📦 Altar Backend API

This backend service provides real-time and RESTful APIs for the Altar.io Full-Stack Exercise, including grid/code logic and payment storage.

⚡ Features

• Real-time grid and code updates via Firebase.
• RESTful API for grid, code, and payment operations.
• Supports grid biasing for testing.
• Simple, stateless backend for easy integration.
• Example requests included for quick start.

📡 Firebase Real-Time Updates

Listen to the updates/current document in Firestore to receive the latest grid and code. Payment events are stored in the payments collection.

Example Firestore structure:

updates/current: { grid: [...], code: "42", timestamp: "..." }
payments/{id}: { name, amount, code, grid, timestamp }

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🟩 Grid Logic

• The backend generates a 10x10 grid of random lowercase letters (a-z).
• If the client provides a bias character via query parameter (?bias=z), 20% of grid cells will use that character, randomly distributed.
• The latest grid and code are pushed to Firebase whenever generated.

---

🔢 Code Logic

• For every new grid, a 2-digit code is generated as follows:
  1. Find the characters at positions [3][6] and [6][3] in the grid.
  2. Count how many times each character appears in the grid.
  3. If a count is greater than 9, repeatedly divide it by 2 (rounding down) until it's ≤ 9.
  4. Concatenate the two single-digit counts to form the code (e.g., 75).

---

🚀 API Endpoints

Method	Endpoint	Description
GET	/api/grid	Returns a new 10x10 grid. Supports ?bias=a-z query.
POST	/api/code	Accepts a grid in body, returns computed 2-digit code.
GET	/api/payments	Returns all payment entries.
POST	/api/payments	Stores a payment with name, amount, code, grid.
GET	/	Returns a simple server status message.

Example: POST /api/code

Request body:

{
  "grid": [
    ["a", "b", ...],
    ...
  ]
}

## 🛠 Deploying on Vercel

This repository now includes a `vercel.json` configuration and serverless functions in the `api/` directory. After installing the [Vercel CLI](https://vercel.com/docs/cli), run:

```bash
vercel --prod

This will build the TypeScript functions and deploy them to Vercel.

GitHub Actions workflows have been removed. Deploy using vercel --prod when ready.