import torch
import torch.nn as nn
import torch.nn.functional as F

class EvoEncoder(nn.Module):
    def __init__(self, d_model=512, num_heads=8, ffn_dim=1024, num_layers=6, memory_enabled=True):
        super().__init__()
        self.embedding = nn.Embedding(30522, d_model)
        encoder_layer = nn.TransformerEncoderLayer(
            d_model=d_model,
            nhead=num_heads,
            dim_feedforward=ffn_dim,
            batch_first=True
        )
        self.transformer = nn.TransformerEncoder(encoder_layer, num_layers=num_layers)
        self.memory_enabled = memory_enabled
        if memory_enabled:
            self.memory_proj = nn.Linear(d_model, d_model)
            self.memory_token = nn.Parameter(torch.zeros(1, 1, d_model))

    def forward(self, input_ids):
        x = self.embedding(input_ids)
        if self.memory_enabled:
            mem = self.memory_token.expand(x.size(0), -1, -1)
            x = torch.cat([mem, x], dim=1)
        x = self.transformer(x)
        return x[:, 0]  # Return memory token or first token

class EvoTransformer(nn.Module):
    def __init__(self, d_model=512, num_heads=8, ffn_dim=1024, num_layers=6, num_classes=1, memory_enabled=True):
        super().__init__()
        self.encoder = EvoEncoder(d_model, num_heads, ffn_dim, num_layers, memory_enabled)
        self.classifier = nn.Linear(d_model, num_classes)

    def forward(self, input_ids):
        x = self.encoder(input_ids)
        return self.classifier(x)