feat: add feed given event handling

- Add FEED_GIVEN to FeedInventoryProjection with apply/revert
- Add give_feed method to FeedService
- Block feed given if no purchase exists <= ts_utc
- Validate feed type and location existence
- 13 new tests for give_feed functionality

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/animaltrack/projections/feed.py

@@ -3,7 +3,7 @@
 
 from typing import Any
 
-from animaltrack.events.types import FEED_PURCHASED
+from animaltrack.events.types import FEED_GIVEN, FEED_PURCHASED
 from animaltrack.models.events import Event
 from animaltrack.projections.base import Projection
 
@@ -25,17 +25,21 @@ class FeedInventoryProjection(Projection):
 
     def get_event_types(self) -> list[str]:
         """Return the event types this projection handles."""
-        return [FEED_PURCHASED]
+        return [FEED_PURCHASED, FEED_GIVEN]
 
     def apply(self, event: Event) -> None:
         """Apply feed event to update inventory."""
         if event.type == FEED_PURCHASED:
             self._apply_feed_purchased(event)
+        elif event.type == FEED_GIVEN:
+            self._apply_feed_given(event)
 
     def revert(self, event: Event) -> None:
         """Revert feed event from inventory."""
         if event.type == FEED_PURCHASED:
             self._revert_feed_purchased(event)
+        elif event.type == FEED_GIVEN:
+            self._revert_feed_given(event)
 
     def _apply_feed_purchased(self, event: Event) -> None:
         """Apply feed purchase to inventory.
@@ -86,3 +90,47 @@ class FeedInventoryProjection(Projection):
             """,
             (total_kg, total_kg, ts_utc, feed_type_code),
         )
+
+    def _apply_feed_given(self, event: Event) -> None:
+        """Apply feed given to inventory.
+
+        - Increment given_kg
+        - Decrement balance_kg
+        - Update last_given_at_utc
+        """
+        feed_type_code = event.entity_refs.get("feed_type_code")
+        amount_kg = event.entity_refs.get("amount_kg")
+        ts_utc = event.ts_utc
+
+        self.db.execute(
+            """
+            UPDATE feed_inventory
+            SET given_kg = given_kg + ?,
+                balance_kg = balance_kg - ?,
+                last_given_at_utc = ?,
+                updated_at_utc = ?
+            WHERE feed_type_code = ?
+            """,
+            (amount_kg, amount_kg, ts_utc, ts_utc, feed_type_code),
+        )
+
+    def _revert_feed_given(self, event: Event) -> None:
+        """Revert feed given from inventory.
+
+        - Decrement given_kg
+        - Increment balance_kg
+        """
+        feed_type_code = event.entity_refs.get("feed_type_code")
+        amount_kg = event.entity_refs.get("amount_kg")
+        ts_utc = event.ts_utc
+
+        self.db.execute(
+            """
+            UPDATE feed_inventory
+            SET given_kg = given_kg - ?,
+                balance_kg = balance_kg + ?,
+                updated_at_utc = ?
+            WHERE feed_type_code = ?
+            """,
+            (amount_kg, amount_kg, ts_utc, feed_type_code),
+        )

src/animaltrack/services/feed.py

@@ -4,13 +4,14 @@
 from typing import Any
 
 from animaltrack.db import transaction
-from animaltrack.events.payloads import FeedPurchasedPayload
+from animaltrack.events.payloads import FeedGivenPayload, FeedPurchasedPayload
 from animaltrack.events.processor import process_event
 from animaltrack.events.store import EventStore
-from animaltrack.events.types import FEED_PURCHASED
+from animaltrack.events.types import FEED_GIVEN, FEED_PURCHASED
 from animaltrack.models.events import Event
 from animaltrack.projections import ProjectionRegistry
 from animaltrack.repositories.feed_types import FeedTypeRepository
+from animaltrack.repositories.locations import LocationRepository
 
 
 class FeedServiceError(Exception):
@@ -45,6 +46,7 @@ class FeedService:
         self.event_store = event_store
         self.registry = registry
         self.feed_type_repo = FeedTypeRepository(db)
+        self.location_repo = LocationRepository(db)
 
     def purchase_feed(
         self,
@@ -108,3 +110,81 @@ class FeedService:
             process_event(event, self.registry)
 
         return event
+
+    def give_feed(
+        self,
+        payload: FeedGivenPayload,
+        ts_utc: int,
+        actor: str,
+        nonce: str | None = None,
+        route: str | None = None,
+    ) -> Event:
+        """Record feed given to animals.
+
+        Creates a FeedGiven event and updates inventory.
+        Decrements balance_kg by the given amount.
+
+        Args:
+            payload: Validated give feed payload.
+            ts_utc: Timestamp in milliseconds since epoch.
+            actor: The user performing the action.
+            nonce: Optional idempotency nonce.
+            route: Required if nonce provided.
+
+        Returns:
+            The created event.
+
+        Raises:
+            ValidationError: If feed type doesn't exist, is inactive,
+                           location doesn't exist, or no prior purchase.
+        """
+        # Validate feed type exists and is active
+        feed_type = self.feed_type_repo.get(payload.feed_type_code)
+        if feed_type is None:
+            msg = f"Feed type '{payload.feed_type_code}' not found"
+            raise ValidationError(msg)
+
+        if not feed_type.active:
+            msg = f"Feed type '{payload.feed_type_code}' is inactive"
+            raise ValidationError(msg)
+
+        # Validate location exists
+        location = self.location_repo.get(payload.location_id)
+        if location is None:
+            msg = f"Location '{payload.location_id}' not found"
+            raise ValidationError(msg)
+
+        # Check that a purchase exists for this feed type <= ts_utc
+        row = self.db.execute(
+            """
+            SELECT 1 FROM feed_inventory
+            WHERE feed_type_code = ? AND last_purchase_at_utc <= ?
+            """,
+            (payload.feed_type_code, ts_utc),
+        ).fetchone()
+
+        if row is None:
+            msg = f"No feed purchased for '{payload.feed_type_code}' before this date"
+            raise ValidationError(msg)
+
+        # Build entity_refs
+        entity_refs = {
+            "feed_type_code": payload.feed_type_code,
+            "location_id": payload.location_id,
+            "amount_kg": payload.amount_kg,
+        }
+
+        with transaction(self.db):
+            event = self.event_store.append_event(
+                event_type=FEED_GIVEN,
+                ts_utc=ts_utc,
+                actor=actor,
+                entity_refs=entity_refs,
+                payload=payload.model_dump(),
+                nonce=nonce,
+                route=route,
+            )
+
+            process_event(event, self.registry)
+
+        return event