From 06e74355c0a993b416b21bb4e9586c37973e8d83 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Tue, 1 Jan 2013 18:27:41 +0100
Subject: Add a skeleton of the guide to ease user contributions

Has some stuff that aren't in master yet, and lacks a lot more
that is already in master.
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+Routing
+=======
+
+@todo Note that this documentation is for the new routing interface
+not available in master at this point.
+
+Purpose
+-------
+
+Cowboy does nothing by default.
+
+To make Cowboy useful, you need to map URLs to Erlang modules that will
+handle the requests. This is called routing.
+
+When Cowboy receives a request, it tries to match the requested host and
+path to the resources given in the dispatch rules. If it matches, then
+the associated Erlang code will be executed.
+
+Routing rules are given per host. Cowboy will first match on the host,
+and then try to find a matching path.
+
+Routes need to be compiled before they can be used by Cowboy.
+
+Structure
+---------
+
+The general structure for the routes is defined as follow.
+
+``` erlang
+Routes = [Host1, Host2, ... HostN].
+```
+
+Each host contains matching rules for the host along with optional
+constraints, and a list of routes for the path component.
+
+``` erlang
+Host1 = {HostMatch, PathsList}.
+Host2 = {HostMatch, Constraints, PathsList}.
+```
+
+The list of routes for the path component is defined similar to the
+list of hosts.
+
+``` erlang
+PathsList = [Path1, Path2, ... PathN].
+```
+
+Finally, each path contains matching rules for the path along with
+optional constraints, and gives us the handler module to be used
+along with options that will be given to it on initialization.
+
+```
+Path1 = {PathMatch, Handler, Module}.
+Path2 = {PathMatch, Constraints, Handler, Module}.
+```
+
+Continue reading to learn more about the match syntax and the optional
+constraints.
+
+Match syntax
+------------
+
+The match syntax is used to associate host names and paths with their
+respective handlers.
+
+The match syntax is the same for host and path with a few subtleties.
+Indeed, the segments separator is different, and the host is matched
+starting from the last segment going to the first. All examples will
+feature both host and path match rules and explain the differences
+when encountered.
+
+Excluding special values that we will explain at the end of this section,
+the simplest match value is a host or a path. It can be given as either
+a `string()` or a `binary()`.
+
+``` erlang
+PathMatch1 = "/".
+PathMatch2 = "/path/to/resource".
+
+HostMatch1 = "cowboy.example.org".
+```
+
+As you can see, all paths defined this way must start with a slash
+character. Note that these two paths are identical as far as routing
+is concerned.
+
+``` erlang
+PathMatch2 = "/path/to/resource".
+PathMatch3 = "/path/to/resource/".
+```
+
+Hosts with and without a trailing dot are equivalent for routing.
+
+``` erlang
+HostMatch1 = "cowboy.example.org".
+HostMatch2 = "cowboy.example.org.".
+```
+
+It is possible to extract segments of the host and path and to store
+the values in the `Req` object for later use. We call these kind of
+values bindings.
+
+The syntax for bindings is very simple. A segment that begins with
+the `:` character means that what follows until the end of the segment
+is the name of the binding in which the segment value will be stored.
+
+``` erlang
+PathMatch = "/hats/:name/prices".
+HostMatch = ":subdomain.example.org".
+```
+
+If these two end up matching when routing, you will end up with two
+bindings defined, `subdomain` and `hat_name`, each containing the
+segment value where they were defined. For example, the URL
+`http://test.example.org/hats/wild_cowboy_legendary/prices` will
+result in having the value `test` bound to the name `subdomain`
+and the value `wild_cowboy_legendary` bound to the name `hat_name`.
+They can later be retrieved using `cowboy_req:binding/{2,3}`.
+
+@todo special binding `'_'`
+@todo optional path or segments
+@todo same binding twice (+ optional + host/path)
+
+Constraints
+-----------
+
+@todo Describe constraints.
+
+Compilation
+-----------
+
+The structure defined in this chapter needs to be compiled before it is
+passed to Cowboy. This allows Cowboy to efficiently lookup the correct
+handler to run instead of having to parse the routes repeatedly.
+
+This can be done with a simple call to `cowboy_routing:compile/1`.
+
+@todo Note that the `routes` option will be specified slightly differently
+when middleware support gets in.
+
+``` erlang
+{ok, Routes} = cowboy_routing:compile([
+    %% {URIHost, list({URIPath, Handler, Opts})}
+    {'_', [{'_', my_handler, []}]}
+]),
+%% Name, NbAcceptors, TransOpts, ProtoOpts
+cowboy:start_http(my_http_listener, 100,
+    [{port, 8080}],
+    [{routes, Routes}]
+).
+```
+
+Note that this function will return `{error, badarg}` if the structure
+given is incorrect.
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