app.py

import gradio as gr
import torch
from torch import nn
from torchvision import models, transforms
import cv2
import numpy as np
import os

# Load OpenCV face detector
face_cascade = cv2.CascadeClassifier(cv2.data.haarcascades + 'haarcascade_frontalface_default.xml')

# --- Model Architecture ---
class DeepfakeModel(nn.Module):
    def __init__(self, num_classes=2, latent_dim=2048, lstm_layers=1, hidden_dim=2048, bidirectional=False):
        super(DeepfakeModel, self).__init__()
        resnext = models.resnext50_32x4d(pretrained=True)
        self.model = nn.Sequential(*list(resnext.children())[:-2])
        self.lstm = nn.LSTM(latent_dim, hidden_dim, lstm_layers, bidirectional)
        self.dp = nn.Dropout(0.4)
        self.linear1 = nn.Linear(2048, num_classes)
        self.avgpool = nn.AdaptiveAvgPool2d(1)

    def forward(self, x):
        batch_size, seq_length, c, h, w = x.shape
        x = x.view(batch_size * seq_length, c, h, w)
        fmap = self.model(x)
        x = self.avgpool(fmap)
        x = x.view(batch_size, seq_length, 2048)
        x_lstm, _ = self.lstm(x, None)
        return fmap, self.dp(self.linear1(x_lstm[:, -1, :]))

device = "cuda" if torch.cuda.is_available() else "cpu"

# Load Model Weights
model = DeepfakeModel().to(device)

MODEL_PATH = "model_93_acc_100_frames_celeb_FF_data.pt"

model_found = False

try:
    model.load_state_dict(torch.load(MODEL_PATH, map_location=device))
    model.eval()
    model_found = True
    print(f"✅ Loaded model: {MODEL_PATH}")
except Exception as e:
    print(f"❌ Error loading model: {e}")

transform = transforms.Compose([
    transforms.ToPILImage(),
    transforms.Resize((112, 112)),
    transforms.ToTensor(),
    transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
])

def predict(video):
    if not model_found:
        return "❌ Error: No .pt model file found in Space.", 0.0

    cap = cv2.VideoCapture(video)
    frames = []
    # Extract up to 20 frames with faces
    while cap.isOpened() and len(frames) < 20:
        ret, frame = cap.read()
        if not ret: break
        
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        faces = face_cascade.detectMultiScale(gray, 1.1, 4)
        if len(faces) > 0:
            (x, y, w, h) = faces[0]
            face_crop = frame[y:y+h, x:x+w]
            rgb_face = cv2.cvtColor(face_crop, cv2.COLOR_BGR2RGB)
            frames.append(transform(rgb_face))
    cap.release()

    if len(frames) < 5:
        return "⚠️ No faces detected in video.", 0.0

    input_tensor = torch.stack(frames).unsqueeze(0).to(device)
    with torch.no_grad():
        _, outputs = model(input_tensor)
        probabilities = torch.softmax(outputs, dim=1)
        confidence, prediction = torch.max(probabilities, 1)

    label = "REAL" if prediction.item() == 1 else "FAKE"
    conf = round(float(confidence.item()) * 100, 2)
    return label, conf

# --- Gradio UI ---
demo = gr.Interface(
    fn=predict,
    inputs=gr.Video(label="Upload Video"),
    outputs=[
        gr.Textbox(label="Result"),
        gr.Number(label="Confidence (%)")
    ],
    title="Deepfake Detection API",
    description="Upload a video to analyze it for deepfakes using our ResNext-LSTM model."
)

if __name__ == "__main__":
    demo.launch()