[PM-28157] Add string extension to prefix URIs with www (#6183)

Co-authored-by: Claude <noreply@anthropic.com>

ui/src/main/kotlin/com/bitwarden/ui/platform/base/util/StringExtensions.kt

@@ -239,6 +239,34 @@ fun String.prefixHttpsIfNecessaryOrNull(): String? =
 fun String.prefixHttpsIfNecessary(): String =
     prefixHttpsIfNecessaryOrNull() ?: this
 
+/**
+ * If the given [String] is a valid URI, "www." will be prepended (or inserted after the scheme
+ * if present) if it is not already present. Otherwise `null` will be returned.
+ *
+ * Examples:
+ * - "example.com" -> "www.example.com"
+ * - "www.example.com" -> "www.example.com"
+ * - "https://example.com" -> "https://www.example.com"
+ * - "https://www.example.com" -> "https://www.example.com"
+ */
+fun String.prefixWwwIfNecessaryOrNull(): String? =
+    when {
+        this.isBlank() || !this.isValidUri() -> null
+        this.startsWith("www.") -> this
+        this.startsWith("http://") || this.startsWith("https://") -> {
+            if ("://www." in this) this else this.replaceFirst("://", "://www.")
+        }
+
+        else -> "www.$this"
+    }
+
+/**
+ * If the given [String] is a valid URI, "www." will be prepended (or inserted after the scheme
+ * if present) if it is not already present. Otherwise the original [String] will be returned.
+ */
+fun String.prefixWwwIfNecessary(): String =
+    prefixWwwIfNecessaryOrNull() ?: this
+
 /**
  * Checks if a string is using base32 digits.
  */

ui/src/test/kotlin/com/bitwarden/ui/platform/base/util/StringExtensionsTest.kt

@@ -281,4 +281,65 @@ class StringExtensionsTest {
     fun `orZeroWidthSpace returns the original value for a non-blank string`() {
         assertEquals("test", "test".orZeroWidthSpace())
     }
+
+    @Suppress("MaxLineLength")
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should prefix www when URI is valid and no scheme and no www`() {
+        val uri = "example.com"
+        val expected = "www.$uri"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should return URI unchanged when starts with www`() {
+        val uri = "www.example.com"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+        assertEquals(uri, actual)
+    }
+
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should prefix www when scheme is http and no www`() {
+        val uri = "http://example.com"
+        val expected = "http://www.example.com"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should prefix www when scheme is https and no www`() {
+        val uri = "https://example.com"
+        val expected = "https://www.example.com"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+        assertEquals(expected, actual)
+    }
+
+    @Suppress("MaxLineLength")
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should return URI unchanged when scheme is http and www is present`() {
+        val uri = "http://www.example.com"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+        assertEquals(uri, actual)
+    }
+
+    @Suppress("MaxLineLength")
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should return URI unchanged when scheme is https and www is present`() {
+        val uri = "https://www.example.com"
+        val actual = uri.prefixWwwIfNecessaryOrNull()
+        assertEquals(uri, actual)
+    }
+
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should return null when URI is empty string`() {
+        val uri = ""
+        assertNull(uri.prefixWwwIfNecessaryOrNull())
+    }
+
+    @Test
+    fun `prefixWwwIfNecessaryOrNull should return null when URI is invalid`() {
+        val invalidUri = "invalid uri"
+        assertNull(invalidUri.prefixWwwIfNecessaryOrNull())
+    }
 }