models/train_model.py

"""
Training script for HateShield-BN Custom Model
Trains SEPARATE models for English and Bengali datasets
Compares multiple algorithms and saves the best one
"""

import pandas as pd
import numpy as np
from sklearn.model_selection import train_test_split
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.linear_model import LogisticRegression
from sklearn.ensemble import RandomForestClassifier
from sklearn.svm import LinearSVC
from sklearn.metrics import classification_report, confusion_matrix, accuracy_score, f1_score
import joblib
import os
from typing import Tuple, Dict
import warnings
from tqdm import tqdm
import time
import json

warnings.filterwarnings('ignore')

# Configuration
ENGLISH_DATASET_PATH = "data/english_hate_speech.csv"
BENGALI_DATASET_PATH = "data/bengali_hate_speech.csv"
MODEL_OUTPUT_PATH = "models/model_weights/custom_models"
RANDOM_STATE = 42

def load_english_dataset() -> pd.DataFrame:
    """Load and preprocess English dataset"""
    print("📄 Loading English dataset...")
    
    try:
        df = pd.read_csv(ENGLISH_DATASET_PATH)
        print(f"  ✓ Loaded: {len(df):,} samples")
        
        # Standardize column names
        if 'content' in df.columns:
            df = df.rename(columns={'content': 'text'})
        elif 'Content' in df.columns:
            df = df.rename(columns={'Content': 'text'})
        
        # Ensure label column
        if 'Label' in df.columns:
            df['label'] = df['Label'].astype(int)
        elif 'label' in df.columns:
            df['label'] = df['label'].astype(int)
        else:
            raise ValueError("English dataset must have 'Label' or 'label' column")
        
        # Keep only text and label
        df = df[['text', 'label']].copy()
        
        # Clean data
        df = df.dropna(subset=['text', 'label'])
        df = df[df['text'].str.strip().str.len() > 0]
        
        # Ensure binary labels (0, 1)
        unique_labels = df['label'].unique()
        print(f"  📊 Unique labels: {sorted(unique_labels)}")
        
        if set(unique_labels) == {0, 1}:
            print("  ✓ Binary classification: 0=Non-Hate, 1=Hate")
        else:
            print(f"  ⚠️  Warning: Expected binary labels, found: {unique_labels}")
            # Convert to binary if needed
            df['label'] = (df['label'] > 0).astype(int)
        
        print(f"  ✓ After preprocessing: {len(df):,} samples")
        
        return df
        
    except FileNotFoundError:
        print(f"  ❌ Error: File not found at {ENGLISH_DATASET_PATH}")
        return pd.DataFrame(columns=['text', 'label'])
    except Exception as e:
        print(f"  ❌ Error loading English dataset: {e}")
        return pd.DataFrame(columns=['text', 'label'])

def load_bengali_dataset() -> pd.DataFrame:
    """Load and preprocess Bengali dataset"""
    print("\n📄 Loading Bengali dataset...")
    
    try:
        df = pd.read_csv(BENGALI_DATASET_PATH)
        print(f"  ✓ Loaded: {len(df):,} samples")
        
        # Standardize column names
        if 'sentence' in df.columns:
            df = df.rename(columns={'sentence': 'text'})
        elif 'sentences' in df.columns:
            df = df.rename(columns={'sentences': 'text'})
        
        # Convert hate/category to standard labels
        if 'hate' in df.columns:
            if 'category' in df.columns:
                category_map = {
                    'non-hate': 0,
                    'offensive': 1,
                    'hate': 2,
                }
                df['label'] = df['category'].map(category_map)
                # Fill missing with hate column
                df.loc[df['label'].isna() & (df['hate'] == 1), 'label'] = 2
                df.loc[df['label'].isna() & (df['hate'] == 0), 'label'] = 0
            else:
                # If only 'hate' column, map: 0=non-hate, 1=hate (as offensive), 2=hate
                df['label'] = df['hate'].apply(lambda x: 2 if x == 1 else 0)
        
        df['label'] = df['label'].astype(int)
        df = df[['text', 'label']].copy()
        
        # Clean data
        df = df.dropna(subset=['text', 'label'])
        df = df[df['text'].str.strip().str.len() > 0]
        
        # Ensure multi-class labels (0, 1, 2)
        unique_labels = df['label'].unique()
        print(f"  📊 Unique labels: {sorted(unique_labels)}")
        
        if set(unique_labels) == {0, 1, 2}:
            print("  ✓ Multi-class: 0=Neutral, 1=Offensive, 2=Hate Speech")
        elif set(unique_labels) == {0, 1}:
            print("  ⚠️  Warning: Only binary labels found, expected 3 classes")
        else:
            print(f"  ⚠️  Warning: Unexpected labels: {unique_labels}")
        
        print(f"  ✓ After preprocessing: {len(df):,} samples")
        
        return df
        
    except FileNotFoundError:
        print(f"  ❌ Error: File not found at {BENGALI_DATASET_PATH}")
        return pd.DataFrame(columns=['text', 'label'])
    except Exception as e:
        print(f"  ❌ Error loading Bengali dataset: {e}")
        return pd.DataFrame(columns=['text', 'label'])

def analyze_distribution(df: pd.DataFrame, name: str):
    """Print dataset statistics"""
    if len(df) == 0:
        print(f"\n{'='*50}")
        print(f"❌ {name} Dataset: EMPTY")
        print('='*50)
        return
    
    print(f"\n{'='*50}")
    print(f"📊 {name} Dataset Distribution")
    print('='*50)
    
    unique_labels = sorted(df['label'].unique())
    print(f"Unique labels: {unique_labels}")
    print(f"Total samples: {len(df):,}\n")
    
    # Dynamic label names
    if set(unique_labels) == {0, 1}:
        label_names = {0: 'Non-Hate/Neutral', 1: 'Hate/Offensive'}
    elif set(unique_labels) == {0, 1, 2}:
        label_names = {0: 'Neutral', 1: 'Offensive', 2: 'Hate Speech'}
    else:
        label_names = {label: f'Class {label}' for label in unique_labels}
    
    # Show distribution
    for label in unique_labels:
        count = len(df[df['label'] == label])
        percentage = count / len(df) * 100
        label_name = label_names.get(label, f'Unknown({label})')
        print(f"  {label} - {label_name:20s}: {count:6,} ({percentage:5.1f}%)")

def train_single_model(X_train, X_test, y_train, y_test, model_type: str, language: str) -> Dict:
    """Train a single model and return results"""
    print(f"\n  🔧 Training {model_type.upper()}...")
    
    # Choose model
    if model_type == 'logistic':
        model = LogisticRegression(
            max_iter=1000, 
            random_state=RANDOM_STATE,
            class_weight='balanced',
            n_jobs=-1
        )
    elif model_type == 'svm':
        model = LinearSVC(
            random_state=RANDOM_STATE,
            class_weight='balanced',
            max_iter=2000
        )
    elif model_type == 'random_forest':
        model = RandomForestClassifier(
            n_estimators=100,
            random_state=RANDOM_STATE,
            class_weight='balanced',
            n_jobs=-1
        )
    else:
        raise ValueError(f"Unknown model type: {model_type}")
    
    # Train
    start_time = time.time()
    
    model.fit(X_train, y_train)
    y_pred = model.predict(X_test)
    
    training_time = time.time() - start_time
    
    # Evaluate
    accuracy = accuracy_score(y_test, y_pred)
    f1 = f1_score(y_test, y_pred, average='weighted')
    
    print(f"     ✓ Accuracy: {accuracy:.4f} ({accuracy*100:.2f}%)")
    print(f"     ✓ F1-Score: {f1:.4f}")
    print(f"     ✓ Time: {training_time:.2f}s")
    
    return {
        'model': model,
        'accuracy': accuracy,
        'f1_score': f1,
        'training_time': training_time,
        'predictions': y_pred
    }

def train_and_compare_models(X_train, X_test, y_train, y_test, language: str) -> Tuple:
    """Train multiple models and return the best one"""
    print(f"\n🤖 Training Multiple Models for {language.upper()}...")
    print("=" * 60)
    
    models_to_train = ['logistic', 'svm']
    results = {}
    
    # Train all models
    for model_type in models_to_train:
        try:
            result = train_single_model(X_train, X_test, y_train, y_test, model_type, language)
            results[model_type] = result
        except Exception as e:
            print(f"     ❌ Error training {model_type}: {e}")
            continue
    
    if not results:
        print("❌ No models trained successfully!")
        return None, None, {}
    
    # Compare models
    print(f"\n{'='*60}")
    print(f"📊 Model Comparison for {language.upper()}")
    print('='*60)
    print(f"{'Model':<20} {'Accuracy':<12} {'F1-Score':<12} {'Time (s)':<10}")
    print('-'*60)
    
    best_model_name = None
    best_score = 0
    
    for model_name, result in results.items():
        accuracy = result['accuracy']
        f1 = result['f1_score']
        time_taken = result['training_time']
        
        # Use F1-score as primary metric (better for imbalanced datasets)
        score = f1
        
        print(f"{model_name:<20} {accuracy:<12.4f} {f1:<12.4f} {time_taken:<10.2f}")
        
        if score > best_score:
            best_score = score
            best_model_name = model_name
    
    print('='*60)
    print(f"🏆 Best Model: {best_model_name.upper()} (F1-Score: {best_score:.4f})")
    print('='*60)
    
    # Get best model
    best_result = results[best_model_name]
    best_model = best_result['model']
    
    # Detailed report for best model
    print(f"\n📈 Detailed Report for {best_model_name.upper()}:")
    
    unique_labels = sorted(np.unique(y_test))
    
    if set(unique_labels) == {0, 1}:
        target_names = ['Non-Hate', 'Hate']
    elif set(unique_labels) == {0, 1, 2}:
        target_names = ['Neutral', 'Offensive', 'Hate Speech']
    else:
        target_names = [f'Class {i}' for i in unique_labels]
    
    print(classification_report(y_test, best_result['predictions'], 
                                target_names=target_names,
                                zero_division=0))
    
    print("🔢 Confusion Matrix:")
    print(confusion_matrix(y_test, best_result['predictions']))
    
    # Return comparison data
    comparison = {
        model_name: {
            'accuracy': result['accuracy'],
            'f1_score': result['f1_score'],
            'training_time': result['training_time']
        }
        for model_name, result in results.items()
    }
    
    return best_model, best_model_name, comparison

def train_language_specific_model(df: pd.DataFrame, language: str):
    """Train model for specific language with comparison"""
    print(f"\n{'='*60}")
    print(f"🎓 Training {language.upper()} Model")
    print('='*60)
    
    if len(df) == 0:
        print(f"❌ No data for {language}!")
        return None, None, None, None, {}
    
    # Analyze distribution
    analyze_distribution(df, language.capitalize())
    
    # Split data
    print(f"\n✂️  Splitting data (80/20 train/test)...")
    X = df['text']
    y = df['label'].astype(int)
    
    X_train, X_test, y_train, y_test = train_test_split(
        X, y,
        test_size=0.2,
        random_state=RANDOM_STATE,
        stratify=y
    )
    
    print(f"  ✓ Train size: {len(X_train):,}")
    print(f"  ✓ Test size: {len(X_test):,}")
    
    # Create TF-IDF vectorizer
    print(f"\n🔤 Creating TF-IDF vectorizer...")
    vectorizer = TfidfVectorizer(
        max_features=5000,
        ngram_range=(1, 2),
        min_df=2,
        max_df=0.8,
        strip_accents='unicode',
        analyzer='word',
        token_pattern=r'\w{1,}',
        sublinear_tf=True
    )
    
    print("  ⏳ Vectorizing text...")
    X_train_vec = vectorizer.fit_transform(X_train)
    X_test_vec = vectorizer.transform(X_test)
    
    print(f"  ✓ Feature dimension: {X_train_vec.shape[1]:,}")
    
    # Train and compare models
    best_model, best_model_name, comparison = train_and_compare_models(
        X_train_vec, X_test_vec, y_train, y_test, language
    )
    
    if best_model is None:
        return None, None, None, None, {}
    
    # Get final accuracy
    y_pred = best_model.predict(X_test_vec)
    final_accuracy = accuracy_score(y_test, y_pred)
    final_f1 = f1_score(y_test, y_pred, average='weighted')
    
    return best_model, vectorizer, best_model_name, final_f1, comparison

def main():
    """Main training pipeline"""
    print("\n" + "=" * 70)
    print("🛡️  HateShield-BN Model Training (Language-Specific with Comparison)")
    print("=" * 70 + "\n")
    
    # Load datasets separately
    df_english = load_english_dataset()
    df_bengali = load_bengali_dataset()
    
    if len(df_english) == 0 and len(df_bengali) == 0:
        print("\n❌ Error: No data found!")
        return
    
    os.makedirs(MODEL_OUTPUT_PATH, exist_ok=True)
    
    results = {}
    
    # Train English model
    if len(df_english) > 0:
        print("\n" + "🇬🇧 " * 35)
        english_model, english_vectorizer, english_best_name, english_f1, english_comparison = train_language_specific_model(
            df_english, 'english'
        )
        
        if english_model is not None:
            # Save English model
            print(f"\n💾 Saving English model ({english_best_name})...")
            english_model_path = os.path.join(MODEL_OUTPUT_PATH, "english_model.pkl")
            english_vec_path = os.path.join(MODEL_OUTPUT_PATH, "english_vectorizer.pkl")
            
            joblib.dump(english_model, english_model_path)
            joblib.dump(english_vectorizer, english_vec_path)
            
            print(f"  ✓ Model saved to: {english_model_path}")
            print(f"  ✓ Vectorizer saved to: {english_vec_path}")
            
            results['english'] = {
                'best_model': english_best_name,
                'f1_score': english_f1,
                'num_classes': len(df_english['label'].unique()),
                'samples': len(df_english),
                'comparison': english_comparison
            }
    
    # Train Bengali model
    if len(df_bengali) > 0:
        print("\n" + "🇧🇩 " * 35)
        bengali_model, bengali_vectorizer, bengali_best_name, bengali_f1, bengali_comparison = train_language_specific_model(
            df_bengali, 'bengali'
        )
        
        if bengali_model is not None:
            # Save Bengali model
            print(f"\n💾 Saving Bengali model ({bengali_best_name})...")
            bengali_model_path = os.path.join(MODEL_OUTPUT_PATH, "bengali_model.pkl")
            bengali_vec_path = os.path.join(MODEL_OUTPUT_PATH, "bengali_vectorizer.pkl")
            
            joblib.dump(bengali_model, bengali_model_path)
            joblib.dump(bengali_vectorizer, bengali_vec_path)
            
            print(f"  ✓ Model saved to: {bengali_model_path}")
            print(f"  ✓ Vectorizer saved to: {bengali_vec_path}")
            
            results['bengali'] = {
                'best_model': bengali_best_name,
                'f1_score': bengali_f1,
                'num_classes': len(df_bengali['label'].unique()),
                'samples': len(df_bengali),
                'comparison': bengali_comparison
            }
    
    # Save metadata
    print(f"\n💾 Saving metadata...")
    metadata = {
        'training_date': time.strftime('%Y-%m-%d %H:%M:%S'),
        'models': results,
        'separate_models': True,
        'algorithms_tested': ['logistic', 'svm', 'random_forest']
    }
    
    with open(os.path.join(MODEL_OUTPUT_PATH, "metadata.json"), 'w') as f:
        json.dump(metadata, f, indent=2)
    
    # Final Summary
    print("\n" + "=" * 70)
    print("✅ Training Complete!")
    print("=" * 70)
    
    if 'english' in results:
        print(f"\n🇬🇧 English Model:")
        print(f"   Best Algorithm: {results['english']['best_model'].upper()}")
        print(f"   F1-Score: {results['english']['f1_score']:.4f}")
        print(f"   Classes: {results['english']['num_classes']}")
        print(f"   Samples: {results['english']['samples']:,}")
        print(f"\n   Model Comparison:")
        for model_name, scores in results['english']['comparison'].items():
            print(f"     {model_name:<15}: Acc={scores['accuracy']:.4f}, F1={scores['f1_score']:.4f}")
    
    if 'bengali' in results:
        print(f"\n🇧🇩 Bengali Model:")
        print(f"   Best Algorithm: {results['bengali']['best_model'].upper()}")
        print(f"   F1-Score: {results['bengali']['f1_score']:.4f}")
        print(f"   Classes: {results['bengali']['num_classes']}")
        print(f"   Samples: {results['bengali']['samples']:,}")
        print(f"\n   Model Comparison:")
        for model_name, scores in results['bengali']['comparison'].items():
            print(f"     {model_name:<15}: Acc={scores['accuracy']:.4f}, F1={scores['f1_score']:.4f}")
    
    print("\n" + "=" * 70 + "\n")

if __name__ == "__main__":
    main()