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%% @author Robert Ahrens <rahrens@basho.com>
%% @author Justin Sheehy <justin@basho.com>
%% @copyright 2007-2009 Basho Technologies
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%% @doc Module for URL-dispatch by pattern matching.
-module(webmachine_dispatcher).
-author('Robert Ahrens <rahrens@basho.com>').
-author('Justin Sheehy <justin@basho.com>').
-author('Bryan Fink <bryan@basho.com>').
-export([dispatch/2, dispatch/3]).
-define(SEPARATOR, $\/).
-define(MATCH_ALL, '*').
%% @spec dispatch(Path::string(), DispatchList::[matchterm()]) ->
%% dispterm() | dispfail()
%% @doc Interface for URL dispatching.
%% See also http://bitbucket.org/justin/webmachine/wiki/DispatchConfiguration
dispatch(PathAsString, DispatchList) ->
dispatch([], PathAsString, DispatchList).
%% @spec dispatch(Host::string(), Path::string(),
%% DispatchList::[matchterm()]) ->
%% dispterm() | dispfail()
%% @doc Interface for URL dispatching.
%% See also http://bitbucket.org/justin/webmachine/wiki/DispatchConfiguration
dispatch(HostAsString, PathAsString, DispatchList) ->
Path = string:tokens(PathAsString, [?SEPARATOR]),
% URIs that end with a trailing slash are implicitly one token
% "deeper" than we otherwise might think as we are "inside"
% a directory named by the last token.
ExtraDepth = case lists:last(PathAsString) == ?SEPARATOR of
true -> 1;
_ -> 0
end,
{Host, Port} = split_host_port(HostAsString),
try_host_binding(DispatchList, lists:reverse(Host), Port,
Path, ExtraDepth).
split_host_port(HostAsString) ->
case string:tokens(HostAsString, ":") of
[HostPart, PortPart] ->
{split_host(HostPart), list_to_integer(PortPart)};
[HostPart] ->
{split_host(HostPart), 80};
[] ->
%% no host header
{[], 80}
end.
split_host(HostAsString) ->
string:tokens(HostAsString, ".").
%% @type matchterm() = hostmatchterm() | pathmatchterm().
% The dispatch configuration is a list of these terms, and the
% first one whose host and path terms match the input is used.
% Using a pathmatchterm() here is equivalent to using a hostmatchterm()
% of the form {{['*'],'*'}, [pathmatchterm()]}.
%% @type hostmatchterm() = {hostmatch(), [pathmatchterm()]}.
% The dispatch configuration contains a list of these terms, and the
% first one whose host and one pathmatchterm match is used.
%% @type hostmatch() = [hostterm()] | {[hostterm()], portterm()}.
% A host header (Host, X-Forwarded-For, etc.) will be matched against
% this term. Using a raws [hostterm()] list is equivalent to using
% {[hostterm()], '*'}.
%% @type hostterm() = '*' | string() | atom().
% A list of hostterms is matched against a '.'-separated hostname.
% The '*' hosterm matches all remaining tokens, and is only allowed at
% the head of the list.
% A string hostterm will match a token of exactly the same string.
% Any atom hostterm other than '*' will match any token and will
% create a binding in the result if a complete match occurs.
%% @type portterm() = '*' | integer() | atom().
% A portterm is matched against the integer port after any ':' in
% the hostname, or 80 if no port is found.
% The '*' portterm patches any port
% An integer portterm will match a port of exactly the same integer.
% Any atom portterm other than '*' will match any port and will
% create a binding in the result if a complete match occurs.
%% @type pathmatchterm() = {[pathterm()], matchmod(), matchopts()}.
% The dispatch configuration contains a list of these terms, and the
% first one whose list of pathterms matches the input path is used.
%% @type pathterm() = '*' | string() | atom().
% A list of pathterms is matched against a '/'-separated input path.
% The '*' pathterm matches all remaining tokens.
% A string pathterm will match a token of exactly the same string.
% Any atom pathterm other than '*' will match any token and will
% create a binding in the result if a complete match occurs.
%% @type matchmod() = atom().
% This atom, if present in a successful matchterm, will appear in
% the resulting dispterm. In Webmachine this is used to name the
% controller module that will handle the matching request.
%% @type matchopts() = [term()].
% This term, if present in a successful matchterm, will appear in
% the resulting dispterm. In Webmachine this is used to provide
% arguments to the controller module handling the matching request.
%% @type dispterm() = {matchmod(), matchopts(), pathtokens(),
%% bindings(), approot(), stringpath()}.
%% @type pathtokens() = [pathtoken()].
% This is the list of tokens matched by a trailing '*' pathterm.
%% @type pathtoken() = string().
%% @type bindings() = [{bindingterm(),pathtoken()}].
% This is a proplist of bindings indicated by atom terms in the
% matching spec, bound to the matching tokens in the request path.
%% @type approot() = string().
%% @type stringpath() = string().
% This is the path portion matched by a trailing '*' pathterm.
%% @type dispfail() = {no_dispatch_match, pathtokens()}.
try_host_binding([], Host, Port, Path, _Depth) ->
{no_dispatch_match, {Host, Port}, Path};
try_host_binding([Dispatch|Rest], Host, Port, Path, Depth) ->
{{HostSpec,PortSpec},PathSpec} =
case Dispatch of
{{H,P},S} -> {{H,P},S};
{H,S} -> {{H,?MATCH_ALL},S};
S -> {{[?MATCH_ALL],?MATCH_ALL},[S]}
end,
case bind_port(PortSpec, Port, []) of
{ok, PortBindings} ->
case bind(lists:reverse(HostSpec), Host, PortBindings, 0) of
{ok, HostRemainder, HostBindings, _} ->
case try_path_binding(PathSpec, Path, HostBindings, Depth) of
{Mod, Props, PathRemainder, PathBindings,
AppRoot, StringPath} ->
{Mod, Props, HostRemainder, Port, PathRemainder,
PathBindings, AppRoot, StringPath};
{no_dispatch_match, _} ->
try_host_binding(Rest, Host, Port, Path, Depth)
end;
fail ->
try_host_binding(Rest, Host, Port, Path, Depth)
end;
fail ->
try_host_binding(Rest, Host, Port, Path, Depth)
end.
bind_port(Port, Port, Bindings) -> {ok, Bindings};
bind_port(?MATCH_ALL, _Port, Bindings) -> {ok, Bindings};
bind_port(PortAtom, Port, Bindings) when is_atom(PortAtom) ->
{ok, [{PortAtom, Port}|Bindings]};
bind_port(_, _, _) -> fail.
try_path_binding([], PathTokens, _, _) ->
{no_dispatch_match, PathTokens};
try_path_binding([{PathSchema, Mod, Props}|Rest], PathTokens,
Bindings, ExtraDepth) ->
case bind(PathSchema, PathTokens, Bindings, 0) of
{ok, Remainder, NewBindings, Depth} ->
{Mod, Props, Remainder, NewBindings,
calculate_app_root(Depth + ExtraDepth), reconstitute(Remainder)};
fail ->
try_path_binding(Rest, PathTokens, Bindings, ExtraDepth)
end.
bind([], [], Bindings, Depth) ->
{ok, [], Bindings, Depth};
bind([?MATCH_ALL], Rest, Bindings, Depth) when is_list(Rest) ->
{ok, Rest, Bindings, Depth + length(Rest)};
bind(_, [], _, _) ->
fail;
bind([Token|RestToken],[Match|RestMatch],Bindings,Depth) when is_atom(Token) ->
bind(RestToken, RestMatch, [{Token, Match}|Bindings], Depth + 1);
bind([Token|RestToken], [Token|RestMatch], Bindings, Depth) ->
bind(RestToken, RestMatch, Bindings, Depth + 1);
bind(_, _, _, _) ->
fail.
reconstitute([]) -> "";
reconstitute(UnmatchedTokens) -> string:join(UnmatchedTokens, [?SEPARATOR]).
calculate_app_root(1) -> ".";
calculate_app_root(N) when N > 1 ->
string:join(lists:duplicate(N, ".."), [?SEPARATOR]).
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