feat: 安全领取并分派采购任务 (#72)

client/src/task_repository.py

@@ -224,6 +224,32 @@ class TaskRepository:
             connection.close()
         return self._to_detail(row) if row is not None else None
 
+    def next_runnable_task(
+        self, *, include_purchase: bool
+    ) -> Optional[TaskDetail]:
+        """按领取顺序返回当前执行器能够处理的最早本地任务。"""
+
+        if include_purchase:
+            where = (
+                "((task_type = 'collect'"
+                " AND status IN ('claimed', 'retry_wait'))"
+                " OR (task_type = 'purchase' AND status = 'claimed'))"
+            )
+        else:
+            where = (
+                "task_type = 'collect'"
+                " AND status IN ('claimed', 'retry_wait')"
+            )
+        connection = open_database(self._db_path)
+        try:
+            row = connection.execute(
+                f"SELECT * FROM pdd_tasks WHERE {where}"
+                " ORDER BY received_at ASC, id ASC LIMIT 1"
+            ).fetchone()
+        finally:
+            connection.close()
+        return self._to_detail(row) if row is not None else None
+
     def validate_collect_rerun(self, remote_task_id: str) -> TaskDetail:
         """校验任务能否重新采集，成功时返回任务详情。"""