=encoding utf8

=head1 NAME

Mojolicious::Guides::Routing - Routing requests

=head1 OVERVIEW

This document contains a simple and fun introduction to the L<Mojolicious> router and its underlying concepts.

=head1 CONCEPTS

Essentials every L<Mojolicious> developer should know.

=head2 Dispatcher

The foundation of every web framework is a tiny black box connecting incoming requests with code generating the
appropriate response.

  GET /user/show/1 -> $c->render(text => 'Daniel');

This black box is usually called a dispatcher. There are many implementations using different strategies to establish
these connections, but pretty much all are based around mapping the path part of the request URL to some kind of
response generator.

  /user/show/2 -> $c->render(text => 'Isabell');
  /user/show/3 -> $c->render(text => 'Sara');
  /user/show/4 -> $c->render(text => 'Stefan');
  /user/show/5 -> $c->render(text => 'Fynn');

While it is very well possible to make all these connections static, it is also rather inefficient. That's why regular
expressions are commonly used to make the dispatch process more dynamic.

  qr!/user/show/(\d+)! -> $c->render(text => $users{$1});

Modern dispatchers have pretty much everything HTTP has to offer at their disposal and can use many more variables than
just the request path, such as request method and headers like C<Host>, C<User-Agent> and C<Accept>.

  GET /user/show/23 HTTP/1.1
  Host: mojolicious.org
  User-Agent: Mojolicious (Perl)
  Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

=head2 Routes

While regular expressions are quite powerful they also tend to be unpleasant to look at and are generally overkill for
ordinary path matching.

  qr!/user/admin/(\d+)! -> $c->render(text => $users{$1});

This is where routes come into play, they have been designed from the ground up to represent paths with placeholders.

  /user/admin/:id -> $c->render(text => $users{$id});

The only difference between a static path and the route above is the C<:id> placeholder. One or more placeholders can
be anywhere in the route.

  /user/:role/:id

A fundamental concept of the L<Mojolicious> router is that extracted placeholder values are turned into a hash.

  /user/admin/23 -> /user/:role/:id -> {role => 'admin', id => 23}

This hash is basically the center of every L<Mojolicious> application, you will learn more about this later on.
Internally, routes get compiled to regular expressions, so you can get the best of both worlds with a little bit of
experience.

  /user/admin/:id -> qr/(?-xism:^\/user\/admin\/([^\/.]+))/

A trailing slash in the path is always optional.

  /user/admin/23/ -> /user/:role/:id -> {role => 'admin', id => 23}

=head2 Reversibility

One more huge advantage routes have over regular expressions is that they are easily reversible, extracted placeholders
can be turned back into a path at any time.

  /sebastian -> /:name -> {name => 'sebastian'}
  {name => 'sebastian'} -> /:name -> /sebastian

Every placeholder has a name, even if it's just an empty string.

=head2 Standard placeholders

Standard placeholders are the simplest form of placeholders, they use a colon prefix and match all characters except
C</> and C<.>, similar to the regular expression C<([^/.]+)>.

  /hello              -> /:name/hello -> undef
  /sebastian/23/hello -> /:name/hello -> undef
  /sebastian.23/hello -> /:name/hello -> undef
  /sebastian/hello    -> /:name/hello -> {name => 'sebastian'}
  /sebastian23/hello  -> /:name/hello -> {name => 'sebastian23'}
  /sebastian 23/hello -> /:name/hello -> {name => 'sebastian 23'}

All placeholders can be surrounded by C<E<lt>> and C<E<gt>> to separate them from the surrounding text.

  /hello             -> /<:name>hello -> undef
  /sebastian/23hello -> /<:name>hello -> undef
  /sebastian.23hello -> /<:name>hello -> undef
  /sebastianhello    -> /<:name>hello -> {name => 'sebastian'}
  /sebastian23hello  -> /<:name>hello -> {name => 'sebastian23'}
  /sebastian 23hello -> /<:name>hello -> {name => 'sebastian 23'}

The colon prefix is optional for standard placeholders that are surrounded by C<E<lt>> and C<E<gt>>.

  /i♥mojolicious -> /<one>♥<two> -> {one => 'i', two => 'mojolicious'}

=head2 Relaxed placeholders

Relaxed placeholders are just like standard placeholders, but use a hash prefix and match all characters except C</>,
similar to the regular expression C<([^/]+)>.

  /hello              -> /#name/hello -> undef
  /sebastian/23/hello -> /#name/hello -> undef
  /sebastian.23/hello -> /#name/hello -> {name => 'sebastian.23'}
  /sebastian/hello    -> /#name/hello -> {name => 'sebastian'}
  /sebastian23/hello  -> /#name/hello -> {name => 'sebastian23'}
  /sebastian 23/hello -> /#name/hello -> {name => 'sebastian 23'}

They can be especially useful for manually matching file names with extensions, rather than using L<format
detection|/"Formats">.

  /music/song.mp3 -> /music/#filename -> {filename => 'song.mp3'}

=head2 Wildcard placeholders

Wildcard placeholders are just like the two types of placeholders above, but use an asterisk prefix and match
absolutely everything, including C</> and C<.>, similar to the regular expression C<(.+)>.

  /hello              -> /*name/hello -> undef
  /sebastian/23/hello -> /*name/hello -> {name => 'sebastian/23'}
  /sebastian.23/hello -> /*name/hello -> {name => 'sebastian.23'}
  /sebastian/hello    -> /*name/hello -> {name => 'sebastian'}
  /sebastian23/hello  -> /*name/hello -> {name => 'sebastian23'}
  /sebastian 23/hello -> /*name/hello -> {name => 'sebastian 23'}

They can be useful for manually matching entire file paths.

  /music/rock/song.mp3 -> /music/*filepath -> {filepath => 'rock/song.mp3'}

=head1 BASICS

Most commonly used features every L<Mojolicious> developer should know about.

=head2 Minimal route

The attribute L<Mojolicious/"routes"> contains a router you can use to generate route structures.

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious', -signatures;

  sub startup ($self) {
    # Router
    my $r = $self->routes;

    # Route
    $r->get('/welcome')->to(controller => 'foo', action => 'welcome');
  }

  1;

The minimal route above will load and instantiate the class C<MyApp::Controller::Foo> and call its C<welcome> method.
Routes are usually configured in the C<startup> method of the application class, but the router can be accessed from
everywhere (even at runtime).

  # Controller
  package MyApp::Controller::Foo;
  use Mojo::Base 'Mojolicious::Controller', -signatures;

  # Action
  sub welcome ($self) {
    # Render response
    $self->render(text => 'Hello there.');
  }

  1;

All routes match in the same order in which they were defined, and matching stops as soon as a suitable route has been
found. So you can improve the routing performance by declaring your most frequently accessed routes first. A routing
cache will also be used automatically to handle sudden traffic spikes more gracefully.

=head2 Routing destination

After you start a new route with methods like L<Mojolicious::Routes::Route/"get">, you can also give it a destination
in the form of a hash using the chained method L<Mojolicious::Routes::Route/"to">.

  # /welcome -> {controller => 'foo', action => 'welcome'}
  $r->get('/welcome')->to(controller => 'foo', action => 'welcome');

Now if the route matches an incoming request it will use the content of this hash to try and find appropriate code to
generate a response.

=head2 HTTP methods

There are already shortcuts for the most common HTTP request methods like L<Mojolicious::Routes::Route/"post">, and for
more control L<Mojolicious::Routes::Route/"any"> accepts an optional array reference with arbitrary request methods as
first argument.

  # PUT /hello  -> undef
  # GET /hello  -> {controller => 'foo', action => 'hello'}
  $r->get('/hello')->to(controller => 'foo', action => 'hello');

  # PUT /hello -> {controller => 'foo', action => 'hello'}
  $r->put('/hello')->to(controller => 'foo', action => 'hello');

  # POST /hello -> {controller => 'foo', action => 'hello'}
  $r->post('/hello')->to(controller => 'foo', action => 'hello');

  # GET|POST /bye  -> {controller => 'foo', action => 'bye'}
  $r->any(['GET', 'POST'] => '/bye')->to(controller => 'foo', action => 'bye');

  # * /whatever -> {controller => 'foo', action => 'whatever'}
  $r->any('/whatever')->to(controller => 'foo', action => 'whatever');

There is one small exception, C<HEAD> requests are considered equal to C<GET>, but content will not be sent with the
response even if it is present.

  # GET /test  -> {controller => 'bar', action => 'test'}
  # HEAD /test -> {controller => 'bar', action => 'test'}
  $r->get('/test')->to(controller => 'bar', action => 'test');

You can also use the C<_method> query parameter to override the request method. This can be very useful when submitting
forms with browsers that only support C<GET> and C<POST>.

  # PUT  /stuff             -> {controller => 'baz', action => 'stuff'}
  # POST /stuff?_method=PUT -> {controller => 'baz', action => 'stuff'}
  $r->put('/stuff')->to(controller => 'baz', action => 'stuff');

=head2 IRIs

IRIs are handled transparently, that means paths are guaranteed to be unescaped and decoded from bytes to characters.

  # GET /☃ (Unicode snowman) -> {controller => 'foo', action => 'snowman'}
  $r->get('/☃')->to(controller => 'foo', action => 'snowman');

=head2 Stash

The generated hash of a matching route is actually the center of the whole L<Mojolicious> request cycle. We call it the
stash, and it persists until a response has been generated.

  # /bye -> {controller => 'foo', action => 'bye', mymessage => 'Bye'}
  $r->get('/bye')->to(controller => 'foo', action => 'bye', mymessage => 'Bye');

There are a few stash values with special meaning, such as C<controller> and C<action>, but you can generally fill it
with whatever data you need to generate a response. Once dispatched the whole stash content can be changed at any time.

  sub bye ($self) {

    # Get message from stash
    my $msg = $self->stash('mymessage');

    # Change message in stash
    $self->stash(mymessage => 'Welcome');
  }

You can use L<Mojolicious/"defaults"> to set default stash values that will be available everywhere in the application.

  $app->defaults(mymessage => 'Howdy');

For a full list of reserved stash values see L<Mojolicious::Controller/"stash">.

=head2 Nested routes

It is also possible to build tree structures from routes to remove repetitive code. A route with children can't match
on its own though, only the actual endpoints of these nested routes can.

  # /foo     -> undef
  # /foo/bar -> {controller => 'foo', action => 'bar'}
  my $foo = $r->any('/foo')->to(controller => 'foo');
  $foo->get('/bar')->to(action => 'bar');

The stash is simply inherited from route to route and newer values override old ones.

  # /cats      -> {controller => 'cats', action => 'index'}
  # /cats/nyan -> {controller => 'cats', action => 'nyan'}
  # /cats/lol  -> {controller => 'cats', action => 'default'}
  my $cats = $r->any('/cats')->to(controller => 'cats', action => 'default');
  $cats->get('/')->to(action => 'index');
  $cats->get('/nyan')->to(action => 'nyan');
  $cats->get('/lol');

With a few common prefixes you can also greatly improve the routing performance of applications with many routes,
because children are only tried if the prefix matched first.

=head2 Special stash values

When the dispatcher sees C<controller> and C<action> values in the stash it will always try to turn them into a class
and method to dispatch to. The C<controller> value gets converted from C<snake_case> to C<CamelCase> using
L<Mojo::Util/"camelize"> and appended to one or more namespaces, defaulting to a controller namespace based on the
application class (C<MyApp::Controller>), as well as the bare application class (C<MyApp>), and these namespaces are
searched in that order. The action value is not changed at all, so both values are case-sensitive.

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious', -signatures;

  sub startup ($self) {
    # /bye -> MyApp::Controller::Foo->bye
    $self->routes->get('/bye')->to(controller => 'foo', action => 'bye');
  }

  1;

  # Controller
  package MyApp::Controller::Foo;
  use Mojo::Base 'Mojolicious::Controller', -signatures;

  # Action
  sub bye ($self) {
    # Render response
    $self->render(text => 'Good bye.');
  }

  1;

Controller classes are perfect for organizing code in larger projects. There are more dispatch strategies, but because
controllers are the most commonly used ones they also got a special shortcut in the form of C<controller#action>.

  # /bye -> {controller => 'foo', action => 'bye', mymessage => 'Bye'}
  $r->get('/bye')->to('foo#bye', mymessage => 'Bye');

During camelization C<-> characters get replaced with C<::>, this allows multi-level C<controller> hierarchies.

  # / -> MyApp::Controller::Foo::Bar->hi
  $r->get('/')->to('foo-bar#hi');

You can also just specify the C<controller> in CamelCase form instead of snake_case.

  # / -> MyApp::Controller::Foo::Bar->hi
  $r->get('/')->to('Foo::Bar#hi');

For security reasons the dispatcher will always check if the C<controller> is actually a subclass of
L<Mojolicious::Controller> or L<Mojo> before dispatching to it.

=head2 Namespaces

You can use the C<namespace> stash value to change the namespace of a whole route with all its children.

  # /bye -> MyApp::MyController::Foo::Bar->bye
  $r->get('/bye')->to(namespace => 'MyApp::MyController', controller => 'Foo::Bar', action => 'bye');

The C<controller> is always converted from C<snake_case> to C<CamelCase> with L<Mojo::Util/"camelize">, and then
appended to this C<namespace>.

  # /bye -> MyApp::MyController::Foo::Bar->bye
  $r->get('/bye')->to('foo-bar#bye', namespace => 'MyApp::MyController');

  # /hey -> MyApp::MyController::Foo::Bar->hey
  $r->get('/hey')->to('Foo::Bar#hey', namespace => 'MyApp::MyController');

You can also change the default namespaces for all routes in the application with the router attribute
L<Mojolicious::Routes/"namespaces">, which usually defaults to a namespace based on the application class
(C<MyApp::Controller>), as well as the bare application class (C<MyApp>).

  $r->namespaces(['MyApp::MyController']);

=head2 Route to callback

The C<cb> stash value, which won't be inherited by nested routes, can be used to bypass controllers and execute a
callback instead.

  $r->get('/bye')->to(cb => sub ($c) {
    $c->render(text => 'Good bye.');
  });

But just like in L<Mojolicious::Lite> you can also pass the callback directly, which usually looks much better.

  $r->get('/bye' => sub ($c) {
    $c->render(text => 'Good bye.');
  });

=head2 Named routes

Naming your routes will allow backreferencing in many methods and helpers throughout the whole framework, most of which
internally rely on L<Mojolicious::Controller/"url_for"> for this.

  # /foo/marcus -> {controller => 'foo', action => 'bar', user => 'marcus'}
  $r->get('/foo/:user')->to('foo#bar')->name('baz');

  # Generate URL "/foo/marcus" for route "baz" (in previous request context)
  my $url = $c->url_for('baz');

  # Generate URL "/foo/jan" for route "baz"
  my $url = $c->url_for('baz', user => 'jan');

  # Generate URL "http://127.0.0.1:3000/foo/jan" for route "baz"
  my $url = $c->url_for('baz', user => 'jan')->to_abs;

You can assign a name with L<Mojolicious::Routes::Route/"name">, or let the router generate one automatically, which
would be equal to the route itself without non-word characters, custom names have a higher precedence though.

  # /foo/bar ("foobar")
  $r->get('/foo/bar')->to('test#stuff');

  # Generate URL "/foo/bar"
  my $url = $c->url_for('foobar');

To refer to the current route you can use the reserved name C<current> or no name at all.

  # Generate URL for current route
  my $url = $c->url_for('current');
  my $url = $c->url_for;

To check or get the name of the current route you can use the helper
L<Mojolicious::Plugin::DefaultHelpers/"current_route">.

  # Name for current route
  my $name = $c->current_route;

  # Check route name in code shared by multiple routes
  $c->stash(button => 'green') if $c->current_route('login');

=head2 Optional placeholders

Extracted placeholder values will simply redefine older stash values if they already exist.

  # /bye -> {controller => 'foo', action => 'bar', mymessage => 'bye'}
  # /hey -> {controller => 'foo', action => 'bar', mymessage => 'hey'}
  $r->get('/:mymessage')->to('foo#bar', mymessage => 'hi');

One more interesting effect, a placeholder automatically becomes optional if there is already a stash value of the same
name present, this works similar to the regular expression C<([^/.]+)?>.

  # / -> {controller => 'foo', action => 'bar', mymessage => 'hi'}
  $r->get('/:mymessage')->to('foo#bar', mymessage => 'hi');

  # /test/123     -> {controller => 'foo', action => 'bar', mymessage => 'hi'}
  # /test/bye/123 -> {controller => 'foo', action => 'bar', mymessage => 'bye'}
  $r->get('/test/:mymessage/123')->to('foo#bar', mymessage => 'hi');

And if two optional placeholders are only separated by a slash, that slash can become optional as well.

=head2 Restrictive placeholders

A very easy way to make placeholders more restrictive are alternatives, you just make a list of possible values, which
then work similar to the regular expression C<(bender|leela)>.

  # /fry    -> undef
  # /bender -> {controller => 'foo', action => 'bar', name => 'bender'}
  # /leela  -> {controller => 'foo', action => 'bar', name => 'leela'}
  $r->get('/:name' => [name => ['bender', 'leela']])->to('foo#bar');

You can also adjust the regular expressions behind placeholders directly, just make sure not to use C<^> and C<$> or
capturing groups C<(...)>, because placeholders become part of a larger regular expression internally, non-capturing
groups C<(?:...)> are fine though.

  # /23   -> {controller => 'foo', action => 'bar', number => 23}
  # /test -> undef
  $r->get('/:number' => [number => qr/\d+/])->to('foo#bar');

  # /23   -> undef
  # /test -> {controller => 'foo', action => 'bar', name => 'test'}
  $r->get('/:name' => [name => qr/[a-zA-Z]+/])->to('foo#bar');

This way you get easily readable routes and the raw power of regular expressions.

=head2 Placeholder types

And if you have multiple routes using restrictive placeholders you can also turn them into placeholder types with
L<Mojolicious::Routes/"add_type">.

  # A type with alternatives
  $r->add_type(futurama_name => ['bender', 'leela']);

  # /fry    -> undef
  # /bender -> {controller => 'foo', action => 'bar', name => 'bender'}
  # /leela  -> {controller => 'foo', action => 'bar', name => 'leela'}
  $r->get('/<name:futurama_name>')->to('foo#bar');

Placeholder types work just like restrictive placeholders, they are just reusable with the
C<E<lt>placeholder:typeE<gt>> notation.

  # A type adjusting the regular expression
  $r->add_type(upper => qr/[A-Z]+/);

  # /user/ROOT -> {controller => 'users', action => 'show', name => 'ROOT'}
  # /user/root -> undef
  # /user/23   -> undef
  $r->get('/user/<name:upper>')->to('users#show');

Some types like C<num> are used so commonly that they are available by default.

  # /article/12   -> {controller => 'article', action => 'show', id => 12}
  # /article/test -> undef
  $r->get('/article/<id:num>')->to('articles#show');

For a full list of available placeholder types see also L<Mojolicious::Routes/"TYPES">.

=head2 Introspection

The command L<Mojolicious::Command::routes> can be used from the command line to list all available routes together
with names and underlying regular expressions.

  $ ./myapp.pl routes -v
  /foo/:name  ....  POST  fooname  ^/foo/([^/.]+)/?(?:\.([^/]+))?$
  /bar        ..U.  *     bar      ^/bar
    +/baz     ...W  GET   baz      ^/baz/?(?:\.([^/]+))?$
  /yada       ....  *     yada     ^/yada/?(?:\.([^/]+))?$

=head2 Under

To share code with multiple nested routes you can use L<Mojolicious::Routes::Route/"under">, because unlike normal
nested routes, the routes generated with it have their own intermediate destination and result in additional dispatch
cycles when they match.

  # /foo     -> undef
  # /foo/bar -> {controller => 'foo', action => 'baz'}
  #             {controller => 'foo', action => 'bar'}
  my $foo = $r->under('/foo')->to('foo#baz');
  $foo->get('/bar')->to('#bar');

The actual action code for this destination needs to return a true value or the dispatch chain will be broken, this can
be a very powerful tool for authentication.

  # /blackjack -> {cb => sub {...}}
  #               {controller => 'hideout', action => 'blackjack'}
  my $auth = $r->under('/' => sub ($c) {

    # Authenticated
    return 1 if $c->req->headers->header('X-Bender');

    # Not authenticated
    $c->render(text => "You're not Bender.", status => 401);
    return undef;
  });
  $auth->get('/blackjack')->to('hideout#blackjack');

Broken dispatch chains can be continued by calling L<Mojolicious::Controller/"continue">, this allows for example,
non-blocking operations to finish before reaching the next dispatch cycle.

  my $maybe = $r->under('/maybe' => sub ($c) {

    # Wait 3 seconds and then give visitors a 50% chance to continue
    Mojo::IOLoop->timer(3 => sub {

      # Loser
      return $c->render(text => 'No luck.') unless int rand 2;

      # Winner
      $c->continue;
    });

    return undef;
  });
  $maybe->get('/')->to('maybe#winner');

Every destination is just a snapshot of the stash at the time the route matched, and only the C<format> value is shared
by all of them. For a little more power you can introspect the preceding and succeeding destinations with
L<Mojolicious::Controller/"match">.

  # Action of the fourth dispatch cycle
  my $action = $c->match->stack->[3]{action};

=head2 Formats

File extensions like C<.html> and C<.txt> at the end of a route can be detected and stored in the stash value C<format>.
Use a restrictive placeholder to declare the possible values.

  # /foo.txt -> undef
  # /foo.rss -> {controller => 'foo', action => 'bar', format => 'rss'}
  # /foo.xml -> {controller => 'foo', action => 'bar', format => 'xml'}
  $r->get('/foo' => [format => ['rss', 'xml']])->to('foo#bar');

This for example, allows multiple templates in different formats to share the same action code. And just like with
placeholders you can use a default value to make the format optional.

  # /foo      -> {controller => 'foo', action => 'bar'}
  # /foo.html -> {controller => 'foo', action => 'bar', format => 'html'}
  # /foo.txt  -> {controller => 'foo', action => 'bar', format => 'txt'}
  $r->get('/foo' => [format => ['html', 'txt']])->to('foo#bar', format => undef);

Formats can be inherited by nested routes.

  # /foo      -> {controller => 'foo', action => 'one', format => undef}
  # /foo.html -> {controller => 'foo', action => 'one', format => 'html'}
  # /foo.json -> {controller => 'foo', action => 'one', format => 'json'}
  # /bar      -> {controller => 'bar', action => 'two', format => undef}
  # /bar.html -> {controller => 'bar', action => 'two', format => 'html'}
  # /bar.json -> {controller => 'bar', action => 'two', format => 'json'}
  my $with_format = $r->any('/' => [format => ['html', 'json']])->to(format => undef);
  $with_format->get('/foo')->to('foo#one');
  $with_format->get('/bar')->to('bar#two');

A C<format> value can also be passed to L<Mojolicious::Controller/"url_for">.

  # /foo/23.txt -> {controller => 'foo', action => 'bar', id => 23, format => 'txt'}
  $r->get('/foo/:id')->to('foo#bar')->name('baz');

  # Generate URL "/foo/24.txt" for route "baz"
  my $url = $c->url_for('baz', id => 24, format => 'txt');

=head2 WebSockets

With the method L<Mojolicious::Routes::Route/"websocket"> you can restrict access to WebSocket handshakes, which are
normal C<GET> requests with some additional information.

  # /echo (WebSocket handshake)
  $r->websocket('/echo')->to('foo#echo');

  # Controller
  package MyApp::Controller::Foo;
  use Mojo::Base 'Mojolicious::Controller', -signatures;

  # Action
  sub echo ($self) {
    $self->on(message => sub ($self, $msg) {
      $self->send("echo: $msg");
    });
  }

  1;

The connection gets established when you respond to the WebSocket handshake request with a C<101> response status,
which happens automatically if you subscribe to an event with L<Mojolicious::Controller/"on"> or send a message with
L<Mojolicious::Controller/"send"> right away.

  GET /echo HTTP/1.1
  Host: mojolicious.org
  User-Agent: Mojolicious (Perl)
  Connection: Upgrade
  Upgrade: websocket
  Sec-WebSocket-Key: IDM3ODE4NDk2MjA1OTcxOQ==
  Sec-WebSocket-Version: 13

  HTTP/1.1 101 Switching Protocols
  Server: Mojolicious (Perl)
  Date: Tue, 03 Feb 2015 17:08:24 GMT
  Connection: Upgrade
  Upgrade: websocket
  Sec-WebSocket-Accept: SWsp5N2iNxPbHlcOTIw8ERvyVPY=

=head2 Catch-all route

Since routes match in the order in which they were defined, you can catch all requests that did not match in your last
route with an optional wildcard placeholder.

  # * /*
  $r->any('/*whatever' => {whatever => ''} => sub ($c) {
    my $whatever = $c->param('whatever');
    $c->render(text => "/$whatever did not match.", status => 404);
  });

=head2 Conditions

Conditions such as C<headers>, C<agent> and C<host> from L<Mojolicious::Plugin::HeaderCondition> can be applied to any
route with the method L<Mojolicious::Routes::Route/"requires">, and allow even more powerful route constructs.

  # / (Origin: http://perl.org)
  $r->get('/')->requires(headers => {Origin => qr/perl\.org/})->to('foo#bar');

  # / (Firefox)
  $r->get('/')->requires(agent => qr/Firefox/)->to('browser-test#firefox');

  # / (Internet Explorer)
  $r->get('/')->requires(agent => qr/Internet Explorer/)->to('browser-test#ie');

  # http://docs.mojolicious.org/Mojolicious
  $r->get('/')->requires(host => 'docs.mojolicious.org')->to('perldoc#index');

Just be aware that conditions are too complex for the routing cache, which normally speeds up recurring requests, and
can therefore reduce performance.

=head2 Hooks

Hooks operate outside the routing system and allow you to extend the framework itself by sharing code with all requests
indiscriminately through L<Mojolicious/"hook">, which makes them a very powerful tool especially for plugins.

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious', -signatures;

  sub startup ($self) {

    # Check all requests for a "/test" prefix
    $self->hook(before_dispatch => sub ($c) {
      $c->render(text => 'This request did not reach the router.') if $c->req->url->path->contains('/test');
    });

    # These will not be reached if the hook above renders a response
    my $r = $self->routes;
    $r->get('/welcome')->to('foo#welcome');
    $r->post('/bye')->to('foo#bye');
  }

  1;

Post-processing the response to add or remove headers is a very common use.

  # Make sure static files are cached
  $app->hook(after_static => sub ($c) {
    $c->res->headers->cache_control('max-age=3600, must-revalidate');
  });

  # Remove a default header
  $app->hook(after_dispatch => sub ($c) {
    $c->res->headers->remove('Server');
  });

Same for pre-processing the request.

  # Choose template variant based on request headers
  $app->hook(before_dispatch => sub ($c) {
    return unless my $agent = $c->req->headers->user_agent;
    $c->stash(variant => 'ie') if $agent =~ /Internet Explorer/;
  });

Or more advanced extensions to add monitoring to your application.

  # Forward exceptions to a web service
  $app->hook(after_dispatch => sub ($c) {
    return unless my $e = $c->stash('exception');
    $c->ua->post('https://example.com/bugs' => form => {exception => $e});
  });

You can even extend much of the core functionality.

  # Make controller object available to actions as $_
  $app->hook(around_action => sub ($next, $c, $action, $last) {
    local $_ = $c;
    return $next->();
  });

  # Pass route name as argument to actions
  $app->hook(around_action => sub ($next, $c, $action, $last) {
    return $c->$action($c->current_route);
  });

For a full list of available hooks see L<Mojolicious/"HOOKS">.

=head1 ADVANCED

Less commonly used and more powerful features.

=head2 Shortcuts

To make route generation more expressive, you can also add your own shortcuts with
L<Mojolicious::Routes/"add_shortcut">.

  # Simple "resource" shortcut
  $r->add_shortcut(resource => sub ($r, $name) {

    # Prefix for resource
    my $resource = $r->any("/$name")->to("$name#");

    # Render a list of resources
    $resource->get('/')->to('#index')->name($name);

    # Render a form to create a new resource (submitted to "store")
    $resource->get('/create')->to('#create')->name("create_$name");

    # Store newly created resource (submitted by "create")
    $resource->post->to('#store')->name("store_$name");

    # Render a specific resource
    $resource->get('/:id')->to('#show')->name("show_$name");

    # Render a form to edit a resource (submitted to "update")
    $resource->get('/:id/edit')->to('#edit')->name("edit_$name");

    # Store updated resource (submitted by "edit")
    $resource->put('/:id')->to('#update')->name("update_$name");

    # Remove a resource
    $resource->delete('/:id')->to('#remove')->name("remove_$name");

    return $resource;
  });

  # GET /users         -> {controller => 'users', action => 'index'}
  # GET /users/create  -> {controller => 'users', action => 'create'}
  # POST /users        -> {controller => 'users', action => 'store'}
  # GET /users/23      -> {controller => 'users', action => 'show', id => 23}
  # GET /users/23/edit -> {controller => 'users', action => 'edit', id => 23}
  # PUT /users/23      -> {controller => 'users', action => 'update', id => 23}
  # DELETE /users/23   -> {controller => 'users', action => 'remove', id => 23}
  $r->resource('users');

=head2 Rearranging routes

From application startup until the first request has arrived, all routes can still be moved around or even removed with
methods like L<Mojolicious::Routes::Route/"add_child"> and L<Mojolicious::Routes::Route/"remove">.

  # GET /example/show -> {controller => 'example', action => 'show'}
  my $show = $r->get('/show')->to('example#show');
  $r->any('/example')->add_child($show);

  # Nothing
  $r->get('/secrets/show')->to('secrets#show')->name('show_secrets');
  $r->find('show_secrets')->remove;

Especially for rearranging routes created by plugins this can be very useful, to find routes by their name you can use
L<Mojolicious::Routes::Route/"find">.

  # GET /example/test -> {controller => 'example', action => 'test'}
  $r->get('/something/else')->to('something#else')->name('test');
  my $test = $r->find('test');
  $test->pattern->parse('/example/test');
  $test->pattern->defaults({controller => 'example', action => 'test'});

Even the route pattern and destination can still be changed with L<Mojolicious::Routes::Pattern/"parse"> and
L<Mojolicious::Routes::Pattern/"defaults">.

=head2 Adding conditions

You can also add your own conditions with the method L<Mojolicious::Routes/"add_condition">. All conditions are
basically router plugins that run every time a new request arrives, and which need to return a true value for the route
to match.

  # A condition that randomly allows a route to match
  $r->add_condition(random => sub ($route, $c, $captures, $num) {

    # Loser
    return undef if int rand $num;

    # Winner
    return 1;
  });

  # /maybe (25% chance)
  $r->get('/maybe')->requires(random => 4)->to('foo#bar');

Use whatever request information you need.

  # A condition to check query parameters (useful for mock web services)
  $r->add_condition(query => sub ($route, $c, $captures, $hash) {

    for my $key (keys %$hash) {
      my $param = $c->req->url->query->param($key);
      return undef unless defined $param && $param eq $hash->{$key};
    }

    return 1;
  });

  # /hello?to=world&test=1
  $r->get('/hello')->requires(query => {test => 1, to => 'world'})->to('foo#bar');

=head2 Condition plugins

You can also package your conditions as reusable plugins.

  # Plugin
  package Mojolicious::Plugin::WerewolfCondition;
  use Mojo::Base 'Mojolicious::Plugin', -signatures;

  use Astro::MoonPhase;

  sub register ($self, $app, $conf) {

    # Add "werewolf" condition
    $app->routes->add_condition(werewolf => sub ($route, $c, $captures, $days) {

      # Keep the werewolves out!
      return undef if abs(14 - (phase(time))[2]) > ($days / 2);

      # It's ok, no werewolf
      return 1;
    });
  }

  1;

Now just load the plugin and you are ready to use the condition in all your applications.

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious', -signatures;

  sub startup ($self) {

    # Plugin
    $self->plugin('WerewolfCondition');

    # /hideout (keep them out for 4 days after full moon)
    $self->routes->get('/hideout')->requires(werewolf => 4)->to(controller => 'foo', action => 'bar');
  }

  1;

=head2 Mount applications

The easiest way to embed one application into another is L<Mojolicious::Plugin::Mount>, which allows you to mount whole
self-contained applications under a domain and/or prefix.

  use Mojolicious::Lite -signatures;

  # Whole application mounted under "/prefix"
  plugin Mount => {'/prefix' => '/home/sri/myapp/script/myapp'};

  # Mount application with subdomain
  plugin Mount => {'test.example.com' => '/home/sri/myapp2.pl'};

  # Normal route
  get '/' => sub ($c) {
    $c->render(text => 'Hello World!');
  };

  app->start;

=head2 Embed applications

For a little more power you can also embed applications by using them instead of a controller. This allows for example,
the use of the L<Mojolicious::Lite> domain specific language in normal L<Mojolicious> controllers.

  # Controller
  package MyApp::Controller::Bar;
  use Mojolicious::Lite -signatures;

  # /hello
  get '/hello' => sub ($c) {
    my $name = $c->param('name');
    $c->render(text => "Hello $name.");
  };

  1;

With the attribute L<Mojolicious::Routes::Route/"partial">, you can allow the route to partially match and use only the
remaining path in the embedded application, the base path will be passed along in the C<path> stash value.

  # /foo/*
  $r->any('/foo')->partial(1)->to('bar#', name => 'Mojo');

A minimal embeddable application is nothing more than a subclass of L<Mojolicious>, containing a C<handler> method
accepting L<Mojolicious::Controller> objects.

  package MyApp::Controller::Bar;
  use Mojo::Base 'Mojolicious', -signatures;

  sub handler ($self, $c) {
    $c->res->code(200);
    my $name = $c->param('name');
    $c->res->body("Hello $name.");
  }

  1;

The host application will only share very little information with the embedded application through the stash. So you
cannot currently use route placeholders in routes leading to embedded applications, since that would cause problems
with L<Mojolicious::Controller/"url_for">.

=head2 Application plugins

You can even package applications as self-contained reusable plugins.

  # Plugin
  package Mojolicious::Plugin::MyEmbeddedApp;
  use Mojo::Base 'Mojolicious::Plugin', -signatures;

  sub register ($self, $app, $conf) {

    # Automatically add route
    $app->routes->any('/foo')->partial(1)->to(app => EmbeddedApp::app());
  }

  package EmbeddedApp;
  use Mojolicious::Lite;

  get '/bar' => 'bar';

  1;
  __DATA__
  @@ bar.html.ep
  Hello World!

The C<app> stash value, which won't be inherited by nested routes, can be used for already instantiated applications.
Now just load the plugin and you're done.

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious', -signatures;

  sub startup ($self) {

    # Plugin
    $self->plugin('MyEmbeddedApp');
  }

  1;

=head1 MORE

You can continue with L<Mojolicious::Guides> now or take a look at the L<Mojolicious
wiki|https://github.com/mojolicious/mojo/wiki>, which contains a lot more documentation and examples by many different
authors.

=head1 SUPPORT

If you have any questions the documentation might not yet answer, don't hesitate to ask in the
L<Forum|https://forum.mojolicious.org>, on L<Matrix|https://matrix.to/#/#mojo:matrix.org>, or
L<IRC|https://web.libera.chat/#mojo>.

=cut