yaws_jsonrpc.erl

%% Copyright (C) 2003 Joakim Grebenö <jocke@gleipnir.com>.
%% All rights reserved.
%%
%% Copyright (C) 2006 Gaspar Chilingarov <nm@web.am>
%%                      Gurgen Tumanyan <barbarian@armkb.com>
%% All rights reserved.
%%
%%
%% Redistribution and use in source and binary forms, with or without
%% modification, are permitted provided that the following conditions
%% are met: 
%%
%% 1. Redistributions of source code must retain the above copyright
%%    notice, this list of conditions and the following disclaimer. 
%% 2. Redistributions in binary form must reproduce the above
%%    copyright notice, this list of conditions and the following
%%    disclaimer in the documentation and/or other materials provided
%%    with the distribution.
%%
%% THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
%% OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
%% WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
%% ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
%% DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
%% DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
%% GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
%% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
%% WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
%% NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
%% SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-module(yaws_jsonrpc).
-author("Gaspar Chilingarov <nm@web.am>, Gurgen Tumanyan <barbarian@armkb.com>").                                    
-export([handler/2]).
-export([handler_session/2, handler_session/3]).

%-define(debug, 1).
%-include("../../yaws/src/yaws_debug.hrl").

-include("../include/yaws_api.hrl").

%%% ###################################################################### 
%%% public interface
%%%

%%%
%%% use jsonrpc handler which can automagically start sessions if we need
%%%
handler_session(Args, Handler) ->
    handler_session(Args, Handler, 'SID').

%%%
%%% allow overriding session Cookie name
%%%
handler_session(Args, Handler, SID_NAME) when is_atom(SID_NAME) ->
    handler_session(Args, Handler, atom_to_list(SID_NAME));

handler_session(Args, Handler, SID_NAME) ->
    handler(Args, Handler, {session, SID_NAME}).    % go to generic handler

%%%
%%% xmlrpc:handler compatible call
%%% no session support will be available
handler(Args, Handler) ->
    handler(Args, Handler, simple).


%%% ###################################################################### 
%%% private functions
%%%

%%% we should be called from yaws page or module
handler(Args, Handler, Type) when is_record(Args, arg) -> % {{{
    case parse_request(Args) of
    ok ->
        handle_payload(Args, Handler, Type);
    {status, StatusCode} ->        % cannot parse request
        send(Args, StatusCode)
    end. % }}}

-define(ERROR_LOG(Reason),
    error_logger:error_report({?MODULE, ?LINE, Reason})).

%%%
%%% check that request come in reasonable protocol version and reasonable method
%%%
parse_request(Args) -> % {{{
    case {(Args#arg.req)#http_request.method, (Args#arg.req)#http_request.version} of
    {'POST', {1,0}} ->
%        ?Debug("HTTP Version 1.0~n", []),
        ok;
    {'POST', {1,1}} ->
%        ?Debug("HTTP Version 1.1~n", []),
        ok;
    {'POST', _HTTPVersion} -> {status, 505};
    {_Method, {1,1}} -> {status, 501};
    _ -> {status, 400}
     end.  % }}}
    
handle_payload(Args, Handler, Type) -> % {{{
    Payload = binary_to_list(Args#arg.clidata),
%    ?Debug("jsonrpc plaintext call ~p ~n", [Payload]),
    case decode_handler_payload(Payload) of
    {ok, DecodedPayload, ID} ->
%        ?Debug("json2erl decoded call ~p ~n", [DecodedPayload]),
        eval_payload(Args, Handler, DecodedPayload, Type, ID);
    {error, Reason} ->
        ?ERROR_LOG({html, json2erl, Payload, Reason}),
        send(Args, 400)
    end. % }}}
    
%%%
%%% call handler/3 and provide session support
eval_payload(Args, {M, F}, Payload, {session, CookieName},ID) -> % {{{
    {SessionValue, Cookie} = case yaws_api:find_cookie_val(CookieName, (Args#arg.headers)#headers.cookie) of
    [] ->      % have no session started, just call handler
        {undefined, undefined};
    Cookie2 -> % get old session data
        case yaws_api:cookieval_to_opaque(Cookie2) of
        {ok, OP} ->
            yaws_api:cookieval_to_opaque(Cookie2),
            {OP, Cookie2};
        {error, _ErrMsg} -> % cannot get corresponding session
            {undefined, undefined}
        end
    end,

    case catch M:F(Args#arg.state, Payload, SessionValue) of
    {'EXIT', Reason} ->
        ?ERROR_LOG({M, F, {'EXIT', Reason}}),
        send(Args, 500);
    {error, Reason} ->
        ?ERROR_LOG({M, F, Reason}),
        send(Args, 500);
    {false, ResponsePayload} ->
        % do not have updates in session data
        encode_send(Args, 200, ResponsePayload, [], ID);
    {true, _NewTimeout, NewSessionValue, ResponsePayload} -> % be compatible with xmlrpc module
        CO = case NewSessionValue of
        undefined when Cookie == undefined -> []; % nothing to do
        undefined -> % rpc handler requested session delete
            yaws_api:delete_cookie_session(Cookie), []; % XXX: may be return set-cookie with empty val?
        _ ->  % any other value will stored in session
            case SessionValue of
            undefined -> % got session data and should start new session now
                Cookie1 = yaws_api:new_cookie_session(NewSessionValue),
                yaws_api:setcookie(CookieName, Cookie1, "/"); % return set_cookie header
            _ -> 
                yaws_api:replace_cookie_session(Cookie, NewSessionValue),
                [] % nothing to add to yaws data
            end
        end,
        encode_send(Args, 200, ResponsePayload, CO, ID)
     end; % }}}

%%%
%%% call handler/2 without session support
%%%
eval_payload(Args, {M, F}, Payload, simple, ID) -> % {{{
    case catch M:F(Args#arg.state, Payload) of
    {'EXIT', Reason} ->
        ?ERROR_LOG({M, F, {'EXIT', Reason}}),
        send(Args, 500);
    {error, Reason} ->
        ?ERROR_LOG({M, F, Reason}),
        send(Args, 500);
    {false, ResponsePayload} ->
        encode_send(Args, 200, ResponsePayload, [],ID);
    {true, _NewTimeout, _NewState, ResponsePayload} ->
        encode_send(Args, 200, ResponsePayload, [],ID)
    end. % }}}  


%%% XXX compatibility with XMLRPC handlers
%%% XXX - potential bug here?
encode_send(Args, StatusCode, [Payload], AddOn, ID) ->  % {{{
    encode_send(Args, StatusCode, Payload, AddOn, ID); % }}}

encode_send(Args, StatusCode, Payload, AddOn, ID) -> % {{{
%    ?Debug("jsonrpc response ~p ~n", [Payload]),
    case encode_handler_payload(Payload, ID) of
    {ok, EncodedPayload} ->
%        ?Debug("jsonpc encoded response ~p ~n", [EncodedPayload]),
        send(Args, StatusCode, EncodedPayload, AddOn);
    {error, Reason} ->
        ?ERROR_LOG({jsonrpc_encode, payload, Payload, Reason}),
        send(Args, 500)
     end. % }}}

send(Args, StatusCode) -> send(Args, StatusCode, "", []). %  {{{

send(Args, StatusCode, Payload, AddOnData) when not is_list(AddOnData) ->
    send(Args, StatusCode, Payload, [AddOnData]);

send(_Args, StatusCode, Payload, AddOnData) ->
    A = [
    {status, StatusCode}, 
    {content, "text/xml", Payload}, 
    {header, {content_length, lists:flatlength(Payload) }}
    ] ++ AddOnData,
    A
     . % }}}

encode_handler_payload({response, [ErlStruct]},ID) ->   % {{{
    encode_handler_payload({response, ErlStruct}, ID);
    
encode_handler_payload({response, ErlStruct},ID) ->  
    StructStr = json:encode({struct, [ {result, ErlStruct}, {id, ID}]}),
    {ok, StructStr}.  % }}}
      
decode_handler_payload(JSonStr) -> %{{{
    try 
        {ok, JSON} = json:decode_string(JSonStr),
        Method = list_to_atom(jsonrpc:s(JSON, method)),
        {array, Args} = jsonrpc:s(JSON, params),
        ID = jsonrpc:s(JSON, id),

        {ok, {call, Method, Args}, ID}
    catch 
        error:Err -> {error, Err}
    end.%}}}

% vim: tabstop=4 ft=erlang