leumas-axios/multiPostMiddleware.js

An advanced Axios wrapper with extended features and Express multi-post middleware for conversational API endpoints.

// multiPostMiddleware.js

/**
 * In-memory session store for multi-step post routes.
 * For production use, consider a persistent store.
 */
const sessions = {};

/**
 * Helper: Generate a simple random session ID.
 */
function generateSessionId() {
  return Math.random().toString(36).substring(2, 15);
}

/**
 * MultiPost Middleware Factory.
 *
 * @param {Array} requiredFields - Array of field names required to complete the request.
 *
 * The middleware:
 * 1. Checks for an existing session (via req.body.sessionId) or creates a new one.
 * 2. Merges req.body.data into the session data.
 * 3. Validates that all required fields are present.
 *    - If any fields are missing, responds with:
 *      { sessionId, status: 'pending', missingFields }
 *    - If all fields are provided, attaches the complete data to req.multiPostData
 *      and calls next() so the final route handler can send a response.
 */
function multiPostMiddleware(requiredFields) {
  return (req, res, next) => {
    // Use provided sessionId or generate a new one.
    let sessionId = req.body.sessionId || generateSessionId();
    req.sessionId = sessionId;

    // Create a new session if one does not exist.
    if (!sessions[sessionId]) {
      sessions[sessionId] = {};
      console.log(`Created new session: ${sessionId}`);
    }

    // Merge incoming data with existing session data.
    sessions[sessionId] = { ...sessions[sessionId], ...req.body.data };
    req.multiPostData = sessions[sessionId];

    // Determine which required fields are missing.
    const missingFields = requiredFields.filter(
      (field) => !req.multiPostData[field]
    );

    if (missingFields.length > 0) {
      console.log(`Session ${sessionId} pending. Missing fields:`, missingFields);
      return res.json({
        sessionId,
        status: 'pending',
        missingFields,
      });
    }

    // All required fields are present; clear session data (if desired) and proceed.
    delete sessions[sessionId];
    next();
  };
}

module.exports = multiPostMiddleware;