# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import dataclasses
import glob
import os
import time
from collections.abc import Generator, Iterable
from typing import cast

import torch
from torch import nn
from transformers.utils import SAFE_WEIGHTS_INDEX_NAME

from vllm.config import ModelConfig
from vllm.config.load import LoadConfig
from vllm.logger import init_logger
from vllm.model_executor.layers.quantization.torchao import torchao_version_at_least
from vllm.model_executor.model_loader.base_loader import BaseModelLoader
from vllm.model_executor.model_loader.ep_weight_filter import (
    compute_local_expert_ids,
)
from vllm.model_executor.model_loader.weight_utils import (
    download_safetensors_index_file_from_hf,
    download_weights_from_hf,
    fastsafetensors_weights_iterator,
    filter_duplicate_safetensors_files,
    filter_files_not_needed_for_inference,
    get_quant_config,
    instanttensor_weights_iterator,
    maybe_download_from_modelscope,
    multi_thread_pt_weights_iterator,
    multi_thread_safetensors_weights_iterator,
    np_cache_weights_iterator,
    pt_weights_iterator,
    safetensors_weights_iterator,
)
from vllm.tracing import instrument
from vllm.transformers_utils.repo_utils import list_filtered_repo_files

logger = init_logger(__name__)


class DefaultModelLoader(BaseModelLoader):
    """Model loader that can load different file types from disk."""

    # default number of thread when enable multithread weight loading
    DEFAULT_NUM_THREADS = 8

    @dataclasses.dataclass
    class Source:
        """A source for weights."""

        model_or_path: str
        """The model ID or path."""

        revision: str | None
        """The optional model revision."""

        subfolder: str | None = None
        """The subfolder inside the model repo."""

        prefix: str = ""
        """A prefix to prepend to all weights."""

        fall_back_to_pt: bool = True
        """Whether .pt weights can be used."""

        allow_patterns_overrides: list[str] | None = None
        """If defined, weights will load exclusively using these patterns."""

    counter_before_loading_weights: float = 0.0
    counter_after_loading_weights: float = 0.0

    def __init__(self, load_config: LoadConfig):
        super().__init__(load_config)
        self.local_expert_ids: set[int] | None = None

        extra_config = load_config.model_loader_extra_config
        allowed_keys = {"enable_multithread_load", "num_threads"}
        unexpected_keys = set(extra_config.keys()) - allowed_keys

        if unexpected_keys:
            raise ValueError(
                f"Unexpected extra config keys for load format "
                f"{load_config.load_format}: "
                f"{unexpected_keys}"
            )

    def _prepare_weights(
        self,
        model_name_or_path: str,
        subfolder: str | None,
        revision: str | None,
        fall_back_to_pt: bool,
        allow_patterns_overrides: list[str] | None,
    ) -> tuple[str, list[str], bool]:
        """Prepare weights for the model.

        If the model is not local, it will be downloaded."""
        model_name_or_path = (
            maybe_download_from_modelscope(model_name_or_path, revision)
            or model_name_or_path
        )

        is_local = os.path.isdir(model_name_or_path)
        load_format = self.load_config.load_format
        use_safetensors = False
        index_file = SAFE_WEIGHTS_INDEX_NAME

        # First check for 'auto' format that mistral files format are present.
        # This is to load mistral models with official format by default.
        if load_format == "auto":
            load_format = (
                "mistral"
                if len(
                    list_filtered_repo_files(
                        model_name_or_path=model_name_or_path,
                        allow_patterns=["consolidated*.safetensors"],
                        revision=revision,
                    )
                )
                > 0
                else "hf"
            )

        # Some quantized models use .pt files for storing the weights.
        if load_format == "hf":
            allow_patterns = ["*.safetensors", "*.bin"]
        elif (
            load_format == "safetensors"
            or load_format == "fastsafetensors"
            or load_format == "instanttensor"
        ):
            use_safetensors = True
            allow_patterns = ["*.safetensors"]
        elif load_format == "mistral":
            use_safetensors = True
            allow_patterns = ["consolidated*.safetensors"]
            index_file = "consolidated.safetensors.index.json"
        elif load_format == "pt":
            allow_patterns = ["*.pt"]
        elif load_format == "npcache":
            allow_patterns = ["*.bin"]
        else:
            raise ValueError(f"Unknown load_format: {load_format}")

        if fall_back_to_pt:
            allow_patterns += ["*.pt"]

        if allow_patterns_overrides is not None:
            allow_patterns = allow_patterns_overrides

        if not is_local:
            hf_folder = download_weights_from_hf(
                model_name_or_path,
                self.load_config.download_dir,
                allow_patterns,
                revision,
                subfolder=subfolder,
                ignore_patterns=self.load_config.ignore_patterns,
            )
        else:
            hf_folder = model_name_or_path

        if subfolder is not None:
            hf_folder = os.path.join(hf_folder, subfolder)

        hf_weights_files: list[str] = []
        for pattern in allow_patterns:
            hf_weights_files += glob.glob(os.path.join(hf_folder, pattern))
            if len(hf_weights_files) > 0:
                if pattern == "*.safetensors":
                    use_safetensors = True
                break

        if use_safetensors:
            # For models like Mistral-7B-Instruct-v0.3
            # there are both sharded safetensors files and a consolidated
            # safetensors file. Using both breaks.
            # Here, we download the `model.safetensors.index.json` and filter
            # any files not found in the index.
            if not is_local:
                download_safetensors_index_file_from_hf(
                    model_name_or_path,
                    index_file,
                    cache_dir=self.load_config.download_dir,
                    subfolder=subfolder,
                    revision=revision,
                )
            hf_weights_files = filter_duplicate_safetensors_files(
                hf_weights_files, hf_folder, index_file
            )
        else:
            hf_weights_files = filter_files_not_needed_for_inference(hf_weights_files)

        if len(hf_weights_files) == 0:
            raise RuntimeError(
                f"Cannot find any model weights with `{model_name_or_path}`"
            )

        return hf_folder, hf_weights_files, use_safetensors

    def _get_weights_iterator(
        self, source: "Source"
    ) -> Generator[tuple[str, torch.Tensor], None, None]:
        """Get an iterator for the model weights based on the load format."""
        extra_config = self.load_config.model_loader_extra_config
        hf_folder, hf_weights_files, use_safetensors = self._prepare_weights(
            source.model_or_path,
            source.subfolder,
            source.revision,
            source.fall_back_to_pt,
            source.allow_patterns_overrides,
        )
        if self.load_config.load_format == "npcache":
            # Currently np_cache only support *.bin checkpoints
            assert use_safetensors is False
            weights_iterator = np_cache_weights_iterator(
                source.model_or_path,
                self.load_config.download_dir,
                hf_folder,
                hf_weights_files,
                self.load_config.use_tqdm_on_load,
            )
        elif use_safetensors:
            if self.load_config.load_format == "fastsafetensors":
                weights_iterator = fastsafetensors_weights_iterator(
                    hf_weights_files,
                    self.load_config.use_tqdm_on_load,
                )
            elif self.load_config.load_format == "instanttensor":
                weights_iterator = instanttensor_weights_iterator(
                    hf_weights_files,
                    self.load_config.use_tqdm_on_load,
                )
            else:
                if extra_config.get("enable_multithread_load"):
                    weights_iterator = multi_thread_safetensors_weights_iterator(
                        hf_weights_files,
                        self.load_config.use_tqdm_on_load,
                        max_workers=extra_config.get(
                            "num_threads", self.DEFAULT_NUM_THREADS
                        ),
                    )
                else:
                    weights_iterator = safetensors_weights_iterator(
                        hf_weights_files,
                        self.load_config.use_tqdm_on_load,
                        self.load_config.safetensors_load_strategy,
                        local_expert_ids=self.local_expert_ids,
                    )
        else:
            if extra_config.get("enable_multithread_load"):
                weights_iterator = multi_thread_pt_weights_iterator(
                    hf_weights_files,
                    self.load_config.use_tqdm_on_load,
                    self.load_config.pt_load_map_location,
                    max_workers=extra_config.get(
                        "num_threads", self.DEFAULT_NUM_THREADS
                    ),
                )
            else:
                weights_iterator = pt_weights_iterator(
                    hf_weights_files,
                    self.load_config.use_tqdm_on_load,
                    self.load_config.pt_load_map_location,
                )

        if self.counter_before_loading_weights == 0.0:
            self.counter_before_loading_weights = time.perf_counter()
        # Apply the prefix.
        return ((source.prefix + name, tensor) for (name, tensor) in weights_iterator)

    def get_all_weights(
        self,
        model_config: ModelConfig,
        model: nn.Module,
    ) -> Generator[tuple[str, torch.Tensor], None, None]:
        primary_weights = DefaultModelLoader.Source(
            model_config.model,
            model_config.revision,
            prefix="",
            fall_back_to_pt=getattr(model, "fall_back_to_pt_during_load", True),
            allow_patterns_overrides=getattr(model, "allow_patterns_overrides", None),
        )
        yield from self._get_weights_iterator(primary_weights)

        secondary_weights = cast(
            Iterable[DefaultModelLoader.Source],
            getattr(model, "secondary_weights", ()),
        )
        for source in secondary_weights:
            yield from self._get_weights_iterator(source)

    def download_model(self, model_config: ModelConfig) -> None:
        self._prepare_weights(
            model_name_or_path=model_config.model,
            subfolder=None,
            revision=model_config.revision,
            fall_back_to_pt=True,
            allow_patterns_overrides=None,
        )

    def _init_ep_weight_filter(self, model_config: ModelConfig) -> None:
        """Compute local expert ids for EP weight filtering.

        When expert parallelism is active, each rank only needs a subset of
        expert weights.  By computing the set upfront we can skip non-local
        expert tensors *before* reading them from disk.
        """
        from vllm.config import get_current_vllm_config

        vllm_config = get_current_vllm_config()
        parallel_config = vllm_config.parallel_config

        if not (
            model_config.is_moe
            and parallel_config.enable_expert_parallel
            and parallel_config.enable_ep_weight_filter
        ):
            return

        # When EPLB is enabled, redundant physical expert slots may map to
        # logical experts that belong to other ranks in the default partition.
        # The weight loader needs to see ALL logical expert weights so it can
        # populate these redundant slots.  Skip the filter entirely.
        if parallel_config.enable_eplb:
            return

        num_experts = model_config.get_num_experts()
        if num_experts <= 0:
            return

        # EP size/rank computation mirrors FusedMoEParallelConfig.make():
        #   ep_size = dp_size * pcp_size * tp_size (flattened)
        #   ep_rank = dp_rank * pcp_size * tp_size + pcp_rank * tp_size + tp_rank
        from vllm.distributed import (
            get_dp_group,
            get_pcp_group,
            get_tensor_model_parallel_rank,
        )

        dp_size = parallel_config.data_parallel_size
        tp_size = parallel_config.tensor_parallel_size
        pcp_size = parallel_config.prefill_context_parallel_size
        dp_rank = get_dp_group().rank_in_group if dp_size > 1 else 0
        tp_rank = get_tensor_model_parallel_rank() if tp_size > 1 else 0
        pcp_rank = get_pcp_group().rank_in_group if pcp_size > 1 else 0
        ep_size = dp_size * pcp_size * tp_size
        ep_rank = dp_rank * pcp_size * tp_size + pcp_rank * tp_size + tp_rank

        self.local_expert_ids = compute_local_expert_ids(
            num_experts,
            ep_size,
            ep_rank,
            placement=parallel_config.expert_placement_strategy,
        )
        if self.local_expert_ids is not None:
            logger.info_once(
                "EP weight filter: ep_size=%d, ep_rank=%d, loading %d/%d experts",
                ep_size,
                ep_rank,
                len(self.local_expert_ids),
                num_experts,
            )

    @instrument(span_name="Load weights")
    def load_weights(self, model: nn.Module, model_config: ModelConfig) -> None:
        if model_config.quantization == "torchao":
            quant_config = get_quant_config(model_config, self.load_config)
            if (
                hasattr(quant_config, "is_checkpoint_torchao_serialized")
                and quant_config.is_checkpoint_torchao_serialized
                and torchao_version_at_least("0.15.0")
            ):
                self.load_config.safetensors_load_strategy = "torchao"

        self._init_ep_weight_filter(model_config)

        weights_to_load = {name for name, _ in model.named_parameters()}
        loaded_weights = model.load_weights(self.get_all_weights(model_config, model))

        self.counter_after_loading_weights = time.perf_counter()
        logger.info_once(
            "Loading weights took %.2f seconds",
            self.counter_after_loading_weights - self.counter_before_loading_weights,
            scope="local",
        )
        # We only enable strict check for non-quantized models
        # that have loaded weights tracking currently.
        if model_config.quantization is None and loaded_weights is not None:
            weights_not_loaded = weights_to_load - loaded_weights
            if weights_not_loaded:
                raise ValueError(
                    "Following weights were not initialized from "
                    f"checkpoint: {weights_not_loaded}"
                )
