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+%% Copyright (c) 2011-2012, Loïc Hoguin <[email protected]>
+%%
+%% Permission to use, copy, modify, and/or distribute this software for any
+%% purpose with or without fee is hereby granted, provided that the above
+%% copyright notice and this permission notice appear in all copies.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+%% @doc Handler for HTTP WebSocket requests.
+%%
+%% WebSocket handlers must implement five callbacks: <em>init/3</em>,
+%% <em>websocket_init/3</em>, <em>websocket_handle/3</em>,
+%% <em>websocket_info/3</em> and <em>websocket_terminate/3</em>.
+%% These callbacks will only be called if the connection is upgraded
+%% to WebSocket in the HTTP handler's <em>init/3</em> callback.
+%% They are then called in that order, although <em>websocket_handle/3</em>
+%% will be called for each packet received, and <em>websocket_info</em>
+%% for each message received.
+%%
+%% <em>websocket_init/3</em> is meant for initialization. It receives
+%% information about the transport and protocol used, along with the handler
+%% options from the dispatch list. You can define a request-wide state here.
+%% If you are going to want to compact the request, you should probably do it
+%% here.
+%%
+%% <em>websocket_handle/3</em> receives the data from the socket. It can reply
+%% something, do nothing or close the connection.
+%%
+%% <em>websocket_info/3</em> receives messages sent to the process. It has
+%% the same reply format as <em>websocket_handle/3</em> described above. Note
+%% that unlike in a <em>gen_server</em>, when <em>websocket_info/3</em>
+%% replies something, it is always to the socket, not to the process that
+%% originated the message.
+%%
+%% <em>websocket_terminate/3</em> is meant for cleaning up. It also receives
+%% the request and the state previously defined, along with a reason for
+%% termination.
+%%
+%% All of <em>websocket_init/3</em>, <em>websocket_handle/3</em> and
+%% <em>websocket_info/3</em> can decide to hibernate the process by adding
+%% an extra element to the returned tuple, containing the atom
+%% <em>hibernate</em>. Doing so helps save memory and improve CPU usage.
+-module(cowboy_websocket_handler).
+
+-type opts() :: any().
+-type state() :: any().
+-type terminate_reason() :: {normal, closed}
+ | {normal, timeout}
+ | {error, closed}
+ | {error, badframe}
+ | {error, atom()}.
+
+-callback websocket_init(atom(), Req, opts())
+ -> {ok, Req, state()}
+ | {ok, Req, state(), hibernate}
+ | {ok, Req, state(), timeout()}
+ | {ok, Req, state(), timeout(), hibernate}
+ | {shutdown, Req}
+ when Req::cowboy_req:req().
+-callback websocket_handle({text | binary | ping | pong, binary()}, Req, State)
+ -> {ok, Req, State}
+ | {ok, Req, State, hibernate}
+ | {reply, {text | binary | ping | pong, binary()}, Req, State}
+ | {reply, {text | binary | ping | pong, binary()}, Req, State, hibernate}
+ | {shutdown, Req, State}
+ when Req::cowboy_req:req(), State::state().
+-callback websocket_info(any(), Req, State)
+ -> {ok, Req, State}
+ | {ok, Req, State, hibernate}
+ | {reply, {text | binary | ping | pong, binary()}, Req, State}
+ | {reply, {text | binary | ping | pong, binary()}, Req, State, hibernate}
+ | {shutdown, Req, State}
+ when Req::cowboy_req:req(), State::state().
+-callback websocket_terminate(terminate_reason(), cowboy_req:req(), state())
+ -> ok.