gmail-to-exchange365/src/server/exchangePusher.ts

Complete Gmail to Exchange 365 migration tool with UI - Migrate emails, attachments, and folders seamlessly

import { Client } from "@microsoft/microsoft-graph-client";
import { EmailMessage } from "./types";

interface MSToken {
  access_token: string;
  refresh_token?: string;
  expires_in?: number;
}

export function getGraphClient(msToken: MSToken) {
  return Client.init({
    authProvider: (done) => {
      done(null, msToken.access_token);
    }
  });
}

export async function uploadEmail(
  client: Client,
  email: EmailMessage,
  folderId: string = "Inbox"
): Promise<void> {
  try {
    const eml = buildMime(email);
    
    // Use the MIME message endpoint
    await client
      .api(`/me/mailFolders/${folderId}/messages`)
      .header("Content-Type", "message/rfc822")
      .post(eml);
  } catch (error: any) {
    // If MIME upload fails, try creating message via Graph API
    if (error.statusCode === 400 || error.statusCode === 415) {
      await uploadEmailAsGraphMessage(client, email, folderId);
    } else {
      throw error;
    }
  }
}

async function uploadEmailAsGraphMessage(
  client: Client,
  email: EmailMessage,
  folderId: string
): Promise<void> {
  const message: any = {
    subject: email.subject,
    from: {
      emailAddress: {
        address: email.from
      }
    },
    toRecipients: email.to.map(addr => ({
      emailAddress: { address: addr }
    })),
    body: {
      contentType: email.htmlBody ? "html" : "text",
      content: email.htmlBody || email.textBody || ""
    },
    receivedDateTime: email.date,
    sentDateTime: email.date
  };

  if (email.cc && email.cc.length > 0) {
    message.ccRecipients = email.cc.map(addr => ({
      emailAddress: { address: addr }
    }));
  }

  if (email.bcc && email.bcc.length > 0) {
    message.bccRecipients = email.bcc.map(addr => ({
      emailAddress: { address: addr }
    }));
  }

  const createdMessage = await client
    .api(`/me/mailFolders/${folderId}/messages`)
    .post(message);

  // Upload attachments separately
  if (email.attachments && email.attachments.length > 0) {
    for (const attachment of email.attachments) {
      await uploadAttachment(client, createdMessage.id, attachment);
    }
  }
}

async function uploadAttachment(
  client: Client,
  messageId: string,
  attachment: { filename: string; mimeType: string; data: Buffer }
): Promise<void> {
  try {
    await client
      .api(`/me/messages/${messageId}/attachments`)
      .post({
        "@odata.type": "#microsoft.graph.fileAttachment",
        name: attachment.filename,
        contentType: attachment.mimeType,
        contentBytes: attachment.data.toString("base64")
      });
  } catch (error: any) {
    console.error(`Error uploading attachment ${attachment.filename}:`, error.message);
  }
}

export function buildMime(email: EmailMessage): Buffer {
  let mime = "";

  // Headers
  mime += `From: ${email.from}\r\n`;
  mime += `To: ${email.to.join(", ")}\r\n`;
  
  if (email.cc && email.cc.length > 0) {
    mime += `Cc: ${email.cc.join(", ")}\r\n`;
  }
  
  if (email.bcc && email.bcc.length > 0) {
    mime += `Bcc: ${email.bcc.join(", ")}\r\n`;
  }
  
  mime += `Subject: ${email.subject}\r\n`;
  mime += `Date: ${email.date}\r\n`;
  mime += `MIME-Version: 1.0\r\n`;

  const boundary = "----=_Part_" + Date.now();
  mime += `Content-Type: multipart/mixed; boundary="${boundary}"\r\n\r\n`;

  // Body
  mime += `--${boundary}\r\n`;
  if (email.htmlBody) {
    mime += `Content-Type: text/html; charset=utf-8\r\n`;
    mime += `Content-Transfer-Encoding: 7bit\r\n\r\n`;
    mime += `${email.htmlBody}\r\n\r\n`;
  } else if (email.textBody) {
    mime += `Content-Type: text/plain; charset=utf-8\r\n`;
    mime += `Content-Transfer-Encoding: 7bit\r\n\r\n`;
    mime += `${email.textBody}\r\n\r\n`;
  }

  // Attachments
  for (const attachment of email.attachments || []) {
    mime += `--${boundary}\r\n`;
    mime += `Content-Type: ${attachment.mimeType}\r\n`;
    mime += `Content-Disposition: attachment; filename="${attachment.filename}"\r\n`;
    mime += `Content-Transfer-Encoding: base64\r\n\r\n`;
    mime += attachment.data.toString("base64") + "\r\n\r\n";
  }

  mime += `--${boundary}--\r\n`;

  return Buffer.from(mime, "utf-8");
}