import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
from torchvision import datasets, transforms
import sys

dataset="MNIST"
if(len(sys.argv) > 1):
    if(sys.argv[1].upper() == "F" or sys.argv[1].upper() == "FASHION"):
        dataset="FashionMNIST"
# Define the CNN architecture
class Net(nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        self.conv1 = nn.Conv2d(in_channels=1, out_channels=6, kernel_size=5, stride=1, padding=2)
        self.conv2 = nn.Conv2d(in_channels=6, out_channels=16, kernel_size=5, stride=1, padding=0)
        self.fc1 = nn.Linear(in_features=400, out_features=120)
        self.fc2 = nn.Linear(in_features=120, out_features=84)
        self.fc3 = nn.Linear(in_features=84, out_features=10)

    def forward(self, x):
        x = F.relu(self.conv1(x))
        x = F.max_pool2d(x, kernel_size=2, stride=2)
        x = F.relu(self.conv2(x))
        x = F.max_pool2d(x, kernel_size=2, stride=2)
        x = torch.flatten(x, 1)
        x = F.relu(self.fc1(x))
        x = F.relu(self.fc2(x))
        x = self.fc3(x)
        return x

# Hyperparameters
batch_size = 64
test_batch_size = 1000
epochs = 10
learning_rate = 0.001
log_interval = 100  # Log training progress every 100 batches

# Set device (GPU if available, else CPU)
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
print(device)

# Data preprocessing and augmentation
transform = transforms.Compose([
    transforms.ToTensor(),  # Convert PIL images to tensors
    transforms.Normalize((0.1307,), (0.3081,))  # Normalize images
])

# Load datasets
if(dataset=="FashionMNIST"):
    train_dataset = datasets.FashionMNIST('data', train=True, download=True, transform=transform)
    test_dataset = datasets.FashionMNIST('data', train=False, transform=transform)
else:
    train_dataset = datasets.MNIST('data', train=True, download=True, transform=transform)
    test_dataset = datasets.MNIST('data', train=False, transform=transform)

train_loader = torch.utils.data.DataLoader(train_dataset, batch_size=batch_size, shuffle=True)
test_loader = torch.utils.data.DataLoader(test_dataset, batch_size=test_batch_size, shuffle=False)

# Initialize model and optimizer
model = Net().to(device)
optimizer = optim.Adam(model.parameters(), lr=learning_rate)
criterion = nn.CrossEntropyLoss()  # Combines softmax and NLL loss

# Training function
def train(model, device, train_loader, optimizer, epoch):
    model.train()
    losses = []
    correct = 0
    for batch_idx, (data, target) in enumerate(train_loader):
        data, target = data.to(device), target.to(device)
        optimizer.zero_grad()
        output = model(data)
        loss = criterion(output, target)
        loss.backward()
        optimizer.step()
        losses.append(loss.item())
        pred = output.argmax(dim=1, keepdim=True)
        correct += pred.eq(target.view_as(pred)).sum().item()

        if batch_idx % log_interval == 0 and batch_idx != 0:
            print(f'{dataset}: Epoch {epoch} [{batch_idx * len(data)}/{len(train_loader.dataset)}] Loss: {loss.item():.6f}')

    avg_loss = sum(losses) / len(losses)
    accuracy = 100. * correct / len(train_loader.dataset)
    print(f'{dataset}: Epoch {epoch} - Avg Loss: {avg_loss:.6f}, Accuracy: {accuracy:.2f}%')

# Test function
def test(model, device, test_loader):
    model.eval()
    test_loss = 0
    correct = 0
    with torch.no_grad():
        for data, target in test_loader:
            data, target = data.to(device), target.to(device)
            output = model(data)
            test_loss += criterion(output, target).item()
            pred = output.argmax(dim=1, keepdim=True)
            correct += pred.eq(target.view_as(pred)).sum().item()

    test_loss /= len(test_loader.dataset)
    accuracy = 100. * correct / len(test_loader.dataset)
    print(f'\nTest Set - Loss: {test_loss:.4f}, Accuracy: {accuracy:.2f}%\n')

# Training loop
for epoch in range(1, epochs + 1):
    train(model, device, train_loader, optimizer, epoch)
    test(model, device, test_loader)

# Save the trained model
torch.save(model.state_dict(), "mnist_cnn.pth")
print("Model saved as mnist_cnn.pth")