From 07bafff0514c29696bccd649a27591b4f6cb1fd2 Mon Sep 17 00:00:00 2001
From: Luis Azedo <luis.azedo@factorlusitano.com>
Date: Sun, 21 May 2017 23:18:56 +0200
Subject: [PATCH] allow extra validator

this will extra validations for schema elements
example : lookup some value in a database an provide an error
---
 src/jesse_schema_validator.hrl |  2 +-
 src/jesse_state.erl            | 13 +++++++++++++
 src/jesse_validator_draft3.erl | 16 +++++++++++++---
 src/jesse_validator_draft4.erl | 15 ++++++++++++---
 4 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/src/jesse_schema_validator.hrl b/src/jesse_schema_validator.hrl
index 15919940..0d0d7795 100644
--- a/src/jesse_schema_validator.hrl
+++ b/src/jesse_schema_validator.hrl
@@ -114,7 +114,7 @@
 -define(not_one_schema_valid,        'not_one_schema_valid').
 -define(not_schema_valid,            'not_schema_valid').
 -define(wrong_not_schema,            'wrong_not_schema').
--define(external_error,              'external_error').
+-define(external,                    'external').
 
 %%
 -define(not_found, not_found).
diff --git a/src/jesse_state.erl b/src/jesse_state.erl
index 875ae3b6..eaced1ed 100644
--- a/src/jesse_state.erl
+++ b/src/jesse_state.erl
@@ -26,6 +26,7 @@
 %% API
 -export([ add_to_path/2
         , get_allowed_errors/1
+        , get_external_validator/1
         , get_current_path/1
         , get_current_schema/1
         , get_current_schema_id/1
@@ -68,10 +69,14 @@
                                           jesse:json_term() |
                                           ?not_found
                                             )
+         , external_validator :: external_validator()
          , id                 :: http_uri:uri() | 'undefined'
          }
        ).
 
+-type external_validator() :: fun((jesse:json_term(), state()) -> state())
+                           | undefined.
+
 -opaque state() :: #state{}.
 
 %%% API
@@ -148,6 +153,9 @@ new(JsonSchema, Options) ->
                                  , Options
                                  , ?default_schema_loader_fun
                                  ),
+  ExternalValidator = proplists:get_value( external_validator
+                                         , Options
+                                         ),
   NewState = #state{ root_schema        = JsonSchema
                    , current_path       = []
                    , allowed_errors     = AllowedErrors
@@ -155,6 +163,7 @@ new(JsonSchema, Options) ->
                    , error_handler      = ErrorHandler
                    , default_schema_ver = DefaultSchemaVer
                    , schema_loader_fun  = LoaderFun
+                   , external_validator = ExternalValidator
                    },
   set_current_schema(NewState, JsonSchema).
 
@@ -385,3 +394,7 @@ load_schema(#state{schema_loader_fun = LoaderFun}, SchemaURI) ->
       %% io:format("load_schema: ~p\n", [{_C, _E, erlang:get_stacktrace()}]),
       ?not_found
   end.
+
+%% @private
+get_external_validator(#state{external_validator = Fun}) ->
+  Fun.
diff --git a/src/jesse_validator_draft3.erl b/src/jesse_validator_draft3.erl
index 6aecb65d..7a2b4ed2 100644
--- a/src/jesse_validator_draft3.erl
+++ b/src/jesse_validator_draft3.erl
@@ -48,7 +48,8 @@
                     | ?not_in_range
                     | ?wrong_length
                     | ?wrong_size
-                    | ?wrong_type.
+                    | ?wrong_type
+                    | ?external.
 
 -type data_error_type() :: data_error()
                          | {data_error(), binary()}.
@@ -209,11 +210,11 @@ check_value(Value, [{?DISALLOW, Disallow} | Attrs], State) ->
 check_value(Value, [{?EXTENDS, Extends} | Attrs], State) ->
   NewState = check_extends(Value, Extends, State),
   check_value(Value, Attrs, NewState);
-check_value(_Value, [], State) ->
-  State;
 check_value(Value, [{?REF, RefSchemaURI} | Attrs], State) ->
   NewState = validate_ref(Value, RefSchemaURI, State),
   check_value(Value, Attrs, NewState);
+check_value(Value, [], State) ->
+  maybe_external_check_value(Value, State);
 check_value(Value, [_Attr | Attrs], State) ->
   check_value(Value, Attrs, State).
 
@@ -1031,3 +1032,12 @@ add_to_path(State, Property) ->
 %% @private
 remove_last_from_path(State) ->
   jesse_state:remove_last_from_path(State).
+
+%% @private
+maybe_external_check_value(Value, State) ->
+  case jesse_state:get_external_validator(State) of
+    undefined ->
+      State;
+    Fun ->
+      Fun(Value, State)
+  end.
diff --git a/src/jesse_validator_draft4.erl b/src/jesse_validator_draft4.erl
index e8bbc12e..49c77903 100644
--- a/src/jesse_validator_draft4.erl
+++ b/src/jesse_validator_draft4.erl
@@ -65,7 +65,8 @@
                     | ?too_many_properties
                     | ?wrong_length
                     | ?wrong_size
-                    | ?wrong_type.
+                    | ?wrong_type
+                    | ?external.
 
 -type data_error_type() :: data_error()
                          | {data_error(), binary()}.
@@ -246,11 +247,11 @@ check_value(Value, [{?ONEOF, Schemas} | Attrs], State) ->
 check_value(Value, [{?NOT, Schema} | Attrs], State) ->
   NewState = check_not(Value, Schema, State),
   check_value(Value, Attrs, NewState);
-check_value(_Value, [], State) ->
-  State;
 check_value(Value, [{?REF, RefSchemaURI} | Attrs], State) ->
   NewState = validate_ref(Value, RefSchemaURI, State),
   check_value(Value, Attrs, NewState);
+check_value(Value, [], State) ->
+  maybe_external_check_value(Value, State);
 check_value(Value, [_Attr | Attrs], State) ->
   check_value(Value, Attrs, State).
 
@@ -1362,3 +1363,11 @@ valid_datetime(DateTimeBin) ->
     _ ->
       false
   end.
+
+maybe_external_check_value(Value, State) ->
+  case jesse_state:get_external_validator(State) of
+    undefined ->
+      State;
+    Fun ->
+      Fun(Value, State)
+  end.