add detached container creation ability to base host (#3986)

packages/hosts/base-host/src/host.ts

@@ -3,6 +3,7 @@
  * Licensed under the MIT License.
  */
 
+import assert from "assert";
 import { IFluidObject } from "@fluidframework/core-interfaces";
 import {
     IFluidCodeDetails,
@@ -73,6 +74,44 @@ export class BaseHost {
         return container;
     }
 
+    /**
+     * Used to create a detached container from code details.
+     * @param codeDetails - codeDetails used to create detached container.
+     */
+    public async createContainer(codeDetails: IFluidCodeDetails): Promise<Container> {
+        const loader = await this.getLoader();
+        const container = await loader.createDetachedContainer(codeDetails);
+
+        assert(container.hasNullRuntime() === false, "Detached container should never have null runtime");
+        return container;
+    }
+
+    /**
+     * Used to create a detached container from snapshot of another detached container.
+     * @param snapshot - Snapshot of detached container.
+     */
+    public async rehydrateContainer(snapshot: string): Promise<Container> {
+        const loader = await this.getLoader();
+        const container = await loader.rehydrateDetachedContainerFromSnapshot(snapshot);
+
+        assert(container.hasNullRuntime() === false, "Detached container should never have null runtime");
+        return container;
+    }
+
+    public async requestFluidObjectFromContainer(container: Container, url: string) {
+        const response = await container.request({ url });
+
+        if (response.status !== 200 ||
+            !(
+                response.mimeType === "fluid/component" ||
+                response.mimeType === "fluid/object"
+            )) {
+            return undefined;
+        }
+
+        return response.value as IFluidObject;
+    }
+
     public async requestFluidObject(url: string) {
         const loader = await this.getLoader();
         const response = await loader.request({ url });