# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

import enum
import time
from typing import Any, Optional, Union

import msgspec
import torch

from vllm.lora.request import LoRARequest
from vllm.multimodal.inputs import MultiModalFeatureSpec
from vllm.pooling_params import PoolingParams
from vllm.sampling_params import SamplingParams
from vllm.v1.metrics.stats import SchedulerStats
from vllm.v1.outputs import LogprobsLists, LogprobsTensors

# These are possible values of RequestOutput.finish_reason,
# so form part of the external API.
FINISH_REASON_STRINGS = ("stop", "length", "abort")


class FinishReason(enum.IntEnum):
    """
    Reason a request finished - stop, length, or abort.

    Int rather than Str for more compact serialization.

    stop - a stop string was emitted
    length - max_tokens was consumed, or max_model_len was reached
    abort - aborted for another reason

    """
    STOP = 0
    LENGTH = 1
    ABORT = 2

    def __str__(self):
        return FINISH_REASON_STRINGS[self.value]


class EngineCoreRequest(
        msgspec.Struct,
        array_like=True,  # type: ignore[call-arg]
        omit_defaults=True,  # type: ignore[call-arg]
        gc=False):  # type: ignore[call-arg]

    request_id: str
    prompt_token_ids: list[int]
    mm_features: Optional[list[MultiModalFeatureSpec]]
    sampling_params: Optional[SamplingParams]
    pooling_params: Optional[PoolingParams]
    eos_token_id: Optional[int]
    arrival_time: float
    lora_request: Optional[LoRARequest]
    cache_salt: Optional[str]
    data_parallel_rank: Optional[int]

    # Index of the client, used to ensure outputs are sent back to the same
    # client for this request when scaling out the front-end.
    client_index: int = 0

    # Used in DP case to indicate which wave of requests this is expected to
    # belong to, to cover a race condition where the request is sent before
    # a wave finished notification is received.
    current_wave: int = 0
    priority: int = 0


class EngineCoreEventType(enum.IntEnum):
    """The type of engine core request event."""
    QUEUED = 1
    SCHEDULED = 2
    PREEMPTED = 3


class EngineCoreEvent(msgspec.Struct):
    """A timestamped engine core event associated with a request.

    The timestamp is a monotonic timestamps and is used for by the engine
    frontend to calculate intervals between engine core events. These
    timestamps should not be compared with timestamps from other processes.
    """
    type: EngineCoreEventType
    timestamp: float

    @classmethod
    def new_event(cls,
                  event_type: EngineCoreEventType,
                  timestamp: Optional[float] = None) -> "EngineCoreEvent":
        timestamp = time.monotonic() if timestamp is None else timestamp
        return cls(event_type, timestamp)


class EngineCoreOutput(
        msgspec.Struct,
        array_like=True,  # type: ignore[call-arg]
        omit_defaults=True,  # type: ignore[call-arg]
        gc=False):  # type: ignore[call-arg]

    request_id: str
    new_token_ids: list[int]

    new_logprobs: Optional[LogprobsLists] = None
    new_prompt_logprobs_tensors: Optional[LogprobsTensors] = None

    pooling_output: Optional[torch.Tensor] = None

    finish_reason: Optional[FinishReason] = None
    stop_reason: Union[int, str, None] = None
    events: Optional[list[EngineCoreEvent]] = None
    kv_transfer_params: Optional[dict[str, Any]] = None

    # The number of tokens with prefix cache hits.
    num_cached_tokens: int = 0

    @property
    def finished(self) -> bool:
        return self.finish_reason is not None


class UtilityResult:
    """Wrapper for special handling when serializing/deserializing."""

    def __init__(self, r: Any = None):
        self.result = r


class UtilityOutput(
        msgspec.Struct,
        array_like=True,  # type: ignore[call-arg]
        gc=False):  # type: ignore[call-arg]

    call_id: int

    # Non-None implies the call failed, result should be None.
    failure_message: Optional[str] = None
    result: Optional[UtilityResult] = None


class EngineCoreOutputs(
        msgspec.Struct,
        array_like=True,  # type: ignore[call-arg]
        omit_defaults=True,  # type: ignore[call-arg]
        gc=False):  # type: ignore[call-arg]

    #NOTE(Nick): We could consider ways to make this more compact,
    # e.g. columnwise layout

    engine_index: int = 0

    # [num_reqs]
    outputs: list[EngineCoreOutput] = []
    scheduler_stats: Optional[SchedulerStats] = None
    timestamp: float = 0.0

    utility_output: Optional[UtilityOutput] = None
    finished_requests: Optional[set[str]] = None

    # In DP case, used to signal that the current wave of requests
    # has finished and the engines are paused.
    wave_complete: Optional[int] = None
    # In DP case, used to signal that a request was received for an
    # "old" wave, so the next wave needs to be started in other engines.
    start_wave: Optional[int] = None

    def __post_init__(self):
        if self.timestamp == 0.0:
            self.timestamp = time.monotonic()


class EngineCoreRequestType(enum.Enum):
    """
    Request types defined as hex byte strings, so it can be sent over sockets
    without separate encoding step.
    """
    ADD = b'\x00'
    ABORT = b'\x01'
    START_DP_WAVE = b'\x02'
    UTILITY = b'\x03'
    # Sentinel used within EngineCoreProc.
    EXECUTOR_FAILED = b'\x04'


class ReconfigureDistributedRequest(msgspec.Struct):
    new_data_parallel_size: int
    new_data_parallel_rank: int
    new_data_parallel_rank_local: int
    new_data_parallel_master_ip: str
    new_data_parallel_master_port: int


class ReconfigureRankType(enum.IntEnum):
    """
    Rank type for reconfiguring distributed request.
    """
    KEEP_CURRENT_RANK = -1
    SHUTDOWN_CURRENT_RANK = -2
