reafator pipeline stage/step pipeline (#1368)

Signed-off-by: asukaqaq-s <1311722138@qq.com>

vllm_omni/diffusion/sched/interface.py

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from __future__ import annotations
+
+import enum
+from dataclasses import dataclass
+
+from vllm_omni.diffusion.request import OmniDiffusionRequest
+
+
+class DiffusionRequestStatus(enum.IntEnum):
+    """Request status tracked by diffusion scheduler."""
+
+    WAITING = enum.auto()
+    RUNNING = enum.auto()
+    PREEMPTED = enum.auto()
+
+    # if any status is after or equal to FINISHED_COMPLETED, it is considered finished
+    FINISHED_COMPLETED = enum.auto()
+    FINISHED_ABORTED = enum.auto()
+    FINISHED_ERROR = enum.auto()
+
+    @staticmethod
+    def is_finished(status: DiffusionRequestStatus) -> bool:
+        return status >= DiffusionRequestStatus.FINISHED_COMPLETED
+
+
+@dataclass
+class DiffusionRequestState:
+    """Scheduler-owned state for one queued OmniDiffusionRequest."""
+
+    sched_req_id: str
+    req: OmniDiffusionRequest
+    status: DiffusionRequestStatus = DiffusionRequestStatus.WAITING
+    error: str | None = None
+
+    def is_finished(self) -> bool:
+        return DiffusionRequestStatus.is_finished(self.status)
+
+
+@dataclass
+class DiffusionSchedulerOutput:
+    """Output of a single scheduling cycle.
+
+    Kept intentionally small so step-execution components can share a stable
+    transport shape while scheduler policy continues to evolve.
+    """
+
+    step_id: int
+    req_states: list[DiffusionRequestState]
+    finished_req_ids: set[str]
+    num_running_reqs: int
+    num_waiting_reqs: int