From f1c3b6d76f0c97e1ab927c288bb94891ae4c253b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Tue, 23 Sep 2014 16:43:29 +0300
Subject: Breaking update of the cowboy_req interface

Simplify the interface for most cowboy_req functions. They all return
a single value except the four body reading functions. The reply functions
now only return a Req value.

Access functions do not return a Req anymore.

Functions that used to cache results do not have a cache anymore.

The interface for accessing query string and cookies has therefore
been changed.

There are now three query string functions: qs/1 provides access
to the raw query string value; parse_qs/1 returns the query string
as a list of key/values; match_qs/2 returns a map containing the
values requested in the second argument, after applying constraints
and default value.

Similarly, there are two cookie functions: parse_cookies/1 and
match_cookies/2. More match functions will be added in future commits.

None of the functions return an error tuple anymore. It either works
or crashes. Cowboy will attempt to provide an appropriate status code
in the response of crashed handlers.

As a result, the content decode function has its return value changed
to a simple binary, and the body reading functions only return on success.
---
 doc/src/guide/cookies.ezdoc | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

(limited to 'doc/src/guide/cookies.ezdoc')

diff --git a/doc/src/guide/cookies.ezdoc b/doc/src/guide/cookies.ezdoc
index fe9246c..459d4d8 100644
--- a/doc/src/guide/cookies.ezdoc
+++ b/doc/src/guide/cookies.ezdoc
@@ -116,22 +116,47 @@ As we said, the client sends cookies with every request.
 But unlike the server, the client only sends the cookie
 name and value.
 
-You can read the value of a cookie.
+Cowboy provides two different ways to read cookies. You
+can either parse them as a list of key/value pairs, or
+match them into a map, optionally applying constraints
+to the values or providing a default if they are missing.
+
+You can parse the cookies and then use standard library
+functions to access individual values.
+
+``` erlang
+Cookies = cowboy_req:parse_cookies(Req),
+{_, Lang} = lists:keyfind(<<"lang">>, 1, Cookies).
+```
+
+You can match the cookies into a map.
 
 ``` erlang
-{CookieVal, Req2} = cowboy_req:cookie(<<"lang">>, Req).
+#{id := ID, lang := Lang} = cowboy_req:match_cookies(Req, [id, lang]).
 ```
 
-You can also get a default value returned when the cookie
-isn't set.
+You can use constraints to validate the values while matching
+them. The following snippet will crash if the `id` cookie is
+not an integer number or if the `lang` cookie is empty. Additionally
+the `id` cookie value will be converted to an integer term, saving
+you a conversion step.
 
 ``` erlang
-{CookieVal, Req2} = cowboy_req:cookie(<<"lang">>, Req, <<"fr">>).
+CookiesMap = cowboy_req:match_cookies(Req, [{id, int}, {lang, nonempty}]).
 ```
 
-And you can obtain all cookies at once as a list of
-key/value tuples.
+Note that if two cookies share the same name, then the map value
+will be a list of the two cookie values.
+
+Read more about ^constraints^.
+
+A default value can be provided. The default will be used
+if the `lang` cookie is not found. It will not be used if
+the cookie is found but has an empty value.
 
 ``` erlang
-{AllCookies, Req2} = cowboy_req:cookies(Req).
+#{lang := Lang} = cowboy_req:match_cookies(Req, [{lang, [], <<"en-US">>}]).
 ```
+
+If no default is provided and the value is missing, the
+query string is deemed invalid and the process will crash.
-- 
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