feat: add basic QEMU and task vertical slice

app/tasks/qemu.py

@@ -0,0 +1,43 @@
+"""Worker semantics for asynchronous QEMU transitions."""
+
+from __future__ import annotations
+
+import json
+import uuid
+
+from app.simulation.clock import Clock
+from app.simulation.transitions import VmState, plan_transition
+from app.tasks.repository import Task, TaskRepository
+from app.tasks.worker import TaskHandler
+
+
+def qemu_handler(repository: TaskRepository, clock: Clock) -> TaskHandler:
+    async def execute(task: Task) -> dict[str, str]:
+        operation = task.task_type.removeprefix("qemu-")
+        resource_id = uuid.UUID(str(task.payload["resource_id"]))
+        async with repository.pool.acquire() as connection:
+            row = await connection.fetchrow("SELECT state FROM resources WHERE id=$1", resource_id)
+            if row is None:
+                raise ValueError("resource disappeared")
+            raw = row["state"]
+            state = json.loads(raw) if isinstance(raw, str) else dict(raw)
+            transition = plan_transition(VmState(str(state["status"])), operation)
+            state["status"] = transition.intermediate
+            await connection.execute(
+                "UPDATE resources SET state=$2::jsonb WHERE id=$1",
+                resource_id,
+                json.dumps(state),
+            )
+        await repository.append_log(task.id, f"VM {operation} started")
+        await clock.sleep(1.0)
+        async with repository.pool.acquire() as connection:
+            state["status"] = transition.after
+            await connection.execute(
+                "UPDATE resources SET state=$2::jsonb WHERE id=$1",
+                resource_id,
+                json.dumps(state),
+            )
+        await repository.append_log(task.id, f"VM {operation} completed")
+        return {"status": str(transition.after)}
+
+    return execute