jsx/src/jsx_verify.erl

%% The MIT License

%% Copyright (c) 2010 Alisdair Sullivan <alisdairsullivan@yahoo.ca>

%% Permission is hereby granted, free of charge, to any person obtaining a copy
%% of this software and associated documentation files (the "Software"), to deal
%% in the Software without restriction, including without limitation the rights
%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
%% copies of the Software, and to permit persons to whom the Software is
%% furnished to do so, subject to the following conditions:

%% The above copyright notice and this permission notice shall be included in
%% all copies or substantial portions of the Software.

%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
%% THE SOFTWARE.


-module(jsx_verify).
-author("alisdairsullivan@yahoo.ca").

-export([is_json/2]).

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

-ifdef(test).
-include_lib("eunit/include/eunit.hrl").
-endif.



-spec is_json(JSON::binary(), Opts::verify_opts()) -> true | false.

is_json(JSON, Opts) ->
    Encoding = proplists:get_value(encoding, Opts, utf8),
    Comments = proplists:get_value(comments, Opts, false),
    P = jsx:parser([{encoding, Encoding}, {comments, Comments}]),
    case proplists:get_value(strict, Opts, true) of
        true -> collect_strict(P(JSON), [[]])
        ; false -> collect(P(JSON), [[]])
    end.
    

%% enforce only arrays and objects at top level
collect_strict({event, start_object, Next}, Keys) ->
    collect(Next(), Keys);
collect_strict({event, start_array, Next}, Keys) ->
    collect(Next(), Keys);
collect_strict(_, _) ->
    false.


collect({event, end_json, _Next}, _Keys) ->
    true;


%% allocate new key accumulator at start_object, discard it at end_object    
collect({event, start_object, Next}, Keys) -> collect(Next(), [[]|Keys]);
collect({event, end_object, Next}, [_|Keys]) -> collect(Next(), [Keys]);


%% check to see if key has already been encountered, if not add it to the key accumulator
%%   and continue, else return false 
collect({event, {key, Key}, Next}, [Current|Keys]) ->
    case lists:member(Key, Current) of
        true -> false
        ; false -> collect(Next(), [[Key] ++ Current] ++ Keys)
    end;

                
collect({event, _, Next}, Keys) ->
    collect(Next(), Keys);


%% needed to parse numbers that don't have trailing whitespace in less strict mode    
collect({incomplete, More}, Keys) ->
    collect(More(end_stream), Keys);

    
collect(_, _) ->
    false.
    
    

%% eunit tests
-ifdef(test).

true_test_() ->
    [
        {"empty object", ?_assert(is_json(<<"{}">>, []) =:= true)},
        {"empty array", ?_assert(is_json(<<"[]">>, []) =:= true)},
        {"whitespace", ?_assert(is_json(<<" \n    \t   \r   [true]   \t    \n\r  ">>, []) =:= true)},
        {"nested terms", ?_assert(is_json(<<"[ { \"key\": [ {}, {}, {} ], \"more key\": [{}] }, {}, [[[]]] ]">>, []) =:= true)},
        {"numbers", ?_assert(is_json(<<"[ -1.0, -1, -0, 0, 1e-1, 1, 1.0, 1e1 ]">>, []) =:= true)},
        {"strings", ?_assert(is_json(<<"[ \"a\", \"string\", \"in\", \"multiple\", \"acts\" ]">>, []) =:= true)},
        {"literals", ?_assert(is_json(<<"[ true, false, null ]">>, []) =:= true)},
        {"nested objects", ?_assert(is_json(<<"{\"key\": { \"key\": true}}">>, []) =:= true)}
    ].

false_test_() ->
    [
        {"naked true", ?_assert(is_json(<<"true">>, []) =:= false)},
        {"naked number", ?_assert(is_json(<<"1">>, []) =:= false)},
        {"naked string", ?_assert(is_json(<<"\"i am not json\"">>, []) =:= false)},
        {"unbalanced list", ?_assert(is_json(<<"[[[]]">>, []) =:= false)},
        {"trailing comma", ?_assert(is_json(<<"[ true, false, null, ]">>, []) =:= false)},
        {"unquoted key", ?_assert(is_json(<<"{ key: false }">>, []) =:= false)},
        {"repeated key", ?_assert(is_json(<<"{\"key\": true, \"key\": true}">>, []) =:= false)},
        {"comments", ?_assert(is_json(<<"[ /* a comment */ ]">>, []) =:= false)}
    ].
    
less_strict_test_() ->
    [
        {"naked true", ?_assert(is_json(<<"true">>, [{strict, false}]) =:= true)},
        {"naked number", ?_assert(is_json(<<"1">>, [{strict, false}]) =:= true)},
        {"naked string", ?_assert(is_json(<<"\"i am not json\"">>, [{strict, false}]) =:= true)},
        {"comments", ?_assert(is_json(<<"[ /* a comment */ ]">>, [{comments, true}]) =:= true)}
    ].
        
    
-endif.