feat(rulebook): service layer — subscriptions + get_applicable_rules

src/fabledassistant/services/rulebooks.py

@@ -343,3 +343,116 @@ async def delete_rule(rule_id: int, user_id: int) -> None:
             return
         await session.delete(rule)
         await session.commit()
+
+
+# ── Subscriptions + get_applicable_rules ───────────────────────────────
+
+from sqlalchemy import insert, delete as sql_delete
+
+
+async def subscribe_project(
+    project_id: int, rulebook_id: int, user_id: int,
+) -> None:
+    """Add a subscription. Idempotent — duplicates raise; we swallow."""
+    from fabledassistant.models.rulebook import project_rulebook_subscriptions
+
+    async with async_session() as session:
+        await _assert_rulebook_owned(session, rulebook_id, user_id)
+        # ON CONFLICT DO NOTHING via try/except to keep dialect-agnostic.
+        try:
+            await session.execute(
+                insert(project_rulebook_subscriptions).values(
+                    project_id=project_id, rulebook_id=rulebook_id,
+                )
+            )
+            await session.commit()
+        except Exception:
+            await session.rollback()  # PK collision = already subscribed; fine.
+
+
+async def unsubscribe_project(
+    project_id: int, rulebook_id: int, user_id: int,
+) -> None:
+    from fabledassistant.models.rulebook import project_rulebook_subscriptions
+
+    async with async_session() as session:
+        await _assert_rulebook_owned(session, rulebook_id, user_id)
+        await session.execute(
+            sql_delete(project_rulebook_subscriptions).where(
+                project_rulebook_subscriptions.c.project_id == project_id,
+                project_rulebook_subscriptions.c.rulebook_id == rulebook_id,
+            )
+        )
+        await session.commit()
+
+
+async def get_applicable_rules(
+    project_id: int, user_id: int, limit: int = 50,
+) -> dict:
+    """Return rules applicable to a project via its subscriptions.
+
+    Shape:
+        {
+          "rules": [{id, title, statement, topic_title, rulebook_title}, ...],
+          "truncated": bool,
+          "subscribed_rulebooks": [{id, title}, ...]
+        }
+    """
+    from fabledassistant.models.rulebook import project_rulebook_subscriptions
+
+    async with async_session() as session:
+        # Subscribed rulebooks for the project (ownership-scoped).
+        sub_q = (
+            select(Rulebook.id, Rulebook.title)
+            .join(
+                project_rulebook_subscriptions,
+                project_rulebook_subscriptions.c.rulebook_id == Rulebook.id,
+            )
+            .where(
+                project_rulebook_subscriptions.c.project_id == project_id,
+                Rulebook.owner_user_id == user_id,
+            )
+            .order_by(Rulebook.title)
+        )
+        sub_rows = (await session.execute(sub_q)).all()
+        subscribed_rulebooks = [
+            {"id": rb_id, "title": rb_title} for rb_id, rb_title in sub_rows
+        ]
+
+        # Applicable rules (limit + 1 so we can detect truncation).
+        rules_q = (
+            select(
+                Rule.id, Rule.title, Rule.statement,
+                RulebookTopic.title.label("topic_title"),
+                Rulebook.title.label("rulebook_title"),
+            )
+            .join(RulebookTopic, Rule.topic_id == RulebookTopic.id)
+            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
+            .join(
+                project_rulebook_subscriptions,
+                project_rulebook_subscriptions.c.rulebook_id == Rulebook.id,
+            )
+            .where(
+                project_rulebook_subscriptions.c.project_id == project_id,
+                Rulebook.owner_user_id == user_id,
+            )
+            .order_by(
+                Rulebook.id, RulebookTopic.order_index, Rule.order_index, Rule.title,
+            )
+            .limit(limit + 1)
+        )
+        rule_rows = (await session.execute(rules_q)).all()
+        truncated = len(rule_rows) > limit
+        rules = [
+            {
+                "id": rid, "title": rtitle, "statement": stmt,
+                "topic_title": tt, "rulebook_title": rbt,
+            }
+            for rid, rtitle, stmt, tt, rbt in rule_rows[:limit]
+        ]
+
+    return {
+        "rules": rules,
+        "truncated": truncated,
+        "subscribed_rulebooks": subscribed_rulebooks,
+    }