# coding=utf-8
# Adapted from
# https://github.com/huggingface/transformers/blob/v4.28.0/src/transformers/models/llama/modeling_llama.py
# Copyright 2023 DeciAI Research Team. All rights reserved.
# Copyright 2023 The vLLM team.
# Copyright 2022 EleutherAI and the HuggingFace Inc. team. All rights reserved.
#
# This code is based on MistralAI GPT-NeoX library and the GPT-NeoX
# and OPT implementations in this library. It has been modified from its
# original forms to accommodate minor architectural differences compared
# to GPT-NeoX and OPT used by the Meta AI team that trained the model.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Inference-only DeciLM model compatible with HuggingFace weights."""

from typing import Optional

import torch
from transformers import PretrainedConfig

from vllm.config import LoRAConfig
from vllm.model_executor.layers.linear import LinearMethodBase
from vllm.model_executor.models.llama import LlamaForCausalLM
from vllm.model_executor.weight_utils import (default_weight_loader,
                                              hf_model_weights_iterator)


class DeciLMForCausalLM(LlamaForCausalLM):
    """
    Implementation for https://huggingface.co/Deci/DeciLM-7b-instruct.
    Based on the llama executor.

    The main difference is that DeciLM uses Variable Grouped Query Attention.
    The constant number of GQA heads in the decoder is overridden with a value
    per layer.

    Usually, in the HuggingFace implementation, instead of
    "config.num_key_value_heads", we use
    "config.num_key_value_heads_per_layer[i]" which varies.

    Currently, PagedAttention does not work well with variable GQA, so we
    normalize the weights upon loading, and use uniform GQA with the max value
    instead.
    """

    def __init__(
        self,
        config: Optional[PretrainedConfig] = None,
        linear_method: Optional[LinearMethodBase] = None,
        lora_config: Optional[LoRAConfig] = None,
    ) -> None:
        config.num_key_value_heads = max(config.num_key_value_heads_per_layer)
        delattr(config, "num_key_value_heads_per_layer")
        super().__init__(config=config,
                         linear_method=linear_method,
                         lora_config=lora_config)

    def load_weights(self,
                     model_name_or_path: str,
                     cache_dir: Optional[str] = None,
                     load_format: str = "auto",
                     revision: Optional[str] = None):
        stacked_params_mapping = [
            # (param_name, shard_name, shard_id)
            ("qkv_proj", "q_proj", "q"),
            ("qkv_proj", "k_proj", "k"),
            ("qkv_proj", "v_proj", "v"),
            ("gate_up_proj", "gate_proj", 0),
            ("gate_up_proj", "up_proj", 1),
        ]
        params_dict = dict(self.named_parameters())
        for name, loaded_weight in hf_model_weights_iterator(
                model_name_or_path, cache_dir, load_format, revision):
            if "rotary_emb.inv_freq" in name:
                continue

            if "k_proj" in name or "v_proj" in name:
                loaded_weight = self._degroup_weight(loaded_weight)

            for (param_name, weight_name, shard_id) in stacked_params_mapping:
                if weight_name not in name:
                    continue
                name = name.replace(weight_name, param_name)
                # Skip loading extra bias for GPTQ models.
                if name.endswith(".bias") and name not in params_dict:
                    continue
                param = params_dict[name]
                weight_loader = param.weight_loader
                weight_loader(param, loaded_weight, shard_id)
                break
            else:
                # Skip loading extra bias for GPTQ models.
                if name.endswith(".bias") and name not in params_dict:
                    continue
                param = params_dict[name]
                weight_loader = getattr(param, "weight_loader",
                                        default_weight_loader)
                weight_loader(param, loaded_weight)

    def _degroup_weight(self, loaded_weight: torch.Tensor) -> torch.Tensor:
        hidden_size = self.config.hidden_size
        head_size = self.config.hidden_size // self.config.num_attention_heads
        target_num_kv_heads = self.config.num_key_value_heads
        num_kv_heads = loaded_weight.shape[0] // head_size
        n_repeats = target_num_kv_heads / num_kv_heads
        assert n_repeats == int(n_repeats)

        n_repeats = int(n_repeats)
        loaded_weight = loaded_weight.view(num_kv_heads, head_size,
                                           hidden_size)
        loaded_weight = torch.repeat_interleave(loaded_weight,
                                                repeats=n_repeats,
                                                dim=0)
        loaded_weight = loaded_weight.reshape(target_num_kv_heads * head_size,
                                              hidden_size)

        return loaded_weight
