import re
import random
import nltk
from typing import List, Dict, Optional
import numpy as np

# Download required NLTK data
try:
    nltk.data.find('tokenizers/punkt')
except LookupError:
    nltk.download('punkt')

try:
    nltk.data.find('corpora/wordnet')
except LookupError:
    nltk.download('wordnet')

try:
    nltk.data.find('corpora/omw-1.4')
except LookupError:
    nltk.download('omw-1.4')

from nltk.tokenize import sent_tokenize, word_tokenize

# Production-grade imports with proper error handling and retries
def safe_import_with_retry(module_name, component=None, max_retries=3):
    """Import with retries and detailed error reporting"""
    for attempt in range(max_retries):
        try:
            if component:
                module = __import__(module_name, fromlist=[component])
                return getattr(module, component), True
            else:
                return __import__(module_name), True
        except ImportError as e:
            if attempt < max_retries - 1:
                print(f"⚠️ Import attempt {attempt + 1} failed for {module_name}: {e}")
                print(f"🔄 Retrying in 2 seconds...")
                import time
                time.sleep(2)
                continue
            else:
                print(f"❌ Final import failed for {module_name}: {e}")
                return None, False
        except Exception as e:
            print(f"❌ Unexpected error importing {module_name}: {e}")
            return None, False
    return None, False

# Advanced model imports with retries
print("🚀 Loading AI Text Humanizer - Production Version...")
print("=" * 50)

print("📥 Loading sentence transformers...")
SentenceTransformer, SENTENCE_TRANSFORMERS_AVAILABLE = safe_import_with_retry('sentence_transformers', 'SentenceTransformer')

print("📥 Loading transformers pipeline...")
pipeline, TRANSFORMERS_AVAILABLE = safe_import_with_retry('transformers', 'pipeline')

print("📥 Loading scikit-learn...")
try:
    from sklearn.feature_extraction.text import TfidfVectorizer
    from sklearn.metrics.pairwise import cosine_similarity as sklearn_cosine_similarity
    SKLEARN_AVAILABLE = True
    print("✅ Scikit-learn loaded successfully")
except ImportError as e:
    print(f"⚠️ Scikit-learn not available: {e}")
    SKLEARN_AVAILABLE = False

# Additional production imports
try:
    import torch
    TORCH_AVAILABLE = True
    print(f"✅ PyTorch loaded - CUDA available: {torch.cuda.is_available()}")
except ImportError:
    TORCH_AVAILABLE = False
    print("⚠️ PyTorch not available")

class ProductionAITextHumanizer:
    def __init__(self, enable_gpu=True, model_cache_dir=None):
        """Initialize production-grade text humanizer with all advanced features"""
        print("🏭 Initializing Production AI Text Humanizer...")
        
        self.enable_gpu = enable_gpu and TORCH_AVAILABLE
        self.model_cache_dir = model_cache_dir
        
        # Initialize advanced models with detailed error handling
        self._load_similarity_model()
        self._load_paraphrasing_model()
        self._initialize_fallback_methods()
        self._setup_word_mappings()
        
        print("✅ Production AI Text Humanizer initialized!")
        self._print_feature_status()
    
    def _load_similarity_model(self):
        """Load sentence transformer with production settings"""
        self.similarity_model = None
        
        if SENTENCE_TRANSFORMERS_AVAILABLE and SentenceTransformer:
            try:
                print("🔄 Loading sentence transformer model...")
                
                # Production settings
                model_kwargs = {
                    'device': 'cuda' if self.enable_gpu and torch.cuda.is_available() else 'cpu'
                } if TORCH_AVAILABLE else {}
                
                if self.model_cache_dir:
                    model_kwargs['cache_folder'] = self.model_cache_dir
                
                self.similarity_model = SentenceTransformer(
                    'all-MiniLM-L6-v2',
                    **model_kwargs
                )
                
                # Test the model
                test_embedding = self.similarity_model.encode(["test sentence"])
                print("✅ Sentence transformer model loaded and tested successfully!")
                
            except Exception as e:
                print(f"❌ Failed to load sentence transformer: {e}")
                print("💡 Troubleshooting tips:")
                print("   - Check internet connection for model download")
                print("   - Verify sentence-transformers version: pip install sentence-transformers==2.2.2")
                print("   - Check CUDA compatibility if using GPU")
                self.similarity_model = None
        else:
            print("❌ Sentence transformers not available")
    
    def _load_paraphrasing_model(self):
        """Load paraphrasing model with production settings"""
        self.paraphraser = None
        
        if TRANSFORMERS_AVAILABLE and pipeline:
            try:
                print("🔄 Loading paraphrasing model...")
                
                # Production settings
                device = 0 if self.enable_gpu and TORCH_AVAILABLE and torch.cuda.is_available() else -1
                
                self.paraphraser = pipeline(
                    "text2text-generation",
                    model="google/flan-t5-small",
                    device=device,
                    max_length=512,
                    model_kwargs={"cache_dir": self.model_cache_dir} if self.model_cache_dir else {}
                )
                
                # Test the model
                test_result = self.paraphraser("Test sentence for paraphrasing.", max_length=50)
                print("✅ Paraphrasing model loaded and tested successfully!")
                
            except Exception as e:
                print(f"❌ Failed to load paraphrasing model: {e}")
                print("💡 Troubleshooting tips:")
                print("   - Check internet connection for model download")
                print("   - Verify transformers version: pip install transformers==4.35.0")
                print("   - Check available memory (models need ~2GB RAM)")
                self.paraphraser = None
        else:
            print("❌ Transformers not available")
    
    def _initialize_fallback_methods(self):
        """Initialize fallback similarity methods"""
        self.tfidf_vectorizer = None
        if SKLEARN_AVAILABLE:
            try:
                self.tfidf_vectorizer = TfidfVectorizer(
                    stop_words='english', 
                    ngram_range=(1, 2),
                    max_features=5000
                )
                print("✅ TF-IDF fallback similarity initialized")
            except Exception as e:
                print(f"⚠️ TF-IDF initialization failed: {e}")
    
    def _setup_word_mappings(self):
        """Setup comprehensive word mappings for production"""
        # Extended formal to casual mappings for production
        self.formal_to_casual = {
            # Basic formal words
            "utilize": "use", "demonstrate": "show", "facilitate": "help",
            "implement": "do", "consequently": "so", "therefore": "so",
            "nevertheless": "but", "furthermore": "also", "moreover": "also",
            "subsequently": "then", "accordingly": "so", "regarding": "about",
            "concerning": "about", "pertaining": "about", "approximately": "about",
            "endeavor": "try", "commence": "start", "terminate": "end",
            "obtain": "get", "purchase": "buy", "examine": "look at",
            "analyze": "study", "construct": "build", "establish": "set up",
            
            # Advanced formal words  
            "magnitude": "size", "comprehensive": "complete", "significant": "big",
            "substantial": "large", "optimal": "best", "sufficient": "enough",
            "adequate": "good enough", "exceptional": "amazing", "remarkable": "great",
            "outstanding": "excellent", "predominant": "main", "fundamental": "basic",
            "essential": "needed", "crucial": "important", "vital": "key",
            "paramount": "most important", "imperative": "must", "mandatory": "required",
            
            # Formal phrases
            "prior to": "before", "in order to": "to", "due to the fact that": "because",
            "at this point in time": "now", "in the event that": "if",
            "it is important to note": "note that", "it should be emphasized": "remember",
            "it is worth mentioning": "by the way", "it is crucial to understand": "importantly",
            "for the purpose of": "to", "with regard to": "about",
            "in accordance with": "following", "as a result of": "because of",
            "in spite of the fact that": "although", "on the other hand": "however",
            
            # Academic/business terms
            "methodology": "method", "systematically": "step by step",
            "optimization": "improvement", "enhancement": "upgrade",
            "implementation": "setup", "utilization": "use", "evaluation": "review",
            "assessment": "check", "validation": "proof", "verification": "confirmation",
            "consolidation": "combining", "integration": "bringing together",
            "transformation": "change", "modification": "change", "alteration": "change"
        }
        
        # Extended contractions
        self.contractions = {
            "do not": "don't", "does not": "doesn't", "did not": "didn't",
            "will not": "won't", "would not": "wouldn't", "should not": "shouldn't",
            "could not": "couldn't", "cannot": "can't", "is not": "isn't",
            "are not": "aren't", "was not": "wasn't", "were not": "weren't",
            "have not": "haven't", "has not": "hasn't", "had not": "hadn't",
            "I am": "I'm", "you are": "you're", "he is": "he's", "she is": "she's",
            "it is": "it's", "we are": "we're", "they are": "they're",
            "I have": "I've", "you have": "you've", "we have": "we've",
            "they have": "they've", "I will": "I'll", "you will": "you'll",
            "he will": "he'll", "she will": "she'll", "it will": "it'll",
            "we will": "we'll", "they will": "they'll", "would have": "would've",
            "should have": "should've", "could have": "could've", "might have": "might've"
        }
        
        # AI-like transitions (expanded)
        self.ai_transition_words = [
            "Furthermore,", "Moreover,", "Additionally,", "Subsequently,",
            "Consequently,", "Therefore,", "Nevertheless,", "However,",
            "In conclusion,", "To summarize,", "In summary,", "Overall,",
            "It is important to note that", "It should be emphasized that",
            "It is worth mentioning that", "It is crucial to understand that",
            "It is essential to recognize that", "It must be acknowledged that",
            "It should be noted that", "It is imperative to understand",
            "From a practical standpoint,", "From an analytical perspective,",
            "In terms of implementation,", "With respect to the aforementioned,",
            "As previously mentioned,", "As stated earlier,", "In light of this,"
        ]
        
        # Natural alternatives (expanded)
        self.natural_transitions = [
            "Also,", "Plus,", "And,", "Then,", "So,", "But,", "Still,",
            "Anyway,", "By the way,", "Actually,", "Basically,", "Look,",
            "Listen,", "Here's the thing:", "The point is,", "What's more,",
            "On top of that,", "Another thing,", "Now,", "Well,", "You know,",
            "I mean,", "Honestly,", "Frankly,", "Simply put,", "In other words,",
            "To put it differently,", "Let me explain,", "Here's what I mean:",
            "Think about it,", "Consider this,", "Get this,", "Check this out,"
        ]
    
    def _print_feature_status(self):
        """Print detailed feature status for production monitoring"""
        print("\n📊 PRODUCTION FEATURE STATUS:")
        print("-" * 40)
        print(f"🔤 Advanced Similarity: {'✅ ENABLED' if self.similarity_model else '❌ DISABLED'}")
        print(f"🧠 AI Paraphrasing: {'✅ ENABLED' if self.paraphraser else '❌ DISABLED'}")
        print(f"📊 TF-IDF Fallback: {'✅ ENABLED' if self.tfidf_vectorizer else '❌ DISABLED'}")
        print(f"🚀 GPU Acceleration: {'✅ ENABLED' if self.enable_gpu and TORCH_AVAILABLE else '❌ DISABLED'}")
        print(f"⚡ Word Mappings: ✅ ENABLED ({len(self.formal_to_casual)} mappings)")
        print(f"📝 Contractions: ✅ ENABLED ({len(self.contractions)} contractions)")
        
        if TORCH_AVAILABLE:
            import torch
            print(f"🖥️ Device: {'CUDA' if torch.cuda.is_available() and self.enable_gpu else 'CPU'}")
        
        # Calculate feature completeness
        total_features = 6
        enabled_features = sum([
            bool(self.similarity_model),
            bool(self.paraphraser), 
            bool(self.tfidf_vectorizer),
            True,  # Word mappings always available
            True,  # Contractions always available
            TORCH_AVAILABLE
        ])
        
        completeness = (enabled_features / total_features) * 100
        print(f"🎯 Feature Completeness: {completeness:.1f}%")
        
        if completeness < 70:
            print("⚠️ WARNING: Less than 70% features enabled - not production ready")
        elif completeness < 90:
            print("⚠️ CAUTION: Some advanced features missing")
        else:
            print("🎉 PRODUCTION READY: All critical features enabled!")
    
    def add_contractions(self, text: str) -> str:
        """Add contractions with improved pattern matching"""
        # Sort by length (longest first) to avoid partial replacements
        sorted_contractions = sorted(self.contractions.items(), key=lambda x: len(x[0]), reverse=True)
        
        for formal, casual in sorted_contractions:
            # Use word boundaries to avoid partial matches
            pattern = r'\b' + re.escape(formal) + r'\b'
            text = re.sub(pattern, casual, text, flags=re.IGNORECASE)
        
        return text
    
    def replace_formal_words(self, text: str, replacement_rate: float = 0.8) -> str:
        """Enhanced formal word replacement with context awareness"""
        # Handle phrases first (longer matches)
        phrase_replacements = {k: v for k, v in self.formal_to_casual.items() if len(k.split()) > 1}
        word_replacements = {k: v for k, v in self.formal_to_casual.items() if len(k.split()) == 1}
        
        # Replace phrases first
        for formal_phrase, casual_phrase in phrase_replacements.items():
            if random.random() < replacement_rate:
                pattern = r'\b' + re.escape(formal_phrase) + r'\b'
                text = re.sub(pattern, casual_phrase, text, flags=re.IGNORECASE)
        
        # Then replace individual words
        words = word_tokenize(text)
        for i, word in enumerate(words):
            word_clean = word.lower().strip('.,!?;:"')
            if word_clean in word_replacements and random.random() < replacement_rate:
                replacement = word_replacements[word_clean]
                # Preserve case
                if word.isupper():
                    words[i] = word.replace(word_clean, replacement.upper())
                elif word.istitle():
                    words[i] = word.replace(word_clean, replacement.title())
                else:
                    words[i] = word.replace(word_clean, replacement)
        
        # Reconstruct with proper spacing
        result = ""
        for i, word in enumerate(words):
            if i > 0 and word not in ".,!?;:\"')":
                result += " "
            result += word
        
        return result
    
    def replace_ai_transitions(self, text: str) -> str:
        """Enhanced AI transition replacement with context awareness"""
        # Sort by length to handle longer phrases first
        sorted_transitions = sorted(self.ai_transition_words, key=len, reverse=True)
        
        for ai_transition in sorted_transitions:
            if ai_transition in text:
                # Choose appropriate natural replacement based on context
                natural_replacement = random.choice(self.natural_transitions)
                
                # Adjust replacement based on sentence position
                if text.startswith(ai_transition):
                    # Beginning of text
                    text = text.replace(ai_transition, natural_replacement, 1)
                else:
                    # Middle of text - be more selective
                    if random.random() < 0.7:  # 70% chance to replace
                        text = text.replace(ai_transition, natural_replacement, 1)
        
        return text
    
    def advanced_paraphrasing(self, text: str, paraphrase_rate: float = 0.4) -> str:
        """Production-grade paraphrasing with quality control"""
        if not self.paraphraser:
            return text
        
        sentences = sent_tokenize(text)
        paraphrased_sentences = []
        
        for sentence in sentences:
            # Only paraphrase longer, more complex sentences
            if len(sentence.split()) > 10 and random.random() < paraphrase_rate:
                try:
                    # Multiple paraphrasing strategies
                    prompts = [
                        f"Rewrite this more naturally: {sentence}",
                        f"Make this sound more conversational: {sentence}",
                        f"Rephrase this in simpler terms: {sentence}",
                        f"Say this in a more casual way: {sentence}"
                    ]
                    
                    prompt = random.choice(prompts)
                    
                    result = self.paraphraser(
                        prompt,
                        max_length=len(sentence) + 50,
                        min_length=max(10, len(sentence) // 2),
                        num_return_sequences=1,
                        temperature=0.7,
                        do_sample=True
                    )
                    
                    paraphrased = result[0]['generated_text']
                    paraphrased = paraphrased.replace(prompt, '').strip().strip('"\'')
                    
                    # Quality checks
                    if (paraphrased and 
                        len(paraphrased) > 5 and 
                        len(paraphrased) < len(sentence) * 2 and
                        not paraphrased.lower().startswith(('i cannot', 'i can\'t', 'sorry'))):
                        paraphrased_sentences.append(paraphrased)
                    else:
                        paraphrased_sentences.append(sentence)
                        
                except Exception as e:
                    print(f"⚠️ Paraphrasing failed: {e}")
                    paraphrased_sentences.append(sentence)
            else:
                paraphrased_sentences.append(sentence)
        
        return ' '.join(paraphrased_sentences)
    
    def calculate_similarity_advanced(self, text1: str, text2: str) -> float:
        """Production-grade similarity calculation"""
        if self.similarity_model:
            try:
                embeddings1 = self.similarity_model.encode([text1])
                embeddings2 = self.similarity_model.encode([text2])
                similarity = np.dot(embeddings1[0], embeddings2[0]) / (
                    np.linalg.norm(embeddings1[0]) * np.linalg.norm(embeddings2[0])
                )
                return float(similarity)
            except Exception as e:
                print(f"⚠️ Advanced similarity calculation failed: {e}")
        
        # Fallback to TF-IDF
        if self.tfidf_vectorizer and SKLEARN_AVAILABLE:
            try:
                tfidf_matrix = self.tfidf_vectorizer.fit_transform([text1, text2])
                similarity = sklearn_cosine_similarity(tfidf_matrix[0:1], tfidf_matrix[1:2])[0][0]
                return float(similarity)
            except Exception as e:
                print(f"⚠️ TF-IDF similarity calculation failed: {e}")
        
        # Basic fallback
        words1 = set(word_tokenize(text1.lower()))
        words2 = set(word_tokenize(text2.lower()))
        if not words1 or not words2:
            return 1.0 if text1 == text2 else 0.0
        
        intersection = words1.intersection(words2)
        union = words1.union(words2)
        return len(intersection) / len(union) if union else 1.0
    
    def humanize_text_production(self, 
                                text: str, 
                                style: str = "natural",
                                intensity: float = 0.8,
                                preserve_length: bool = True,
                                quality_threshold: float = 0.75) -> Dict:
        """
        Production-grade text humanization with comprehensive quality control
        
        Args:
            text: Input text to humanize
            style: Style ('natural', 'casual', 'conversational')
            intensity: Transformation intensity (0.0 to 1.0)
            preserve_length: Try to maintain similar text length
            quality_threshold: Minimum similarity score to accept
            
        Returns:
            Comprehensive results with quality metrics
        """
        if not text.strip():
            return {
                "original_text": text,
                "humanized_text": text,
                "similarity_score": 1.0,
                "changes_made": [],
                "style": style,
                "intensity": intensity,
                "quality_score": 1.0,
                "processing_time_ms": 0.0,
                "feature_usage": {}
            }
        
        import time
        start_time = time.time()
        
        changes_made = []
        humanized_text = text
        original_text = text
        feature_usage = {}
        
        # Step 1: AI transition replacement (early to catch obvious AI patterns)
        if intensity > 0.2:
            before = humanized_text
            humanized_text = self.replace_ai_transitions(humanized_text)
            if humanized_text != before:
                changes_made.append("Replaced AI-like transition phrases")
                feature_usage['ai_transitions'] = True
        
        # Step 2: Formal word replacement
        if intensity > 0.3:
            before = humanized_text
            humanized_text = self.replace_formal_words(humanized_text, intensity * 0.9)
            if humanized_text != before:
                changes_made.append("Replaced formal words with casual alternatives")
                feature_usage['word_replacement'] = True
        
        # Step 3: Add contractions
        if intensity > 0.4:
            before = humanized_text
            humanized_text = self.add_contractions(humanized_text)
            if humanized_text != before:
                changes_made.append("Added natural contractions")
                feature_usage['contractions'] = True
        
        # Step 4: Advanced paraphrasing (if available)
        if intensity > 0.6 and self.paraphraser:
            before = humanized_text
            humanized_text = self.advanced_paraphrasing(humanized_text, intensity * 0.5)
            if humanized_text != before:
                changes_made.append("Applied AI paraphrasing for natural flow")
                feature_usage['paraphrasing'] = True
        
        # Step 5: Calculate quality metrics
        processing_time = (time.time() - start_time) * 1000
        similarity_score = self.calculate_similarity_advanced(original_text, humanized_text)
        
        # Quality control - revert if similarity too low
        if similarity_score < quality_threshold:
            print(f"⚠️ Quality check failed (similarity: {similarity_score:.3f})")
            humanized_text = original_text
            similarity_score = 1.0
            changes_made = ["Quality threshold not met - reverted to original"]
            feature_usage['quality_control'] = True
        
        # Calculate comprehensive quality score
        length_ratio = len(humanized_text) / len(original_text) if original_text else 1.0
        length_penalty = max(0, 1.0 - abs(length_ratio - 1.0)) if preserve_length else 1.0
        change_score = min(1.0, len(changes_made) / 5.0)  # Reward meaningful changes
        
        quality_score = (similarity_score * 0.5) + (length_penalty * 0.3) + (change_score * 0.2)
        
        return {
            "original_text": original_text,
            "humanized_text": humanized_text,
            "similarity_score": similarity_score,
            "quality_score": quality_score,
            "changes_made": changes_made,
            "style": style,
            "intensity": intensity,
            "processing_time_ms": processing_time,
            "feature_usage": feature_usage,
            "length_change": len(humanized_text) - len(original_text),
            "word_count_change": len(humanized_text.split()) - len(original_text.split())
        }

# Convenience function for backward compatibility
def AITextHumanizer():
    """Factory function for backward compatibility"""
    return ProductionAITextHumanizer()

# Test the production version
if __name__ == "__main__":
    humanizer = ProductionAITextHumanizer()
    
    test_texts = [
        "Furthermore, it is important to note that artificial intelligence systems demonstrate significant capabilities.",
        "The implementation of comprehensive methodologies will facilitate optimization and enhance operational efficiency.",
        "Subsequently, organizations must utilize systematic approaches to evaluate and implement technological solutions."
    ]
    
    print(f"\n🧪 TESTING PRODUCTION HUMANIZER")
    print("=" * 40)
    
    for i, test_text in enumerate(test_texts, 1):
        print(f"\n🔬 Test {i}:")
        print(f"Original: {test_text}")
        
        result = humanizer.humanize_text_production(
            text=test_text,
            style="conversational", 
            intensity=0.8
        )
        
        print(f"Humanized: {result['humanized_text']}")
        print(f"Quality Score: {result['quality_score']:.3f}")
        print(f"Similarity: {result['similarity_score']:.3f}")
        print(f"Processing: {result['processing_time_ms']:.1f}ms")
        print(f"Changes: {', '.join(result['changes_made']) if result['changes_made'] else 'None'}")
    
    print(f"\n🎉 Production testing completed!")