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% vim: sw=4 ts=4 et ft=erlang
% Nitrogen Web Framework for Erlang
% Copyright (c) 2008-2010 Rusty Klophaus
% See MIT-LICENSE for licensing information.
-module (dynamic_route_handler).
-behaviour (route_handler).
-include("wf.hrl").
-export ([
init/2,
finish/2
]).
%% @doc
%% dynamic_route_handler looks at the requested path and file extension
%% to determine how a request should be served. If the request path has no
%% extension, then it assumes this request should be handled by a Nitrogen
%% page module that matches the path with slashes converted to underscores.
%% If no module is found, then it will chop off the last part of the path
%% (storing it for later access in wf:path_info/0) and try again, repeating
%% until either a module is found, or there are no more parts to chop. If
%% a module still can't be found, then the web_404 module is used if defined
%% by the user, otherwise a 404 is generated internally.
%%
%% Requests for "/" are automatically sent to index.
%%
%% If the request path does have an extension, then it is treated like a request
%% for a static file. This is delegated back to the HTTP server.
init(_Config, State) ->
% Get the path...
Bridge = wf_context:bridge(),
Path = sbw:path(Bridge),
% Convert the path to a module. If there are no routes defined, then just
% convert everything without an extension to a module.
% Otherwise, look through all routes for the first matching route.
{Module, EntryPoint, PathInfo} = route(Path),
{Module1, PathInfo1} = check_for_404(Module, PathInfo, Path),
wf_context:page_module(Module1),
wf_context:path_info(PathInfo1),
wf_context:entry_point(EntryPoint),
{ok, State}.
finish(_Config, State) ->
{ok, State}.
%%% PRIVATE FUNCTIONS %%%
% First, check if this is a request for the root path. If so
% then just send it to index.
% Check if there is an extension, if so, it's static.
% Otherwise, try to load a module according to each part of the path.
% First, cycle through code:all_loaded(). If not there, then check erl_prim_loader:get_file()
% If still not there, then 404.
route("/") ->
{list_to_atom(module_name(["index"])), main, []};
route(Path) ->
InitialEntryPoint = determine_initial_entry_point(Path),
handle_initial_entry_point(Path, InitialEntryPoint).
handle_initial_entry_point(Path, static) ->
{static_file, main, Path};
handle_initial_entry_point(Path, {module, EntryFun, ProcessingFun}) ->
Path1 = string:strip(filename:rootname(Path), both, $/),
Tokens = string:tokens(Path1, "/"),
% Check for a loaded module. If not found, then try to load it.
case try_load_module(EntryFun, ProcessingFun, Tokens) of
{Module, EntryPoint, PathInfo} ->
{Module, EntryPoint, PathInfo};
undefined ->
{web_404, main, Path1}
end.
determine_initial_entry_point(Filename) ->
SmartExtensions = wf:config_default(smart_extensions, []),
Ext = string:strip(filename:extension(Filename), left, $.),
case lists:keyfind(Ext, 1, SmartExtensions) of
{Ext, EntryFun, ProcessingFun={_,_}} ->
{module, EntryFun, ProcessingFun};
{Ext, EntryFun, undefined} ->
{module, EntryFun, undefined};
{Ext, EntryFun} ->
{module, EntryFun, undefined};
false when Ext==[] ->
{module, main, undefined};
false ->
static;
Other ->
throw({invalid_smart_extension_definition, Other})
end.
module_name(Tokens) ->
ModulePrefix = wf:config_default(module_prefix, ""),
AllTokens = case ModulePrefix of
"" -> Tokens;
_ -> [ ModulePrefix | Tokens ]
end,
_ModuleName = string:join(AllTokens, "_").
verify_and_atomize_module(ModuleName) when is_list(ModuleName) ->
try
list_to_existing_atom(ModuleName)
catch _:_ ->
case erl_prim_loader:get_file(ModuleName ++ ".beam") of
{ok, _, _} -> list_to_atom(ModuleName);
_ -> list_to_atom("$not_found")
end
end.
try_load_module(EntryFun, ProcessingFun, Tokens) ->
try_load_module(EntryFun, ProcessingFun, Tokens, []).
try_load_module(_EntryFun, _ProcessingFun, [], _ExtraTokens) ->
undefined;
try_load_module(EntryFun, ProcessingFun, Tokens, ExtraTokens) ->
ModuleName = module_name(Tokens),
Module = verify_and_atomize_module(ModuleName),
%% Load the module, check if it exports the right method...
code:ensure_loaded(Module),
%% EntryFun will usually be 'main', meaning we're looking for Module:main()
%% to enter by default. Smart Extensions might look for a different entry
%% function like 'json_main'.
case erlang:function_exported(Module, EntryFun, 0) of
true ->
PathInfo = string:join(ExtraTokens, "/"),
RealEntry = case ProcessingFun of
undefined ->
%% There's no processing function, so we just enter the
%% module normally
EntryFun;
{ProcMod, ProcFun} ->
%% We've identified that this has the entry point for the
%% associated smart extension, and this smart extension has
%% a processing Mod:Fun combination, so we'll pass that as
%% the entry point.
fun() -> ProcMod:ProcFun(fun Module:EntryFun/0) end
end,
{Module, RealEntry, PathInfo};
false ->
case is_rest_module(Module) of
true ->
PathInfo = string:join(ExtraTokens, "/"),
%% If this is a rest request, we handle it with the nitrogen_rest module
Entry = fun() -> nitrogen_rest:handle_request(Module) end,
{Module, Entry, PathInfo};
false ->
next_try_load_module(EntryFun, ProcessingFun, Tokens, ExtraTokens)
end
end.
next_try_load_module(EntryFun, ProcessingFun, Tokens, ExtraTokens) ->
Tokens1 = lists:reverse(tl(lists:reverse(Tokens))),
ExtraTokens1 = [hd(lists:reverse(Tokens))|ExtraTokens],
try_load_module(EntryFun, ProcessingFun, Tokens1, ExtraTokens1).
is_rest_module(Module) ->
wf_utils:has_behaviour(Module, nitrogen_rest).
check_for_404(static_file, _PathInfo, Path) ->
{static_file, Path};
check_for_404(Module, PathInfo, Path) ->
% Make sure the requested module is loaded. If it
% is not, then try to load the web_404 page. If that
% is not available, then default to the 'file_not_found_page' module.
case code:ensure_loaded(Module) of
{module, Module} -> {Module, PathInfo};
_ ->
case code:ensure_loaded(web_404) of
{module, web_404} -> {web_404, Path};
_ -> {file_not_found_page, Path}
end
end.
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