HELP-14771: Add min_shortdial_destination config option (#6552)

Allows for shortdial correction to only be applied if the destination
is of at least a certain length.

And also refactor short-dial correction code in order to be able to
add unit tests for that functionality.

applications/crossbar/priv/api/swagger.json

@@ -35251,7 +35251,7 @@
                     "type": "boolean"
                 },
                 "fixed_length_shortdial_correction": {
-                    "description": "stepswitch fixed_length_shortdial_correction",
+                    "description": "add {FIXED} digits from caller ID to destination",
                     "minimum": 1,
                     "type": "integer"
                 },
@@ -35262,13 +35262,18 @@
                 },
                 "max_shortdial_correction": {
                     "default": 5,
-                    "description": "stepswitch maximum shortdial correction",
+                    "description": "add up to {MAX} digits from caller ID to destination number",
                     "minimum": 1,
                     "type": "integer"
                 },
                 "min_shortdial_correction": {
                     "default": 2,
-                    "description": "stepswitch minimum shortdial correction",
+                    "description": "add at least {MIN} digits from caller ID to destination number",
+                    "minimum": 1,
+                    "type": "integer"
+                },
+                "min_shortdial_destination": {
+                    "description": "do short-dial correction if dialed number's length is equal to this value",
                     "minimum": 1,
                     "type": "integer"
                 },

applications/crossbar/priv/couchdb/schemas/system_config.stepswitch.json

@@ -114,7 +114,7 @@
             "type": "boolean"
         },
         "fixed_length_shortdial_correction": {
-            "description": "stepswitch fixed_length_shortdial_correction",
+            "description": "add {FIXED} digits from caller ID to destination",
             "minimum": 1,
             "type": "integer"
         },
@@ -125,13 +125,18 @@
         },
         "max_shortdial_correction": {
             "default": 5,
-            "description": "stepswitch maximum shortdial correction",
+            "description": "add up to {MAX} digits from caller ID to destination number",
             "minimum": 1,
             "type": "integer"
         },
         "min_shortdial_correction": {
             "default": 2,
-            "description": "stepswitch minimum shortdial correction",
+            "description": "add at least {MIN} digits from caller ID to destination number",
+            "minimum": 1,
+            "type": "integer"
+        },
+        "min_shortdial_destination": {
+            "description": "do short-dial correction if dialed number's length is equal to this value",
             "minimum": 1,
             "type": "integer"
         },

applications/stepswitch/src/stepswitch_util.erl

@@ -16,6 +16,16 @@
 -export([resources_to_endpoints/3]).
 -export([json_to_template_props/1]).
 
+-ifdef(TEST).
+-export([maybe_constrain_shortdial_correction/3
+        ,shortdial_correction_length/3
+        ,maybe_deny_reclassified_number/3
+        ,do_correct_shortdial/3
+        ,should_correct_shortdial/2
+        ,correct_shortdial/4
+        ]).
+-endif.
+
 -include("stepswitch.hrl").
 -include_lib("kazoo_stdlib/include/kazoo_json.hrl").
 -include_lib("kazoo_amqp/include/kapi_offnet_resource.hrl").
@@ -91,61 +101,100 @@ correct_shortdial(<<"+", Number/binary>>, CIDNum, DeniedCallRestrictions) ->
 correct_shortdial(Number, <<"+", CIDNum/binary>>, DeniedCallRestrictions) ->
     correct_shortdial(Number, CIDNum, DeniedCallRestrictions);
 correct_shortdial(Number, CIDNum, DeniedCallRestrictions) when is_binary(CIDNum) ->
+    correct_shortdial(Number, CIDNum, DeniedCallRestrictions, should_correct_shortdial(Number)).
+
+-spec correct_shortdial(kz_term:ne_binary(), kz_term:ne_binary(), kz_json:object(), {boolean(), pos_integer()}) -> kz_term:api_ne_binary().
+correct_shortdial(Number, CIDNum, DeniedCallRestrictions, {'true', _Length}) ->
     case shortdial_correction_length(Number, CIDNum) of
         0 ->
             lager:debug("unable to correct shortdial ~s via CID ~s"
                        ,[Number, CIDNum]
                        ),
             'undefined';
         Length ->
-            try_to_correct(Number, CIDNum, DeniedCallRestrictions, Length)
-    end.
-
--spec try_to_correct(kz_term:ne_binary(), kz_term:ne_binary(), kz_json:object(), non_neg_integer()) -> kz_term:api_ne_binary().
-try_to_correct(Number, CIDNum, DeniedCallRestrictions, Length) ->
+            maybe_deny_reclassified_number(do_correct_shortdial(Number, CIDNum, Length)
+                                          ,CIDNum
+                                          ,DeniedCallRestrictions
+                                          )
+    end;
+correct_shortdial(Number, _CIDNum, _DeniedCallRestrictions, {'false', Length}) ->
+    lager:debug("~s's lenght (~p) doesn't match min_shortdial_destination param's value (~p), skipping"
+               ,[Number, byte_size(Number), Length]
+               ),
+    'undefined'.
+
+-spec should_correct_shortdial(kz_term:ne_binary()) -> {boolean(), pos_integer()}.
+should_correct_shortdial(Number) ->
+    should_correct_shortdial(Number
+                            ,kapps_config:get_integer(?SS_CONFIG_CAT
+                                                     ,<<"min_shortdial_destination">>
+                                                     )
+                            ).
+
+-spec should_correct_shortdial(kz_term:ne_binary(), pos_integer()) -> {boolean(), pos_integer()}.
+should_correct_shortdial(_Number, 'undefined') ->
+    {'true', 0};
+should_correct_shortdial(Number, Length) ->
+    %% The length is also included on the response just to avoid having to read this configuration
+    %% parameter again when printing the debug line. So it is only useful for the `{false, N}' branch.
+    {byte_size(Number) =:= Length, Length}.
+
+-spec do_correct_shortdial(kz_term:ne_binary(), kz_term:ne_binary(), non_neg_integer()) -> kz_term:api_ne_binary().
+do_correct_shortdial(Number, CIDNum, Length) ->
     Correction = kz_binary:truncate_right(CIDNum, Length),
     CorrectedNumber = knm_converters:normalize(<<Correction/binary, Number/binary>>),
-    lager:debug("corrected shortdial ~s via CID ~s to ~s"
-               ,[Number, CIDNum, CorrectedNumber]
-               ),
-    case should_deny_reclassified_number(CorrectedNumber, DeniedCallRestrictions) of
-        'true' ->
-            lager:info("unable to correct shortdial ~s via CID ~s due to a call restriction"
-                      ,[Number, CIDNum]
-                      ),
-            'undefined';
-        'false' ->
-            CorrectedNumber
-    end.
+    lager:debug("corrected shortdial ~s via CID ~s to ~s", [Number, CIDNum, CorrectedNumber]),
+    CorrectedNumber.
 
--spec should_deny_reclassified_number(kz_term:ne_binary(), kz_json:object()) -> boolean().
-should_deny_reclassified_number(CorrectedNumber, DeniedCallRestrictions) ->
+-spec maybe_deny_reclassified_number(kz_term:ne_binary(), kz_term:ne_binary(), kz_json:object()) -> kz_term:api_ne_binary().
+maybe_deny_reclassified_number(CorrectedNumber, CIDNum, DeniedCallRestrictions) ->
     Classification = knm_converters:classify(CorrectedNumber),
     lager:debug("re-classified corrected number ~s as ~s, testing for call restrictions"
                ,[CorrectedNumber, Classification]
                ),
-    kz_json:get_ne_binary_value([Classification, <<"action">>], DeniedCallRestrictions)
-        =:= <<"deny">>.
+    case kz_json:get_ne_binary_value([Classification, <<"action">>], DeniedCallRestrictions) of
+        <<"deny">> ->
+            lager:info("unable to correct shortdial via CID ~s due to a call restriction", [CIDNum]),
+            'undefined';
+        _ ->
+            CorrectedNumber
+    end.
 
 -spec shortdial_correction_length(kz_term:ne_binary(), kz_term:ne_binary()) -> integer().
 shortdial_correction_length(Number, CIDNum) ->
-    case kapps_config:get_integer(?SS_CONFIG_CAT, <<"fixed_length_shortdial_correction">>) of
-        'undefined' ->
-            Length = byte_size(CIDNum) - byte_size(Number),
-            maybe_constrain_shortdial_correction(Length);
-        FixedLength -> FixedLength
-    end.
+    shortdial_correction_length(Number
+                               ,CIDNum
+                               ,kapps_config:get_integer(?SS_CONFIG_CAT
+                                                        ,<<"fixed_length_shortdial_correction">>
+                                                        )
+                               ).
+
+-spec shortdial_correction_length(kz_term:ne_binary(), kz_term:ne_binary(), integer()) -> integer().
+shortdial_correction_length(Number, CIDNum, 'undefined') ->
+    Length = byte_size(CIDNum) - byte_size(Number),
+    maybe_constrain_shortdial_correction(Length);
+shortdial_correction_length(_Number, _CIDNum, FixedLength) ->
+    FixedLength.
 
 -spec maybe_constrain_shortdial_correction(integer()) -> integer().
 maybe_constrain_shortdial_correction(Length) ->
-    MaxCorrection = kapps_config:get_integer(?SS_CONFIG_CAT, <<"max_shortdial_correction">>, 5),
-    MinCorrection = kapps_config:get_integer(?SS_CONFIG_CAT, <<"min_shortdial_correction">>, 2),
-    case Length =< MaxCorrection
-        andalso Length >= MinCorrection
-    of
-        'true' -> Length;
-        'false' -> 0
-    end.
+    maybe_constrain_shortdial_correction(Length
+                                        ,kapps_config:get_integer(?SS_CONFIG_CAT
+                                                                 ,<<"min_shortdial_correction">>
+                                                                 ,2
+                                                                 )
+                                        ,kapps_config:get_integer(?SS_CONFIG_CAT
+                                                                 ,<<"max_shortdial_correction">>
+                                                                 ,5
+                                                                 )
+                                        ).
+
+-spec maybe_constrain_shortdial_correction(integer(), integer(), integer()) -> integer().
+maybe_constrain_shortdial_correction(Length, Min, Max) when Length >= Min
+                                                            andalso Length =< Max ->
+    Length;
+maybe_constrain_shortdial_correction(_Length, _Min, _Max) ->
+    0.
 
 -spec get_sip_headers(kapi_offnet_resource:req()) -> kz_json:object().
 get_sip_headers(OffnetReq) ->
@@ -165,7 +214,6 @@ get_sip_headers(OffnetReq) ->
 maybe_remove_diversions(JObj) ->
     kz_json:delete_key(<<"Diversions">>, JObj).
 
-
 -spec get_diversions(kz_json:object()) ->
           'undefined' |
           kz_term:ne_binaries().