A cf worker to sumamrize emails even before they hit your inbox. (DOES NOT WORK as there's no way to edit the email content)

index.js

const { default: PostalMime } = require("postal-mime");
const AI_MODEL = "gpt-3.5-turbo";
const OPEN_AI_API_KEY = "YOUR_API_KEY_HERE";

const streamToArrayBuffer = async (stream, streamSize) => {
  const result = new Uint8Array(streamSize);
  let bytesRead = 0;
  const reader = stream.getReader();
  while (bytesRead < streamSize) {
    const { done, value } = await reader.read();
    if (done) {
      break;
    }
    result.set(value, bytesRead);
    bytesRead += value.length;
  }
  return result;
};

const generateSystemMessage = () => {
  return {
    role: "system",
    content: `You are an AI summarizer. Summarize the email below. You will tell us what the email is about and write a small summary. Response format - { "type": "Event Invitation", "summary": Email invitation from John Doe to attend his daughters birthday party on June 1st}`,
  };
};

function generateUserMessage(subject, message) {
  return {
    role: "user",
    content: `Email subject: ${subject} \n Email body: ${message}`,
  };
}

const isKeyInvalid = ({ error }) => {
  return (
    error?.type === "invalid_request_error" && error?.code === "invalid_api_key"
  );
};

const getSummaryfromOpenAi = async (subject, message) => {
  const messages = [
    generateSystemMessage(),
    generateUserMessage(subject, message),
  ];
  const response = await fetch("https://api.openai.com/v1/chat/completions", {
    method: "POST",
    body: JSON.stringify({
      model: AI_MODEL,
      messages,
    }),
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${OPEN_AI_API_KEY}`,
    },
  });
  const completion = await response.json();
  if (isKeyInvalid(completion)) {
    console.error("Invalid OpenAI API key");
  } else {
    const { choices } = completion;
    const { type, summary } = choices[0].message.content;
    const summaryString = `Email type: ${type} \n Email summary: ${summary}`;
    return summaryString;
  }
};

const email = async (message) => {
  try {
    const rawEmail = await streamToArrayBuffer(message.raw, message.rawSize);
    const parser = new PostalMime();
    const parsedEmail = await parser.parse(rawEmail);
    const summaryData = await getSummaryfromOpenAi(parsedEmail.text);
    const emailWithSummary = generateEmailWithSummary(parsedEmail, summaryData);
    const headers = new Headers();
    headers.set("Content-Type", "message/rfc822");
    await message.forward(message.to, { body: emailWithSummary, headers });
    console.log("Email with summary sent");
  } catch (error) {
    console.error(`Error processing email: ${error}`);
  } finally {
    console.log("Email processed");
  }
};

export default {
  email,
};