# Story 5.1: Cache System (Redis)

## Metadata
- **Story ID**: 5.1
- **Title**: Cache System (Redis)
- **Epic**: 5 - Infrastructure Adapters
- **Status**: Pending
- **Priority**: High
- **Estimated Time**: 4-5 hours
- **Dependencies**: 1.1

## Goal
Implement a complete Redis-based caching system with a clean interface that can be swapped for other cache implementations.

## Description
This story implements a Redis cache adapter with a clean interface, allowing modules to cache data efficiently. The cache system supports TTL, key-based operations, and optional cache middleware for HTTP responses.

## Deliverables

### 1. Cache Interface (`pkg/infra/cache/cache.go`)
- `Cache` interface with:
  - `Get(ctx context.Context, key string) ([]byte, error)`
  - `Set(ctx context.Context, key string, value []byte, ttl time.Duration) error`
  - `Delete(ctx context.Context, key string) error`
  - `Exists(ctx context.Context, key string) (bool, error)`
  - `Clear(ctx context.Context) error`

### 2. Redis Implementation (`internal/infra/cache/redis_cache.go`)
- Redis client setup
- Connection pooling
- All interface methods implemented
- Error handling
- Connection health checks

### 3. Configuration
- Redis config in `config/default.yaml`:
  - Connection URL
  - Pool settings
  - Default TTL

### 4. DI Integration
- Provider function for Cache
- Register in DI container

### 5. Optional Cache Middleware
- HTTP response caching middleware
- Configurable cache keys
- TTL per route

## Acceptance Criteria
- [ ] Cache interface is defined
- [ ] Redis implementation works correctly
- [ ] Cache operations (get, set, delete) work
- [ ] TTL is respected
- [ ] Cache is injectable via DI
- [ ] Configuration is loaded from config
- [ ] Optional middleware works

## Files to Create/Modify
- `pkg/infra/cache/cache.go` - Cache interface
- `internal/infra/cache/redis_cache.go` - Redis implementation
- `internal/di/providers.go` - Add cache provider
- `config/default.yaml` - Add Redis config