# Story 5.3: Blob Storage System

## Metadata
- **Story ID**: 5.3
- **Title**: Blob Storage System
- **Epic**: 5 - Infrastructure Adapters
- **Status**: Pending
- **Priority**: Medium
- **Estimated Time**: 5-6 hours
- **Dependencies**: 1.1, 1.5

## Goal
Implement a complete blob storage system using S3 with a clean interface for file upload, download, and management.

## Description
This story implements S3-based blob storage with support for file uploads, downloads, signed URLs, and file deletion. It includes an API endpoint for file uploads.

## Deliverables

### 1. Blob Storage Interface (`pkg/infra/blob/blob.go`)
- `BlobStore` interface with:
  - `Upload(ctx context.Context, key string, data []byte) error`
  - `Download(ctx context.Context, key string) ([]byte, error)`
  - `Delete(ctx context.Context, key string) error`
  - `GetSignedURL(ctx context.Context, key string, ttl time.Duration) (string, error)`
  - `Exists(ctx context.Context, key string) (bool, error)`

### 2. S3 Implementation (`internal/infra/blob/s3_store.go`)
- AWS S3 client setup
- All interface methods implemented
- Error handling
- Content type detection

### 3. File Upload API
- `POST /api/v1/files/upload` - Upload file
- File validation
- Size limits
- Content type validation

### 4. Configuration
- S3 config in `config/default.yaml`:
  - Bucket name
  - Region
  - Credentials (or use IAM role)

### 5. DI Integration
- Provider function for BlobStore
- Register in DI container

## Acceptance Criteria
- [ ] Blob storage interface is defined
- [ ] S3 implementation works correctly
- [ ] Files can be uploaded and downloaded
- [ ] Signed URLs are generated correctly
- [ ] File upload API works
- [ ] Configuration is loaded from config
- [ ] Blob store is injectable via DI

## Files to Create/Modify
- `pkg/infra/blob/blob.go` - Blob storage interface
- `internal/infra/blob/s3_store.go` - S3 implementation
- `internal/infra/blob/handler.go` - File upload handler
- `internal/di/providers.go` - Add blob store provider
- `config/default.yaml` - Add S3 config

