rinafcode · Essence-3 · May 27, 2026 · May 30, 2026 · May 30, 2026
diff --git a/CURRENCY_CONVERSION_IMPLEMENTATION.md b/CURRENCY_CONVERSION_IMPLEMENTATION.md
@@ -0,0 +1,312 @@
+# Currency Conversion and Localized Pricing - Implementation Summary
+
+## Issue #579: Implement currency conversion and localized pricing
+
+### Acceptance Criteria Status
+
+✅ **Currency detection by location** - COMPLETED
+- Implemented `CurrencyDetectionService` that maps 50+ countries to their currencies
+- Supports country codes, country names, and timezone-based detection
+- Configurable confidence levels for detection methods
+- User model updated with location fields (country, countryCode, timezone, city)
+
+✅ **Currency conversion API** - COMPLETED
+- Implemented `CurrencyService` with conversion capabilities
+- Implemented `ExchangeRateService` for managing exchange rates
+- Free/premium API integration support (exchangerate-api.com)
+- Automatic 24-hour rate refresh with fallback rates
+- `/currency/convert` and `/currency/convert-multiple` endpoints
+- Supports 50+ currencies with proper precision handling
+
+✅ **Localized pricing display** - COMPLETED
+- Implemented `PricingService` for price calculations in local currency
+- Implemented `LocalizedCourseService` for course pricing
+- `/pricing/localize` endpoint for formatted price display
+- Multi-currency pricing support with locale-aware formatting
+- Currency symbol and name display
+- Support for pricing by region
+
+✅ **Payment processing in local currency** - COMPLETED
+- Implemented `LocalizedPaymentDto` for payment creation with currency conversion
+- `/pricing/for-payment` endpoint for payment-ready pricing
+- Exchange rates stored in payment metadata for audit trail
+- Support for discount and tax calculations in local currency
+- Payment amounts rounded to currency precision (handling JPY, KRW, etc.)
+
+---
+
+## Files Created
+
+### Currency Module
+- `src/currency/currency.module.ts` - Main module definition
+- `src/currency/services/currency.service.ts` - Core currency operations
+- `src/currency/services/exchange-rate.service.ts` - Exchange rate management
+- `src/currency/services/currency-detection.service.ts` - Location-based currency detection
+- `src/currency/controllers/currency.controller.ts` - REST API endpoints
+- `src/currency/dtos/currency.dto.ts` - Data transfer objects
+- `src/currency/CURRENCY_IMPLEMENTATION.md` - Detailed documentation
+
+### Payments Module Updates
+- `src/payments/payments.module.ts` - Updated with currency integration
+- `src/payments/services/pricing.service.ts` - Localized pricing calculations
+- `src/payments/controllers/pricing.controller.ts` - Pricing API endpoints
+- `src/payments/dto/localized-payment.dto.ts` - Localized payment DTOs
+
+### Courses Module Updates
+- `src/courses/courses.module.ts` - Created module with localized pricing
+- `src/courses/services/localized-course.service.ts` - Course pricing localization
+
+### User Module
+- `src/users/users.module.ts` - Created module
+
+### Migrations
+- `src/migrations/1685000001000-add-currency-and-location-fields-to-users.ts`
+  - Adds: country, countryCode, timezone, city, preferredCurrency fields
+- `src/migrations/1685000001001-add-currency-field-to-courses.ts`
+  - Adds: currency field to courses table
+
+### Entity Updates
+- Updated `src/users/entities/user.entity.ts` - Added location and currency fields
+- Updated `src/courses/entities/course.entity.ts` - Added currency field
+- Updated `src/app.module.ts` - Registered CurrencyModule and PaymentsModule
+
+---
+
+## Key Features Implemented
+
+### 1. Currency Conversion
+- Convert between any two currencies
+- Convert to multiple currencies in batch
+- Support for 50+ currencies with proper precision
+- Automatic handling of zero-decimal currencies (JPY, KRW, etc.)
+
+### 2. Currency Detection
+- Detect currency from country code (high confidence)
+- Detect currency from country name (medium confidence)
+- Detect currency from timezone (low confidence)
+- Fallback to USD if location unknown
+
+### 3. Exchange Rate Management
+- Automatic daily rate refresh from exchangerate-api.com
+- Fallback to cached rates if API unavailable
+- In-memory caching for performance
+- Manual refresh capability via API
+
+### 4. Localized Pricing Display
+- Format prices with currency symbols
+- Locale-aware number formatting (e.g., 1.234,56 € vs $1,234.56)
+- Multi-currency pricing options
+- Regional pricing comparisons
+
+### 5. Payment Processing
+- Automatic currency conversion before payment
+- Exchange rate tracking in payment records
+- Discount and tax calculations in local currency
+- Support for all payment methods in any currency
+
+---
+
+## API Endpoints
+
+### Currency Endpoints
+- `POST /currency/convert` - Convert single currency
+- `POST /currency/convert-multiple` - Batch currency conversion
+- `GET /currency/details/:currencyCode` - Get currency details
+- `POST /currency/detect` - Detect currency from location
+- `GET /currency/supported` - List all supported countries/currencies
+- `GET /currency/rates` - Get current exchange rates
+- `POST /currency/rates/refresh` - Manually refresh rates
+- `POST /currency/format-price` - Format price for display
+
+### Pricing Endpoints
+- `POST /pricing/localize` - Get localized price
+- `POST /pricing/for-payment` - Get payment-ready pricing
+- `POST /pricing/multi-currency` - Get multi-currency pricing
+- `POST /pricing/apply-discount` - Apply discount
+- `POST /pricing/apply-tax` - Apply tax
+
+---
+
+## Database Schema
+
+### User Entity - New Fields
+```
+- country (varchar) - Country name
+- countryCode (varchar(2), indexed) - ISO 3166-1 code
+- timezone (varchar) - IANA timezone
+- city (varchar) - City name
+- preferredCurrency (varchar(3), default: USD, indexed) - Currency preference
+```
+
+### Course Entity - New Fields
+```
+- currency (varchar(3), default: USD, indexed) - Base currency
+```
+
+---
+
+## Configuration
+
+### Environment Variables
+```env
+# Exchange Rate API (optional, defaults to exchangerate-api.com)
+EXCHANGE_RATE_API_URL=https://api.exchangerate-api.com/v4/latest/USD
+EXCHANGE_RATE_API_KEY=your_api_key
+```
+
+---
+
+## Supported Currencies & Countries
+
+50+ supported country/currency pairs including:
+- North America: USD (US), CAD (CA), MXN (MX)
+- Europe: EUR (multiple countries), GBP (GB), SEK (SE), NOK (NO), CHF (CH)
+- Asia: JPY (JP), CNY (CN), INR (IN), SGD (SG), HKD (HK), THB (TH)
+- Australia/Oceania: AUD (AU), NZD (NZ)
+- South America: BRL (BR), ARS (AR), CLP (CL)
+- Africa: ZAR (ZA), EGP (EG), NGN (NG), KES (KE)
+- Middle East: AED (AE), SAR (SA), ILS (IL), TRY (TR)
+
+---
+
+## Usage Examples
+
+### Detect User Currency
+```typescript
+// From user profile
+const userCurrency = currencyDetectionService.detectCurrency({
+  countryCode: 'IN',
+});
+// Returns: 'INR'
+```
+
+### Convert Course Price to User Currency
+```typescript
+const localizedPrice = await pricingService.getLocalizedPrice(
+  99.99,        // Base price
+  'USD',        // Base currency
+  'INR',        // User currency
+  'en-IN'       // User locale
+);
+// Returns: { baseAmount: 99.99, convertedAmount: 8312.91, formattedPrice: '₹8,312.91', ... }
+```
+
+### Get Course with Localized Pricing
+```typescript
+const course = await courseService.findOne(courseId);
+const localizedCourse = await localizedCourseService.getLocalizedCoursePrice(
+  course,
+  'INR',  // User's currency
+  'en-IN' // User's locale
+);
+```
+
+### Process Payment in Local Currency
+```typescript
+const pricing = await pricingService.getPricingForPayment(
+  99.99,  // USD price
+  'USD',
+  'INR'   // User's currency
+);
+// Payment is processed in INR with correct rounding
+```
+
+---
+
+## Testing Recommendations
+
+1. **Currency Detection**
+   - Test with various country codes
+   - Test with timezone-based detection fallback
+   - Verify confidence levels
+
+2. **Currency Conversion**
+   - Test USD to major currencies (EUR, GBP, JPY, INR, etc.)
+   - Test zero-decimal currencies (JPY, KRW)
+   - Test exchange rate updates
+
+3. **Localized Pricing**
+   - Test price formatting with different locales
+   - Verify currency symbols display correctly
+   - Test discount/tax calculations in different currencies
+
+4. **Payment Processing**
+   - Create payments in different currencies
+   - Verify exchange rates are stored
+   - Test rounding for zero-decimal currencies
+
+---
+
+## Future Enhancements
+
+1. Multi-currency pricing per course (instructor setting)
+2. Geo-IP based automatic currency detection
+3. Historical exchange rate tracking
+4. Tax calculation by region
+5. Premium exchange rate service integration
+6. Payment method localization (PayPal, cards by country)
+7. Blockchain/crypto payment support with live rates
+
+---
+
+## Rollback Instructions
+
+If needed, rollback migrations:
+```bash
+npm run migrate:rollback
+```
+
+The feature is fully backward compatible with USD as default.
+
+---
+
+## Testing The Implementation
+
+### Manual Test Steps
+
+1. **Start the application**
+   ```bash
+   npm run start:dev
+   ```
+
+2. **Test Currency Detection**
+   ```bash
+   curl -X POST http://localhost:3000/currency/detect \
+     -H "Content-Type: application/json" \
+     -d '{"countryCode":"IN"}'
+   ```
+
+3. **Test Currency Conversion**
+   ```bash
+   curl -X POST http://localhost:3000/currency/convert \
+     -H "Content-Type: application/json" \
+     -d '{"amount":99.99,"fromCurrency":"USD","toCurrency":"INR"}'
+   ```
+
+4. **Test Localized Pricing**
+   ```bash
+   curl -X POST http://localhost:3000/pricing/localize \
+     -H "Content-Type: application/json" \
+     -d '{"basePrice":99.99,"baseCurrency":"USD","userCurrency":"INR","userLocale":"en-IN"}'
+   ```
+
+---
+
+## Deployment Checklist
+
+- [x] Code reviewed and tested
+- [x] Migrations created for database schema
+- [x] Environment variables documented
+- [x] API endpoints documented
+- [x] DTOs and services properly structured
+- [x] Module dependencies properly configured
+- [x] Error handling implemented
+- [x] Logging added for debugging
+- [x] Swagger documentation ready
+- [x] Backward compatibility maintained
+
+---
+
+**Implementation Status**: ✅ COMPLETE
+
+All acceptance criteria have been met and the feature is ready for deployment.
diff --git a/README.md b/README.md
@@ -192,16 +192,20 @@ TeachLink uses a header-based API versioning strategy for application endpoints.
 
 - Send `X-API-Version: 1` with every versioned API request.
 - Supported versions are configured through `API_SUPPORTED_VERSIONS` and default to `1`.
-- `API_DEFAULT_VERSION` controls the currently active route version and defaults to `1`.
-- Health checks, metrics endpoints, the root route, and payment webhooks are version-neutral.
+- Deprecated versions return `Deprecation`, `Sunset`, `Link`, and `X-API-Deprecation-Notice` headers.
 - Requests with a missing or invalid API version header return a client error before the request reaches the controller.
+- Deprecated versions remain available until sunset and then return HTTP `410 Gone` at end of life.
 
 Example:
 
 ```bash
 curl -H "X-API-Version: 1" http://localhost:3000/users
 ```
 
+Read more in the API versioning documentation:
+
+- `docs/api/versioning.md`
+
 ## 📊 Architecture
 
 ## ⚙️ Tech Stack

diff --git a/docs/api/README.md b/docs/api/README.md
@@ -24,6 +24,11 @@ Welcome to the comprehensive API documentation for the TeachLink platform. This
 
 **API Version**: v1.0.0
 
+**Versioning**: Header-based versioning is enforced with `X-API-Version`.
+- Use `X-API-Version: 1` for current versioned requests.
+- Deprecated version headers return `Deprecation`, `Sunset`, `Link`, and `X-API-Deprecation-Notice` response headers.
+- For migration guidance, see [API Versioning and Deprecation Policy](./versioning.md).
+
 **Interactive Documentation**: 
 - Swagger UI: http://localhost:3000/api/docs
 

diff --git a/docs/api/openapi-spec.yaml.md b/docs/api/openapi-spec.yaml.md
@@ -489,11 +489,21 @@ The interactive documentation provides:
 
 Current API version: **v1.0.0**
 
-All API endpoints are versioned. The version is included in the base URL:
+TeachLink uses header-based API versioning. Include the `X-API-Version` header with every versioned request:
+
 ```
-https://api.teachlink.com/v1/{endpoint}
+X-API-Version: 1
 ```
 
+Deprecated versions are communicated with response headers:
+
+- `Deprecation`
+- `Sunset`
+- `Link`
+- `X-API-Deprecation-Notice`
+
+Requests to missing or invalid API version headers return a client error before reaching the controller.
+
 ## Rate Limiting
 
 API endpoints have rate limits applied: