import os
import torch
import torch.nn as nn
from torchvision import transforms, utils
from torch.utils.data import DataLoader
from torchvision.datasets import ImageFolder
from tqdm import tqdm
import torch.multiprocessing


# ----------------------------
# 1. 判别器
# ----------------------------
class Detector(nn.Module):
    def __init__(self):
        super(Detector, self).__init__()
        self.model = nn.Sequential(
            # 3 x 64 x 64 -> 64 x 32 x 32
            nn.Conv2d(3, 64, 4, 2, 1, bias=False),
            nn.LeakyReLU(0.2, inplace=True),

            # 64 x 32 x 32 -> 128 x 16 x 16
            nn.Conv2d(64, 128, 4, 2, 1, bias=False),
            nn.BatchNorm2d(128),
            nn.LeakyReLU(0.2, inplace=True),

            # 128 x 16 x 16 -> 256 x 8 x 8
            nn.Conv2d(128, 256, 4, 2, 1, bias=False),
            nn.BatchNorm2d(256),
            nn.LeakyReLU(0.2, inplace=True),

            # 256 x 8 x 8 -> 512 x 4 x 4
            nn.Conv2d(256, 512, 4, 2, 1, bias=False),
            nn.BatchNorm2d(512),
            nn.LeakyReLU(0.2, inplace=True),

            # 512 x 4 x 4 -> 1024 x 2 x 2
            nn.Conv2d(512, 1024, 4, 2, 1, bias=False),
            nn.BatchNorm2d(1024),
            nn.LeakyReLU(0.2, inplace=True),

            # 1024 x 2 x 2 -> 1 x 1 x 1
            nn.Conv2d(1024, 1, 2, 1, 0, bias=False),
            nn.Sigmoid()
        )

    def forward(self, x):
        return self.model(x)


# ----------------------------
# 2. 生成器
# ----------------------------
class Generator(nn.Module):
    def __init__(self, z_dim=100):
        super(Generator, self).__init__()
        self.model = nn.Sequential(
            # z -> 1024 x 4 x 4
            nn.ConvTranspose2d(z_dim, 1024, 4, 1, 0, bias=False),
            nn.BatchNorm2d(1024),
            nn.ReLU(True),

            # 1024 x 4 x 4 -> 512 x 8 x 8
            nn.ConvTranspose2d(1024, 512, 4, 2, 1, bias=False),
            nn.BatchNorm2d(512),
            nn.ReLU(True),

            # 512 x 8 x 8 -> 256 x 16 x 16
            nn.ConvTranspose2d(512, 256, 4, 2, 1, bias=False),
            nn.BatchNorm2d(256),
            nn.ReLU(True),

            # 256 x 16 x 16 -> 128 x 32 x 32
            nn.ConvTranspose2d(256, 128, 4, 2, 1, bias=False),
            nn.BatchNorm2d(128),
            nn.ReLU(True),

            # 128 x 32 x 32 -> 3 x 64 x 64
            nn.ConvTranspose2d(128, 3, 4, 2, 1, bias=False),
            nn.Tanh()
        )

    def forward(self, z):
        return self.model(z)


# ----------------------------
# 3. 数据集加载
# ----------------------------
transform = transforms.Compose([
    transforms.Resize(64),
    transforms.CenterCrop(64),
    transforms.ToTensor(),
    transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5))
])

dataset = ImageFolder(root='./data', transform=transform)
dataloader = DataLoader(dataset, batch_size=64, shuffle=True, num_workers=4)

# ----------------------------
# 4. 参数与设备
# ----------------------------
z_dim = 100
num_epochs = 100
lr = 0.002
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

# ----------------------------
# 5. 模型与优化器
# ----------------------------
d = Detector().to(device)
g = Generator(z_dim=z_dim).to(device)
criterion = nn.BCELoss()
optimizer_d = torch.optim.Adam(d.parameters(), lr=lr, betas=(0.5, 0.999))
optimizer_g = torch.optim.Adam(g.parameters(), lr=lr, betas=(0.5, 0.999))

# 固定噪声用于观察训练过程
z_fixed = torch.randn(64, z_dim, 1, 1, device=device)

# 创建保存目录
os.makedirs("results", exist_ok=True)

# ----------------------------
# 6. 训练循环
# ----------------------------
def train():
    for epoch in range(1, num_epochs + 1):
        loss_d_total, loss_g_total = 0, 0
        for real_images, _ in tqdm(dataloader, desc=f"Epoch {epoch}/{num_epochs}", leave=False):
            real_images = real_images.to(device)
            B = real_images.size(0)

            # 标签平滑（真实 = 0.9, 假 = 0.0）
            real_labels = torch.full((B, 1, 1, 1), 0.9, device=device)
            fake_labels = torch.zeros((B, 1, 1, 1), device=device)

            # 生成假图像
            z = torch.randn(B, z_dim, 1, 1, device=device)
            fake_images = g(z)

            # 判别器训练
            output_real = d(real_images)
            output_fake = d(fake_images.detach())

            loss_real = criterion(output_real, real_labels)
            loss_fake = criterion(output_fake, fake_labels)
            loss_d = loss_real + loss_fake

            optimizer_d.zero_grad()
            loss_d.backward()
            optimizer_d.step()

            # 生成器训练
            output = d(fake_images)
            loss_g = criterion(output, real_labels)  # 欺骗D：希望D输出真
            optimizer_g.zero_grad()
            loss_g.backward()
            optimizer_g.step()

            loss_d_total += loss_d.item()
            loss_g_total += loss_g.item()

        # 平均损失
        avg_loss_d = loss_d_total / len(dataloader)
        avg_loss_g = loss_g_total / len(dataloader)
        print(f"Epoch [{epoch}/{num_epochs}]  Loss_D: {avg_loss_d:.4f}  Loss_G: {avg_loss_g:.4f}")

        # 每5轮保存一次生成图像
        if epoch % 5 == 0:
            with torch.no_grad():
                fake = g(z_fixed).detach().cpu()
                utils.save_image(fake, f"results/epoch_{epoch}.png", normalize=True, nrow=8)

if __name__ == "__main__":
    torch.multiprocessing.freeze_support()  # ✅ Windows 兼容性
    train()  # 把训练过程封装成 main() 函数