From b9a39e94ddd1f4a277c62d1b5643ea5952e381b4 Mon Sep 17 00:00:00 2001
From: michaelawyu <chenyu1@microsoft.com>
Date: Mon, 3 Jul 2023 17:58:29 +0800
Subject: [PATCH] feat: scheduler (9/): add uniquename utility for preparing
 binding names (#404)

---
 .../framework/uniquename/uniquename.go        | 57 +++++++++++++
 .../framework/uniquename/uniquename_test.go   | 79 +++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 pkg/scheduler/framework/uniquename/uniquename.go
 create mode 100644 pkg/scheduler/framework/uniquename/uniquename_test.go

diff --git a/pkg/scheduler/framework/uniquename/uniquename.go b/pkg/scheduler/framework/uniquename/uniquename.go
new file mode 100644
index 000000000..12b11dcb3
--- /dev/null
+++ b/pkg/scheduler/framework/uniquename/uniquename.go
@@ -0,0 +1,57 @@
+/*
+Copyright (c) Microsoft Corporation.
+Licensed under the MIT license.
+*/
+
+// package uniquename features some utilities that are used to generate unique names in use
+// by the scheduler.
+package uniquename
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/uuid"
+	"k8s.io/apimachinery/pkg/util/validation"
+)
+
+const (
+	uuidLength = 6
+)
+
+// minInt returns the smaller one of two integers.
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+// NewClusterResourceBindingName returns a unique name for a cluster resource binding in the
+// format of DNS subdomain names (RFC 1123).
+//
+// The name is generated using the following format:
+// * [CRP-NAME] - [TARGET-CLUSTER-NAME] - [RANDOM-SUFFIX]
+//
+// Segments will be truncated if necessary.
+//
+// Note that the name generation is, in essence, a best-effort process, though the chances
+// of name collisions are extremely low.
+//
+// In addition, note that this function assumes that both the CRP name and the cluster name
+// are valid DNS subdomain names (RFC 1123).
+func NewClusterResourceBindingName(CRPName string, clusterName string) (string, error) {
+	reservedSlots := 2 + uuidLength // 2 dashs + 6 character UUID string
+
+	slotsPerSeg := (validation.DNS1123SubdomainMaxLength - reservedSlots) / 2
+	uniqueName := fmt.Sprintf("%s-%s-%s",
+		CRPName[:minInt(slotsPerSeg, len(CRPName))],
+		clusterName[:minInt(slotsPerSeg, len(clusterName))],
+		uuid.NewUUID()[:uuidLength],
+	)
+
+	if errs := validation.IsDNS1123Subdomain(uniqueName); len(errs) != 0 {
+		// Do a sanity check here; normally this would not occur.
+		return "", fmt.Errorf("failed to format a unique RFC 1123 DNS subdomain name with namespace %s, name %s: %v", CRPName, clusterName, errs)
+	}
+	return uniqueName, nil
+}
diff --git a/pkg/scheduler/framework/uniquename/uniquename_test.go b/pkg/scheduler/framework/uniquename/uniquename_test.go
new file mode 100644
index 000000000..76b75c4b7
--- /dev/null
+++ b/pkg/scheduler/framework/uniquename/uniquename_test.go
@@ -0,0 +1,79 @@
+/*
+Copyright (c) Microsoft Corporation.
+Licensed under the MIT license.
+*/
+
+package uniquename
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+const (
+	crpName     = "app"
+	clusterName = "bravelion"
+
+	longName = "c7t2c6oppjnryqcihwweexeobs7tlmf08ha4qb5htc4cifzpalhb5ec2lbh3" +
+		"j73reciaz2f0jfd2rl5qba6rzuuwgyw6d9e6la19bo89k41lphln4s4dy1gr" +
+		"h1dvua17iu4ro61dxo91ayovns8cgnmshlsflmi68e3najm7dw5dqe17pih7" +
+		"up0dtyvrqxyp90sxedbf"
+)
+
+// TO-DO (chenyu1): Expand the test cases as development proceeds.
+
+// TestClusterResourceBindingUniqueName tests the ClusterResourceBindingUniqueName function.
+func TestClusterResourceBindingUniqueName(t *testing.T) {
+	testCases := []struct {
+		name           string
+		crpName        string
+		clusterName    string
+		wantPrefix     string
+		wantLength     int
+		expectedToFail bool
+	}{
+		{
+			name:        "valid name",
+			crpName:     crpName,
+			clusterName: clusterName,
+			wantPrefix:  fmt.Sprintf("%s-%s", crpName, clusterName),
+			wantLength:  len(crpName) + len(clusterName) + 2 + uuidLength,
+		},
+		{
+			name:        "valid name (truncated)",
+			crpName:     longName,
+			clusterName: longName,
+			wantPrefix:  fmt.Sprintf("%s-%s", longName[:122], longName[:122]),
+			wantLength:  252,
+		},
+		{
+			name:           "invalid name",
+			crpName:        crpName,
+			clusterName:    clusterName + "!",
+			expectedToFail: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			name, err := NewClusterResourceBindingName(tc.crpName, tc.clusterName)
+
+			if tc.expectedToFail {
+				if err == nil {
+					t.Errorf("ClusterResourceBindingUniqueName(%s, %s) = %v, %v, want error", tc.crpName, tc.clusterName, name, err)
+				}
+				return
+			}
+			if err != nil {
+				t.Errorf("ClusterResourceBindingUniqueName(%s, %s) = %v, %v, want no error", tc.crpName, tc.clusterName, name, err)
+			}
+			if !strings.HasPrefix(name, tc.wantPrefix) {
+				t.Errorf("ClusterResourceBindingUniqueName(%s, %s) = %s, want to have prefix %s", tc.crpName, tc.clusterName, name, tc.wantPrefix)
+			}
+			if len(name) != tc.wantLength {
+				t.Errorf("ClusterResourceBindingUniqueName(%s, %s) = %s, want to have length %d", tc.crpName, tc.clusterName, name, tc.wantLength)
+			}
+		})
+	}
+}