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Interactive Story Generator

The following code snippets provide example implementations of Text-to-Speech (TTS) functionality in an interactive story generator application using Next.js with Mastra as a separate backend integration. This example demonstrates how to use the Mastra client-js SDK to connect to your Mastra backend. For more details on integrating Mastra with Next.js, please refer to our Integrate with Next.js documentation.

Creating an Agent with TTS Capabilities​

The following example shows how to set up a story generator agent with TTS capabilities on the backend:

src/mastra/agents/index.ts
import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { OpenAIVoice } from "@mastra/voice-openai";
import { Memory } from "@mastra/memory";

const instructions = `
    You are an Interactive Storyteller Agent. Your job is to create engaging
    short stories with user choices that influence the narrative. // omitted for brevity
`;

export const storyTellerAgent = new Agent({
  name: "Story Teller Agent",
  instructions: instructions,
  model: openai("gpt-4o"),
  voice: new OpenAIVoice(),
});

Registering the Agent with Mastra​

This snippet demonstrates how to register the agent with your Mastra instance:

src/mastra/index.ts
import { PinoLogger } from "@mastra/loggers";
import { Mastra } from "@mastra/core/mastra";
import { storyTellerAgent } from "./agents";

export const mastra = new Mastra({
  agents: { storyTellerAgent },
  logger: new PinoLogger({
    name: "Mastra",
    level: "info",
  }),
});

Connecting to Mastra from the Frontend​

Here we use the Mastra Client SDK to interact with our Mastra server. For more information about the Mastra Client SDK, check out the documentation.

src/app/page.tsx
import { MastraClient } from "@mastra/client-js";

export const mastraClient = new MastraClient({
  baseUrl: "http://localhost:4111", // Replace with your Mastra backend URL
});

Generating Story Content and Converting to Speech​

This example demonstrates how to get a reference to a Mastra agent, generate story content based on user input, and then convert that content to speech:

/app/components/StoryManager.tsx
const handleInitialSubmit = async (formData: FormData) => {
  setIsLoading(true);
  try {
    const agent = mastraClient.getAgent("storyTellerAgent");
    const message = `Current phase: BEGINNING. Story genre: ${formData.genre}, Protagonist name: ${formData.protagonistDetails.name}, Protagonist age: ${formData.protagonistDetails.age}, Protagonist gender: ${formData.protagonistDetails.gender}, Protagonist occupation: ${formData.protagonistDetails.occupation}, Story Setting: ${formData.setting}`;
    const storyResponse = await agent.generate({
      messages: [{ role: "user", content: message }],
      threadId: storyState.threadId,
      resourceId: storyState.resourceId,
    });

    const storyText = storyResponse.text;

    const audioResponse = await agent.voice.speak(storyText);

    if (!audioResponse.body) {
      throw new Error("No audio stream received");
    }

    const audio = await readStream(audioResponse.body);

    setStoryState((prev) => ({
      phase: "beginning",
      threadId: prev.threadId,
      resourceId: prev.resourceId,
      content: {
        ...prev.content,
        beginning: storyText,
      },
    }));

    setAudioBlob(audio);
    return audio;
  } catch (error) {
    console.error("Error generating story beginning:", error);
  } finally {
    setIsLoading(false);
  }
};

Playing the Audio​

This snippet demonstrates how to handle text-to-speech audio playback by monitoring for new audio data. When audio is received, the code creates a browser-playable URL from the audio blob, assigns it to an audio element, and attempts to play it automatically:

/app/components/StoryManager.tsx
useEffect(() => {
  if (!audioRef.current || !audioData) return;

  // Store a reference to the HTML audio element
  const currentAudio = audioRef.current;

  // Convert the Blob/File audio data from Mastra into a URL the browser can play
  const url = URL.createObjectURL(audioData);

  const playAudio = async () => {
    try {
      currentAudio.src = url;
      await currentAudio.load();
      await currentAudio.play();
      setIsPlaying(true);
    } catch (error) {
      console.error("Auto-play failed:", error);
    }
  };

  playAudio();

  return () => {
    if (currentAudio) {
      currentAudio.pause();
      currentAudio.src = "";
      URL.revokeObjectURL(url);
    }
  };
}, [audioData]);

You can view the complete implementation of the Interactive Story Generator on our GitHub repository.





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