# Contract: region-request

**Component**: WebApi (`SatelliteProvider.Api`) producing rows via RegionProcessing (`SatelliteProvider.Services.RegionProcessing`)
**Producer task**: AZ-808 — `_docs/02_tasks/done/AZ-808_region_endpoint_validation.md` (validator + this contract); AZ-812 — `_docs/02_tasks/done/AZ-812_region_field_rename_to_osm.md` (OSM-convention wire-format `lat`/`lon`)
**Consumer tasks**: `gps-denied-onboard` AZ-777 Phase 2 (seeds Derkachi reference tile catalog via this endpoint)
**Version**: 1.0.0
**Status**: frozen
**Last Updated**: 2026-05-22

## Purpose

Defines the HTTP contract for `POST /api/satellite/request` — the region-onboarding endpoint that enqueues a square region of tiles for asynchronous backfill from Google Maps. Callers submit a `(lat, lon, sizeMeters, zoomLevel)` envelope identified by a client-provided `id` (idempotency key); the API responds immediately with the queued region's status. Actual tile downloads run in the background via `RegionProcessingService` (`system-flows.md` Flow F2). Callers poll `GET /api/satellite/region/{id}` until `status == completed`.

This is the v1.0.0 of the contract — published alongside AZ-808's validator landing. There is no prior contract document. AZ-812 had already renamed the wire-format fields `Latitude/Longitude` → `lat/lon` (OSM convention) earlier in cycle 8; this contract publishes the post-rename shape directly with no transitional period.

## Endpoint

```
POST /api/satellite/request
Content-Type: application/json
Authorization: Bearer <JWT>
```

The request MUST carry a valid JWT (AZ-487). No `permissions` claim is required. Anonymous requests are rejected with HTTP 401.

## Shape

### Request body

```jsonc
{
  "id": "8f5e6d3e-1a2b-4c3d-9e8f-0123456789ab",
  "lat": 47.461747,
  "lon": 37.647063,
  "sizeMeters": 200,
  "zoomLevel": 18,
  "stitchTiles": false
}
```

Per-field constraints:

| Field | Type | Required | Description | Constraints |
|-------|------|----------|-------------|-------------|
| `id` | UUID | yes | Client-provided idempotency key. POSTing the same `id` twice returns the existing region (idempotent per AZ-362). | Non-zero GUID. `00000000-...` → HTTP 400. |
| `lat` | number | yes | Region centre latitude (WGS84, decimal degrees). | `[-90.0, 90.0]`. |
| `lon` | number | yes | Region centre longitude (WGS84, decimal degrees). | `[-180.0, 180.0]`. |
| `sizeMeters` | number | yes | Square region side length. | `[100.0, 10000.0]`. Anything larger → HTTP 400. |
| `zoomLevel` | integer | yes | Slippy-map zoom level for the resulting tiles. | `[0, 22]`. |
| `stitchTiles` | bool | yes | If true, a stitched composite image is produced once all tiles are present. No default — caller MUST declare intent. | true / false. |

Strict parsing: unknown fields at root are rejected with HTTP 400 by `JsonSerializerOptions.UnmappedMemberHandling.Disallow` (AZ-795). Missing required fields are caught by `[JsonRequired]` on the DTO and surface as HTTP 400 with the field name in `errors`.

### Response body

```jsonc
{
  "id": "8f5e6d3e-1a2b-4c3d-9e8f-0123456789ab",
  "status": "queued",
  "csvFilePath": null,
  "summaryFilePath": null,
  "tilesDownloaded": 0,
  "tilesReused": 0,
  "createdAt": "2026-05-22T12:34:56.789Z",
  "updatedAt": "2026-05-22T12:34:56.789Z"
}
```

Per-field semantics:

| Field | Type | Description |
|-------|------|-------------|
| `id` | UUID | Echo of the request `id`. |
| `status` | string enum | `"queued"` immediately after enqueue; transitions through `"processing"` → `"completed"` (or `"failed"`) on the background worker. |
| `csvFilePath` | string \| null | Path to the per-region tile-manifest CSV. Null until processing produces it. |
| `summaryFilePath` | string \| null | Path to the human-readable summary. Null until processing produces it. |
| `tilesDownloaded` | integer | Count of tiles fetched fresh from Google Maps. Updated as processing progresses. |
| `tilesReused` | integer | Count of tiles served from existing cache. Updated as processing progresses. |
| `createdAt` | ISO-8601 UTC | Initial enqueue timestamp. Stable across retries (per AZ-362 idempotency). |
| `updatedAt` | ISO-8601 UTC | Last status-row write. Bumps as the background worker progresses. |

### Endpoint summary

| Method | Path | Request body | Response | Status codes |
|--------|------|--------------|----------|--------------|
| `POST` | `/api/satellite/request` | `RequestRegionRequest` | `RegionStatusResponse` | 200, 400, 401 |

## Error shape

All `400` responses conform to `_docs/02_document/contracts/api/error-shape.md` v1.0.0. Two enforcement layers produce identically-shaped bodies:

1. **JSON deserializer rules** — wire-format failures: unknown fields (`UnmappedMemberHandling.Disallow`), missing `[JsonRequired]` properties, type mismatches. Surface via `BadHttpRequestException(JsonException)` → `GlobalExceptionHandler`.
2. **`RegionRequestValidator`** (FluentValidation, AZ-808) — business rules: non-zero `id`, range checks for `lat` / `lon` / `sizeMeters` / `zoomLevel`. Surface via `ValidationEndpointFilter<RequestRegionRequest>`.

Example body for a missing-id failure (the pre-AZ-808 silent-coercion gap surfaced by the 2026-05-22 black-box probe):

```jsonc
{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "errors": {
    "id": ["The id field is required."]
  }
}
```

Example body for a zero-Guid id (validator-level rejection):

```jsonc
{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "errors": {
    "id": ["`id` must be a non-zero GUID (the caller's idempotency key)."]
  }
}
```

## Invariants

- **Inv-1**: `id` MUST be a non-zero GUID. Pre-AZ-808, omitting `id` silently coerced to `Guid.Empty` and queued a region under the zero key; AZ-808 fails this with HTTP 400 and `errors["id"]`.
- **Inv-2**: `lat ∈ [-90.0, 90.0]`. Out-of-range → 400 with `errors["lat"]`.
- **Inv-3**: `lon ∈ [-180.0, 180.0]`. Out-of-range → 400 with `errors["lon"]`.
- **Inv-4**: `sizeMeters ∈ [100.0, 10000.0]`. Out-of-range → 400 with `errors["sizeMeters"]`. Pre-AZ-808 this rule lived as an inline `if` in the handler; AZ-808 moves it into the validator.
- **Inv-5**: `zoomLevel ∈ [0, 22]` (slippy-map zoom range, matching `tile-inventory.md` Inv-8).
- **Inv-6**: `stitchTiles` MUST be explicitly provided. No defaulting to `false` — callers declare intent.
- **Inv-7**: Unknown fields at root are rejected with HTTP 400 + the field name in `errors`.
- **Inv-8** (idempotency, AZ-362): Two POSTs with the same `id` return the existing region resource with HTTP 200 and do NOT enqueue duplicate background processing. The post-rename `lat`/`lon` wire format does not affect this invariant.
- **Inv-9** (async semantics): The endpoint returns immediately after enqueuing. Status transitions to `completed`/`failed` happen on the background `RegionProcessingService`. Callers MUST poll `GET /api/satellite/region/{id}` to observe completion.

## Non-Goals

- **Not covered**: tile body fetch. The background worker writes tiles into the `tiles` table; callers fetch bodies via `GET /tiles/{z}/{x}/{y}` after polling shows `status == completed`.
- **Not covered**: backward-compatibility shim for `Latitude/Longitude` wire field names. AZ-812 ships v1.0.0 of this contract directly with the post-rename names; pre-rename callers receive HTTP 400 with `errors["latitude"]: ["could not be mapped"]`. There is no transitional accept-both period.
- **Not covered**: geofencing semantics. Geofences are a Route concern, not a Region concern; documented in `route-create.md` (forthcoming, AZ-809).
- **Not covered**: cancellation of a queued region. The current API has no DELETE / cancel verb. Tracked separately if needed.

## Versioning Rules

- **Patch (1.0.x)**: Documentation clarifications, additional invariants that do not change wire behaviour.
- **Minor (1.x.0)**: Adding an optional response field consumers may safely ignore (e.g. ETA estimate); relaxing a range constraint within `[-90,90]` / `[-180,180]` envelope (e.g. accepting decimal degrees with extra precision).
- **Major (2.0.0)**: Changing a field name; tightening a range constraint (breaks today's valid callers); making `stitchTiles` optional with a default again; removing idempotency.

## Test Cases

| Case | Input | Expected | Notes |
|------|-------|----------|-------|
| happy-path | `{id:<guid>, lat:47.46, lon:37.64, sizeMeters:200, zoomLevel:18, stitchTiles:false}` | HTTP 200 + RegionStatusResponse(status="queued") | AC-2 |
| missing-id | body without `id` field | HTTP 400 + `errors["id"]` | Inv-1 (probe gap) |
| zero-guid-id | `id: "00000000-..."` | HTTP 400 + `errors["id"]` | Inv-1 |
| missing-lat | body without `lat` | HTTP 400 + `errors["lat"]` | JsonRequired |
| lat-out-of-range | `lat: 91` | HTTP 400 + `errors["lat"]` | Inv-2 |
| missing-lon | body without `lon` | HTTP 400 + `errors["lon"]` | JsonRequired |
| lon-out-of-range | `lon: 181` | HTTP 400 + `errors["lon"]` | Inv-3 |
| missing-sizeMeters | body without `sizeMeters` | HTTP 400 + `errors["sizeMeters"]` | JsonRequired |
| sizeMeters-out-of-range | `sizeMeters: 1000000` | HTTP 400 + `errors["sizeMeters"]` | Inv-4 |
| missing-zoomLevel | body without `zoomLevel` | HTTP 400 + `errors["zoomLevel"]` | JsonRequired |
| zoomLevel-out-of-range | `zoomLevel: 30` | HTTP 400 + `errors["zoomLevel"]` | Inv-5 |
| missing-stitchTiles | body without `stitchTiles` | HTTP 400 + `errors["stitchTiles"]` | Inv-6 |
| lat-type-mismatch | `lat: "fifty"` | HTTP 400 (deserializer JsonException) | wire-format failure |
| unknown-root-field | body with `unknownField: 1` | HTTP 400 + `errors["unknownField"]` | Inv-7 |
| legacy-latitude-name | body with `latitude:` instead of `lat:` | HTTP 400 + `errors["latitude"]` | AZ-812 hard switch |
| auth-anonymous | no Bearer token | HTTP 401 | Standard `.RequireAuthorization()` baseline |
| idempotent-double-post | same body POSTed twice | both HTTP 200; same `createdAt`; no duplicate background work | AC-2 + AZ-362 |

## Change Log

| Version | Date | Change | Author |
|---------|------|--------|--------|
| 1.0.0 | 2026-05-22 | Initial contract for `POST /api/satellite/request`. Publishes the post-AZ-812 OSM-convention wire format (`lat`/`lon`) and the AZ-808 strict-validation rules (non-zero `id`, range-checked `lat`/`lon`/`sizeMeters`/`zoomLevel`, explicit `stitchTiles`, unknown-field rejection). References `error-shape.md` v1.0.0 for the 400 body shape and `tile-inventory.md` v2.0.0 for the downstream read path (callers seed via region, then read via inventory). | autodev (Step 10, cycle 8) |