refactor: deduplicate filter upstreams code

internal/route/always_route_filtering_strategy.go

@@ -1,7 +1,6 @@
 package route
 
 import (
-	"github.com/satsuma-data/node-gateway/internal/config"
 	"github.com/satsuma-data/node-gateway/internal/metadata"
 	"github.com/satsuma-data/node-gateway/internal/types"
 	"go.uber.org/zap"
@@ -25,7 +24,12 @@ func (s *AlwaysRouteFilteringStrategy) RouteNextRequest(
 	filters := s.NodeFilters // WARNING: Slice assignment, not a copy!
 	for len(filters) > 0 {
 		// Get all healthy upstreams for the current set of filters.
-		upstreams := s.FilterUpstreams(upstreamsByPriority, requestMetadata, filters)
+		upstreams := filterUpstreams(
+			upstreamsByPriority,
+			requestMetadata,
+			filters,
+			s.Logger,
+		)
 
 		// If there is at least one healthy upstream, route using the backing strategy.
 		if len(upstreams) > 0 {
@@ -52,50 +56,6 @@ func (s *AlwaysRouteFilteringStrategy) RouteNextRequest(
 	return s.BackingStrategy.RouteNextRequest(upstreamsByPriority, requestMetadata)
 }
 
-// FilterUpstreams filters upstreams based on the provided NodeFilter.
-// WARNING: If a given priority does not have any healthy upstreams,
-// it will not be included in the returned map.
-func (s *AlwaysRouteFilteringStrategy) FilterUpstreams(
-	upstreamsByPriority types.PriorityToUpstreamsMap,
-	requestMetadata metadata.RequestMetadata,
-	nodeFilters []NodeFilter,
-) types.PriorityToUpstreamsMap {
-	priorityToHealthyUpstreams := make(types.PriorityToUpstreamsMap)
-
-	// Iterate over each priority and filter the associated upstreams.
-	for priority, upstreamConfigs := range upstreamsByPriority {
-		s.Logger.Debug(
-			"Determining healthy upstreams at priority.",
-			zap.Int("priority", priority),
-			zap.Any("upstreams", upstreamConfigs),
-		)
-
-		filteredUpstreams := make([]*config.UpstreamConfig, 0)
-
-		// Iterate over each upstream and apply the filters.
-		for _, upstreamConfig := range upstreamConfigs {
-			pass := true
-			for _, nodeFilter := range nodeFilters {
-				pass = nodeFilter.Apply(requestMetadata, upstreamConfig, len(upstreamConfigs))
-				if !pass {
-					break
-				}
-			}
-
-			if pass {
-				filteredUpstreams = append(filteredUpstreams, upstreamConfig)
-			}
-		}
-
-		// Only add the priority to the map if there is at least one healthy upstream.
-		if len(filteredUpstreams) > 0 {
-			priorityToHealthyUpstreams[priority] = filteredUpstreams
-		}
-	}
-
-	return priorityToHealthyUpstreams
-}
-
 // removeFilters returns a new slice of filters with the given filter type removed.
 func removeFilters(filters []NodeFilter, filterToRemove NodeFilterType) []NodeFilter {
 	retFilters := make([]NodeFilter, 0)

internal/route/filtering_strategy.go

@@ -24,16 +24,34 @@ func (s *FilteringRoutingStrategy) RouteNextRequest(
 func (s *FilteringRoutingStrategy) filter(
 	upstreamsByPriority types.PriorityToUpstreamsMap,
 	requestMetadata metadata.RequestMetadata,
+) types.PriorityToUpstreamsMap {
+	return filterUpstreams(
+		upstreamsByPriority,
+		requestMetadata,
+		[]NodeFilter{s.NodeFilter},
+		s.Logger,
+	)
+}
+
+func filterUpstreams(
+	upstreamsByPriority types.PriorityToUpstreamsMap,
+	requestMetadata metadata.RequestMetadata,
+	nodeFilters []NodeFilter,
+	logger *zap.Logger,
 ) types.PriorityToUpstreamsMap {
 	priorityToHealthyUpstreams := make(types.PriorityToUpstreamsMap)
+	nodeFilter := AndFilter{
+		filters: nodeFilters,
+		logger:  logger,
+	}
 
 	for priority, upstreamConfigs := range upstreamsByPriority {
-		s.Logger.Debug("Determining healthy upstreams at priority.", zap.Int("priority", priority), zap.Any("upstreams", upstreamConfigs))
+		logger.Debug("Determining healthy upstreams at priority.", zap.Int("priority", priority), zap.Any("upstreams", upstreamConfigs))
 
 		filteredUpstreams := make([]*config.UpstreamConfig, 0)
 
 		for _, upstreamConfig := range upstreamConfigs {
-			ok := s.NodeFilter.Apply(requestMetadata, upstreamConfig, len(upstreamConfigs))
+			ok := nodeFilter.Apply(requestMetadata, upstreamConfig, len(upstreamConfigs))
 			if ok {
 				filteredUpstreams = append(filteredUpstreams, upstreamConfig)
 			}