add: validation of sucscriptionID

validator/subscription.go

@@ -0,0 +1,26 @@
+package validator
+
+import "unicode"
+
+// Check empty strings, control characters (including NUL),
+// Check characters that would affect URL parsing such as '/', '?', '#'.
+func IsValidSubscriptionID(id string) bool {
+    if len(id) == 0 {
+        return false
+    }
+
+    for _, r := range id {
+        if r <= 31 || r == 127 { // control characters
+            return false
+        }
+        switch r {
+        case '/', '?', '#':
+            return false
+        }
+        if unicode.IsSpace(r) {
+            return false
+        }
+    }
+
+    return true
+}

validator/subscription_test.go

@@ -0,0 +1,57 @@
+package validator
+
+import (
+    "testing"
+)
+
+func TestIsValidSubscriptionID(t *testing.T) {
+    type Args struct {
+        id string
+    }
+
+    type testCase struct {
+        name string
+        Args Args
+        Want bool
+    }
+
+    runTests := func(t *testing.T, tests []testCase) {
+        t.Helper()
+        for _, tt := range tests {
+            t.Run(tt.name, func(t *testing.T) {
+                if got := IsValidSubscriptionID(tt.Args.id); got != tt.Want {
+                    t.Errorf("IsValidSubscriptionID() = %v, Want %v (input: %q)", got, tt.Want, tt.Args.id)
+                }
+            })
+        }
+    }
+
+    t.Run("Valid", func(t *testing.T) {
+        tests := []testCase{
+            {"Numeric", Args{"123"}, true},
+            {"AlphaNumeric", Args{"sub-abc-123"}, true},
+            {"LongID", Args{"a-very-long-subscription-id-0123456789"}, true},
+        }
+        runTests(t, tests)
+    })
+
+    t.Run("Invalid_ControlChars", func(t *testing.T) {
+        tests := []testCase{
+            {"Empty", Args{""}, false},
+            {"NullByte", Args{"abc\x00def"}, false},
+            {"Ctrl1", Args{"abc\x01"}, false},
+            {"DEL", Args{"abc\x7f"}, false},
+            {"ContainsSpace", Args{"sub id"}, false},
+        }
+        runTests(t, tests)
+    })
+
+    t.Run("Invalid_URLChars", func(t *testing.T) {
+        tests := []testCase{
+            {"Slash", Args{"a/b"}, false},
+            {"Question", Args{"a?b"}, false},
+            {"Hash", Args{"a#b"}, false},
+        }
+        runTests(t, tests)
+    })
+}