"""
Life cycle of a request in the prefill server

1. Bootstrap Queue
    a. Initialize a sender for each request
    b. Use the queue to store requests whose bootstrap (handshake and preallocation) has not finished
    c. Poll senders to check bootstrap state
    d. Once bootstrap is complete, move request to Waiting Queue

2. Waiting Queue
    a. Use PrefillAdder to pop requests
    b. Run forward
    c. Add the request to Inflight Queue

3. Inflight Queue
    a. Poll (non-blocking) the sender of the request
    b. Once the transfer has finished, return the request
"""

from __future__ import annotations

import logging
from collections import deque
from http import HTTPStatus
from typing import TYPE_CHECKING, List, Optional

import torch

from sglang.srt.disaggregation.base import KVPoll
from sglang.srt.disaggregation.common.conn import CommonKVManager
from sglang.srt.disaggregation.utils import (
    FAKE_BOOTSTRAP_HOST,
    DisaggregationMode,
    KVClassType,
    MetadataBuffers,
    ReqToMetadataIdxAllocator,
    TransferBackend,
    get_kv_class,
    is_mla_backend,
    kv_to_page_indices,
    kv_to_page_num,
    poll_and_all_reduce_attn_cp_tp_group,
    prepare_abort,
)
from sglang.srt.managers.schedule_batch import (
    FINISH_ABORT,
    FINISH_LENGTH,
    Req,
    ScheduleBatch,
)
from sglang.srt.mem_cache.common import release_kv_cache
from sglang.srt.mem_cache.memory_pool import HybridLinearKVPool, NSATokenToKVPool
from sglang.srt.mem_cache.swa_memory_pool import SWAKVPool
from sglang.srt.observability.req_time_stats import set_schedule_time_batch

if TYPE_CHECKING:
    from torch.distributed import ProcessGroup

    from sglang.srt.managers.scheduler import GenerationBatchResult, Scheduler
    from sglang.srt.mem_cache.memory_pool import KVCache

logger = logging.getLogger(__name__)


def release_req_to_metadata_buffer(
    req: Req, allocator: ReqToMetadataIdxAllocator
) -> None:
    """
    Release the metadata buffer index allocated for a request in prefill disaggregation mode.

    This function safely releases the metadata buffer index if it was allocated.

    Args:
        req: The request object that may have a metadata_buffer_index allocated
        allocator: The ReqToMetadataIdxAllocator instance to free the index
    """
    if (
        hasattr(req, "metadata_buffer_index")
        and req.metadata_buffer_index is not None
        and req.metadata_buffer_index >= 0
    ):
        allocator.free(req.metadata_buffer_index)
        req.metadata_buffer_index = -1


class PrefillBootstrapQueue:
    """
    Store the requests in bootstrapping
    """

    def __init__(
        self,
        token_to_kv_pool: KVCache,
        draft_token_to_kv_pool: Optional[KVCache],
        req_to_metadata_buffer_idx_allocator: ReqToMetadataIdxAllocator,
        metadata_buffers: MetadataBuffers,
        tp_rank: int,
        tp_size: int,
        gpu_id: int,
        bootstrap_port: int,
        gloo_group: ProcessGroup,
        max_total_num_tokens: int,
        scheduler: Scheduler,
        pp_rank: int,
        pp_size: int,
        transfer_backend: TransferBackend,
    ):
        self.token_to_kv_pool = token_to_kv_pool
        self.draft_token_to_kv_pool = draft_token_to_kv_pool
        self.is_mla_backend = is_mla_backend(token_to_kv_pool)
        self.metadata_buffers = metadata_buffers
        self.req_to_metadata_buffer_idx_allocator = req_to_metadata_buffer_idx_allocator
        self.tp_rank = tp_rank
        self.tp_size = tp_size
        self.pp_rank = pp_rank
        self.pp_size = pp_size
        self.gpu_id = gpu_id
        self.bootstrap_port = bootstrap_port
        self.queue: List[Req] = []
        self.gloo_group = gloo_group
        self.max_total_num_tokens = max_total_num_tokens
        self.scheduler = scheduler
        self.transfer_backend = transfer_backend
        self.kv_manager = self._init_kv_manager()

        if self.scheduler.tp_worker.is_hybrid_swa:
            # FIXME: current SWA allocation allocate full kv cache size in prefill
            self.max_total_num_tokens = min(
                self.max_total_num_tokens,
                self.scheduler.tp_worker.model_runner.swa_max_total_num_tokens,
            )

    def _init_kv_manager(self) -> CommonKVManager:
        kv_args_class = get_kv_class(self.transfer_backend, KVClassType.KVARGS)
        kv_args = kv_args_class()
        kv_args.engine_rank = self.tp_rank
        kv_args.pp_rank = self.pp_rank
        kv_args.system_dp_rank = self.scheduler.dp_rank
        kv_args.prefill_start_layer = self.token_to_kv_pool.start_layer
        kv_data_ptrs, kv_data_lens, kv_item_lens = (
            self.token_to_kv_pool.get_contiguous_buf_infos()
        )

        if self.draft_token_to_kv_pool is not None:
            # We should also transfer draft model kv cache. The indices are
            # always shared with a target model.
            draft_kv_data_ptrs, draft_kv_data_lens, draft_kv_item_lens = (
                self.draft_token_to_kv_pool.get_contiguous_buf_infos()
            )
            kv_data_ptrs += draft_kv_data_ptrs
            kv_data_lens += draft_kv_data_lens
            kv_item_lens += draft_kv_item_lens

        kv_args.kv_data_ptrs = kv_data_ptrs
        kv_args.kv_data_lens = kv_data_lens
        kv_args.kv_item_lens = kv_item_lens
        if not self.is_mla_backend:
            kv_args.kv_head_num = self.token_to_kv_pool.head_num
            kv_args.total_kv_head_num = (
                self.scheduler.model_config.get_total_num_kv_heads()
            )
        kv_args.page_size = self.token_to_kv_pool.page_size

        kv_args.aux_data_ptrs, kv_args.aux_data_lens, kv_args.aux_item_lens = (
            self.metadata_buffers.get_buf_infos()
        )
        kv_args.ib_device = self.scheduler.server_args.disaggregation_ib_device
        kv_args.gpu_id = self.scheduler.gpu_id

        if hasattr(self.token_to_kv_pool, "get_state_buf_infos"):
            state_data_ptrs, state_data_lens, state_item_lens = (
                self.token_to_kv_pool.get_state_buf_infos()
            )
            kv_args.state_data_ptrs = state_data_ptrs
            kv_args.state_data_lens = state_data_lens
            kv_args.state_item_lens = state_item_lens

            if isinstance(self.token_to_kv_pool, SWAKVPool):
                kv_args.state_type = "swa"
            elif isinstance(self.token_to_kv_pool, HybridLinearKVPool):
                kv_args.state_type = "mamba"
                # Get state dimension info for cross-TP slice transfer
                if hasattr(self.token_to_kv_pool, "get_state_dim_per_tensor"):
                    kv_args.state_dim_per_tensor = (
                        self.token_to_kv_pool.get_state_dim_per_tensor()
                    )
            elif isinstance(self.token_to_kv_pool, NSATokenToKVPool):
                kv_args.state_type = "nsa"
            else:
                kv_args.state_type = "none"
        else:
            kv_args.state_data_ptrs = []
            kv_args.state_data_lens = []
            kv_args.state_item_lens = []
            kv_args.state_type = "none"

        kv_manager_class = get_kv_class(self.transfer_backend, KVClassType.MANAGER)
        kv_manager = kv_manager_class(
            kv_args,
            DisaggregationMode.PREFILL,
            self.scheduler.server_args,
            self.is_mla_backend,
        )
        return kv_manager

    def add(self, req: Req, num_kv_heads: int) -> None:
        if self._check_if_req_exceed_kv_capacity(req):
            return

        backend = (
            TransferBackend.FAKE
            if req.bootstrap_host == FAKE_BOOTSTRAP_HOST
            else self.transfer_backend
        )
        kv_sender_class = get_kv_class(backend, KVClassType.SENDER)

        dest_tp_ranks = [self.tp_rank]

        req.disagg_kv_sender = kv_sender_class(
            mgr=self.kv_manager,
            bootstrap_addr=f"{req.bootstrap_host}:{self.bootstrap_port}",
            bootstrap_room=req.bootstrap_room,
            dest_tp_ranks=dest_tp_ranks,
            pp_rank=self.pp_rank,
        )
        self._process_req(req)
        self.queue.append(req)

    def extend(self, reqs: List[Req], num_kv_heads: int) -> None:
        for req in reqs:
            self.add(req, num_kv_heads)

    def _check_if_req_exceed_kv_capacity(self, req: Req) -> bool:
        if len(req.origin_input_ids) > self.max_total_num_tokens:
            message = f"Request {req.rid} exceeds the maximum number of tokens: {len(req.origin_input_ids)} > {self.max_total_num_tokens}"
            logger.error(message)
            req.time_stats.trace_ctx.abort(abort_info={"reason": message})
            prepare_abort(req, message, status_code=HTTPStatus.BAD_REQUEST)
            self.scheduler.stream_output([req], req.return_logprob)
            return True
        return False

    def _process_req(self, req: Req) -> None:
        """
        Set max_new_tokens = 1, so PrefillAdder memory estimation is accurate
        """
        req.sampling_params.max_new_tokens = 1

    def pop_bootstrapped(
        self,
        return_failed_reqs: bool = False,
        rids_to_check: Optional[List[str]] = None,
    ) -> List[Req]:
        """
        pop the reqs which has finished bootstrapping

        return_failed_reqs: For PP, on rank 0, also return the failed reqs to notify the next rank
        rids_to_check: For PP, on rank > 0, check the rids from the previous rank has consensus with the current rank.
        """

        bootstrapped_reqs = []
        failed_reqs = []
        indices_to_remove = set()

        if len(self.queue) == 0:
            if return_failed_reqs is False:
                return []
            else:
                return [], []

        polls = poll_and_all_reduce_attn_cp_tp_group(
            [req.disagg_kv_sender for req in self.queue],
            self.scheduler.attn_cp_cpu_group,
            self.scheduler.attn_tp_cpu_group,
        )

        for i, (req, poll) in enumerate(zip(self.queue, polls)):
            if rids_to_check is not None:
                # if req not in reqs_info_to_check, skip
                if req.rid not in rids_to_check:
                    continue

            if poll == KVPoll.Bootstrapping:
                continue
            elif poll == KVPoll.Failed:
                error_message = f"Prefill bootstrap failed for request rank={self.tp_rank} {req.rid=} {req.bootstrap_room=}"
                try:
                    req.disagg_kv_sender.failure_exception()
                except Exception as e:
                    error_message += f" with exception {e}"
                logger.error(error_message)
                req.time_stats.trace_ctx.abort(abort_info={"reason": error_message})
                prepare_abort(
                    req, error_message, status_code=HTTPStatus.INTERNAL_SERVER_ERROR
                )
                self.scheduler.stream_output([req], req.return_logprob)
                indices_to_remove.add(i)
                failed_reqs.append(req)
                if self.scheduler.enable_metrics:
                    self.scheduler.metrics_collector.increment_bootstrap_failed_reqs()
                if self.scheduler.enable_hicache_storage:
                    # to release prefetch events associated with the request
                    self.scheduler.tree_cache.release_aborted_request(req.rid)
                continue

            # KV.WaitingForInput - init here
            req.time_stats.set_bootstrap_done_time()
            num_kv_indices = len(req.origin_input_ids)
            if self.req_to_metadata_buffer_idx_allocator.available_size() == 0:
                break

            req.metadata_buffer_index = (
                self.req_to_metadata_buffer_idx_allocator.alloc()
            )
            assert req.metadata_buffer_index is not None

            num_pages = kv_to_page_num(num_kv_indices, self.token_to_kv_pool.page_size)
            req.disagg_kv_sender.init(num_pages, req.metadata_buffer_index)

            bootstrapped_reqs.append(req)
            indices_to_remove.add(i)
            req.time_stats.set_wait_queue_entry_time()

        self.queue = [
            entry for i, entry in enumerate(self.queue) if i not in indices_to_remove
        ]

        if return_failed_reqs is False:
            return bootstrapped_reqs
        else:
            return bootstrapped_reqs, failed_reqs


class SchedulerDisaggregationPrefillMixin:
    """
    Mixin for Scheduler to handle disaggregation prefill
    """

    def get_next_disagg_prefill_batch_to_run(
        self: Scheduler,
    ) -> Optional[ScheduleBatch]:
        # HACK (byronhsu): reset the batch_is_full flag because we never enter update_running_batch which resets it
        # Otherwise, it hangs under high concurrency
        self.running_batch.batch_is_full = False

        self.process_prefill_chunk()

        batch = self.get_new_batch_prefill()
        batch = self.maybe_prepare_mlp_sync_batch(batch)

        if batch:
            set_schedule_time_batch(batch)

        return batch

    @torch.no_grad()
    def event_loop_normal_disagg_prefill(self: Scheduler) -> None:
        """A normal scheduler loop for prefill worker in disaggregation mode."""

        while True:
            # Receive requests
            recv_reqs = self.recv_requests()
            self.process_input_requests(recv_reqs)
            self.waiting_queue.extend(
                self.disagg_prefill_bootstrap_queue.pop_bootstrapped()
            )

            # Get the next batch to run
            batch = self.get_next_disagg_prefill_batch_to_run()
            self.cur_batch = batch

            # Launch the current batch
            if batch:
                result = self.run_batch(batch)
                self.process_batch_result(batch, result)
            else:
                self.self_check_during_idle()

            self.process_disagg_prefill_inflight_queue()

            # Update last_batch
            self.last_batch = batch

    @torch.no_grad()
    def event_loop_overlap_disagg_prefill(self: Scheduler) -> None:
        self.result_queue = deque()

        while True:
            # Receive requests
            recv_reqs = self.recv_requests()
            self.process_input_requests(recv_reqs)
            self.waiting_queue.extend(
                self.disagg_prefill_bootstrap_queue.pop_bootstrapped()
            )

            # Get the next batch to run
            batch = self.get_next_disagg_prefill_batch_to_run()
            self.cur_batch = batch

            # Launch the current batch
            if batch:
                batch_result = self.run_batch(batch)
                self.result_queue.append((batch.copy(), batch_result))
            else:
                batch_result = None

            # Process the last batch
            if self.last_batch:
                tmp_batch, tmp_result = self.result_queue.popleft()
                self.process_batch_result(tmp_batch, tmp_result)
            elif batch is None:
                # When the server is idle, do self-check and re-init some states
                self.self_check_during_idle()

            self.process_disagg_prefill_inflight_queue()

            # Run sample of the current batch
            # It depends on the result of the last batch (e.g., grammar), so we run it after the last batch is processed.
            self.launch_batch_sample_if_needed(batch_result)

            # Update last_batch
            self.last_batch = batch

    def process_batch_result_disagg_prefill(
        self: Scheduler,
        batch: ScheduleBatch,
        result: GenerationBatchResult,
    ) -> None:
        """
        Transfer kv for prefill completed requests and add it into disagg_prefill_inflight_queue
        Adapted from process_batch_result_prefill
        """
        (
            logits_output,
            next_token_ids,
            extend_input_len_per_req,
            extend_logprob_start_len_per_req,
            copy_done,
        ) = (
            result.logits_output,
            result.next_token_ids,
            result.extend_input_len_per_req,
            result.extend_logprob_start_len_per_req,
            result.copy_done,
        )

        if copy_done is not None:
            copy_done.synchronize()

        logprob_pt = 0
        # Transfer kv for prefill completed requests and add it into disagg_prefill_inflight_queue
        next_token_ids = result.next_token_ids.tolist()
        if batch.return_logprob:
            if logits_output.next_token_logprobs is not None:
                logits_output.next_token_logprobs = (
                    logits_output.next_token_logprobs.tolist()
                )
            if logits_output.input_token_logprobs is not None:
                logits_output.input_token_logprobs = tuple(
                    logits_output.input_token_logprobs.tolist()
                )

        for i, (req, next_token_id) in enumerate(
            zip(batch.reqs, next_token_ids, strict=True)
        ):
            if req.is_chunked <= 0:
                req.time_stats.set_prefill_finished_time()

                # There is no output_ids for prefill
                req.output_ids.append(next_token_id)
                self.tree_cache.cache_unfinished_req(req)  # update the tree and lock
                self.disagg_prefill_inflight_queue.append(req)
                if self.spec_algorithm.is_eagle() and batch.spec_info is not None:
                    req.output_topk_p = batch.spec_info.topk_p[i]
                    req.output_topk_index = batch.spec_info.topk_index[i]
                    req.hidden_states_tensor = (
                        batch.spec_info.hidden_states[i].cpu().clone()
                    )
                else:
                    req.hidden_states_tensor = None
                if req.return_logprob:
                    assert extend_logprob_start_len_per_req is not None
                    assert extend_input_len_per_req is not None
                    extend_logprob_start_len = extend_logprob_start_len_per_req[i]
                    extend_input_len = extend_input_len_per_req[i]
                    num_input_logprobs = extend_input_len - extend_logprob_start_len
                    self.add_logprob_return_values(
                        i,
                        req,
                        logprob_pt,
                        next_token_ids,
                        num_input_logprobs,
                        logits_output,
                    )
                    logprob_pt += num_input_logprobs
                self.send_kv_chunk(req, last_chunk=True)
                req.time_stats.set_prefill_transfer_queue_entry_time()

                if req.grammar is not None:
                    # FIXME: this try-except block is for handling unexpected xgrammar issue.
                    try:
                        req.grammar.accept_token(next_token_id)
                    except ValueError as e:
                        # Grammar accept_token can raise ValueError if the token is not in the grammar.
                        # This can happen if the grammar is not set correctly or the token is invalid.
                        error_message = f"Grammar accept_token failed for req {req.rid} with token {next_token_id}: {e}"
                        release_kv_cache(req, self.tree_cache)
                        prepare_abort(
                            req,
                            error_message,
                            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
                        )
                    req.grammar.finished = req.finished()
            else:
                # being chunked reqs' prefill is not finished
                req.is_chunked -= 1

                if req.return_logprob:
                    extend_logprob_start_len = extend_logprob_start_len_per_req[i]
                    extend_input_len = extend_input_len_per_req[i]
                    if extend_logprob_start_len < extend_input_len:
                        # Update input logprobs.
                        num_input_logprobs = extend_input_len - extend_logprob_start_len
                        self.add_input_logprob_return_values(
                            i,
                            req,
                            logits_output,
                            logprob_pt,
                            num_input_logprobs,
                            last_prefill_chunk=False,
                        )
                        logprob_pt += num_input_logprobs

                if self.enable_overlap:
                    self.send_kv_chunk(req, last_chunk=False, end_idx=req.tmp_end_idx)
                req.time_stats.set_last_chunked_prefill_finish_time()

        can_run_cuda_graph = getattr(result, "can_run_cuda_graph", False)
        self.report_prefill_stats(
            prefill_stats=batch.prefill_stats,
            can_run_cuda_graph=can_run_cuda_graph,
            dp_cooperation_info=batch.dp_cooperation_info,
        )

    def process_disagg_prefill_inflight_queue(
        self: Scheduler, rids_to_check: Optional[List[str]] = None
    ) -> List[Req]:
        """
        Poll the requests in the middle of transfer. If done, return the request.
        rids_to_check: For PP, on rank > 0, check the rids from the previous rank has consensus with the current rank.
        """
        if len(self.disagg_prefill_inflight_queue) == 0:
            return []

        done_reqs = []

        polls = poll_and_all_reduce_attn_cp_tp_group(
            [req.disagg_kv_sender for req in self.disagg_prefill_inflight_queue],
            self.attn_cp_cpu_group,
            self.attn_tp_cpu_group,
        )

        undone_reqs: List[Req] = []
        # Check .poll() for the reqs in disagg_prefill_inflight_queue. If Success, respond to the client and remove it from the queue
        for req, poll in zip(self.disagg_prefill_inflight_queue, polls):

            if rids_to_check is not None:
                if req.rid not in rids_to_check:
                    undone_reqs.append(req)
                    continue

                # In PP mode, the previous rank may have reached a terminal
                # state (Success/Failed) while this rank's local poll is still
                # in a transient state due to clock skew or propagation delay.
                # Treat non-terminal states as undone instead of crashing.
                if poll not in (
                    KVPoll.Success,
                    KVPoll.Failed,
                ):
                    logger.warning(
                        f"PP rank {self.pp_rank}: unexpected poll state {poll} for rid {req.rid} "
                        f"from consensus; treating as undone"
                    )
                    undone_reqs.append(req)
                    continue

            if poll in [KVPoll.WaitingForInput, KVPoll.Transferring]:
                undone_reqs.append(req)
            elif poll == KVPoll.Success:  # transfer done
                release_kv_cache(req, self.tree_cache)  # unlock the tree
                req.finished_reason = FINISH_LENGTH(length=0)
                # FIXME: clean up req's data in transfer engine
                if hasattr(req.disagg_kv_sender, "clear"):
                    req.disagg_kv_sender.clear()
                done_reqs.append(req)
                req.time_stats.set_prefill_kv_transfer_finish_time()
            elif poll == KVPoll.Failed:
                error_message = f"Prefill transfer failed for request rank={self.tp_rank} {req.rid=} {req.bootstrap_room=}"
                try:
                    req.disagg_kv_sender.failure_exception()
                except Exception as e:
                    error_message += f" with exception {e}"
                logger.warning(error_message)
                req.time_stats.trace_ctx.abort(abort_info={"reason": error_message})
                release_kv_cache(req, self.tree_cache)  # unlock the tree
                prepare_abort(
                    req, error_message, status_code=HTTPStatus.INTERNAL_SERVER_ERROR
                )
                done_reqs.append(req)
                if self.enable_metrics:
                    self.metrics_collector.increment_transfer_failed_reqs()
            else:
                logger.warning(
                    f"Unexpected polling state {poll} for rid {req.rid} in inflight queue; "
                    f"treating as undone"
                )
                undone_reqs.append(req)

        for req in done_reqs:
            req.time_stats.set_completion_time()

        page_size = self.token_to_kv_pool_allocator.page_size
        kv_item_lens = (
            self.disagg_prefill_bootstrap_queue.kv_manager.kv_args.kv_item_lens
        )
        bytes_per_page_all_layers = sum(kv_item_lens)

        for req in done_reqs:
            if isinstance(req.finished_reason, FINISH_ABORT):
                continue
            metrics = req.time_stats.compute_and_observe_kv_transfer_metrics(
                num_tokens=len(req.origin_input_ids),
                page_size=page_size,
                bytes_per_page_all_layers=bytes_per_page_all_layers,
            )
            if metrics:
                # Update last-value for REST API
                if "latency_ms" in metrics:
                    self.kv_transfer_latency_ms = metrics["latency_ms"]
                if "speed_gb_s" in metrics:
                    self.kv_transfer_speed_gb_s = metrics["speed_gb_s"]

        # Stream requests which have finished transfer
        self.stream_output(
            done_reqs,
            any(req.return_logprob for req in done_reqs),
            None,
        )
        for req in done_reqs:
            req: Req

            release_req_to_metadata_buffer(
                req, self.req_to_metadata_buffer_idx_allocator
            )

        self.disagg_prefill_inflight_queue = undone_reqs

        return done_reqs

    def get_transferred_rids(self: Scheduler) -> List[str]:
        """
        Used by PP, get the transferred rids but **do not pop**
        """
        polls = poll_and_all_reduce_attn_cp_tp_group(
            [req.disagg_kv_sender for req in self.disagg_prefill_inflight_queue],
            self.attn_cp_cpu_group,
            self.attn_tp_cpu_group,
        )

        transferred_rids: List[str] = []

        for req, poll in zip(self.disagg_prefill_inflight_queue, polls):
            if poll == KVPoll.Success or poll == KVPoll.Failed:
                transferred_rids.append(req.rid)

        return transferred_rids

    def process_prefill_chunk(self: Scheduler) -> None:
        chunked_req_to_exclude = set()
        if self.chunked_req:
            chunked_req_to_exclude.add(self.chunked_req)
            self.tree_cache.cache_unfinished_req(self.chunked_req, chunked=True)
            if self.enable_overlap:
                # Delay KV transfer to process_batch_result_disagg_prefill when overlap is enabled to ensure results are resolved
                self.chunked_req.tmp_end_idx = min(
                    len(self.chunked_req.fill_ids),
                    len(self.chunked_req.origin_input_ids),
                )
            else:
                self.send_kv_chunk(self.chunked_req)
            self.running_batch.batch_is_full = False

        if self.last_batch and self.last_batch.forward_mode.is_extend():
            if self.last_batch.chunked_req:
                # In the context pipeline parallelism, after the last chunk, the current microbatch still track outdated chunked_req.
                # We need to discard it.
                chunked_req_to_exclude.add(self.last_batch.chunked_req)

            last_bs = self.last_batch.batch_size()
            self.last_batch.filter_batch(
                chunked_req_to_exclude=list(chunked_req_to_exclude)
            )
            if self.last_batch.batch_size() < last_bs:
                self.running_batch.batch_is_full = False

    def send_kv_chunk(
        self: Scheduler,
        req: Req,
        last_chunk: bool = False,
        end_idx: Optional[int] = None,
    ) -> None:
        """
        Send a prefilled chunk to the decode server
        """
        page_size = self.token_to_kv_pool_allocator.page_size
        start_idx = req.start_send_idx
        end_idx = (
            end_idx
            if end_idx is not None
            else min(len(req.fill_ids), len(req.origin_input_ids))
        )

        if not last_chunk:
            # if not the last chunk and the last page is partial, delay the last partial page to the next send
            end_idx = end_idx - end_idx % page_size

        kv_indices = (
            self.req_to_token_pool.req_to_token[req.req_pool_idx, start_idx:end_idx]
            .cpu()
            .numpy()
        )
        req.start_send_idx = end_idx
        state_indices = None
        if last_chunk:
            self.disagg_metadata_buffers.set_buf(req)

            # Prepare extra pool indices for hybrid models
            if isinstance(
                self.token_to_kv_pool_allocator.get_kvcache(), HybridLinearKVPool
            ):
                # Mamba hybrid model: send single mamba state index
                state_indices = [
                    self.req_to_token_pool.req_index_to_mamba_index_mapping[
                        req.req_pool_idx
                    ]
                    .cpu()
                    .numpy()
                ]
            elif isinstance(self.token_to_kv_pool_allocator.get_kvcache(), SWAKVPool):
                # SWA hybrid model: send last window KV indices
                seq_len = len(req.fill_ids)
                window_size = self.sliding_window_size
                window_start = max(0, seq_len - window_size)
                window_start = (window_start // page_size) * page_size

                window_kv_indices_full = self.req_to_token_pool.req_to_token[
                    req.req_pool_idx, window_start:seq_len
                ]

                # Translate to SWA pool indices
                window_kv_indices_swa = (
                    self.token_to_kv_pool_allocator.translate_loc_from_full_to_swa(
                        window_kv_indices_full
                    )
                )
                state_indices = window_kv_indices_swa.cpu().numpy()
                state_indices = kv_to_page_indices(state_indices, page_size)
            elif isinstance(
                self.token_to_kv_pool_allocator.get_kvcache(), NSATokenToKVPool
            ):
                seq_len = len(req.fill_ids)
                kv_indices_full = self.req_to_token_pool.req_to_token[
                    req.req_pool_idx, :seq_len
                ]
                state_indices = kv_indices_full.cpu().numpy()
                state_indices = kv_to_page_indices(state_indices, page_size)

        page_indices = kv_to_page_indices(kv_indices, page_size)
        if len(page_indices) == 0:
            logger.info(
                f"Skip sending kv chunk for request {req.rid=} {req.bootstrap_room=} because page_indices is empty"
            )
            return
        req.disagg_kv_sender.send(page_indices, state_indices)
