Add replicate.stream method

README.md

@@ -172,6 +172,49 @@ const input = { prompt: "a 19th century portrait of a raccoon gentleman wearing
 const output = await replicate.run(model, { input });
 ```
 
+### `replicate.stream`
+
+Run a model and stream its output. Unlike [`replicate.prediction.create`](#replicatepredictionscreate), this method returns only the prediction output rather than the entire prediction object.
+
+```js
+for await (const event of replicate.stream(identifier, options)) { /* ... */ }
+```
+
+| name                            | type     | description                                                                                                                                              |
+| ------------------------------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `identifier`                    | string   | **Required**. The model version identifier in the format `{owner}/{name}` or `{owner}/{name}:{version}`, for example `meta/llama-2-70b-chat`             |
+| `options.input`                 | object   | **Required**. An object with the model inputs.                                                                                                           |
+| `options.webhook`               | string   | An HTTPS URL for receiving a webhook when the prediction has new output                                                                                  |
+| `options.webhook_events_filter` | string[] | An array of events which should trigger [webhooks](https://replicate.com/docs/webhooks). Allowable values are `start`, `output`, `logs`, and `completed` |
+| `options.signal`                | object   | An [AbortSignal](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) to cancel the prediction                                                  |
+
+Throws `Error` if the prediction failed.
+
+Returns `AsyncGenerator<ServerSentEvent>` which yields the events of running the model.
+
+Example:
+
+```js
+for await (const event of replicate.stream("meta/llama-2-70b-chat")) {
+    process.stdout.write(`${event}`);
+}
+```
+
+### Server-sent events
+
+A stream generates server-sent events with the following properties:
+
+| name    | type   | description                                                                  |
+| ------- | ------ | ---------------------------------------------------------------------------- |
+| `event` | string | The type of event. Possible values are `output`, `logs`, `error`, and `done` |
+| `data`  | string | The event data                                                               |
+| `id`    | string | The event id                                                                 |
+| `retry` | number | The number of milliseconds to wait before reconnecting to the server         |
+
+As the prediction runs, the generator yields `output` and `logs` events. If an error occurs, the generator yields an `error` event with a JSON object containing the error message set to the `data` property. When the prediction is done, the generator yields a `done` event with an empty JSON object set to the `data` property.
+
+Events with the `output` event type have their `toString()` method overridden to return the event data as a string. Other event types return an empty string.
+
 ### `replicate.models.get`
 
 Get metadata for a public model or a private model that you own.

index.d.ts

@@ -75,6 +75,13 @@ declare module "replicate" {
     results: T[];
   }
 
+  export interface ServerSentEvent {
+    event: string;
+    data: string;
+    id?: string;
+    retry?: number;
+  }
+
   export default class Replicate {
     constructor(options?: {
       auth?: string;
@@ -103,6 +110,16 @@ declare module "replicate" {
       progress?: (prediction: Prediction) => void
     ): Promise<object>;
 
+    stream(
+      identifier: `${string}/${string}` | `${string}/${string}:${string}`,
+      options: {
+        input: object;
+        webhook?: string;
+        webhook_events_filter?: WebhookEventType[];
+        signal?: AbortSignal;
+      }
+    ): AsyncGenerator<ServerSentEvent>;
+
     request(
       route: string | URL,
       options: {

index.js

@@ -1,5 +1,6 @@
 const ApiError = require("./lib/error");
 const ModelVersionIdentifier = require("./lib/identifier");
+const { Stream } = require("./lib/stream");
 const { withAutomaticRetries } = require("./lib/util");
 
 const collections = require("./lib/collections");
@@ -235,6 +236,47 @@ class Replicate {
     return response;
   }
 
+  /**
+   * Stream a model and wait for its output.
+   *
+   * @param {string} identifier - Required. The model version identifier in the format "{owner}/{name}:{version}"
+   * @param {object} options
+   * @param {object} options.input - Required. An object with the model inputs
+   * @param {string} [options.webhook] - An HTTPS URL for receiving a webhook when the prediction has new output
+   * @param {string[]} [options.webhook_events_filter] - You can change which events trigger webhook requests by specifying webhook events (`start`|`output`|`logs`|`completed`)
+   * @param {AbortSignal} [options.signal] - AbortSignal to cancel the prediction
+   * @throws {Error} If the prediction failed
+   * @yields {ServerSentEvent} Each streamed event from the prediction
+   */
+  async *stream(ref, options) {
+    const { wait, ...data } = options;
+
+    const identifier = ModelVersionIdentifier.parse(ref);
+
+    let prediction;
+    if (identifier.version) {
+      prediction = await this.predictions.create({
+        ...data,
+        version: identifier.version,
+        stream: true,
+      });
+    } else {
+      prediction = await this.models.predictions.create(
+        identifier.owner,
+        identifier.name,
+        { ...data, stream: true }
+      );
+    }
+
+    if (prediction.urls && prediction.urls.stream) {
+      const { signal } = options;
+      const stream = new Stream(prediction.urls.stream, { signal });
+      yield* stream;
+    } else {
+      throw new Error("Prediction does not support streaming");
+    }
+  }
+
   /**
    * Paginate through a list of results.
    *

lib/stream.js

@@ -0,0 +1,123 @@
+const { Readable } = require("stream");
+
+/**
+ * A server-sent event.
+ */
+class ServerSentEvent {
+  /**
+   * Create a new server-sent event.
+   *
+   * @param {string} event The event name.
+   * @param {string} data The event data.
+   * @param {string} id The event ID.
+   * @param {number} retry The retry time.
+   */
+  constructor(event, data, id, retry) {
+    this.event = event;
+    this.data = data;
+    this.id = id;
+    this.retry = retry;
+  }
+
+  /**
+   * Convert the event to a string.
+   */
+  toString() {
+    if (this.event === "output") {
+      return this.data;
+    }
+
+    return "";
+  }
+}
+
+/**
+ * A stream of server-sent events.
+ */
+class Stream extends Readable {
+  /**
+   * Create a new stream of server-sent events.
+   *
+   * @param {string} url The URL to connect to.
+   * @param {object} options The fetch options.
+   */
+  constructor(url, options) {
+    super();
+    this.url = url;
+    this.options = options;
+
+    this.event = null;
+    this.data = [];
+    this.lastEventId = null;
+    this.retry = null;
+  }
+
+  decode(line) {
+    if (!line) {
+      if (!this.event && !this.data.length && !this.lastEventId) {
+        return null;
+      }
+
+      const sse = new ServerSentEvent(
+        this.event,
+        this.data.join("\n"),
+        this.lastEventId
+      );
+
+      this.event = null;
+      this.data = [];
+      this.retry = null;
+
+      return sse;
+    }
+
+    if (line.startsWith(":")) {
+      return null;
+    }
+
+    const [field, value] = line.split(": ");
+    if (field === "event") {
+      this.event = value;
+    } else if (field === "data") {
+      this.data.push(value);
+    } else if (field === "id") {
+      this.lastEventId = value;
+    }
+
+    return null;
+  }
+
+  async *[Symbol.asyncIterator]() {
+    const response = await fetch(this.url, {
+      ...this.options,
+      headers: {
+        Accept: "text/event-stream",
+      },
+    });
+
+    for await (const chunk of response.body) {
+      const decoder = new TextDecoder("utf-8");
+      const text = decoder.decode(chunk);
+      const lines = text.split("\n");
+      for (const line of lines) {
+        const sse = this.decode(line);
+        if (sse) {
+          if (sse.event === "error") {
+            throw new Error(sse.data);
+          }
+
+          yield sse;
+
+          if (sse.event === "done") {
+            return;
+          }
+        }
+      }
+    }
+  }
+}
+
+module.exports = {
+  Stream,
+  ServerSentEvent,
+};