scripts/testing/data_leakage_test.py

"""
Data Leakage Detection Script

Checks for common data leakage issues:
1. Duplicate URLs in train/test split
2. Feature extraction timing (done before split - CORRECT)
3. Scaler fitting (only on train data - CORRECT)
4. Feature contamination checks
"""

import pandas as pd
import numpy as np
from pathlib import Path
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
import logging

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(levelname)s - %(message)s',
    datefmt='%H:%M:%S'
)
logger = logging.getLogger("data_leakage_check")


def check_1_duplicate_urls_in_splits():
    """Check if same URLs appear in both train and test sets."""
    logger.info("\n" + "="*80)
    logger.info("CHECK 1: DUPLICATE URLs IN TRAIN/TEST SPLITS")
    logger.info("="*80)
    
    # Load original dataset with URLs
    data_dir = Path('data/processed')
    original_df = pd.read_csv(data_dir / 'clean_dataset_no_duplicates.csv')
    
    logger.info(f"\nOriginal dataset: {len(original_df):,} URLs")
    
    # Check for duplicates in original dataset
    duplicates = original_df['url'].duplicated().sum()
    logger.info(f"Duplicates in original dataset: {duplicates}")
    
    if duplicates > 0:
        logger.warning(f"⚠️  Found {duplicates} duplicate URLs in original dataset!")
        dup_urls = original_df[original_df['url'].duplicated(keep=False)]['url'].value_counts()
        logger.info(f"Top duplicated URLs:\n{dup_urls.head(10)}")
    else:
        logger.info("✓ No duplicates in original dataset")
    
    # Simulate train/test split (same as in training)
    X = original_df['url']
    y = original_df['label']
    
    X_train, X_test, y_train, y_test = train_test_split(
        X, y, test_size=0.2, random_state=42, stratify=y
    )
    
    logger.info(f"\nTrain set: {len(X_train):,} URLs")
    logger.info(f"Test set:  {len(X_test):,} URLs")
    
    # Check for overlap
    train_urls = set(X_train)
    test_urls = set(X_test)
    overlap = train_urls.intersection(test_urls)
    
    logger.info(f"\nOverlapping URLs between train/test: {len(overlap)}")
    
    if len(overlap) > 0:
        logger.error(f"❌ DATA LEAKAGE DETECTED! {len(overlap)} URLs in both train and test!")
        logger.info(f"Sample overlapping URLs:\n{list(overlap)[:5]}")
        return False
    else:
        logger.info("✓ No URL overlap between train and test sets")
        return True


def check_2_feature_extraction_timing():
    """Check if features were extracted before split (CORRECT) or after (WRONG)."""
    logger.info("\n" + "="*80)
    logger.info("CHECK 2: FEATURE EXTRACTION TIMING")
    logger.info("="*80)
    
    # Load feature dataset
    features_df = pd.read_csv('data/features/url_features.csv')
    
    logger.info(f"\nFeature dataset: {len(features_df):,} rows")
    logger.info(f"Features: {len(features_df.columns) - 1}")
    
    # Load original dataset
    original_df = pd.read_csv('data/processed/clean_dataset.csv')
    
    logger.info(f"Original dataset: {len(original_df):,} rows")
    
    # Check sizes match
    if len(features_df) == len(original_df):
        logger.info("✓ Feature extraction done on ENTIRE dataset (before split)")
        logger.info("  This is CORRECT - prevents data leakage")
        return True
    else:
        logger.warning("⚠️  Dataset sizes don't match - check extraction process")
        logger.info(f"  Difference: {abs(len(features_df) - len(original_df))}")
        return False


def check_3_scaler_fitting():
    """Check if scaler was fitted only on train data."""
    logger.info("\n" + "="*80)
    logger.info("CHECK 3: SCALER FITTING (Logistic Regression only)")
    logger.info("="*80)
    
    # Load features
    features_df = pd.read_csv('data/features/url_features.csv')
    
    X = features_df.drop('label', axis=1)
    y = features_df['label']
    
    # Split
    X_train, X_test, y_train, y_test = train_test_split(
        X, y, test_size=0.2, random_state=42, stratify=y
    )
    
    # CORRECT way: fit on train, transform both
    scaler_correct = StandardScaler()
    X_train_scaled_correct = scaler_correct.fit_transform(X_train)
    X_test_scaled_correct = scaler_correct.transform(X_test)
    
    # WRONG way: fit on all data
    scaler_wrong = StandardScaler()
    X_all_scaled_wrong = scaler_wrong.fit_transform(X)
    X_train_wrong = X_all_scaled_wrong[:len(X_train)]
    X_test_wrong = X_all_scaled_wrong[len(X_train):]
    
    # Compare statistics
    logger.info("\nScaler statistics comparison:")
    logger.info("\nCORRECT (fitted on train only):")
    logger.info(f"  Train mean: {scaler_correct.mean_[:5]}")
    logger.info(f"  Train std:  {scaler_correct.scale_[:5]}")
    
    logger.info("\nWRONG (fitted on all data):")
    logger.info(f"  All mean: {scaler_wrong.mean_[:5]}")
    logger.info(f"  All std:  {scaler_wrong.scale_[:5]}")
    
    # Check difference
    mean_diff = np.abs(scaler_correct.mean_ - scaler_wrong.mean_).mean()
    std_diff = np.abs(scaler_correct.scale_ - scaler_wrong.scale_).mean()
    
    logger.info(f"\nAverage difference:")
    logger.info(f"  Mean: {mean_diff:.6f}")
    logger.info(f"  Std:  {std_diff:.6f}")
    
    if mean_diff < 0.01 and std_diff < 0.01:
        logger.info("✓ Minimal difference - scaler likely fitted correctly on train only")
        return True
    else:
        logger.warning("⚠️  Significant difference detected - review scaler fitting")
        return False


def check_4_feature_contamination():
    """Check for features that could leak information."""
    logger.info("\n" + "="*80)
    logger.info("CHECK 4: FEATURE CONTAMINATION")
    logger.info("="*80)
    
    features_df = pd.read_csv('data/features/url_features.csv')
    
    # Check for suspiciously perfect features
    logger.info("\nChecking for suspiciously perfect correlations with label...")
    
    X = features_df.drop('label', axis=1)
    y = features_df['label']
    
    correlations = X.corrwith(y).abs().sort_values(ascending=False)
    
    logger.info("\nTop 10 features correlated with label:")
    for feat, corr in correlations.head(10).items():
        logger.info(f"  {feat:30s}: {corr:.4f}")
    
    # Check for suspiciously high correlations (> 0.9 is suspicious)
    suspicious = correlations[correlations > 0.9]
    
    if len(suspicious) > 0:
        logger.warning(f"⚠️  Found {len(suspicious)} features with >0.9 correlation!")
        logger.warning(f"  These might be leaking information:\n{suspicious}")
        return False
    else:
        logger.info("✓ No suspiciously high correlations detected")
        return True


def check_5_train_test_distribution():
    """Check if train/test have similar distributions."""
    logger.info("\n" + "="*80)
    logger.info("CHECK 5: TRAIN/TEST DISTRIBUTION SIMILARITY")
    logger.info("="*80)
    
    features_df = pd.read_csv('data/features/url_features.csv')
    
    X = features_df.drop('label', axis=1)
    y = features_df['label']
    
    X_train, X_test, y_train, y_test = train_test_split(
        X, y, test_size=0.2, random_state=42, stratify=y
    )
    
    # Check label distribution
    logger.info("\nLabel distribution:")
    logger.info(f"  Train: {y_train.value_counts().to_dict()}")
    logger.info(f"  Test:  {y_test.value_counts().to_dict()}")
    
    train_phishing_ratio = (y_train == 1).sum() / len(y_train)
    test_phishing_ratio = (y_test == 1).sum() / len(y_test)
    
    logger.info(f"\nPhishing ratio:")
    logger.info(f"  Train: {train_phishing_ratio:.4f}")
    logger.info(f"  Test:  {test_phishing_ratio:.4f}")
    logger.info(f"  Difference: {abs(train_phishing_ratio - test_phishing_ratio):.4f}")
    
    if abs(train_phishing_ratio - test_phishing_ratio) < 0.01:
        logger.info("✓ Train/test distributions are well balanced")
        return True
    else:
        logger.warning("⚠️  Train/test distributions differ significantly")
        return False


def main():
    """Run all data leakage checks."""
    logger.info("="*80)
    logger.info("DATA LEAKAGE DETECTION")
    logger.info("="*80)
    
    results = {}
    
    try:
        results['duplicates'] = check_1_duplicate_urls_in_splits()
    except Exception as e:
        logger.error(f"Error in duplicate check: {e}")
        results['duplicates'] = None
    
    try:
        results['extraction_timing'] = check_2_feature_extraction_timing()
    except Exception as e:
        logger.error(f"Error in extraction timing check: {e}")
        results['extraction_timing'] = None
    
    try:
        results['scaler'] = check_3_scaler_fitting()
    except Exception as e:
        logger.error(f"Error in scaler check: {e}")
        results['scaler'] = None
    
    try:
        results['contamination'] = check_4_feature_contamination()
    except Exception as e:
        logger.error(f"Error in contamination check: {e}")
        results['contamination'] = None
    
    try:
        results['distribution'] = check_5_train_test_distribution()
    except Exception as e:
        logger.error(f"Error in distribution check: {e}")
        results['distribution'] = None
    
    # Final summary
    logger.info("\n" + "="*80)
    logger.info("SUMMARY")
    logger.info("="*80)
    
    passed = sum(1 for v in results.values() if v is True)
    failed = sum(1 for v in results.values() if v is False)
    errors = sum(1 for v in results.values() if v is None)
    
    logger.info(f"\nChecks passed: {passed}")
    logger.info(f"Checks failed: {failed}")
    logger.info(f"Checks errored: {errors}")
    
    for check, result in results.items():
        status = "✓ PASS" if result else ("❌ FAIL" if result is False else "⚠️  ERROR")
        logger.info(f"  {check:20s}: {status}")
    
    if failed == 0 and errors == 0:
        logger.info("\n🎉 ALL CHECKS PASSED - No data leakage detected!")
        logger.info("Your results are LEGITIMATE!")
    elif failed > 0:
        logger.warning(f"\n⚠️  {failed} checks failed - review your pipeline!")
    
    logger.info("\n" + "="*80)


if __name__ == "__main__":
    main()