# Slice Query and Replay REST APIs

## Module
Scanner

## Status
VERIFIED

## Description
REST API for on-demand reachability slice generation (POST /api/slices/query), retrieval by digest (GET /api/slices/{digest}), and byte-for-byte replay verification (POST /api/slices/replay) with detailed diff output on mismatch. Includes in-memory slice cache with configurable TTL.

## Implementation Details
- **Slice Endpoints**:
  - `src/Scanner/StellaOps.Scanner.WebService/Endpoints/SliceEndpoints.cs` - `SliceEndpoints` providing REST API for slice query (POST), retrieval by digest (GET), and replay verification (POST)
- **Slice Query Service**:
  - `src/Scanner/StellaOps.Scanner.WebService/Services/SliceQueryService.cs` - `SliceQueryService` executing on-demand reachability slice generation and retrieval
  - `src/Scanner/StellaOps.Scanner.WebService/Services/ISliceQueryService.cs` - Interface for slice query operations
- **Score Replay**:
  - `src/Scanner/StellaOps.Scanner.WebService/Services/ScoreReplayService.cs` - `ScoreReplayService` performing byte-for-byte replay verification of slices with detailed diff output on mismatch
  - `src/Scanner/StellaOps.Scanner.WebService/Services/IScoreReplayService.cs` - Interface for replay service
  - `src/Scanner/StellaOps.Scanner.WebService/Endpoints/ScoreReplayEndpoints.cs` - `ScoreReplayEndpoints` REST API for replay verification
- **Slice Cache**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.Reachability/Slices/SliceCache.cs` - `SliceCache` caching slices with configurable TTL
  - `src/Scanner/__Libraries/StellaOps.Scanner.Reachability/Slices/InMemorySliceCache.cs` - `InMemorySliceCache` in-memory implementation
  - `src/Scanner/__Libraries/StellaOps.Scanner.Reachability/Slices/ISliceCache.cs` - Interface for slice caching
- **Slice Core**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.Reachability/Slices/SliceExtractor.cs` - `SliceExtractor` extracting reachability slices
  - `src/Scanner/__Libraries/StellaOps.Scanner.Reachability/Slices/SliceModels.cs` - Slice data models
- **OCI Storage**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage.Oci/SlicePushService.cs` - `SlicePushService` pushing slices to OCI registries
  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage.Oci/SliceOciManifestBuilder.cs` - Building OCI manifests for slice storage
- **Tests**:
  - `src/Scanner/__Tests/StellaOps.Scanner.WebService.Tests/SliceEndpointsTests.cs` - Endpoint integration tests
  - `src/Scanner/__Tests/StellaOps.Scanner.Reachability.Tests/Slices/SliceCacheTests.cs` - Cache tests
  - `src/Scanner/__Tests/StellaOps.Scanner.Reachability.Tests/Slices/InMemorySliceCacheTests.cs` - In-memory cache tests

## E2E Test Plan
- [ ] POST to /api/slices/query with a scan reference and verify a reachability slice is generated and returned with its content-addressed digest
- [ ] GET /api/slices/{digest} and verify the previously generated slice is retrieved with correct content
- [ ] POST to /api/slices/replay with a slice and verify byte-for-byte replay produces an identical slice (determinism check)
- [ ] Introduce a modification and verify replay produces a detailed diff showing the mismatch
- [ ] Verify the in-memory slice cache returns cached slices within TTL and regenerates after expiry
- [ ] Verify slices are pushable to OCI registries via `SlicePushService`

---

## Verification

| Check | Result |
|-------|--------|
| Tier 0 - Source files exist | PASS |
| Tier 1 - Build + code review | PASS |
| Tier 2 - Integration tests | PASS |
| Verified | 2026-02-13T18:10:00Z |