TD-820: Fixes limits rollback for route candidates (#110)

* TD-820: Fixes limits rollback for route candidates

* Fixes limit-hold routes stash

apps/hellgate/src/hg_invoice_payment.erl

@@ -1988,7 +1988,8 @@ produce_routing_events(Ctx = #{error := Error}, _Revision, St) when Error =/= un
 produce_routing_events(Ctx, Revision, _St) ->
     ok = log_route_choice_meta(Ctx, Revision),
     Route = hg_route:to_payment_route(hg_routing_ctx:choosen_route(Ctx)),
-    Candidates = ordsets:from_list([hg_route:to_payment_route(R) || R <- hg_routing_ctx:candidates(Ctx)]),
+    Candidates =
+        ordsets:from_list([hg_route:to_payment_route(R) || R <- hg_routing_ctx:considered_candidates(Ctx)]),
     [?route_changed(Route, Candidates)].
 
 route_args(St) ->
@@ -2475,9 +2476,10 @@ get_provider_terms(St, Revision) ->
     VS1 = collect_validation_varset(get_party(Opts), get_shop(Opts), Payment, VS0),
     hg_routing:get_payment_terms(Route, VS1, Revision).
 
-filter_routes_with_limit_hold(Ctx, VS, Iter, St) ->
-    {_Routes, RejectedRoutes} = hold_limit_routes(hg_routing_ctx:candidates(Ctx), VS, Iter, St),
-    reject_routes(limit_misconfiguration, RejectedRoutes, Ctx).
+filter_routes_with_limit_hold(Ctx0, VS, Iter, St) ->
+    {_Routes, RejectedRoutes} = hold_limit_routes(hg_routing_ctx:candidates(Ctx0), VS, Iter, St),
+    Ctx1 = reject_routes(limit_misconfiguration, RejectedRoutes, Ctx0),
+    hg_routing_ctx:stash_current_candidates(Ctx1).
 
 filter_routes_by_limit_overflow(Ctx, VS, St) ->
     {_Routes, RejectedRoutes} = get_limit_overflow_routes(hg_routing_ctx:candidates(Ctx), VS, St),
@@ -3362,7 +3364,7 @@ get_limit_values(St) ->
             Acc#{PaymentRoute => TurnoverLimitValues}
         end,
         #{},
-        hg_routing_ctx:candidates(Ctx)
+        hg_routing_ctx:considered_candidates(Ctx)
     ).
 
 -spec get_limit_values(st(), opts()) -> route_limit_context().

apps/hellgate/src/hg_recurrent_paytool.erl

@@ -275,7 +275,7 @@ init(EncodedParams, #{id := RecPaymentToolID}) ->
 gather_routes(PaymentInstitution, VS, Revision, Ctx) ->
     Predestination = recurrent_paytool,
     RoutingCtx = hg_routing:gather_routes(Predestination, PaymentInstitution, VS, Revision, Ctx),
-    case {hg_routing_ctx:candidates(RoutingCtx), hg_routing_ctx:error(RoutingCtx)} of
+    case {hg_routing_ctx:considered_candidates(RoutingCtx), hg_routing_ctx:error(RoutingCtx)} of
         {[], undefined} ->
             throw({no_route_found, {unknown, hg_routing_ctx:rejected_routes(RoutingCtx)}});
         {Routes, undefined} ->

apps/hellgate/src/hg_routing_ctx.erl

@@ -11,6 +11,8 @@
 -export([rejections/1]).
 -export([candidates/1]).
 -export([initial_candidates/1]).
+-export([stash_current_candidates/1]).
+-export([considered_candidates/1]).
 -export([choosen_route/1]).
 -export([process/2]).
 -export([with_guard/1]).
@@ -27,6 +29,7 @@
     error := error() | undefined,
     choosen_route := hg_route:t() | undefined,
     choice_meta := hg_routing:route_choice_context() | undefined,
+    stashed_candidates => [hg_route:t()],
     fail_rates => [hg_routing:fail_rated_route()]
 }.
 
@@ -102,14 +105,32 @@ rejected_routes(#{rejections := Rejections}) ->
     {_, RejectedRoutes} = lists:unzip(maps:to_list(Rejections)),
     lists:flatten(RejectedRoutes).
 
+%% @doc List of currently considering candidates.
+%%      Route will be choosen among these.
 -spec candidates(t()) -> [hg_route:t()].
 candidates(#{candidates := Candidates}) ->
     Candidates.
 
+%% @doc Lists candidates provided at very start of routing context formation.
 -spec initial_candidates(t()) -> [hg_route:t()].
 initial_candidates(#{initial_candidates := InitialCandidates}) ->
     InitialCandidates.
 
+%% @doc Lists candidates (same as 'candidates/1') with only difference that list
+%%      includes previously considered candidates that were stashed to be
+%%      accounted for later.
+%%
+%%      For __example__, it may consist of routes that were successfully staged
+%%      by limits accountant and thus stashed to be optionally rolled back
+%%      later.
+-spec considered_candidates(t()) -> [hg_route:t()].
+considered_candidates(Ctx) ->
+    maps:get(stashed_candidates, Ctx, candidates(Ctx)).
+
+-spec stash_current_candidates(t()) -> t().
+stash_current_candidates(Ctx) ->
+    Ctx#{stashed_candidates => candidates(Ctx)}.
+
 -spec choosen_route(t()) -> hg_route:t() | undefined.
 choosen_route(#{choosen_route := ChoosenRoute}) ->
     ChoosenRoute.

apps/hellgate/test/hg_route_rules_tests_SUITE.erl

@@ -928,4 +928,4 @@ maybe_set_risk_coverage(true, V) ->
     {value, V}.
 
 unwrap_routing_context(RoutingCtx) ->
-    {ok, {hg_routing_ctx:candidates(RoutingCtx), hg_routing_ctx:rejected_routes(RoutingCtx)}}.
+    {ok, {hg_routing_ctx:considered_candidates(RoutingCtx), hg_routing_ctx:rejected_routes(RoutingCtx)}}.