feat(api): validate canon log at every role endpoint (422 on invalid)

api/app/main.py

@@ -1,15 +1,31 @@
 """FastAPI proxy entrypoint — the guarding proxy of charter §4.
 
-Skeleton only: a health check plus the five role endpoints as stubs so the
+Skeleton: a health check plus the five role endpoints. Each role endpoint now
-container runs and the client has something to point at. Real prompt routing,
+validates the posted canon log against the contract (charter §11) before doing
-model selection, logging, and auth land later — all server-side (§4, §5).
+anything else — an invalid log is rejected with 422 and never reaches a prompt.
+Prompt routing, model selection, and logging land later.
 """
 
-from fastapi import FastAPI
+from fastapi import Depends, FastAPI, HTTPException
+from pydantic import BaseModel
+
+from .canon_log import validate_canon_log
 
 app = FastAPI(title="coc-rpg proxy", version="0.0.1")
 
 
+class TurnRequest(BaseModel):
+    canon_log: dict
+
+
+def valid_turn(req: TurnRequest) -> TurnRequest:
+    """Shared dependency: reject any request whose canon log breaks the contract."""
+    errors = validate_canon_log(req.canon_log)
+    if errors:
+        raise HTTPException(status_code=422, detail={"canon_log_errors": errors})
+    return req
+
+
 @app.get("/health")
 def health() -> dict:
     """Liveness probe for compose / fly.io."""
@@ -18,30 +34,30 @@ def health() -> dict:
 
 # ── Role endpoints (charter §4) ──────────────────────────────────────────────
 # The client knows these paths and nothing about which model or prompt serves
-# them. Stubs for now; each will load its prompt from api/prompts/ and route to
+# them. Bodies are validated against the canon log contract; the AI half is a
-# the configured model.
+# stub until prompt routing lands.
 
 
 @app.post("/dm/narrate")
-def narrate() -> dict:
+def narrate(req: TurnRequest = Depends(valid_turn)) -> dict:
     return {"detail": "not implemented"}
 
 
 @app.post("/dm/adjudicate")
-def adjudicate() -> dict:
+def adjudicate(req: TurnRequest = Depends(valid_turn)) -> dict:
     return {"detail": "not implemented"}
 
 
 @app.post("/dm/improvise")
-def improvise() -> dict:
+def improvise(req: TurnRequest = Depends(valid_turn)) -> dict:
     return {"detail": "not implemented"}
 
 
 @app.post("/npc/speak")
-def npc_speak() -> dict:
+def npc_speak(req: TurnRequest = Depends(valid_turn)) -> dict:
     return {"detail": "not implemented"}
 
 
 @app.post("/party/banter")
-def banter() -> dict:
+def banter(req: TurnRequest = Depends(valid_turn)) -> dict:
     return {"detail": "not implemented"}

api/tests/test_endpoints.py

@@ -0,0 +1,38 @@
+import json
+from pathlib import Path
+
+from fastapi.testclient import TestClient
+
+from app.main import app
+
+client = TestClient(app)
+VALID_LOG = json.load(open(Path(__file__).parent / "fixtures" / "canon_log_valid.json"))
+
+ROLE_ENDPOINTS = [
+    "/dm/narrate", "/dm/adjudicate", "/dm/improvise",
+    "/npc/speak", "/party/banter",
+]
+
+
+def test_health_ok():
+    assert client.get("/health").json() == {"status": "ok"}
+
+
+def test_every_role_endpoint_accepts_a_valid_canon_log():
+    for path in ROLE_ENDPOINTS:
+        r = client.post(path, json={"canon_log": VALID_LOG})
+        assert r.status_code == 200, f"{path} rejected a valid log: {r.text}"
+
+
+def test_every_role_endpoint_rejects_an_invalid_canon_log():
+    bad = json.loads(json.dumps(VALID_LOG))
+    bad["player"]["luck"] = 5  # §7 leak
+    for path in ROLE_ENDPOINTS:
+        r = client.post(path, json={"canon_log": bad})
+        assert r.status_code == 422, f"{path} accepted an invalid log"
+        assert "canon_log_errors" in r.json()["detail"]
+
+
+def test_missing_canon_log_is_a_422():
+    r = client.post("/dm/narrate", json={})
+    assert r.status_code == 422