Invoke workflows via the SDK (#14040)

* Refactor `_makeRequest` to accept an optional `baseURL` argument, so
  that it can target URLs other than the API
* Implement `invokeWorkflow` to make a request to the HTTP interface of
  a workflow
* Make OAuth client optional

Author: jverce

packages/sdk/src/server/index.ts

@@ -258,6 +258,11 @@ interface RequestOptions extends Omit<RequestInit, "headers"> {
    * Headers to include in the request.
    */
   headers?: Record<string, string>;
+
+  /**
+   * The URL to make the request to.
+   */
+  baseURL?: string;
 }
 
 /**
@@ -284,7 +289,7 @@ class ServerClient {
   environment?: string;
   secretKey: string;
   publicKey: string;
-  oauthClient: ClientCredentials;
+  oauthClient?: ClientCredentials;
   oauthToken?: AccessToken;
   baseURL: string;
 
@@ -339,6 +344,10 @@ class ServerClient {
   }
 
   async _oauthAuthorizationHeader(): Promise<string> {
+    if (!this.oauthClient) {
+      throw new Error("OAuth client not configured");
+    }
+
     if (!this.oauthToken || this.oauthToken.expired()) {
       this.oauthToken = await this.oauthClient.getToken({});
     }
@@ -364,9 +373,10 @@ class ServerClient {
       headers: customHeaders,
       body,
       method = "GET",
+      baseURL = this.baseURL,
       ...fetchOpts
     } = opts;
-    const url = new URL(`${this.baseURL}${path}`);
+    const url = new URL(`${baseURL}${path}`);
 
     if (params) {
       Object.entries(params).forEach(([
@@ -615,4 +625,51 @@ class ServerClient {
       method: "GET",
     });
   }
+
+  /**
+   * Invokes a workflow using the URL of its HTTP interface(s), by sending an
+   * HTTP POST request with the provided body.
+   *
+   * @param url - The URL of the workflow's HTTP interface.
+   * @param opts - The options for the request.
+   * @param opts.body - The body of the request. It must be a JSON-serializable
+   * value (e.g. an object, `null`, a string, etc.).
+   * @param opts.headers - The headers to include in the request. Note that the
+   * `Authorization` header will always be set with an OAuth access token
+   * retrieved by the client.
+   *
+   * @returns A promise resolving to the response from the workflow.
+   *
+   * @example
+   * ```typescript
+   * const response: JSON = await client.invokeWorkflow(
+   *   "https://eoy64t2rbte1u2p.m.pipedream.net",
+   *   {
+   *     body: {
+   *       foo: 123,
+   *       bar: "abc",
+   *       baz: null,
+   *     },
+   *     headers: {
+   *       "Accept": "application/json",
+   *     },
+   *   },
+   * );
+   */
+  async invokeWorkflow(url: string, opts: RequestOptions = {}): Promise<unknown> {
+    const {
+      body = null,
+      headers = {},
+    } = opts;
+
+    return this._makeRequest("", {
+      baseURL: url,
+      method: "POST",
+      headers: {
+        ...headers,
+        "Authorization": await this._oauthAuthorizationHeader(),
+      },
+      body: JSON.stringify(body),
+    });
+  }
 }