Use NestJS with the Sinch SMS API to build an SMS scheduling application. Create a NestJS backend that interacts with the Sinch API to send SMS messages at specified times, storing reminder details in a database like PostgreSQL.

The Sinch SMS API enables sending and receiving SMS messages globally within a NestJS application. Its send_at parameter allows direct scheduling of messages, simplifying the application logic.

Prisma, an ORM for Node.js and TypeScript, enhances type safety and simplifies database interactions. It's used with PostgreSQL for reliable data persistence and integrity in the SMS scheduling application.

Always convert the desired send time (sendAt) to UTC using a library like Luxon before sending it to the Sinch API. Sinch's send_at parameter expects a UTC ISO 8601 string for accurate scheduling.

The Sinch API has batch cancellation capabilities, so cancelling scheduled SMS messages may be possible. Check Sinch's documentation for how to use the necessary endpoints and methods for cancellation.

Use the NestJS CLI to create a new project, then install dependencies like @sinch/sdk-core, luxon, @nestjs/axios, and Prisma. Configure environment variables for Sinch and database credentials.

Luxon is a date and time handling library used for its immutable nature and clear API for time zone management. This ensures accurate conversion of scheduled times to UTC for the Sinch API.

Store Sinch API credentials (Project ID, Key ID, Key Secret) in a .env file. Load these environment variables into your NestJS application using the @nestjs/config module, ensuring they are not committed to version control.

SinchService encapsulates interactions with the Sinch SMS API, initializing the Sinch client and providing methods to schedule SMS messages using credentials and the send_at parameter.

Use class-validator and class-transformer to define a Data Transfer Object (DTO) with validation rules. Enable a global ValidationPipe in main.ts to automatically validate incoming requests against the DTO schema.

PostgreSQL is used for persistent storage of appointment details like patient name, phone number, appointment time, and the SMS message content.

Implement error handling within the SinchService and AppointmentsService. Catch potential errors from the Sinch API call, log them for debugging, and update the appointment status in the database accordingly.

Docker Compose simplifies local database setup, providing a consistent environment. The provided docker-compose.yml file sets up a PostgreSQL container with defined credentials and port mappings.

Log in to your Sinch account dashboard, navigate to your project, and go to Settings -> API Credentials. There you'll find your Project ID, Key ID, and Key Secret.