interpolated = self.template % dict(
              code=self.code, brief=self.brief, detail=self.detail
          )
          if isinstance(interpolated, str):
              return interpolated.encode("utf-8")
          return interpolated
  
      def getChild(self, chnam, request):
          return self
  
  
  class NoResource(ErrorPage):
      """
      L{NoResource} is a specialization of L{ErrorPage} which returns the HTTP
      response code I{NOT FOUND}.
      """
  
      def __init__(self, message="Sorry. No luck finding that resource."):
          ErrorPage.__init__(self, NOT_FOUND, "No Such Resource", message)
  
  
  class ForbiddenResource(ErrorPage):
      """
      L{ForbiddenResource} is a specialization of L{ErrorPage} which returns the
      I{FORBIDDEN} HTTP response code.
      """
  
      def __init__(self, message="Sorry, resource is forbidden."):
          ErrorPage.__init__(self, FORBIDDEN, "Forbidden Resource", message)
  
  
  class _IEncodingResource(Interface):
      """
      A resource which knows about L{_IRequestEncoderFactory}.
  
      @since: 12.3
      """
  
      def getEncoder(request):
          """
          Parse the request and return an encoder if applicable, using
          L{_IRequestEncoderFactory.encoderForRequest}.
  
          @return: A L{_IRequestEncoder}, or L{None}.
          """
  
  
  @implementer(_IEncodingResource)
  class EncodingResourceWrapper(proxyForInterface(IResource)):  # type: ignore[misc]
      """
      Wrap a L{IResource}, potentially applying an encoding to the response body
      generated.
  
      Note that the returned children resources won't be wrapped, so you have to
      explicitly wrap them if you want the encoding to be applied.
  
      @ivar encoders: A list of
          L{_IRequestEncoderFactory<twisted.web.iweb._IRequestEncoderFactory>}
          returning L{_IRequestEncoder<twisted.web.iweb._IRequestEncoder>} that
          may transform the data passed to C{Request.write}. The list must be
          sorted in order of priority: the first encoder factory handling the
          request will prevent the others from doing the same.
      @type encoders: C{list}.
  
      @since: 12.3
      """
  
      def __init__(self, original, encoders):
          super().__init__(original)
          self._encoders = encoders
  
      def getEncoder(self, request):
          """
          Browser the list of encoders looking for one applicable encoder.
          """
          for encoderFactory in self._encoders:
              encoder = encoderFactory.encoderForRequest(request)
              if encoder is not None:
                  return encoder
  