import time

import torch
import torch.nn as nn
from typing import Dict, Tuple, Optional

from task import input_t, output_t


# Reference code in PyTorch
class Expert(nn.Module):
    def __init__(self, config: Dict, d_expert: Optional[int] = None):
        super().__init__()
        self.config = config
        self.act_fn = nn.SiLU()
        self.d_hidden: int = config["d_hidden"]
        self.d_expert: int = config["d_expert"] if d_expert is None else d_expert

        self.W_gate = nn.Linear(self.d_hidden, self.d_expert, bias=False)
        self.W_up = nn.Linear(self.d_hidden, self.d_expert, bias=False)
        self.W_down = nn.Linear(self.d_expert, self.d_hidden, bias=False)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        gate = self.act_fn(self.W_gate(x))
        out = self.W_down(gate * self.W_up(x))
        return out


class MoEGate(nn.Module):
    def __init__(self, config: Dict):
        super().__init__()
        self.top_k: int = config["n_experts_per_token"]
        self.num_experts: int = config["n_routed_experts"]
        self.d_hidden: int = config["d_hidden"]

        self.W_g = nn.Linear(self.d_hidden, self.num_experts, bias=False)

    def forward(self, x: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
        logits = self.W_g(x)
        scores = logits.softmax(dim=-1)
        topk_scores, topk_indices = torch.topk(scores, k=self.top_k, dim=-1, sorted=False)

        return topk_indices, topk_scores


class MoE(nn.Module):
    def __init__(self, config: Dict):
        super().__init__()
        self.config = config
        self.experts = nn.ModuleList([
            Expert(config)
            for _ in range(config["n_routed_experts"])
        ])
        self.gating_network = MoEGate(config)
        shared_expert_dim = config["d_expert"] * config["n_shared_experts"]
        self.shared_expert = Expert(config=config, d_expert=shared_expert_dim)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        shared_output = self.shared_expert(x)
        expert_indices, expert_scores = self.gating_network(x)
        batch_size, seq_len, hidden_dim = x.shape
        orig_shape = x.shape
        x_flat = x.view(-1, hidden_dim)
        flat_expert_indices = expert_indices.view(-1)
        flat_expert_weights = expert_scores.view(-1, 1)
        routed_output_flat = self.moe_infer(x_flat,
                                            flat_expert_indices,
                                            flat_expert_weights)

        routed_output = routed_output_flat.view(*orig_shape)
        return routed_output + shared_output

    @torch.no_grad()
    def moe_infer(self,
                  x: torch.Tensor,
                  flat_expert_indices: torch.Tensor,
                  flat_expert_weights: torch.Tensor
                 ) -> torch.Tensor:
        expert_cache = torch.zeros_like(x)
        idxs = flat_expert_indices.argsort()
        counts = flat_expert_indices.bincount().cpu().numpy()
        tokens_per_expert = counts.cumsum()
        num_per_tok = self.config["n_experts_per_token"]
        token_idxs = idxs // num_per_tok
        for expert_id, end_idx in enumerate(tokens_per_expert):
            start_idx = 0 if expert_id == 0 else tokens_per_expert[expert_id - 1]
            if start_idx == end_idx:
                continue

            expert = self.experts[expert_id]
            exp_token_idxs = token_idxs[start_idx:end_idx]
            expert_tokens = x[exp_token_idxs]
            expert_out    = expert(expert_tokens)
            expert_out.mul_(flat_expert_weights[idxs[start_idx:end_idx]])
            expert_cache.scatter_reduce_(
                0,
                exp_token_idxs.view(-1, 1).repeat(1, x.shape[-1]),
                expert_out,
                reduce='sum'
            )

        return expert_cache


def custom_kernel(data: input_t) -> output_t:
    """
    Reference implementation of DeepSeek-style Mixture of Experts using PyTorch.
    
    Args:
        data: Tuple of (input: torch.Tensor, weights: Dict[str, torch.Tensor], config: Dict)
            - input: Input tensor of shape [batch_size, seq_len, hidden_dim]
            - weights: Dictionary containing model weights
            - config: Dictionary containing model configuration parameters
            
    Returns:
        Tuple containing:
            - output: Processed tensor [batch_size, seq_len, d_model]
            - aux_data: Dictionary with auxiliary data
    """
    print(f"begin kernel {time.time()}")
    input_tensor, weights, config = data
    num_experts = config["n_routed_experts"]
    moe = MoE(config)
    print(f"begin copy {time.time()}")
    # Fill in the given weights of the model
    moe.gating_network.W_g.weight = nn.Parameter(weights['router.weight'])

    for i in range(num_experts):
        gate_proj_weight = weights[f'experts.{i}.0.weight']
        up_proj_weight = weights[f'experts.{i}.1.weight']
        down_proj_weight = weights[f'experts.{i}.2.weight']

        # Transpose weights to match expected shape for nn.Linear
        moe.experts[i].W_gate.weight = nn.Parameter(gate_proj_weight.t())
        moe.experts[i].W_up.weight = nn.Parameter(up_proj_weight.t())
        moe.experts[i].W_down.weight = nn.Parameter(down_proj_weight.t())

    moe.shared_expert.W_gate.weight = nn.Parameter(weights['shared_experts.0.weight'].t())
    moe.shared_expert.W_up.weight = nn.Parameter(weights['shared_experts.1.weight'].t())
    moe.shared_expert.W_down.weight = nn.Parameter(weights['shared_experts.2.weight'].t())

    # print(f"begin compute {time.time()}")
    output = moe(input_tensor)
    # print(f"end compute {time.time()}")

    return output

python eval.py leaderboard /tmp/tmp9guqwwqs
begin kernel 1747136428.900362
begin copy 1747136436.2073312
begin kernel 1747136445.4466503
begin copy 1747136452.7371674
begin kernel 1747136452.9515064
begin copy 1747136460.232797
begin kernel 1747136460.445301
begin copy 1747136467.7259853
begin kernel 1747136467.9453435
begin copy 1747136475.2163317
begin kernel 1747136482.9338205
begin copy 1747136490.1902514
begin kernel 1747136497.872399
begin copy 1747136505.1253529
begin kernel 1747136512.8023226
begin copy 1747136520.0546045
begin kernel 1747136527.7299218
begin copy 1747136534.9845579
begin kernel 1747136542.6715186
begin copy 1747136549.9033356
begin kernel 1747136557.586839
begin copy 1747136564.8187535
begin kernel 1747136572.5035734
begin copy 1747136579.7401502
