Whatsapp-web.js

This Node.js application utilizes the whatsapp-web.js library to create a WhatsApp client server. Here's a breakdown of its functionality: Initialization and Setup: The application sets up an Express server and defines necessary dependencies like express, whatsapp-web.js, qrcode, cors, http, and mysql for database connectivity.

Database Connection: It establishes a connection with a MySQL database to store session data.

Client Initialization: The createClient function initializes a WhatsApp client instance using the provided instanceId. It handles events like QR code generation, client readiness, authentication, authentication failure, and disconnection.

Endpoints:

/add-device/:instanceId: Initializes a new device session.

/get-qr/:instanceId: Fetches the QR code for a specific instance.

/send-message/:instanceId: Sends a text message to a specified number.

/send-media/:instanceId: Sends media (image or video) to a specified number.

/get-chat-backup/:instanceId: Retrieves chat backup for a specific instance.

/get-messages/:instanceId/:userId/:limitme: Retrieves messages for a specific user within a specified limit.

/get-media/:instanceId/:messageId: Retrieves media associated with a specific message.

/instance-status/:instanceId: Checks the status of a specific instance.

/get-active-instance-info/:instanceId: Retrieves information about the active instance, such as phone number and platform.

/get-contacts/:instanceId: Retrieves contacts for a specific instance.

/delete-device/:instanceId: Deletes an existing device session.

/reinit-client/:instanceId: Attempts to reinitialize the client connection without destroying the session.

/reinit-session/:instanceId: Reinitializes a session for a specific instance.

/reinit-all-sessions: Reinitializes all sessions with timeout handling.

Database Operations:

Loading sessions from the database during initialization. Saving authenticated sessions to the database. Updating session status in the database on disconnection. Error Handling: The application handles errors gracefully, logging them and providing appropriate responses to clients.

Server Setup:

The server listens on port 4000.

Overall, this application provides a robust backend for managing WhatsApp client sessions and interacting with the WhatsApp API programmatically.