Implement getBackend.

Author: annajowang

Diff for: src/apphosting/backend.ts

@@ -17,7 +17,7 @@ import { Backend, BackendOutputOnlyFields, API_VERSION } from "../gcp/apphosting
 import { addServiceAccountToRoles } from "../gcp/resourceManager";
 import * as iam from "../gcp/iam";
 import { FirebaseError, getErrStatus, getError } from "../error";
-import { promptOnce } from "../prompt";
+import { promptOnce, confirm } from "../prompt";
 import { DEFAULT_LOCATION } from "./constants";
 import { ensure } from "../ensureApiEnabled";
 import * as deploymentTool from "../deploymentTool";
@@ -474,3 +474,51 @@ export async function getBackendForAmbiguousLocation(
   });
   return backendsByLocation.get(location)!;
 }
+
+/**
+ * Fetches a backend from the server. If there are multiple backends with the name, it will fetch the first
+ * in the list and warn the user that there are other backends with the same name that need to be deleted. If
+ * the force option is specified nad multiple backends have the same name, it throws an error.
+ */
+export async function getBackend(
+  projectId: string,
+  backendId: string,
+  force?: boolean,
+): Promise<apphosting.Backend> {
+  // TODO: call apphosting.getBackend() once all duplicate named backends have been deleted.
+  let { unreachable, backends } = await apphosting.listBackends(projectId, "-");
+  backends = backends.filter(
+    (backend) => apphosting.parseBackendName(backend.name).id === backendId,
+  );
+  if (backends.length > 0) {
+    if (backends.length > 1) {
+      logWarning(
+        `You have multiple backends with the same ${backendId} ID. This is no longer supported. ` +
+        "Please delete and recreate any backends that share an ID with another backend."
+      )
+      if (force) {
+        throw new FirebaseError(
+          `Force cannot be used when multiple backends share the same ID`,
+        );
+      };
+      const options = { force: force, nonInteractive: false };
+      const confirmed = await confirm({
+	...options,
+	message: `Using backend ${backends[0].name} continue?`,
+      });
+      if (!confirmed) {
+	throw new FirebaseError("Command aborted.");
+      }
+    }
+    return backends[0];
+  }
+  if (unreachable && unreachable.length !== 0) {
+    logWarning(
+      `Backends with the following primary regions are unreachable: ${unreachable}.\n` +
+	"If your backend is in one of these regions, please try again later."
+    );
+  };
+  throw new FirebaseError(
+    `No backend named ${backendId} found.`,
+  );
+}