"""Memory Layer Implementation for LangGraph Agent System"""
import os
import time
import hashlib
import sqlite3
from typing import Optional, List, Dict, Any, Tuple
from langchain_community.vectorstores import SupabaseVectorStore
from langchain_huggingface import HuggingFaceEmbeddings
from supabase.client import Client, create_client
from langgraph.checkpoint.sqlite import SqliteSaver
from langchain_core.messages import BaseMessage, HumanMessage


# Constants for memory management
TTL = 300  # seconds – how long we keep similarity-search results
SIMILARITY_THRESHOLD = 0.85  # cosine score above which we assume we already know the answer


class MemoryManager:
    """Manages short-term, long-term memory and checkpointing for the agent system"""
    
    def __init__(self):
        self.embeddings = HuggingFaceEmbeddings(model_name="sentence-transformers/all-mpnet-base-v2")
        self.vector_store = None
        self.checkpointer = None
        self._sqlite_connection = None
        
        # In-memory caches
        self.query_cache: Dict[str, Tuple[float, List]] = {}
        self.processed_tasks: set[str] = set()
        self.seen_hashes: set[str] = set()
        
        self._initialize_vector_store()
        self._initialize_checkpointer()
    
    def _initialize_vector_store(self) -> None:
        """Initialize Supabase vector store for long-term memory"""
        try:
            supabase_url = os.environ.get("SUPABASE_URL")
            supabase_key = os.environ.get("SUPABASE_SERVICE_KEY")
            
            if not supabase_url or not supabase_key:
                print("Warning: Supabase credentials not found, vector store will be disabled")
                return
                
            supabase: Client = create_client(supabase_url, supabase_key)
            self.vector_store = SupabaseVectorStore(
                client=supabase,
                embedding=self.embeddings,
                table_name="documents",
                query_name="match_documents_langchain",
            )
            print("Vector store initialized successfully")
        except Exception as e:
            print(f"Warning: Could not initialize Supabase vector store: {e}")
    
    def _initialize_checkpointer(self) -> None:
        """Initialize SQLite checkpointer for short-term memory"""
        try:
            # Create a direct SQLite connection
            self._sqlite_connection = sqlite3.connect(":memory:", check_same_thread=False)
            self.checkpointer = SqliteSaver(self._sqlite_connection)
            print("Checkpointer initialized successfully")
        except Exception as e:
            print(f"Warning: Could not initialize checkpointer: {e}")
    
    def get_checkpointer(self) -> Optional[SqliteSaver]:
        """Get the checkpointer instance"""
        return self.checkpointer
    
    def close_checkpointer(self) -> None:
        """Close the checkpointer and its SQLite connection"""
        if self._sqlite_connection:
            try:
                self._sqlite_connection.close()
                print("SQLite connection closed")
            except Exception as e:
                print(f"Warning: Error closing SQLite connection: {e}")
    
    def similarity_search(self, query: str, k: int = 2) -> List[Any]:
        """Search for similar questions with caching"""
        if not self.vector_store:
            return []
        
        # Check cache first
        q_hash = hashlib.sha256(query.encode()).hexdigest()
        now = time.time()
        
        if q_hash in self.query_cache and now - self.query_cache[q_hash][0] < TTL:
            print("Memory: Cache hit for similarity search")
            return self.query_cache[q_hash][1]
        
        try:
            print("Memory: Searching vector store for similar questions...")
            similar_questions = self.vector_store.similarity_search_with_relevance_scores(query, k=k)
            self.query_cache[q_hash] = (now, similar_questions)
            return similar_questions
        except Exception as e:
            print(f"Memory: Vector store search error – {e}")
            return []
    
    def should_ingest(self, query: str) -> bool:
        """Determine if this query/answer should be ingested to long-term memory"""
        if not self.vector_store:
            return False
        
        similar_questions = self.similarity_search(query, k=1)
        top_score = similar_questions[0][1] if similar_questions else 0.0
        return top_score < SIMILARITY_THRESHOLD
    
    def ingest_qa_pair(self, question: str, answer: str, attachments: str = "") -> None:
        """Store Q/A pair in long-term memory"""
        if not self.vector_store:
            print("Memory: Vector store not available for ingestion")
            return
        
        try:
            payload = f"Question:\n{question}\n\nAnswer:\n{answer}"
            if attachments:
                payload += f"\n\n{attachments}"
            
            hash_id = hashlib.sha256(payload.encode()).hexdigest()
            if hash_id in self.seen_hashes:
                print("Memory: Duplicate payload within session – skip")
                return
            
            self.seen_hashes.add(hash_id)
            self.vector_store.add_texts(
                [payload], 
                metadatas=[{"hash_id": hash_id, "timestamp": time.time()}]
            )
            print("Memory: Stored new Q/A pair in vector store")
        except Exception as e:
            print(f"Memory: Error while upserting – {e}")
    
    def get_similar_qa(self, query: str) -> Optional[str]:
        """Get similar Q/A for context"""
        similar_questions = self.similarity_search(query, k=1)
        if not similar_questions:
            return None
        
        example_doc = similar_questions[0][0] if isinstance(similar_questions[0], tuple) else similar_questions[0]
        return example_doc.page_content
    
    def add_processed_task(self, task_id: str) -> None:
        """Mark a task as processed to avoid re-downloading attachments"""
        self.processed_tasks.add(task_id)
    
    def is_task_processed(self, task_id: str) -> bool:
        """Check if a task has already been processed"""
        return task_id in self.processed_tasks
    
    def clear_session_cache(self) -> None:
        """Clear session-specific caches"""
        self.query_cache.clear()
        self.processed_tasks.clear()
        self.seen_hashes.clear()
        print("Memory: Session cache cleared")


# Global memory manager instance
memory_manager = MemoryManager()