From 62a4a431036f7352b739ff2e820288669bcd16ec Mon Sep 17 00:00:00 2001
From: Guilherme Cassolato <guicassolato@gmail.com>
Date: Sun, 25 Jun 2023 10:22:14 +0200
Subject: [PATCH] generate wasm rules only for routeSelector-filtered hostnames
 that belong to the targeted route

---
 pkg/common/common.go            | 16 +++++++++
 pkg/common/common_test.go       | 62 +++++++++++++++++++++++++++++++++
 pkg/rlptools/wasm_utils.go      |  6 ++--
 pkg/rlptools/wasm_utils_test.go |  8 +++++
 4 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/pkg/common/common.go b/pkg/common/common.go
index f8ac965fa..4330caeef 100644
--- a/pkg/common/common.go
+++ b/pkg/common/common.go
@@ -122,6 +122,22 @@ func Intersect[T comparable](slice1, slice2 []T) bool {
 	return false
 }
 
+func Intersection[T comparable](slice1, slice2 []T) []T {
+	smallerSlice := slice1
+	largerSlice := slice2
+	if len(slice1) > len(slice2) {
+		smallerSlice = slice2
+		largerSlice = slice1
+	}
+	var result []T
+	for _, item := range smallerSlice {
+		if Contains(largerSlice, item) {
+			result = append(result, item)
+		}
+	}
+	return result
+}
+
 func Find[T any](slice []T, match func(T) bool) (*T, bool) {
 	for _, item := range slice {
 		if match(item) {
diff --git a/pkg/common/common_test.go b/pkg/common/common_test.go
index ebea4a5d2..d6752e4dc 100644
--- a/pkg/common/common_test.go
+++ b/pkg/common/common_test.go
@@ -456,6 +456,68 @@ func TestIntersectWithInts(t *testing.T) {
 	}
 }
 
+func TestIntersection(t *testing.T) {
+	testCases := []struct {
+		name     string
+		slice1   []string
+		slice2   []string
+		expected []string
+	}{
+		{
+			name:     "when slice1 and slice2 have one common item then return true",
+			slice1:   []string{"test-gw1", "test-gw2"},
+			slice2:   []string{"test-gw1", "test-gw3", "test-gw4"},
+			expected: []string{"test-gw1"},
+		},
+		{
+			name:     "when slice1 and slice2 have no common item then return false",
+			slice1:   []string{"test-gw1", "test-gw2"},
+			slice2:   []string{"test-gw3", "test-gw4"},
+			expected: nil,
+		},
+		{
+			name:     "when slice1 is empty then return false",
+			slice1:   []string{},
+			slice2:   []string{"test-gw3", "test-gw4"},
+			expected: nil,
+		},
+		{
+			name:     "when slice2 is empty then return false",
+			slice1:   []string{"test-gw1", "test-gw2"},
+			slice2:   []string{},
+			expected: nil,
+		},
+		{
+			name:     "when both slices are empty then return false",
+			slice1:   []string{},
+			slice2:   []string{},
+			expected: nil,
+		},
+		{
+			name:     "when slice1 is nil then return false",
+			slice2:   []string{"test-gw3", "test-gw4"},
+			expected: nil,
+		},
+		{
+			name:     "when slice2 is nil then return false",
+			slice1:   []string{"test-gw1", "test-gw2"},
+			expected: nil,
+		},
+		{
+			name:     "when both slices are nil then return false",
+			expected: nil,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if r := Intersection(tc.slice1, tc.slice2); !reflect.DeepEqual(r, tc.expected) {
+				t.Errorf("expected=%v; got=%v", tc.expected, r)
+			}
+		})
+	}
+}
+
 func TestMap(t *testing.T) {
 	slice1 := []int{1, 2, 3, 4}
 	f1 := func(x int) int { return x + 1 }
diff --git a/pkg/rlptools/wasm_utils.go b/pkg/rlptools/wasm_utils.go
index bb4630a3f..34c8a48c1 100644
--- a/pkg/rlptools/wasm_utils.go
+++ b/pkg/rlptools/wasm_utils.go
@@ -65,8 +65,10 @@ func conditionsFromLimit(limit *kuadrantv1beta2.Limit, route *gatewayapiv1beta1.
 	// build conditions from the rules selected by the route selectors
 	for _, routeSelector := range limit.RouteSelectors {
 		for _, rule := range HTTPRouteRulesFromRouteSelector(routeSelector, route) {
-			hostnames := routeSelector.Hostnames // FIXME(guicassolato): it should be the intersection between routeSelector.Hostnames and route.Spec.Hostnames
-			if len(hostnames) == 0 {
+			var hostnames []gatewayapiv1beta1.Hostname
+			if len(routeSelector.Hostnames) > 0 {
+				hostnames = common.Intersection(routeSelector.Hostnames, route.Spec.Hostnames)
+			} else {
 				hostnames = route.Spec.Hostnames
 			}
 			routeConditions = append(routeConditions, conditionsFromRule(rule, hostnames)...)
diff --git a/pkg/rlptools/wasm_utils_test.go b/pkg/rlptools/wasm_utils_test.go
index 5717c3a42..f1c5206a1 100644
--- a/pkg/rlptools/wasm_utils_test.go
+++ b/pkg/rlptools/wasm_utils_test.go
@@ -58,6 +58,14 @@ func TestWasmRules(t *testing.T) {
 								Unit:     kuadrantv1beta2.TimeUnit("minute"),
 							},
 						},
+						RouteSelectors: []kuadrantv1beta2.RouteSelector{
+							{
+								Hostnames: []gatewayapiv1beta1.Hostname{
+									"*.example.com",
+									"myapp.apps.example.com", // ignored
+								},
+							},
+						},
 					},
 				},
 			},