import torch
import torch.nn as nn
from transformers import PreTrainedModel, PretrainedConfig

# 1. СНАЧАЛА ОПРЕДЕЛЯЕМ КОНФИГ
class AlphaDepthConfig(PretrainedConfig):
    model_type = "alpha-depth"
    
    def __init__(self, input_size=[3, 128, 128], **kwargs):
        self.input_size = input_size
        super().__init__(**kwargs)

# 2. ВСПОМОГАТЕЛЬНЫЕ БЛОКИ
class ConvBlock(nn.Module):
    def __init__(self, in_c, out_c):
        super().__init__()
        self.conv = nn.Sequential(
            nn.Conv2d(in_c, out_c, 3, padding=1),
            nn.BatchNorm2d(out_c),
            nn.ReLU(),
            nn.Conv2d(out_c, out_c, 3, padding=1),
            nn.BatchNorm2d(out_c),
            nn.ReLU()
        )
    def forward(self, x): return self.conv(x)

# 3. САМА МОДЕЛЬ (Наследуемся от PreTrainedModel!)
class AlphaUNet(PreTrainedModel):
    config_class = AlphaDepthConfig
    
    def __init__(self, config):
        super().__init__(config)
        # Encoder
        self.enc1 = ConvBlock(3, 32)
        self.pool = nn.MaxPool2d(2)
        self.enc2 = ConvBlock(32, 64)
        self.enc3 = ConvBlock(64, 128)
        
        # Decoder
        self.up2 = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
        self.dec2 = ConvBlock(128 + 64, 64)
        self.up1 = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
        self.dec1 = ConvBlock(64 + 32, 32)
        
        self.final = nn.Conv2d(32, 1, 1)
        self.sigmoid = nn.Sigmoid()

    def forward(self, x):
        e1 = self.enc1(x)
        e2 = self.enc2(self.pool(e1))
        e3 = self.enc3(self.pool(e2))
        
        d2 = self.up2(e3)
        d2 = torch.cat([d2, e2], dim=1)
        d2 = self.dec2(d2)
        
        d1 = self.up1(d2)
        d1 = torch.cat([d1, e1], dim=1)
        d1 = self.dec1(d1)
        
        return self.sigmoid(self.final(d1))