Add Workflow binding module

src/cloudflare/internal/test/workflows/BUILD.bazel

@@ -0,0 +1,7 @@
+load("//:build/wd_test.bzl", "wd_test")
+
+wd_test(
+    src = "workflows-api-test.wd-test",
+    args = ["--experimental"],
+    data = glob(["*.js"]),
+)

src/cloudflare/internal/test/workflows/workflows-api-test.js

@@ -0,0 +1,21 @@
+// Copyright (c) 2024 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
+import * as assert from 'node:assert';
+
+export const tests = {
+  async test(_, env) {
+    {
+      // Test create instance
+      const instance = await env.workflow.create('foo', { bar: 'baz' });
+      assert.deepStrictEqual(instance.id, 'foo');
+    }
+
+    {
+      // Test get instance
+      const instance = await env.workflow.get('bar');
+      assert.deepStrictEqual(instance.id, 'bar');
+    }
+  },
+};

src/cloudflare/internal/test/workflows/workflows-api-test.wd-test

@@ -0,0 +1,36 @@
+using Workerd = import "/workerd/workerd.capnp";
+
+const unitTests :Workerd.Config = (
+  services = [
+    ( name = "workflows-api-test",
+      worker = (
+        modules = [
+          (name = "worker", esModule = embed "workflows-api-test.js")
+        ],
+        compatibilityDate = "2024-09-02",
+        compatibilityFlags = ["experimental", "nodejs_compat"],
+        bindings = [
+        (
+          name = "workflow",
+          wrapped = (
+            moduleName = "cloudflare-internal:workflows-api",
+            innerBindings = [(
+              name = "fetcher",
+              service = "workflows-mock"
+            )],
+          )
+        )
+        ],
+      )
+    ),
+    ( name = "workflows-mock",
+      worker = (
+        compatibilityDate = "2024-09-02",
+        compatibilityFlags = ["experimental", "nodejs_compat"],
+        modules = [
+          (name = "worker", esModule = embed "workflows-mock.js")
+        ],
+      )
+    )
+  ]
+);

src/cloudflare/internal/test/workflows/workflows-mock.js

@@ -0,0 +1,41 @@
+// Copyright (c) 2024 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
+export default {
+  async fetch(request, env, ctx) {
+    const data = await request.json();
+
+    if (request.url.includes('/get') && request.method === 'POST') {
+      return Response.json(
+        {
+          result: {
+            instanceId: data.id,
+          },
+        },
+        {
+          status: 200,
+          headers: {
+            'content-type': 'application/json',
+          },
+        }
+      );
+    }
+
+    if (request.url.includes('/create') && request.method === 'POST') {
+      return Response.json(
+        {
+          result: {
+            instanceId: data.id,
+          },
+        },
+        {
+          status: 201,
+          headers: {
+            'content-type': 'application/json',
+          },
+        }
+      );
+    }
+  },
+};

src/cloudflare/internal/workflows-api.ts

@@ -1,12 +1,121 @@
+// Copyright (c) 2024 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
 export class NonRetryableError extends Error {
-  // `__brand` is needed for Workflows' engine to validate if the user returned a NonRetryableError
-  // this provides better DX because they can just extend NonRetryableError for their own Errors
-  // and override name.
-  // This needs to be a public field because it's serialized over RPC to the Workflows' engine
+  // `__brand` is how engine validates that the user returned a `NonRetryableError`
+  // imported from "cloudflare:workflows"
+  // This enables them to extend NonRetryableError for their own Errors
+  // as well by overriding name
+  // Private fields are not serialized over RPC
   public readonly __brand: string = 'NonRetryableError';
 
   public constructor(message: string, name = 'NonRetryableError') {
     super(message);
     this.name = name;
   }
 }
+
+interface Fetcher {
+  fetch: typeof fetch;
+}
+
+async function callFetcher<T>(
+  fetcher: Fetcher,
+  path: string,
+  body: object
+): Promise<T> {
+  const res = await fetcher.fetch(`http://workflow-binding.local${path}`, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'X-Version': '1',
+    },
+    body: JSON.stringify(body),
+  });
+
+  const response = (await res.json()) as {
+    result: T;
+    error?: WorkflowError;
+  };
+
+  if (res.ok) {
+    return response.result;
+  } else {
+    throw new Error(response.error?.message);
+  }
+}
+
+class InstanceImpl implements Instance {
+  private readonly fetcher: Fetcher;
+  public readonly id: string;
+
+  public constructor(id: string, fetcher: Fetcher) {
+    this.id = id;
+    this.fetcher = fetcher;
+  }
+
+  public async pause(): Promise<void> {
+    await callFetcher(this.fetcher, '/pause', {
+      id: this.id,
+    });
+  }
+  public async resume(): Promise<void> {
+    await callFetcher(this.fetcher, '/resume', {
+      id: this.id,
+    });
+  }
+
+  public async abort(): Promise<void> {
+    await callFetcher(this.fetcher, '/abort', {
+      id: this.id,
+    });
+  }
+
+  public async restart(): Promise<void> {
+    await callFetcher(this.fetcher, '/restart', {
+      id: this.id,
+    });
+  }
+
+  public async status(): Promise<InstanceStatus> {
+    const result = await callFetcher<InstanceStatus>(this.fetcher, '/status', {
+      id: this.id,
+    });
+    return result;
+  }
+}
+
+class WorkflowImpl {
+  private readonly fetcher: Fetcher;
+
+  public constructor(fetcher: Fetcher) {
+    this.fetcher = fetcher;
+  }
+
+  public async get(id: string): Promise<Instance> {
+    const result = await callFetcher<{ instanceId: string }>(
+      this.fetcher,
+      '/get',
+      { id }
+    );
+
+    return new InstanceImpl(result.instanceId, this.fetcher);
+  }
+
+  public async create(id: string, params: object): Promise<Instance> {
+    const result = await callFetcher<{ instanceId: string }>(
+      this.fetcher,
+      '/create',
+      { id, params }
+    );
+
+    return new InstanceImpl(result.instanceId, this.fetcher);
+  }
+}
+
+export function makeBinding(env: { fetcher: Fetcher }): Workflow {
+  return new WorkflowImpl(env.fetcher);
+}
+
+export default makeBinding;

src/cloudflare/internal/workflows.d.ts

@@ -0,0 +1,87 @@
+// Copyright (c) 2022-2023 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
+/*****************************
+ *
+ * NOTE: this is copy & pasted from the types/ folder, as when bazel
+ * runs it doesn't have access to that directly and thusly is sad.
+ * TODO: come up with a better system for this.
+ *
+ ****************************** /
+
+/**
+ * NonRetryableError allows for a user to throw a fatal error
+ * that makes a Workflow instance fail immediately without triggering a retry
+ */
+declare abstract class NonRetryableError extends Error {
+  /**
+   * `__brand` is used to differentiate between `NonRetryableError` and `Error`
+   * and is omitted from the constructor because users should not set it
+   */
+  public constructor(message: string, name?: string);
+}
+
+declare abstract class Workflow {
+  /**
+   * Get a handle to an existing instance of the Workflow.
+   * @param id Id for the instance of this Workflow
+   * @returns A promise that resolves with a handle for the Instance
+   */
+  public get(id: string): Promise<Instance>;
+
+  /**
+   * Create a new instance and return a handle to it. If a provided id exists, an error will be thrown.
+   * @param id Id to create the instance of this Workflow with
+   * @param params The payload to send over to this instance
+   * @returns A promise that resolves with a handle for the Instance
+   */
+  public create(id: string, params: object): Promise<Instance>;
+}
+
+type InstanceStatus = {
+  status:
+    | 'queued'
+    | 'running'
+    | 'paused'
+    | 'errored'
+    | 'terminated'
+    | 'complete'
+    | 'unknown';
+  error?: string;
+  output?: object;
+};
+
+interface WorkflowError {
+  code?: number;
+  message: string;
+}
+
+declare abstract class Instance {
+  public id: string;
+
+  /**
+   * Pause the instance.
+   */
+  public pause(): Promise<void>;
+
+  /**
+   * Resume the instance. If it is already running, an error will be thrown.
+   */
+  public resume(): Promise<void>;
+
+  /**
+   * Abort the instance. If it is errored, terminated or complete, an error will be thrown.
+   */
+  public abort(): Promise<void>;
+
+  /**
+   * Restart the instance.
+   */
+  public restart(): Promise<void>;
+
+  /**
+   * Returns the current status of the instance.
+   */
+  public status(): Promise<InstanceStatus>;
+}

src/cloudflare/workflows.ts

@@ -1 +1,5 @@
+// Copyright (c) 2024 Cloudflare, Inc.
+// Licensed under the Apache 2.0 license found in the LICENSE file or at:
+//     https://opensource.org/licenses/Apache-2.0
+
 export { NonRetryableError } from 'cloudflare-internal:workflows-api';