feat(ml,backend): implemente le service de scoring et GET /predictions (#37)

apps/backend/app/services/prediction.py

@@ -0,0 +1,68 @@
+from dataclasses import dataclass
+from datetime import UTC, datetime
+
+from app.models.energy import Prediction, Site
+from app.repositories.prediction import PredictionRepository
+from app.repositories.site import SiteRepository
+
+
+@dataclass(frozen=True, slots=True)
+class SitePrediction:
+    target_at: datetime
+    target_metric: str
+    period_minutes: int | None
+    predicted_value: float | None
+    status: str
+    failure_reason: str | None
+    model_reference: str
+    created_at: datetime
+
+
+@dataclass(frozen=True, slots=True)
+class SitePredictionSummary:
+    site_id: str
+    site_name: str
+    prediction: SitePrediction | None
+
+
+@dataclass(frozen=True, slots=True)
+class PredictionSummary:
+    timestamp: datetime
+    sites: list[SitePredictionSummary]
+
+
+class PredictionService:
+    def __init__(self, sites: SiteRepository, predictions: PredictionRepository) -> None:
+        self._sites = sites
+        self._predictions = predictions
+
+    async def summary(self) -> PredictionSummary:
+        sites = await self._sites.list_all()
+        dernieres = {p.site_id: p for p in await self._predictions.latest_by_site()}
+
+        return PredictionSummary(
+            timestamp=datetime.now(UTC),
+            sites=[_resume_site(site, dernieres.get(site.site_id)) for site in sites],
+        )
+
+
+def _resume_site(site: Site, derniere: Prediction | None) -> SitePredictionSummary:
+    # Piège : l'absence de ligne signifie « jamais scoré », pas une valeur pseudo-statut, qui
+    # n'existe pas dans la contrainte de la table. `prediction` reste `None` plutôt que de
+    # fabriquer un statut absent du domaine `available`/`insufficient_data`/`error`.
+    prediction = None
+    if derniere is not None:
+        prediction = SitePrediction(
+            target_at=derniere.target_at,
+            target_metric=derniere.target_metric,
+            period_minutes=derniere.period_minutes,
+            predicted_value=derniere.predicted_value,
+            status=derniere.status,
+            failure_reason=derniere.failure_reason,
+            model_reference=derniere.model_reference,
+            created_at=derniere.created_at,
+        )
+
+    return SitePredictionSummary(
+        site_id=site.site_id, site_name=site.site_name, prediction=prediction
+    )