from datetime import datetime
import time

from utils import json_file_to_pyobj, get_loaders
from WideResNet import WideResNet
from opacus.validators import ModuleValidator
import os
from pathlib import Path
from torch.optim.lr_scheduler import MultiStepLR
from torchvision.datasets import CIFAR10
from torch.utils.data import DataLoader
import os
import torch
import torch.nn as nn
from torchvision import models, transforms
import student_model 
import torch.optim as optim
import torch.nn.functional as F
import opacus
import warnings
warnings.filterwarnings("ignore")


def train_knowledge_distillation(teacher, student, train_dl, epochs, learning_rate, T, soft_target_loss_weight, ce_loss_weight, device):
    # Dataset
    ce_loss = nn.CrossEntropyLoss()
    optimizer = optim.Adam(student.parameters(), lr=learning_rate)

    teacher.eval()  # Teacher set to evaluation mode
    student.train() # Student to train mode

    for epoch in range(epochs):
        running_loss = 0.0
        for inputs, labels in train_dl:
            inputs, labels = inputs.to(device), labels.to(device)

            optimizer.zero_grad()

            # Forward pass with the teacher model - do not save gradients here as we do not change the teacher's weights
            with torch.no_grad():
                teacher_logits, _, _, _ = teacher(inputs)

            # Forward pass with the student model
            student_logits = student(inputs)
            #Soften the student logits by applying softmax first and log() second
            soft_targets = nn.functional.softmax(teacher_logits / T, dim=-1)
            soft_prob = nn.functional.log_softmax(student_logits / T, dim=-1)

            # Calculate the soft targets loss. Scaled by T**2 as suggested by the authors of the paper "Distilling the knowledge in a neural network"
            soft_targets_loss = torch.sum(soft_targets * (soft_targets.log() - soft_prob)) / soft_prob.size()[0] * (T**2)

            # Calculate the true label loss
            label_loss = ce_loss(student_logits, labels)

            # Weighted sum of the two losses
            loss = soft_target_loss_weight * soft_targets_loss + ce_loss_weight * label_loss

            loss.backward()
            optimizer.step()

            running_loss += loss.item()

        print(f"Epoch {epoch+1}/{epochs}, Loss: {running_loss / len(train_dl)}")

@torch.no_grad()
def test(model, device, test_dl, teacher=False):
    model.to(device)
    model.eval()

    correct = 0
    total = 0

    for inputs, labels in test_dl:
        inputs, labels = inputs.to(device), labels.to(device)
        if teacher:
            outputs, _, _, _ = model(inputs)
        else:
            outputs = model(inputs)
        _, predicted = torch.max(outputs.data, 1)

        total += labels.size(0)
        correct += (predicted == labels).sum().item()

    accuracy = 100 * correct / total
    print(f"Test Accuracy: {accuracy:.2f}%")
    return accuracy

def main():
    json_options = json_file_to_pyobj("wresnet16-audit-cifar10.json")
    training_configurations = json_options.training

    wrn_depth = training_configurations.wrn_depth
    wrn_width = training_configurations.wrn_width
    dataset = training_configurations.dataset.lower()

    if torch.cuda.is_available():
        device = torch.device('cuda:0')
    else:
        device = torch.device('cpu')
    epochs=10

    print("Load the teacher model")
    # instantiate teacher model
    strides = [1, 1, 2, 2]    
    teacher = WideResNet(d=wrn_depth, k=wrn_width, n_classes=10, input_features=3, output_features=16, strides=strides)
    teacher = ModuleValidator.fix(teacher)    
    criterion = nn.CrossEntropyLoss()
    optimizer = optim.SGD(teacher.parameters(), lr=0.1, momentum=0.9, nesterov=True, weight_decay=5e-4)
    scheduler = MultiStepLR(optimizer, milestones=[int(elem*epochs) for elem in [0.3, 0.6, 0.8]], gamma=0.2)
    train_loader, test_loader = get_loaders(dataset, training_configurations.batch_size)
    best_test_set_accuracy = 0
    dp_epsilon = 8
    dp_delta = 1e-5
    norm = 1.0 
    privacy_engine = opacus.PrivacyEngine()
    teacher, optimizer, train_loader = privacy_engine.make_private_with_epsilon(
            module=teacher,
            optimizer=optimizer,
            data_loader=train_loader,
            epochs=epochs,
            target_epsilon=dp_epsilon,
            target_delta=dp_delta,
            max_grad_norm=norm,
        )

    teacher.load_state_dict(torch.load(os.path.join("wrn-1733078278-8e-1e-05d-12.0n-dict.pt"), weights_only=True))
    teacher.to(device)
    teacher.eval()
    #instantiate istudent
    student = student_model.Model(num_classes=10).to(device)


    print("Training student")
    train_knowledge_distillation(teacher=teacher, student=student, train_dl=train_loader, epochs=100, learning_rate=0.001, T=2, soft_target_loss_weight=0.25, ce_loss_weight=0.75, device=device)
    print("Saving student")
    current_datetime = datetime.now()
    filename = f"students/studentmodel{current_datetime.strftime('%Y%m%d_%H%M%S')}.pt"
    torch.save(student.state_dict(), filename)
    print("Testing student and teacher")
    test_student = test(student, device, test_loader,)
    test_teacher = test(teacher, device, test_loader, True)
    print(f"Teacher accuracy: {test_teacher:.2f}%")
    print(f"Student accuracy: {test_student:.2f}%")


if __name__ == "__main__":
    main()