add documentation and custom uri for imagen in google-ai

Author: David Motsonashvili

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/FirebaseGenAI.kt

@@ -20,20 +20,32 @@ import com.google.firebase.Firebase
 import com.google.firebase.FirebaseApp
 import com.google.firebase.app
 
+/** Entry point for all Firebase Generative AI functionality. */
 public class FirebaseGenAI {
+
+  /**
+   * Returns the [FirebaseVertexAI] instance for the provided [FirebaseApp] and [location].
+   *
+   * @param location location identifier, defaults to `us-central1`; see available
+   * [Vertex AI regions](https://firebase.google.com/docs/vertex-ai/locations?platform=android#available-locations)
+   * .
+   */
   @JvmOverloads
   public fun vertexAI(
     app: FirebaseApp = Firebase.app,
     location: String = "us-central1",
   ): FirebaseVertexAI = FirebaseVertexAI.getInstance(app, location)
 
+  /** Returns the [FirebaseGoogleAI] instance for the provided [FirebaseApp]. */
   @JvmOverloads
   public fun googleAI(app: FirebaseApp = Firebase.app): FirebaseGoogleAI =
     FirebaseGoogleAI.getInstance(app)
 
+  /** Returns the [FirebaseGoogleAI] instance of the default [FirebaseApp]. */
   public val googleAI: FirebaseGoogleAI
     get() = FirebaseGoogleAI.instance
 
+  /** Returns the [FirebaseVertexAI] instance of the default [FirebaseApp]. */
   public val vertexAI: FirebaseVertexAI
     get() = FirebaseVertexAI.instance
 

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/FirebaseGoogleAI.kt

@@ -30,6 +30,7 @@ import com.google.firebase.vertexai.type.SafetySetting
 import com.google.firebase.vertexai.type.Tool
 import com.google.firebase.vertexai.type.ToolConfig
 
+/** Entry point for all _Google AI in Vertex for Firebase_ functionality. */
 public class FirebaseGoogleAI internal constructor(private val proxy: FirebaseVertexAI) {
 
   /**

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/FirebaseVertexAI.kt

@@ -109,11 +109,18 @@ internal constructor(
     safetySettings: ImagenSafetySettings? = null,
     requestOptions: RequestOptions = RequestOptions(),
   ): ImagenModel {
+    val modelUri =
+      when (backend) {
+        GenerativeBackend.VERTEX_AI ->
+          "projects/${firebaseApp.options.projectId}/locations/${location}/publishers/google/models/${modelName}"
+        GenerativeBackend.GOOGLE_AI ->
+          "projects/${firebaseApp.options.projectId}/models/${modelName}"
+      }
     if (location.trim().isEmpty() || location.contains("/")) {
       throw InvalidLocationException(location)
     }
     return ImagenModel(
-      "projects/${firebaseApp.options.projectId}/locations/${location}/publishers/google/models/${modelName}",
+      modelUri,
       firebaseApp.options.apiKey,
       generationConfig,
       safetySettings,