from typing import List, Dict, Optional, Tuple
import torch
from transformers import Qwen2_5_VLForConditionalGeneration, AutoProcessor, AutoTokenizer
from qwen_vl_utils import process_vision_info
from PIL import Image
import io


class TokenChunker:
    """Handle token counting and chunking for model context limits."""
    
    def __init__(self, model_name: str = "Qwen/Qwen2.5-VL-3B-Instruct"):
        """Initialize tokenizer for token counting."""
        self.tokenizer = AutoTokenizer.from_pretrained(model_name, trust_remote_code=True)
        # Qwen2.5-VL has max context of 131,072 tokens
        self.max_tokens = 100000  # Conservative limit (use 100K of 131K available)
    
    def count_tokens(self, text: str) -> int:
        """Count tokens in text."""
        try:
            tokens = self.tokenizer.encode(text, add_special_tokens=False)
            return len(tokens)
        except Exception as e:
            print(f"Error counting tokens: {e}")
            # Rough estimate: 1 token ≈ 4 characters for English/Russian
            return len(text) // 4
    
    def chunk_text(self, text: str, chunk_size: int = 50000) -> List[str]:
        """Split text into chunks that fit within token limits."""
        if len(text) <= chunk_size:
            return [text]
        
        chunks = []
        current_chunk = ""
        
        # Split by paragraphs first
        paragraphs = text.split("\n\n")
        
        for paragraph in paragraphs:
            if len(current_chunk) + len(paragraph) < chunk_size:
                current_chunk += paragraph + "\n\n"
            else:
                if current_chunk:
                    chunks.append(current_chunk.strip())
                current_chunk = paragraph + "\n\n"
        
        if current_chunk:
            chunks.append(current_chunk.strip())
        
        return chunks
    
    def truncate_to_token_limit(self, text: str, token_limit: int = 50000) -> str:
        """Truncate text to fit within token limit."""
        current_tokens = self.count_tokens(text)
        
        if current_tokens <= token_limit:
            return text
        
        print(f"Text too long ({current_tokens} tokens). Truncating to {token_limit}...")
        
        # Estimate characters per token
        char_per_token = len(text) / current_tokens
        target_chars = int(token_limit * char_per_token * 0.9)  # 90% to be safe
        
        truncated = text[:target_chars]
        return truncated


class Qwen25VLInferencer:
    """Handle inference with Qwen2.5-VL-3B model - FIXED meta tensor issue."""
    
class Qwen25VLInferencer:
    """Handle inference with Qwen2.5-VL-3B model - FIXED meta tensor issue."""
    
    def __init__(self, model_name: str = "Qwen/Qwen2.5-VL-3B-Instruct", device: str = "cuda"):
        """Initialize Qwen2.5-VL model with proper device handling."""
        self.device = device if torch.cuda.is_available() else "cpu"
        print(f"Loading Qwen2.5-VL-3B model on device: {self.device}")
        
        try:
            # FIXED: Load model without device_map first, then move to device
            # This avoids the meta tensor issue
            
            # Determine data type based on device
            if self.device == "cuda":
                dtype = torch.float16  # GPU: use half precision
            else:
                dtype = torch.float32  # CPU: use full precision
            
            print(f"Using dtype: {dtype}")
            
            # Load model
            print("Loading model weights...")
            self.model = Qwen2_5_VLForConditionalGeneration.from_pretrained(
                model_name,
                torch_dtype=dtype,
                trust_remote_code=True,
                # IMPORTANT: Don't use device_map="auto" here - causes meta tensor issue
            )
            
            # Move to device explicitly AFTER loading
            print(f"Moving model to {self.device}...")
            if self.device == "cuda":
                self.model = self.model.to("cuda")
            else:
                self.model = self.model.to("cpu")
            
            # Set to evaluation mode
            self.model.eval()
            
            print("✅ Model loaded successfully")
            
        except RuntimeError as e:
            if "meta tensor" in str(e):
                print(f"⚠️ Meta tensor error detected: {e}")
                print("Falling back to CPU mode...")
                self.device = "cpu"
                
                self.model = Qwen2_5_VLForConditionalGeneration.from_pretrained(
                    model_name,
                    torch_dtype=torch.float32,
                    trust_remote_code=True,
                )
                self.model = self.model.to("cpu")
                self.model.eval()
                print("✅ Model loaded on CPU")
            else:
                raise
        
        except Exception as e:
            print(f"❌ Error loading model: {e}")
            print("Trying fallback CPU loading...")
            
            self.device = "cpu"
            self.model = Qwen2_5_VLForConditionalGeneration.from_pretrained(
                model_name,
                torch_dtype=torch.float32,
                trust_remote_code=True,
            )
            self.model = self.model.to("cpu")
            self.model.eval()
        
        # Load processor
        print("Loading processor...")
        self.processor = AutoProcessor.from_pretrained(
            model_name,
            trust_remote_code=True
        )
        
        # Initialize token chunker
        self.token_chunker = TokenChunker(model_name)
        
        print("✅ Model initialization complete")
    
    def _prepare_text_message(self, text: str) -> List[Dict]:
        """Prepare text-only message for the model."""
        return [{"type": "text", "text": text}]
    
    def _prepare_image_text_message(self, image_path: str, text: str) -> List[Dict]:
        """Prepare message with image and text."""
        return [
            {"type": "image", "image": image_path},
            {"type": "text", "text": text}
        ]
    
    def generate_answer(
        self,
        query: str,
        retrieved_docs: List[Dict],
        retrieved_images: List[str] = None,
        max_new_tokens: int = 128
    ) -> str:
        """
        Generate answer based on query and retrieved documents.
        FIXED: Includes token chunking and context length management
        """
        # Build context from retrieved documents
        context = "КОНТЕКСТ ИЗ ДОКУМЕНТОВ:\n"
        for doc in retrieved_docs:
            relevance = doc.get('relevance_score', 0)
            context += f"\n[Релевантность: {relevance:.2f}]\n{doc['document']}\n"
        
        # FIXED: Truncate context if too long
        context = self.token_chunker.truncate_to_token_limit(context, token_limit=50000)
        
        # Build system prompt
        system_prompt = "Ты помощник для анализа документов. Используй предоставленный контекст для ответа на вопросы. Отвечай на русском языке. Будь кратким и точным."
        
        # Prepare the full query
        full_query = f"{system_prompt}\n\n{context}\n\nВопрос: {query}\n\nОтвет:"
        
        # FIXED: Check and limit token count
        query_tokens = self.token_chunker.count_tokens(full_query)
        print(f"Query token count: {query_tokens}")
        
        if query_tokens > 100000:
            print(f"Query exceeds token limit. Reducing context...")
            # Keep only first 3 documents instead of all
            context = "КОНТЕКСТ ИЗ ДОКУМЕНТОВ:\n"
            for doc in retrieved_docs[:3]:
                relevance = doc.get('relevance_score', 0)
                context += f"\n[Релевантность: {relevance:.2f}]\n{doc['document']}\n"
            
            context = self.token_chunker.truncate_to_token_limit(context, token_limit=30000)
            full_query = f"{system_prompt}\n\n{context}\n\nВопрос: {query}\n\nОтвет:"
        
        # Prepare messages
        messages = self._prepare_text_message(full_query)
        
        # If images are provided, add them
        if retrieved_images and len(retrieved_images) > 0:
            try:
                image_message = self._prepare_image_text_message(
                    retrieved_images[0],
                    f"Проанализируй это изображение в контексте вопроса: {query}"
                )
                messages = image_message + [{"type": "text", "text": full_query}]
            except Exception as e:
                print(f"Warning: Could not include images: {e}")
        
        # Process vision info if images are included
        image_inputs = []
        video_inputs = []
        
        try:
            if any(msg.get('type') == 'image' for msg in messages):
                image_inputs, video_inputs = process_vision_info(messages)
        except Exception as e:
            print(f"Warning: Could not process images: {e}")
        
        # Prepare inputs for model
        try:
            inputs = self.processor(
                text=[full_query],
                images=image_inputs if image_inputs else None,
                videos=video_inputs if video_inputs else None,
                padding=True,
                return_tensors='pt',
            )
        except Exception as e:
            print(f"Error preparing inputs: {e}")
            return f"Error preparing inputs: {e}"
        
        # Move inputs to device
        if self.device == "cuda":
            inputs = inputs.to("cuda")
        
        # Generate response with error handling
        try:
            with torch.no_grad():
                generated_ids = self.model.generate(
                    **inputs,
                    max_new_tokens=min(max_new_tokens, 512),  # Cap at 512
                    num_beams=1,
                    do_sample=False
                )
        except Exception as e:
            print(f"Error during generation: {e}")
            return f"Error generating response: {e}"
        
        # Decode output
        try:
            generated_ids_trimmed = [
                out_ids[len(in_ids):] 
                for in_ids, out_ids in zip(inputs.input_ids, generated_ids)
            ]
            
            response = self.processor.batch_decode(
                generated_ids_trimmed,
                skip_special_tokens=True,
                clean_up_tokenization_spaces=False
            )
            
            return response[0] if response else "Could not generate response"
        except Exception as e:
            print(f"Error decoding response: {e}")
            return f"Error decoding response: {e}"
    
    def summarize_document(
        self,
        document_text: str,
        max_new_tokens: int = 512
    ) -> str:
        """Summarize a document with token limit management."""
        
        # FIXED: Truncate document to fit in context
        document_text = self.token_chunker.truncate_to_token_limit(
            document_text,
            token_limit=40000
        )
        
        prompt = f"""Пожалуйста, создай подробное резюме следующего документа на русском языке.
        
Документ:
{document_text}

Резюме:"""
        
        messages = self._prepare_text_message(prompt)
        
        try:
            inputs = self.processor(
                text=[prompt],
                padding=True,
                return_tensors='pt',
            )
            
            if self.device == "cuda":
                inputs = inputs.to("cuda")
            
            with torch.no_grad():
                generated_ids = self.model.generate(
                    **inputs,
                    max_new_tokens=min(max_new_tokens, 512),
                    num_beams=1,
                    do_sample=False
                )
            
            generated_ids_trimmed = [
                out_ids[len(in_ids):] 
                for in_ids, out_ids in zip(inputs.input_ids, generated_ids)
            ]
            
            response = self.processor.batch_decode(
                generated_ids_trimmed,
                skip_special_tokens=True,
                clean_up_tokenization_spaces=False
            )
            
            return response[0] if response else "Could not generate summary"
        except Exception as e:
            print(f"Error generating summary: {e}")
            return f"Error: {e}"


class RAGPipeline:
    """Complete RAG pipeline combining retrieval and generation."""
    
    def __init__(self, chroma_manager, device: str = "cuda"):
        """Initialize RAG pipeline."""
        self.chroma_manager = chroma_manager
        self.inferencer = Qwen25VLInferencer(device=device)
    
    def answer_question(
        self,
        query: str,
        n_retrieved: int = 5,
        max_new_tokens: int = 512
    ) -> Dict:
        """
        Answer user question using RAG pipeline.
        1. Retrieve relevant documents
        2. Generate answer using Qwen2.5-VL
        """
        # Step 1: Retrieve
        retrieved_docs = self.chroma_manager.search(query, n_results=n_retrieved)
        
        if not retrieved_docs:
            return {
                "answer": "Не найдены релевантные документы для ответа на вопрос.",
                "retrieved_docs": [],
                "query": query,
                "error": "No documents found"
            }
        
        # Extract images from retrieved results if available
        retrieved_images = []
        
        # Step 2: Generate
        try:
            answer = self.inferencer.generate_answer(
                query=query,
                retrieved_docs=retrieved_docs,
                retrieved_images=retrieved_images,
                max_new_tokens=max_new_tokens
            )
        except Exception as e:
            answer = f"Error generating answer: {e}"
        
        return {
            "answer": answer,
            "retrieved_docs": retrieved_docs,
            "query": query,
            "model": "Qwen2.5-VL-3B",
            "doc_count": len(retrieved_docs)
        }
    
    def summarize_all_documents(self, max_chars: int = 100000) -> str:
        """Create summary of all indexed documents with token limits."""
        collection_info = self.chroma_manager.get_collection_info()
        doc_count = collection_info['document_count']
        
        if doc_count == 0:
            return "No documents in database to summarize."
        
        # Retrieve documents
        try:
            all_docs = self.chroma_manager.collection.get(include=['documents'])
            
            if not all_docs['documents']:
                return "Could not retrieve documents for summarization."
            
            # Combine first documents with char limit
            combined_text = ""
            for doc in all_docs['documents'][:10]:  # Max 10 docs
                if len(combined_text) + len(doc) < max_chars:
                    combined_text += doc + "\n\n"
                else:
                    break
            
            if not combined_text:
                combined_text = all_docs['documents'][0][:max_chars]
            
            summary = self.inferencer.summarize_document(combined_text)
            return summary
        except Exception as e:
            return f"Error summarizing documents: {e}"