"""
Main RAG (Retrieval-Augmented Generation) engine implementation.
"""

import os
import logging
from typing import List, Dict, Any, Optional, Tuple, Union
import numpy as np

# Configure logging
logger = logging.getLogger(__name__)


class RAGEngine:
    """Retrieval-Augmented Generation (RAG) engine for question answering."""
    
    def __init__(
        self,
        embedder,
        vector_db,
        llm=None,
        top_k: int = 5,
        search_type: str = "hybrid",
        prompt_template: Optional[str] = None
    ):
        """
        Initialize the RAG engine.
        
        Args:
            embedder: Embedding model
            vector_db: Vector database for document storage and retrieval
            llm: Language model for text generation (optional)
            top_k: Number of documents to retrieve
            search_type: Type of search ('semantic', 'keyword', 'hybrid')
            prompt_template: Optional custom prompt template
        """
        self.embedder = embedder
        self.vector_db = vector_db
        self.llm = llm
        self.top_k = top_k
        self.search_type = search_type
        
        # Set default prompt template if none provided
        if prompt_template is None:
            from ..config import DEFAULT_PROMPT_TEMPLATE
            self.prompt_template = DEFAULT_PROMPT_TEMPLATE
        else:
            self.prompt_template = prompt_template
    
    def add_documents(
        self,
        texts: List[str],
        metadata: Optional[List[Dict[str, Any]]] = None,
        batch_size: int = 32
    ) -> List[str]:
        """
        Add documents to the database.
        
        Args:
            texts: List of text chunks
            metadata: Optional list of metadata dictionaries for each text
            batch_size: Batch size for embedding generation
            
        Returns:
            List of document IDs
        """
        from ..storage.vector_db import Document
        
        # Handle metadata
        if metadata is None:
            metadata = [{} for _ in texts]
        elif len(metadata) != len(texts):
            raise ValueError(f"Length mismatch: got {len(texts)} texts but {len(metadata)} metadata entries")
        
        # Generate embeddings in batches
        doc_ids = []
        
        for i in range(0, len(texts), batch_size):
            batch_texts = texts[i:i+batch_size]
            batch_metadata = metadata[i:i+batch_size]
            
            # Generate embeddings
            logger.info(f"Generating embeddings for batch {i//batch_size + 1}/{(len(texts)-1)//batch_size + 1}")
            batch_embeddings = self.embedder.embed(batch_texts)
            
            # Create document objects
            documents = []
            for text, meta, embedding in zip(batch_texts, batch_metadata, batch_embeddings):
                doc = Document(text=text, metadata=meta, embedding=embedding)
                documents.append(doc)
            
            # Add to database
            batch_ids = self.vector_db.add_documents(documents)
            doc_ids.extend(batch_ids)
        
        logger.info(f"Added {len(doc_ids)} documents to database")
        return doc_ids
    
    def search(
        self,
        query: str,
        top_k: Optional[int] = None,
        search_type: Optional[str] = None,
        filter_dict: Optional[Dict[str, Any]] = None
    ) -> List[Dict[str, Any]]:
        """
        Search for relevant documents.
        
        Args:
            query: Query string
            top_k: Number of results to return (defaults to self.top_k)
            search_type: Type of search (defaults to self.search_type)
            filter_dict: Dictionary of metadata filters
            
        Returns:
            List of document dictionaries
        """
        if top_k is None:
            top_k = self.top_k
            
        if search_type is None:
            search_type = self.search_type
        
        # Create filter function if filter_dict is provided
        filter_func = None
        if filter_dict:
            def filter_func(doc):
                for key, value in filter_dict.items():
                    # Handle nested keys (e.g., "metadata.source")
                    if "." in key:
                        parts = key.split(".")
                        current = doc.metadata
                        for part in parts[:-1]:
                            if part not in current:
                                return False
                            current = current[part]
                        if parts[-1] not in current or current[parts[-1]] != value:
                            return False
                    elif key not in doc.metadata or doc.metadata[key] != value:
                        return False
                return True
        
        # Generate query embedding
        query_embedding = self.embedder.embed(query)
        
        # Perform search
        results = self.vector_db.search(query_embedding, top_k, filter_func)
        
        # Convert results to dictionaries
        return [
            {
                "id": doc.id,
                "text": doc.text,
                "metadata": doc.metadata,
                "score": score
            }
            for doc, score in results
        ]
    
    def generate_response(
        self,
        query: str,
        top_k: Optional[int] = None,
        search_type: Optional[str] = None,
        filter_dict: Optional[Dict[str, Any]] = None,
        max_tokens: int = 512
    ) -> Dict[str, Any]:
        """
        Generate a response to a query using RAG.
        
        Args:
            query: Query string
            top_k: Number of documents to retrieve
            search_type: Type of search
            filter_dict: Optional filter for document retrieval
            max_tokens: Maximum number of tokens in the response
            
        Returns:
            Dictionary with query, response, and retrieved documents
        """
        # Retrieve relevant documents
        retrieved_docs = self.search(query, top_k, search_type, filter_dict)
        
        # If no documents were found, return a default message
        if not retrieved_docs:
            return {
                "query": query,
                "response": "I couldn't find any relevant information to answer your question.",
                "retrieved_documents": [],
                "search_type": search_type or self.search_type
            }
        
        # Format context from retrieved documents
        context = self._format_context(retrieved_docs)
        
        # Format prompt with context and query
        prompt = self.prompt_template.format(context=context, query=query)
        
        # Generate response using LLM
        if self.llm is None:
            logger.warning("No LLM provided, returning only retrieved documents")
            response = "No language model available to generate a response. Here's what I found in the documents."
        else:
            response = self._generate_llm_response(prompt, max_tokens)
        
        # Return the results
        return {
            "query": query,
            "response": response,
            "retrieved_documents": retrieved_docs,
            "search_type": search_type or self.search_type
        }
    
    def _format_context(self, documents: List[Dict[str, Any]]) -> str:
        """
        Format retrieved documents into context for the prompt.
        
        Args:
            documents: List of retrieved documents
            
        Returns:
            Formatted context string
        """
        context_parts = []
        
        for i, doc in enumerate(documents):
            # Extract relevant fields
            text = doc["text"]
            metadata = doc["metadata"]
            source = metadata.get("source", "Unknown")
            
            # Format the document
            doc_text = f"Document {i+1}: [Source: {source}]\n{text}\n"
            context_parts.append(doc_text)
        
        return "\n".join(context_parts)
    
    def _generate_llm_response(self, prompt: str, max_tokens: int) -> str:
        """
        Generate a response using the LLM.
        
        Args:
            prompt: The formatted prompt
            max_tokens: Maximum number of tokens in the response
            
        Returns:
            Generated response
        """
        if hasattr(self.llm, "generate_openai_response"):
            # OpenAI-compatible LLM
            return self.llm.generate_openai_response(prompt, max_tokens)
        elif hasattr(self.llm, "generate_huggingface_response"):
            # HuggingFace-compatible LLM
            return self.llm.generate_huggingface_response(prompt, max_tokens)
        else:
            # Default implementation
            try:
                return self.llm.generate_response(prompt, max_tokens)
            except Exception as e:
                logger.error(f"Error generating response: {e}")
                return "I encountered an error while generating a response."
    
    def update_prompt_template(self, new_template: str) -> None:
        """
        Update the prompt template.
        
        Args:
            new_template: New prompt template
        """
        self.prompt_template = new_template
        logger.info("Updated prompt template")
    
    def count_documents(self) -> int:
        """
        Get the number of documents in the database.
        
        Returns:
            Number of documents
        """
        return self.vector_db.count_documents()
    
    def clear_documents(self) -> None:
        """Clear all documents from the database."""
        self.vector_db.clear()
        logger.info("Cleared all documents from database")


# Factory function to create the RAG engine
def create_rag_engine(
    embedder=None,
    vector_db=None,
    llm=None,
    config=None
) -> RAGEngine:
    """
    Factory function to create a RAG engine.
    
    Args:
        embedder: Embedding model (if None, created based on config)
        vector_db: Vector database (if None, created based on config)
        llm: Language model (if None, created based on config)
        config: Configuration module or dictionary
        
    Returns:
        Configured RAGEngine instance
    """
    # Load configuration if provided
    if config is None:
        from ..config import (
            TOP_K,
            SEARCH_TYPE,
            DEFAULT_PROMPT_TEMPLATE
        )
    else:
        TOP_K = config.get("TOP_K", 5)
        SEARCH_TYPE = config.get("SEARCH_TYPE", "hybrid")
        DEFAULT_PROMPT_TEMPLATE = config.get(
            "DEFAULT_PROMPT_TEMPLATE",
            """
            Answer the following question based ONLY on the provided context.
            
            Context:
            {context}
            
            Question: {query}
            
            Answer:
            """
        )
    
    # Create embedding model if not provided
    if embedder is None:
        from ..embedding.model import create_embedding_model
        embedder = create_embedding_model()
    
    # Create vector database if not provided
    if vector_db is None:
        from ..storage.vector_db import create_vector_database
        vector_db = create_vector_database(dimension=embedder.dimension)
    
    # Create language model if not provided and requested
    if llm is None:
        try:
            from ..llm.model import create_llm
            llm = create_llm()
        except (ImportError, ModuleNotFoundError):
            logger.warning("LLM module not found, proceeding without an LLM")
    
    # Create and return the RAG engine
    return RAGEngine(
        embedder=embedder,
        vector_db=vector_db,
        llm=llm,
        top_k=TOP_K,
        search_type=SEARCH_TYPE,
        prompt_template=DEFAULT_PROMPT_TEMPLATE
    )