# Module 1 Implementation: Production Database

## Design Explanation

Module 1 establishes the production database foundation for the existing Subhakamana Store Management System. The current HTML ERP and e-commerce prototype remain unchanged. The database module is designed so the existing screens can later connect to backend APIs without losing the current workflows.

The design is product-first. Products and variants are the main business objects, inventory is attached to variants, and customer records are used only for order and delivery context. This matches the store requirement that the system tracks products rather than treating the customer as the main inventory object.

## Database Implementation

Implemented in:

- `module-01-database/prisma/schema.prisma`
- `module-01-database/prisma/seed.js`
- `module-01-database/.env.example`

The schema uses PostgreSQL through Prisma and includes:

- UUID primary keys
- Foreign-key relationships
- Unique constraints for email, phone, SKU, barcode, bill number, purchase number, return number, and idempotency key
- Audit timestamps
- Soft delete using `deletedAt`
- Record status fields
- Optimistic locking on inventory with `version`
- Immutable inventory movement records
- Order product and price snapshots
- Delivery lookup by bill number
- Idempotency support for payment and checkout safety

## API Changes

No live API behavior is changed yet. This module prepares the database for the backend API layer. The next implementation module should connect authentication and product APIs to this schema.

Prepared API areas:

- Authentication and sessions
- Product catalog and variants
- Inventory ledger
- POS and online orders
- Bill-number delivery
- Payments and refunds
- Reports and audit logs

## Frontend Changes

No redesign was made. No existing screen was removed. The current ERP dashboard, product onboarding, POS, checkout, delivery, reports, customer website, manuals, and local launcher remain available.

Later frontend migration should replace localStorage module by module:

1. Authentication
2. Products
3. Inventory
4. Orders and checkout
5. Delivery
6. POS
7. Returns and reports

## Security Review

The database module supports production security by storing:

- Role-based permissions
- User sessions
- Password hashes only
- Refresh token hashes only
- Audit logs for important activity
- Idempotency keys to reduce duplicate payment/order risk

Actual password hashing, login rate limiting, cookie security, and permission middleware belong to Module 2 or Module 4 backend implementation.

## Test Coverage

Implemented:

- `module-01-database/scripts/verify-database-module.js`

The verification checks that the Prisma schema includes required production models, enums, UUIDs, unique constraints, soft-delete fields, inventory versioning, bill-number support, and seed data for Subhakamana Store.

## Documentation Update

Added:

- Module README
- Environment example
- Prisma schema
- Seed script
- Verification script
- This Module 1 implementation report

## Current Limitation

This is the database module only. It does not yet replace the browser prototype with live backend calls. The existing front-end prototype still runs locally as before while the production backend is introduced in stages.

## Next Module

The next production module should be authentication and RBAC:

- Argon2 password hashing
- JWT access token
- Refresh token session storage
- HTTP-only cookie strategy
- Permission middleware
- Login audit logs
- Rate limiting and brute-force protection