app.py

import pandas as pd
import numpy as np
import torch
import torch.nn as nn
from transformers import BertTokenizer, BertModel
from sklearn.preprocessing import StandardScaler, LabelEncoder
from sklearn.ensemble import IsolationForest
import warnings
warnings.filterwarnings('ignore')

class FraudDetectionTester:
    def __init__(self, model_path='fraud_detection_model.pth'):
        """Initialize the fraud detection tester"""
        self.device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
        self.tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
        self.model_path = model_path
        self.model = None
        self.scaler = None
        self.label_encoder = None
        self.isolation_forest = None
        
        # Load the model
        self.load_model()
    
    def create_bert_fraud_model(self, numerical_features_dim):
        """Recreate the BERT fraud detection model architecture"""
        
        class BERTFraudDetector(nn.Module):
            def __init__(self, bert_model_name, numerical_features_dim, dropout_rate=0.3):
                super(BERTFraudDetector, self).__init__()
                
                # BERT for text processing
                self.bert = BertModel.from_pretrained(bert_model_name)
                
                # Freeze BERT parameters for faster training (optional)
                for param in self.bert.parameters():
                    param.requires_grad = False
                
                # Unfreeze last few layers for fine-tuning
                for param in self.bert.encoder.layer[-2:].parameters():
                    param.requires_grad = True
                
                # Feature processing layers
                self.text_projection = nn.Linear(self.bert.config.hidden_size, 256)
                self.numerical_projection = nn.Linear(numerical_features_dim, 256)
                
                # Anomaly detection features
                self.anomaly_detector = nn.Sequential(
                    nn.Linear(256, 128),
                    nn.ReLU(),
                    nn.Dropout(dropout_rate),
                    nn.Linear(128, 64),
                    nn.ReLU(),
                    nn.Linear(64, 1)
                )
                
                # Combined classifier
                self.classifier = nn.Sequential(
                    nn.Linear(512 + 1, 256),  # 256 + 256 + 1 (anomaly score)
                    nn.ReLU(),
                    nn.Dropout(dropout_rate),
                    nn.Linear(256, 128),
                    nn.ReLU(),
                    nn.Dropout(dropout_rate),
                    nn.Linear(128, 64),
                    nn.ReLU(),
                    nn.Linear(64, 1),
                    nn.Sigmoid()
                )
                
            def forward(self, input_ids, attention_mask, numerical_features):
                # Process text with BERT
                bert_output = self.bert(input_ids=input_ids, attention_mask=attention_mask)
                text_features = self.text_projection(bert_output.pooler_output)
                
                # Process numerical features
                numerical_features = self.numerical_projection(numerical_features)
                
                # Anomaly detection
                anomaly_score = self.anomaly_detector(numerical_features)
                
                # Combine all features
                combined_features = torch.cat([text_features, numerical_features, anomaly_score], dim=1)
                
                # Final classification
                fraud_probability = self.classifier(combined_features)
                
                return fraud_probability.squeeze(), anomaly_score.squeeze()
        
        return BERTFraudDetector('bert-base-uncased', numerical_features_dim)
    
    def load_model(self):
        """Load the pre-trained fraud detection model"""
        try:
            print(f"🔄 Loading model from {self.model_path}...")
            
            # Add safe globals for sklearn objects
            torch.serialization.add_safe_globals([
                StandardScaler,
                LabelEncoder, 
                IsolationForest
            ])
            
            # Load with weights_only=False for backward compatibility
            # This is safe if you trust the source of the model file
            checkpoint = torch.load(self.model_path, map_location=self.device, weights_only=False)
            
            # Load preprocessing objects
            self.scaler = checkpoint['scaler']
            self.label_encoder = checkpoint['label_encoder']
            self.isolation_forest = checkpoint['isolation_forest']
            
            # Create and load model
            numerical_features_dim = 14  # Same as training
            self.model = self.create_bert_fraud_model(numerical_features_dim)
            self.model.load_state_dict(checkpoint['model_state_dict'])
            self.model.to(self.device)
            self.model.eval()
            
            print("✅ Model loaded successfully!")
            
        except FileNotFoundError:
            print(f"❌ Error: Model file '{self.model_path}' not found!")
            print("Make sure you have trained and saved the model first.")
            raise
        except Exception as e:
            print(f"❌ Error loading model: {str(e)}")
            print("If you're still getting errors, try updating PyTorch or ensure the model file is from a trusted source.")
            raise
    
    def tokenize_descriptions(self, descriptions, max_length=128):
        """Tokenize transaction descriptions for BERT"""
        # Convert pandas Series to list if needed
        if hasattr(descriptions, 'tolist'):
            descriptions = descriptions.tolist()
        elif isinstance(descriptions, str):
            descriptions = [descriptions]
        elif not isinstance(descriptions, list):
            descriptions = list(descriptions)
        
        # Ensure all descriptions are strings
        descriptions = [str(desc) for desc in descriptions]
        
        encoded = self.tokenizer(
            descriptions,
            truncation=True,
            padding=True,
            max_length=max_length,
            return_tensors='pt'
        )
        
        return encoded['input_ids'], encoded['attention_mask']
    
    def preprocess_single_transaction(self, transaction):
        """Preprocess a single transaction for prediction"""
        # Create DataFrame from transaction
        if isinstance(transaction, dict):
            df = pd.DataFrame([transaction])
        else:
            df = pd.DataFrame(transaction)
        
        # Feature engineering (same as training)
        df['amount_log'] = np.log1p(df['amount'])
        df['is_weekend'] = (df['day_of_week'] >= 5).astype(int)
        df['is_night'] = ((df['hour'] >= 22) | (df['hour'] <= 6)).astype(int)
        df['high_frequency'] = (df['transaction_count_1h'] > 3).astype(int)
        df['amount_deviation'] = abs(df['amount'] - df['avg_amount_1h']) / (df['avg_amount_1h'] + 1)
        
        # Handle unknown categories for merchant_category
        try:
            df['merchant_category_encoded'] = self.label_encoder.transform(df['merchant_category'])
        except ValueError as e:
            print(f"⚠️  Warning: Unknown merchant category '{df['merchant_category'].iloc[0]}'. Using default value.")
            # Use the first category as default or assign a default encoded value
            df['merchant_category_encoded'] = 0
        
        # Prepare numerical features
        numerical_features = ['amount_log', 'hour', 'day_of_week', 'days_since_last_transaction',
                            'transaction_count_1h', 'transaction_count_24h', 'avg_amount_1h',
                            'location_risk_score', 'account_age_days', 'merchant_category_encoded',
                            'is_weekend', 'is_night', 'high_frequency', 'amount_deviation']
        
        X_numerical = self.scaler.transform(df[numerical_features])
        
        # Process text - ensure it's a string
        df['processed_description'] = df['description'].astype(str).str.lower().str.replace(r'[^\w\s]', '', regex=True)
        
        return df, X_numerical
    
    def predict_fraud(self, transactions):
        """Predict fraud for one or more transactions"""
        print("🔍 Analyzing transactions for fraud...")
        
        # Handle single transaction
        if isinstance(transactions, dict):
            transactions = [transactions]
        
        results = []
        
        for i, transaction in enumerate(transactions):
            try:
                # Preprocess transaction
                df, X_numerical = self.preprocess_single_transaction(transaction)
                
                # Tokenize description - extract the actual string values
                processed_descriptions = df['processed_description'].tolist()
                input_ids, attention_masks = self.tokenize_descriptions(processed_descriptions)
                
                # Make prediction
                with torch.no_grad():
                    batch_num = torch.tensor(X_numerical).float().to(self.device)
                    batch_ids = input_ids.to(self.device)
                    batch_masks = attention_masks.to(self.device)
                    
                    fraud_prob, anomaly_score = self.model(batch_ids, batch_masks, batch_num)
                    
                    # Get isolation forest prediction
                    isolation_pred = self.isolation_forest.decision_function(X_numerical)
                    
                    # Handle single prediction vs batch
                    if isinstance(fraud_prob, torch.Tensor):
                        if fraud_prob.dim() == 0:  # Single prediction
                            fraud_prob_val = fraud_prob.item()
                            anomaly_score_val = anomaly_score.item()
                        else:  # Batch prediction
                            fraud_prob_val = fraud_prob[0].item()
                            anomaly_score_val = anomaly_score[0].item()
                    else:
                        fraud_prob_val = float(fraud_prob)
                        anomaly_score_val = float(anomaly_score)
                    
                    # Combine predictions (ensemble approach)
                    combined_score = (0.6 * fraud_prob_val + 
                                    0.3 * (1 - (isolation_pred[0] + 0.5)) + 
                                    0.1 * anomaly_score_val)
                
                # Create result
                result = {
                    'transaction_id': transaction.get('transaction_id', f'test_{i+1}'),
                    'amount': transaction['amount'],
                    'description': transaction['description'],
                    'fraud_probability': float(combined_score),
                    'is_fraud_predicted': bool(combined_score > 0.5),
                    'risk_level': self.get_risk_level(combined_score),
                    'anomaly_score': float(anomaly_score_val),
                    'bert_score': float(fraud_prob_val),
                    'isolation_score': float(isolation_pred[0])
                }
                
                results.append(result)
                
            except Exception as e:
                print(f"❌ Error processing transaction {i+1}: {str(e)}")
                import traceback
                traceback.print_exc()  # Print full error traceback for debugging
                results.append({
                    'transaction_id': transaction.get('transaction_id', f'test_{i+1}'),
                    'error': str(e)
                })
        
        return results
    
    def get_risk_level(self, score):
        """Determine risk level based on fraud probability"""
        if score > 0.8:
            return 'CRITICAL'
        elif score > 0.6:
            return 'HIGH'
        elif score > 0.4:
            return 'MEDIUM'
        elif score > 0.2:
            return 'LOW'
        else:
            return 'MINIMAL'
    
    def display_results(self, results):
        """Display prediction results in a nice format"""
        print("\n" + "="*80)
        print("🚨 FRAUD DETECTION RESULTS")
        print("="*80)
        
        for i, result in enumerate(results):
            if 'error' in result:
                print(f"\n❌ Transaction {i+1}: ERROR - {result['error']}")
                continue
            
            print(f"\n📋 Transaction {i+1}:")
            print(f"   ID: {result['transaction_id']}")
            print(f"   Amount: ${result['amount']:.2f}")
            print(f"   Description: {result['description']}")
            print(f"   🎯 Fraud Probability: {result['fraud_probability']:.4f} ({result['fraud_probability']*100:.2f}%)")
            
            # Color-coded prediction
            if result['is_fraud_predicted']:
                print(f"   🚨 Prediction: FRAUD DETECTED")
            else:
                print(f"   ✅ Prediction: LEGITIMATE")
            
            print(f"   📊 Risk Level: {result['risk_level']}")
            print(f"   🔍 Anomaly Score: {result['anomaly_score']:.4f}")
            print(f"   🤖 BERT Score: {result['bert_score']:.4f}")
            print(f"   🏝️  Isolation Score: {result['isolation_score']:.4f}")
            
            # Risk indicator
            risk_bar = "█" * int(result['fraud_probability'] * 20)
            print(f"   📈 Risk Meter: [{risk_bar:<20}] {result['fraud_probability']*100:.1f}%")
        
        print("\n" + "="*80)

def create_sample_transactions():
    """Create sample transactions for testing"""
    return [
        {
            'transaction_id': 'TEST_001',
            'amount': 45.67,
            'merchant_category': 'grocery',
            'description': 'WALMART SUPERCENTER CA 1234',
            'hour': 14,
            'day_of_week': 2,
            'days_since_last_transaction': 1.0,
            'transaction_count_1h': 1,
            'transaction_count_24h': 3,
            'avg_amount_1h': 50.0,
            'location_risk_score': 0.1,
            'account_age_days': 730
        },
        {
            'transaction_id': 'TEST_002',
            'amount': 2999.99,
            'merchant_category': 'online',
            'description': 'SUSPICIOUS ELECTRONICS STORE XX 9999',
            'hour': 3,
            'day_of_week': 6,
            'days_since_last_transaction': 60.0,
            'transaction_count_1h': 12,
            'transaction_count_24h': 25,
            'avg_amount_1h': 150.0,
            'location_risk_score': 0.95,
            'account_age_days': 15
        },
        {
            'transaction_id': 'TEST_003',
            'amount': 89.50,
            'merchant_category': 'restaurant',
            'description': 'STARBUCKS COFFEE NY 5678',
            'hour': 8,
            'day_of_week': 1,
            'days_since_last_transaction': 0.5,
            'transaction_count_1h': 1,
            'transaction_count_24h': 4,
            'avg_amount_1h': 85.0,
            'location_risk_score': 0.2,
            'account_age_days': 1095
        },
        {
            'transaction_id': 'TEST_004',
            'amount': 500.00,
            'merchant_category': 'atm',
            'description': 'ATM WITHDRAWAL FOREIGN COUNTRY 0000',
            'hour': 23,
            'day_of_week': 0,
            'days_since_last_transaction': 0.1,
            'transaction_count_1h': 5,
            'transaction_count_24h': 8,
            'avg_amount_1h': 200.0,
            'location_risk_score': 0.8,
            'account_age_days': 365
        }
    ]

def create_custom_transaction():
    """Interactive function to create custom transaction"""
    print("\n🛠️  CREATE CUSTOM TRANSACTION")
    print("-" * 40)
    
    transaction = {}
    
    try:
        transaction['transaction_id'] = input("Transaction ID (optional): ") or 'CUSTOM_001'
        transaction['amount'] = float(input("Amount ($): "))
        
        print("Merchant categories: grocery, gas_station, restaurant, online, retail, atm")
        transaction['merchant_category'] = input("Merchant category: ") or 'online'
        
        transaction['description'] = input("Transaction description: ") or 'Unknown merchant'
        transaction['hour'] = int(input("Hour (0-23): "))
        transaction['day_of_week'] = int(input("Day of week (0=Monday, 6=Sunday): "))
        transaction['days_since_last_transaction'] = float(input("Days since last transaction: "))
        transaction['transaction_count_1h'] = int(input("Transactions in last hour: "))
        transaction['transaction_count_24h'] = int(input("Transactions in last 24 hours: "))
        transaction['avg_amount_1h'] = float(input("Average amount in last hour ($): "))
        transaction['location_risk_score'] = float(input("Location risk score (0-1): "))
        transaction['account_age_days'] = float(input("Account age in days: "))
        
        return transaction
        
    except ValueError as e:
        print(f"❌ Invalid input: {e}")
        return None

def main():
    """Main testing function"""
    print("🚀 FRAUD DETECTION MODEL TESTER")
    print("="*50)
    
    # Initialize tester
    try:
        tester = FraudDetectionTester('fraud_detection_model.pth')
    except:
        print("Make sure you have the trained model file 'fraud_detection_model.pth' in the same directory!")
        return
    
    while True:
        print("\n📋 TESTING OPTIONS:")
        print("1. Test with sample transactions")
        print("2. Create custom transaction")
        print("3. Test single transaction")
        print("4. Exit")
        
        choice = input("\nEnter your choice (1-4): ").strip()
        
        if choice == '1':
            # Test with sample transactions
            sample_transactions = create_sample_transactions()
            results = tester.predict_fraud(sample_transactions)
            tester.display_results(results)
            
        elif choice == '2':
            # Create custom transaction
            custom_transaction = create_custom_transaction()
            if custom_transaction:
                results = tester.predict_fraud([custom_transaction])
                tester.display_results(results)
            
        elif choice == '3':
            # Quick single transaction test
            print("\n⚡ QUICK TRANSACTION TEST")
            print("-" * 30)
            
            try:
                quick_transaction = {
                    'transaction_id': 'QUICK_TEST',
                    'amount': float(input("Amount ($): ")),
                    'merchant_category': 'online',
                    'description': input("Description: ") or 'Unknown transaction',
                    'hour': int(input("Hour (0-23): ")),
                    'day_of_week': 2,
                    'days_since_last_transaction': 1.0,
                    'transaction_count_1h': int(input("Transactions in last hour: ")),
                    'transaction_count_24h': 5,
                    'avg_amount_1h': 100.0,
                    'location_risk_score': float(input("Risk score (0-1): ")),
                    'account_age_days': 365
                }
                
                results = tester.predict_fraud([quick_transaction])
                tester.display_results(results)
                
            except ValueError as e:
                print(f"❌ Invalid input: {e}")
            
        elif choice == '4':
            print("👋 Goodbye!")
            break
            
        else:
            print("❌ Invalid choice! Please enter 1-4.")

if __name__ == "__main__":
    main()