# Module: Api/Program.cs

## Purpose
Application entry point. Configures DI container, sets up middleware, defines minimal API endpoints, runs database migrations on startup, and starts background services.

## Public Interface

### API Endpoints
| Method | Route | Handler | Description |
|--------|-------|---------|-------------|
| GET | `/tiles/{z}/{x}/{y}` | `ServeTile` | Slippy map tile server with in-memory caching |
| GET | `/api/satellite/tiles/latlon` | `GetTileByLatLon` | Download single tile by lat/lon/zoom |
| GET | `/api/satellite/tiles/mgrs` | `GetSatelliteTilesByMgrs` | MGRS stub (returns empty) |
| POST | `/api/satellite/upload` | `UploadUavTileBatch` | UAV tile batch upload (AZ-488) — multipart envelope, 5-rule quality gate, per-source UPSERT with `source='uav'`. Requires the `RequiresGpsPermission` policy. |
| POST | `/api/satellite/request` | `RequestRegion` | Queue region for async tile processing |
| GET | `/api/satellite/region/{id}` | `GetRegionStatus` | Get region processing status |
| POST | `/api/satellite/route` | `CreateRoute` | Create route with intermediate points |
| GET | `/api/satellite/route/{id}` | `GetRoute` | Get route with all points |

### Local Records (defined in Program.cs)
- `GetSatelliteTilesResponse`, `SatelliteTile` — MGRS response stubs
- `DownloadTileResponse` — tile download response
- `RequestRegionRequest` — region request body
- `ParameterDescriptionFilter` — Swagger operation filter

### Api/DTOs (AZ-488)
- `UavTileBatchUploadRequest` — multipart envelope with `metadata` (JSON string) and `files` (`IFormFileCollection`)

### Common/DTO (AZ-488)
- `UavTileMetadata`, `UavTileBatchMetadataPayload` — per-item metadata + envelope shape
- `UavTileBatchUploadResponse`, `UavTileUploadResultItem` — per-item response shape
- `UavTileUploadStatus`, `UavTileRejectReasons` — string-constant enumerations exposed in the v1.0.0 contract

## Internal Logic

### DI Registration
1. Serilog configured from `appsettings.json`
2. Connection string extracted from `ConnectionStrings:DefaultConnection`
3. Config bindings: `MapConfig`, `StorageConfig`, `ProcessingConfig`, `UavQualityConfig` (AZ-488)
4. **Request size limits (AZ-488)**: `KestrelServerOptions.Limits.MaxRequestBodySize` and `FormOptions.MultipartBodyLengthLimit` are set to `UavQualityConfig.MaxBatchSize × UavQualityConfig.MaxBytes` (default 100 × 5 MiB = 500 MiB) so an oversized UAV batch is rejected at the framework layer before reaching the handler.
5. Singletons: repositories (`TileRepository`, `RegionRepository`, `RouteRepository`), `GoogleMapsDownloaderV2`, `ITileService`, `IRegionService`, `IRouteService`, `IUavTileQualityGate`, `IUavTileUploadHandler` (AZ-488)
6. `IRegionRequestQueue` with configurable capacity
7. Hosted services: `RegionProcessingService`, `RouteProcessingService`
8. CORS policy: `TilesCors` — configured origins from `CorsConfig:AllowedOrigins`, falls back to allow-any
9. JSON options: camelCase, case-insensitive
10. **JWT authentication (AZ-487 + AZ-494)**: `AddSatelliteJwt(builder.Configuration)` (extension in `SatelliteProvider.Api.Authentication`) registers `JwtBearer` with `TokenValidationParameters` set per the suite auth contract: signature + lifetime + issuer + audience validation, 30 s clock skew, ≥ 32-byte HMAC key. The `iss` value comes from `JWT_ISSUER` env (fallback `Jwt:Issuer` config); the `aud` value comes from `JWT_AUDIENCE` env (fallback `Jwt:Audience` config). All three values (secret, iss, aud) are fail-fast — the API throws `InvalidOperationException` at startup if any is unset or whitespace-only. Production deploys MUST set the env vars with admin-team-confirmed values; `appsettings.json` ships empty so the fail-fast triggers. `appsettings.Development.json` ships clearly-tagged DEV-ONLY values (`DEV-ONLY-iss-admin-azaion-local` / `DEV-ONLY-aud-satellite-provider`) so local dev works out-of-the-box. Followed by `AddAuthorization` with the `RequiresGpsPermission` policy (AZ-488).

### Startup
1. Database migration via `DatabaseMigrator.RunMigrations()` — throws on failure
2. Creates tiles and ready directories
3. Swagger enabled in Development mode
4. Middleware chain (order matters): `UseExceptionHandler` → `UseHttpsRedirection` → `UseCors("TilesCors")` → `UseAuthentication` → `UseAuthorization` → endpoint mapping.
5. Every `MapGet`/`MapPost` endpoint is decorated with `.RequireAuthorization()`; the framework returns 401 before the handler runs for any anonymous, expired, or invalid-signature request.

### ServeTile Handler
1. Checks `IMemoryCache` for tile bytes (1h absolute, 30min sliding expiration)
2. If cache miss: queries `ITileRepository.GetByTileCoordinatesAsync`
3. If no DB record: downloads tile via `GoogleMapsDownloaderV2.DownloadSingleTileAsync`, creates `TileEntity`, inserts
4. Returns image bytes with cache headers (`Cache-Control: public, max-age=86400`)

### GetTileByLatLon Handler
Downloads a tile, persists it, returns metadata as `DownloadTileResponse`.

### RequestRegion Handler
Validates size (100–10000m), delegates to `IRegionService.RequestRegionAsync`.

### UploadUavTileBatch Handler (AZ-488)
Buffers each `IFormFile` into memory, packages them as `UavUploadFile` records (filename, content-type, bytes), and delegates to `IUavTileUploadHandler.HandleAsync`. Envelope-level errors (mismatched batch, oversized batch, malformed metadata) are surfaced as HTTP 400 ProblemDetails; per-item rejects are returned in the HTTP 200 response payload. The endpoint is protected by `.RequireAuthorization(SatellitePermissions.UavUploadPolicy)` so 401 (no token) and 403 (no `GPS` permission) are returned before the handler runs.

## Dependencies
All project references: Common, DataAccess, Services.
NuGet: `Serilog.AspNetCore`, `Swashbuckle.AspNetCore`, `Microsoft.AspNetCore.OpenApi` (8.0.25, bumped from 8.0.21 by AZ-496), `Microsoft.AspNetCore.Authentication.JwtBearer` (8.0.25, added at 8.0.21 by AZ-487, bumped by AZ-496), `SixLabors.ImageSharp`, `Newtonsoft.Json`.

## Consumers
- HTTP clients (external)
- Integration tests (via HTTP)

## Data Models
Defines several local request/response records that are not shared with other projects.

## Configuration
All configuration sections are consumed here:
- `ConnectionStrings:DefaultConnection`
- `MapConfig`, `StorageConfig`, `ProcessingConfig`
- `UavQuality` (AZ-488) — `MinBytes`, `MaxBytes`, `MaxAgeDays`, `CapturedAtFutureSkewSeconds`, `MinLuminanceVariance`, `MaxBatchSize`, `LuminanceSampleSize`. Drives the 5-rule quality gate AND the per-request body-size limits.
- `CorsConfig:AllowedOrigins`
- `Jwt:Secret` — HMAC-SHA256 signing key for JWT validation (AZ-487). Resolution: `JWT_SECRET` env var (preferred, opaque production secret) → `Jwt:Secret` configuration key (`appsettings.Development.json` placeholder only). Startup fails fast if the resolved value is unset, empty, or shorter than 32 bytes.
- `Jwt:Issuer` — Expected `iss` claim value (AZ-494). Resolution: `JWT_ISSUER` env → `Jwt:Issuer` config. Startup fails fast if unset/empty.
- `Jwt:Audience` — Expected `aud` claim value (AZ-494). Resolution: `JWT_AUDIENCE` env → `Jwt:Audience` config. Startup fails fast if unset/empty.
- `Serilog` section

## External Integrations
- Google Maps (indirectly via `GoogleMapsDownloaderV2`)
- PostgreSQL (via repositories and DatabaseMigrator)
- File system (`./tiles/`, `./ready/`)

## Security
- CORS configured (permissive by default when no origins specified)
- Swagger only in Development; Bearer token "Authorize" button registered via `AddSecurityDefinition`/`AddSecurityRequirement` (AZ-487)
- HTTPS redirection enabled
- JWT bearer authentication (AZ-487) — every endpoint requires a valid HS256-signed token. Anonymous, expired, or signature-tampered requests return 401 before the handler runs.
- Permission-claim policies (AZ-488) — `POST /api/satellite/upload` is wrapped in `.RequireAuthorization(SatellitePermissions.UavUploadPolicy)`. The `PermissionsAuthorizationHandler` reads the `permissions` claim (repeated-string OR JSON-array shape) and returns 403 if `GPS` is not present.

## Tests
Integration tests exercise all endpoints. Unit test project has only a dummy test.