- Add a chapter titled "Request and Response" to the narrative

  documentation, content cribbed from the WebOb documentation.

2 files changed, 311 insertions, 0 deletions

diff --git a/docs/index.rst b/docs/index.rst
index 1305104c4..5fcdfb225 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -32,6 +32,7 @@ Narrative documentation in chapter form explaining how to use
    narr/traversal
    narr/urldispatch
    narr/views
+   narr/webob
    narr/templates
    narr/models
    narr/security
diff --git a/docs/narr/webob.rst b/docs/narr/webob.rst
new file mode 100644
index 000000000..32845ee5b
--- /dev/null
+++ b/docs/narr/webob.rst
@@ -0,0 +1,310 @@
+Request and Response Objects
+============================
+
+:mod:`repoze.bfg` uses the :term:`WebOb` package to supply
+:term:`request` and :term:`response` object implementations.  The
+:term:`request` object that is passed to a :mod:`repoze.bfg`
+:term:`view` is an instance of the :mod:`webob.Request` class.  The
+:term:`response` returned from a :mod:`repoze.bfg` :term:`view`
+:term:`renderer` is an instance of the :mod:`webob.Response` class.
+Users can also return an instance of :mod:`webob.Response` directly
+from a view as necessary.
+
+WebOb is a project separate from :mod:`repoze.bfg` with a separate set
+of authors and a fully separate `set of documentation
+<http://pythonpaste.org/webob/>`_.
+
+.. warning:: The following information is only an overview of the
+   request and response objects provided by :term:`WebOb`.  See the
+   `reference documentation
+   <http://pythonpaste.org/webob/reference.html>`_ for more detailed
+   API reference information.
+
+WebOb provides objects for HTTP requests and responses.  Specifically
+it does this by wrapping the `WSGI <http://wsgi.org>`_ request
+environment and response status/headers/app_iter(body).
+
+The request and response objects provide many conveniences for parsing
+HTTP request and forming HTTP responses.  Both objects are read/write:
+as a result, WebOb is also a nice way to create HTTP requests and
+parse HTTP responses; however, we won't cover that use case in this
+document.  The `reference documentation
+<http://pythonpaste.org/webob/reference.html>`_ shows many examples of
+creating requests.
+
+Request
+~~~~~~~
+
+The request object is a wrapper around the `WSGI environ dictionary
+<http://www.python.org/dev/peps/pep-0333/#environ-variables>`_.  This
+dictionary contains keys for each header, keys that describe the
+request (including the path and query string), a file-like object for
+the request body, and a variety of custom keys.  You can always access
+the environ with ``req.environ``.
+
+Some of the most important/interesting attributes of a request
+object:
+
+``req.method``:
+    The request method, e.g., ``'GET'``, ``'POST'``
+
+``req.GET``:
+    A `dictionary-like object`_ with all the variables in the query
+    string.
+
+``req.POST``:
+    A `dictionary-like object`_ with all the variables in the request
+    body.  This only has variables if the request was a ``POST`` and
+    it is a form submission.  
+
+``req.params``:
+    A `dictionary-like object`_ with a combination of everything in
+    ``req.GET`` and ``req.POST``.
+
+``req.body``:
+    The contents of the body of the request.  This contains the entire
+    request body as a string.  This is useful when the request is a
+    ``POST`` that is *not* a form submission, or a request like a
+    ``PUT``.  You can also get ``req.body_file`` for a file-like
+    object.
+
+``req.cookies``:
+    A simple dictionary of all the cookies.
+
+``req.headers``:
+    A dictionary of all the headers.  This is dictionary is case-insensitive.
+
+``req.urlvars`` and ``req.urlargs``:
+    ``req.urlvars`` is the keyword parameters associated with the
+    request URL.  ``req.urlargs`` are the positional parameters.
+    These are set by products like `Routes
+    <http://routes.groovie.org/>`_ and `Selector
+    <http://lukearno.com/projects/selector/>`_.
+
+.. _`dictionary-like object`: #multidict
+
+Also, for standard HTTP request headers there are usually attributes,
+for instance: ``req.accept_language``, ``req.content_length``,
+``req.user_agent``, as an example.  These properties expose the
+*parsed* form of each header, for whatever parsing makes sense.  For
+instance, ``req.if_modified_since`` returns a `datetime
+<http://python.org/doc/current/lib/datetime-datetime.html>`_ object
+(or None if the header is was not provided).  Details are in the
+`Request reference
+<http://pythonpaste.org/webob/class-webob.Request.html>`_.
+
+URLs
+++++
+
+In addition to these attributes, there are several ways to get the URL
+of the request.  I'll show various values for an example URL
+``http://localhost/app-root/doc?article_id=10``, where the application
+is mounted at ``http://localhost/app-root``.
+
+``req.url``:
+    The full request URL, with query string, e.g.,
+    ``'http://localhost/app-root/doc?article_id=10'``
+
+``req.application_url``:
+    The URL of the application (just the SCRIPT_NAME portion of the
+    path, not PATH_INFO).  E.g., ``'http://localhost/app-root'``
+
+``req.host_url``:
+    The URL with the host, e.g., ``'http://localhost'``
+
+``req.relative_url(url, to_application=False)``:
+    Gives a URL, relative to the current URL.  If ``to_application``
+    is True, then resolves it relative to ``req.application_url``.
+
+Methods
++++++++
+
+There are `several methods
+<http://pythonpaste.org/webob/class-webob.Request.html#__init__>`_ but
+only a few you'll use often:
+
+``Request.blank(base_url)``:
+    Creates a new request with blank information, based at the given
+    URL.  This can be useful for subrequests and artificial requests.
+    You can also use ``req.copy()`` to copy an existing request, or
+    for subrequests ``req.copy_get()`` which copies the request but
+    always turns it into a GET (which is safer to share for
+    subrequests).
+
+``req.get_response(wsgi_application)``:
+    This method calls the given WSGI application with this request,
+    and returns a `Response`_ object.  You can also use this for
+    subrequests or testing.
+
+Unicode
++++++++
+
+Many of the properties in the request object will return unicode
+values if the request encoding/charset is provided.  The client *can*
+indicate the charset with something like ``Content-Type:
+application/x-www-form-urlencoded; charset=utf8``, but browsers seldom
+set this.  You can set the charset with ``req.charset = 'utf8'``, or
+during instantiation with ``Request(environ, charset='utf8')``.  If
+you subclass ``Request`` you can also set ``charset`` as a class-level
+attribute.
+
+If it is set, then ``req.POST``, ``req.GET``, ``req.params``, and
+``req.cookies`` will contain unicode strings.  Each has a
+corresponding ``req.str_*`` (like ``req.str_POST``) that is always
+``str`` and never unicode.
+
+Response
+~~~~~~~~
+
+The response object looks a lot like the request object, though with
+some differences.  The request object wraps a single ``environ``
+object; the response object has three fundamental parts (based on
+WSGI):
+
+``response.status``:
+    The response code plus message, like ``'200 OK'``.  To set the
+    code without the reason, use ``response.status_int = 200``.
+
+``response.headerlist``:
+    A list of all the headers, like ``[('Content-Type',
+    'text/html')]``.  There's a case-insensitive `dictionary-like
+    object`_ in ``response.headers`` that also allows you to access
+    these same headers.
+
+``response.app_iter``:
+    An iterable (such as a list or generator) that will produce the
+    content of the response.  This is also accessible as
+    ``response.body`` (a string), ``response.unicode_body`` (a
+    unicode object, informed by ``response.charset``), and
+    ``response.body_file`` (a file-like object; writing to it appends
+    to ``app_iter``).
+
+Everything else in the object derives from this underlying state.
+Here's the highlights:
+
+``response.content_type``:
+    The content type *not* including the ``charset`` parameter.
+    Typical use: ``response.content_type = 'text/html'``.  You can
+    subclass ``Response`` and add a class-level attribute
+    ``default_content_type`` to set this automatically on
+    instantiation.
+
+``response.charset``:
+    The ``charset`` parameter of the content-type, it also informs
+    encoding in ``response.unicode_body``.
+    ``response.content_type_params`` is a dictionary of all the
+    parameters.
+
+``response.request``:
+    This optional attribute can point to the request object associated
+    with this response object.
+
+``response.set_cookie(key, value, max_age=None, path='/', domain=None, secure=None, httponly=False, version=None, comment=None)``:
+    Set a cookie.  The keyword arguments control the various cookie
+    parameters.  The ``max_age`` argument is the length for the cookie
+    to live in seconds (you may also use a timedelta object).  The
+    `Expires`` key will also be set based on the value of ``max_age``.
+
+``response.delete_cookie(key, path='/', domain=None)``:
+    Delete a cookie from the client.  This sets ``max_age`` to 0 and
+    the cookie value to ``''``.
+
+``response.cache_expires(seconds=0)``:
+    This makes this response cachable for the given number of seconds,
+    or if ``seconds`` is 0 then the response is uncacheable (this also
+    sets the ``Expires`` header).
+
+``response(environ, start_response)``: The response object is a WSGI
+    application.  As an application, it acts according to how you
+    creat it.  It *can* do conditional responses if you pass
+    ``conditional_response=True`` when instantiating (or set that
+    attribute later).  It can also do HEAD and Range requests.
+
+Headers
++++++++
+
+Like the request, most HTTP response headers are available as
+properties.  These are parsed, so you can do things like
+``response.last_modified = os.path.getmtime(filename)``.
+
+The details are available in the `extracted Response documentation
+<http://pythonpaste.org/webob/class-webob.Response.html>`_.
+
+Instantiating the Response
+++++++++++++++++++++++++++
+
+Of course most of the time you just want to *make* a response.  
+Generally any attribute of the response can be passed in as a keyword
+argument to the class; e.g.:
+
+.. code-block:: python
+
+  from webob import Response
+
+  response = Response(body='hello world!', content_type='text/plain')
+
+The status defaults to ``'200 OK'``.  The content_type does not
+default to anything, though if you subclass ``Response`` and set
+``default_content_type`` you can override this behavior.
+
+Exceptions
+++++++++++
+
+To facilitate error responses like 404 Not Found, the module
+``webob.exc`` contains classes for each kind of error response.  These
+include boring but appropriate error bodies.
+
+Each class is named ``webob.exc.HTTP*``, where ``*`` is the reason for
+the error.  For instance, ``webob.exc.HTTPNotFound``.  It subclasses
+``Response``, so you can manipulate the instances in the same way.  A
+typical example is:
+
+.. code-block:: python
+
+    from webob.exc import HTTPNotFound
+    from webob.exc import HTTPMovedPermanently
+
+    response = HTTPNotFound('There is no such resource')
+    # or:
+    response = HTTPMovedPermanently(location=new_url)
+
+These are not exceptions unless you are using Python 2.5+, because
+they are new-style classes which are not allowed as exceptions until
+Python 2.5.  To get an exception object use ``response.exception``.
+You can use this like:
+
+.. code-block:: python
+
+    try:
+        ... stuff ...
+        raise HTTPNotFound('No such resource').exception
+    except HTTPException, e:
+        return e(environ, start_response)
+
+The exceptions are still WSGI applications, but you cannot set
+attributes like ``content_type``, ``charset``, etc. on these exception
+objects.
+
+Multidict
++++++++++
+
+Several parts of WebOb use a "multidict"; this is a dictionary where a
+key can have multiple values.  The quintessential example is a query
+string like ``?pref=red&pref=blue``; the ``pref`` variable has two
+values: ``red`` and ``blue``.
+
+In a multidict, when you do ``request.GET['pref']`` you'll get back
+only ``'blue'`` (the last value of ``pref``).  Sometimes returning a
+string, and sometimes returning a list, is the cause of frequent
+exceptions.  If you want *all* the values back, use
+``request.GET.getall('pref')``.  If you want to be sure there is *one
+and only one* value, use ``request.GET.getone('pref')``, which will
+raise an exception if there is zero or more than one value for
+``pref``.
+
+When you use operations like ``request.GET.items()`` you'll get back
+something like ``[('pref', 'red'), ('pref', 'blue')]``.  All the
+key/value pairs will show up.  Similarly ``request.GET.keys()``
+returns ``['pref', 'pref']``.  Multidict is a view on a list of
+tuples; all the keys are ordered, and all the values are ordered.
+