"""
Module for managing PostgreSQL database operations.
- Replaces SQLite (sq_db.py) with PostgreSQL using SQLAlchemy
- Provides functions to track user uploaded/generated files/data
- Includes creating tables, adding files and embeddings, and managing users
"""

import bcrypt
import os
from typing import List, Optional, Dict, Any
from datetime import datetime, timedelta
from contextlib import contextmanager

import pytz
from sqlalchemy import create_engine, Column, String, Integer, DateTime, Boolean, Text, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, Session, relationship
from logger import get_logger

log = get_logger(name="pg_db")

# Get DATABASE_URL from environment or use default
DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://raguser:ragpass@localhost:5432/ragdb")

# Create engine
engine = create_engine(DATABASE_URL, pool_pre_ping=True, echo=False)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

IST = pytz.timezone('Asia/Kolkata')


# ------------------------------------------------------------------------------
# SQLAlchemy Models
# ------------------------------------------------------------------------------

class User(Base):
    """User model"""
    __tablename__ = "users"
    
    user_id = Column(String, primary_key=True, index=True)
    password_hash = Column(String, nullable=False)
    created_at = Column(DateTime, default=lambda: datetime.now(IST))
    last_login = Column(DateTime, nullable=True)
    available = Column(Boolean, default=True)
    
    # Relationships
    files = relationship("UserFile", back_populates="user")
    embeddings = relationship("UserEmbedding", back_populates="user")


class UserFile(Base):
    """User uploaded files model"""
    __tablename__ = "user_files"
    
    id = Column(Integer, primary_key=True, autoincrement=True)
    user_id = Column(String, ForeignKey("users.user_id"), nullable=False, index=True)
    file_name = Column(String, nullable=False)
    file_path = Column(String, nullable=False)
    file_type = Column(String, nullable=True)
    uploaded_at = Column(DateTime, default=lambda: datetime.now(IST))
    available = Column(Boolean, default=True)
    
    # Relationship
    user = relationship("User", back_populates="files")


class UserEmbedding(Base):
    """User embeddings/documents model"""
    __tablename__ = "user_embeddings"
    
    id = Column(Integer, primary_key=True, autoincrement=True)
    user_id = Column(String, ForeignKey("users.user_id"), nullable=False, index=True)
    qdrant_doc_id = Column(String, nullable=True)  # ID in Qdrant
    source = Column(String, nullable=True)
    created_at = Column(DateTime, default=lambda: datetime.now(IST))
    available = Column(Boolean, default=True)
    
    # Relationship
    user = relationship("User", back_populates="embeddings")


# ------------------------------------------------------------------------------
# Database Management Functions
# ------------------------------------------------------------------------------

def init_database():
    """Initialize the database by creating all tables."""
    try:
        Base.metadata.create_all(bind=engine)
        log.info("Database tables created successfully.")
        return True
    except Exception as e:
        log.error(f"Error creating database tables: {e}")
        return False


@contextmanager
def get_db():
    """Context manager for database sessions."""
    db = SessionLocal()
    try:
        yield db
        db.commit()
    except Exception:
        db.rollback()
        raise
    finally:
        db.close()


def get_connection():
    """Returns a new database session. (For compatibility with existing code)"""
    return SessionLocal()


def delete_database() -> bool:
    """Drop all tables (equivalent to deleting SQLite file)."""
    try:
        Base.metadata.drop_all(bind=engine)
        log.info("All database tables dropped successfully.")
        return True
    except Exception as e:
        log.error(f"Error dropping database tables: {e}")
        return False


# ------------------------------------------------------------------------------
# User Management Functions
# ------------------------------------------------------------------------------

def create_user(user_id: str, password: str) -> bool:
    """Create a new user with hashed password."""
    try:
        with get_db() as db:
            # Check if user already exists
            existing_user = db.query(User).filter(User.user_id == user_id).first()
            if existing_user:
                log.warning(f"User '{user_id}' already exists.")
                return False
            
            # Hash password
            password_hash = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt()).decode('utf-8')
            
            # Create user
            user = User(user_id=user_id, password_hash=password_hash)
            db.add(user)
            
        log.info(f"User '{user_id}' created successfully.")
        return True
    except Exception as e:
        log.error(f"Error creating user '{user_id}': {e}")
        return False


def verify_user(user_id: str, password: str) -> bool:
    """Verify user credentials."""
    try:
        with get_db() as db:
            user = db.query(User).filter(User.user_id == user_id, User.available == True).first()
            
            if not user:
                log.warning(f"User '{user_id}' not found.")
                return False
            
            # Verify password
            if bcrypt.checkpw(password.encode('utf-8'), user.password_hash.encode('utf-8')):
                # Update last login
                user.last_login = datetime.now(IST)
                log.info(f"User '{user_id}' authenticated successfully.")
                return True
            else:
                log.warning(f"Invalid password for user '{user_id}'.")
                return False
                
    except Exception as e:
        log.error(f"Error verifying user '{user_id}': {e}")
        return False


def get_all_users() -> List[Dict[str, Any]]:
    """Get all users."""
    try:
        with get_db() as db:
            users = db.query(User).filter(User.available == True).all()
            return [
                {
                    "user_id": u.user_id,
                    "created_at": u.created_at.isoformat() if u.created_at else None,
                    "last_login": u.last_login.isoformat() if u.last_login else None
                }
                for u in users
            ]
    except Exception as e:
        log.error(f"Error getting all users: {e}")
        return []


def delete_user(user_id: str) -> bool:
    """Mark user as unavailable (soft delete)."""
    try:
        with get_db() as db:
            user = db.query(User).filter(User.user_id == user_id).first()
            if user:
                user.available = False
                log.info(f"User '{user_id}' marked as deleted.")
                return True
            else:
                log.warning(f"User '{user_id}' not found.")
                return False
    except Exception as e:
        log.error(f"Error deleting user '{user_id}': {e}")
        return False


# ------------------------------------------------------------------------------
# File Management Functions
# ------------------------------------------------------------------------------

def add_file(user_id: str, file_name: str, file_path: str, file_type: Optional[str] = None) -> bool:
    """Add a file record for a user."""
    try:
        with get_db() as db:
            file_record = UserFile(
                user_id=user_id,
                file_name=file_name,
                file_path=file_path,
                file_type=file_type
            )
            db.add(file_record)
            
        log.info(f"File '{file_name}' added for user '{user_id}'.")
        return True
    except Exception as e:
        log.error(f"Error adding file '{file_name}' for user '{user_id}': {e}")
        return False


def get_user_files(user_id: str) -> List[Dict[str, Any]]:
    """Get all files for a user."""
    try:
        with get_db() as db:
            files = db.query(UserFile).filter(
                UserFile.user_id == user_id,
                UserFile.available == True
            ).all()
            
            return [
                {
                    "id": f.id,
                    "file_name": f.file_name,
                    "file_path": f.file_path,
                    "file_type": f.file_type,
                    "uploaded_at": f.uploaded_at.isoformat() if f.uploaded_at else None
                }
                for f in files
            ]
    except Exception as e:
        log.error(f"Error getting files for user '{user_id}': {e}")
        return []


def delete_file(file_id: int) -> bool:
    """Mark file as unavailable (soft delete)."""
    try:
        with get_db() as db:
            file_record = db.query(UserFile).filter(UserFile.id == file_id).first()
            if file_record:
                file_record.available = False
                log.info(f"File ID {file_id} marked as deleted.")
                return True
            else:
                log.warning(f"File ID {file_id} not found.")
                return False
    except Exception as e:
        log.error(f"Error deleting file ID {file_id}: {e}")
        return False


# ------------------------------------------------------------------------------
# Embedding Management Functions
# ------------------------------------------------------------------------------

def add_embedding(user_id: str, qdrant_doc_id: Optional[str] = None, source: Optional[str] = None) -> bool:
    """Add an embedding record for a user."""
    try:
        with get_db() as db:
            embedding = UserEmbedding(
                user_id=user_id,
                qdrant_doc_id=qdrant_doc_id,
                source=source
            )
            db.add(embedding)
            
        log.info(f"Embedding added for user '{user_id}'.")
        return True
    except Exception as e:
        log.error(f"Error adding embedding for user '{user_id}': {e}")
        return False


def get_user_embeddings(user_id: str) -> List[Dict[str, Any]]:
    """Get all embeddings for a user."""
    try:
        with get_db() as db:
            embeddings = db.query(UserEmbedding).filter(
                UserEmbedding.user_id == user_id,
                UserEmbedding.available == True
            ).all()
            
            return [
                {
                    "id": e.id,
                    "qdrant_doc_id": e.qdrant_doc_id,
                    "source": e.source,
                    "created_at": e.created_at.isoformat() if e.created_at else None
                }
                for e in embeddings
            ]
    except Exception as e:
        log.error(f"Error getting embeddings for user '{user_id}': {e}")
        return []


def delete_embedding(embedding_id: int) -> bool:
    """Mark embedding as unavailable (soft delete)."""
    try:
        with get_db() as db:
            embedding = db.query(UserEmbedding).filter(UserEmbedding.id == embedding_id).first()
            if embedding:
                embedding.available = False
                log.info(f"Embedding ID {embedding_id} marked as deleted.")
                return True
            else:
                log.warning(f"Embedding ID {embedding_id} not found.")
                return False
    except Exception as e:
        log.error(f"Error deleting embedding ID {embedding_id}: {e}")
        return False


# ==============================================================================
# Compatibility Functions for sq_db.py API
# ==============================================================================

def create_tables():
    """Alias for init_database() to match sq_db.py API."""
    init_database()


def add_user(user_id: str, name: str, password: str) -> bool:
    """
    Add user with name parameter (sq_db.py compatibility).
    Note: name parameter is ignored in PostgreSQL version as schema doesn't include it.
    """
    return create_user(user_id=user_id, password=password)


def check_user_exists(user_id: str) -> bool:
    """Check if user exists in database."""
    try:
        with get_db() as db:
            user = db.query(User).filter(User.user_id == user_id, User.available == True).first()
            return user is not None
    except Exception as e:
        log.error(f"Error checking if user '{user_id}' exists: {e}")
        return False


def authenticate_user(user_id: str, password: str) -> tuple[bool, str]:
    """
    Authenticate user and return status with message.
    Returns: (success: bool, message: str)
    """
    try:
        if verify_user(user_id=user_id, password=password):
            # Update last_login
            with get_db() as db:
                user = db.query(User).filter(User.user_id == user_id).first()
                if user:
                    user.last_login = datetime.now()
                    log.info(f"User '{user_id}' authenticated successfully.")
            return (True, "Authentication successful")
        else:
            return (False, "Invalid credentials")
    except Exception as e:
        log.error(f"Error authenticating user '{user_id}': {e}")
        return (False, f"Error: {str(e)}")


def get_file_id_by_name(user_id: str, file_name: str) -> int:
    """Get file ID by user ID and filename."""
    try:
        with get_db() as db:
            file = db.query(UserFile).filter(
                UserFile.user_id == user_id,
                UserFile.file_name == file_name,
                UserFile.available == True
            ).first()
            return file.id if file else -1
    except Exception as e:
        log.error(f"Error getting file ID for '{file_name}': {e}")
        return -1


def mark_file_removed(user_id: str, file_id: int) -> bool:
    """Mark file as unavailable (soft delete)."""
    try:
        with get_db() as db:
            file = db.query(UserFile).filter(
                UserFile.id == file_id,
                UserFile.user_id == user_id
            ).first()
            if file:
                file.available = False
                log.info(f"File ID {file_id} marked as removed.")
                return True
            else:
                log.warning(f"File ID {file_id} not found for user '{user_id}'.")
                return False
    except Exception as e:
        log.error(f"Error marking file ID {file_id} as removed: {e}")
        return False


def mark_embeddings_removed(vector_ids: List[str]) -> bool:
    """Mark embeddings as unavailable by qdrant_doc_id list."""
    try:
        with get_db() as db:
            embeddings = db.query(UserEmbedding).filter(
                UserEmbedding.qdrant_doc_id.in_(vector_ids)
            ).all()
            for embedding in embeddings:
                embedding.available = False
            log.info(f"Marked {len(embeddings)} embeddings as removed.")
            return True
    except Exception as e:
        log.error(f"Error marking embeddings as removed: {e}")
        return False


def get_old_files(user_id: str, time: int = 12*3600) -> dict:
    """
    Get files older than specified time (in seconds).
    Returns: dict with 'files' (list of filenames) and 'embeddings' (list of qdrant_doc_ids)
    """
    try:
        with get_db() as db:
            cutoff_time = datetime.now() - timedelta(seconds=time)
            old_files = db.query(UserFile).filter(
                UserFile.user_id == user_id,
                UserFile.uploaded_at < cutoff_time,
                UserFile.available == True
            ).all()
            
            filenames = [f.file_name for f in old_files]
            file_ids = [f.id for f in old_files]
            
            # Get embeddings for these files
            if file_ids:
                embeddings = db.query(UserEmbedding).join(UserFile).filter(
                    UserFile.id.in_(file_ids),
                    UserEmbedding.available == True
                ).all()
                embedding_ids = [e.qdrant_doc_id for e in embeddings if e.qdrant_doc_id]
            else:
                embedding_ids = []
            
            return {
                'files': filenames,
                'embeddings': embedding_ids
            }
    except Exception as e:
        log.error(f"Error getting old files for user '{user_id}': {e}")
        return {'files': [], 'embeddings': []}


# Modified add_file to match sq_db signature (filename only)
def add_file_compat(user_id: str, filename: str) -> int:
    """
    Add file with only filename parameter (sq_db.py compatibility).
    Returns file ID.
    """
    try:
        file_path = f"/fastAPI/user_uploads/{user_id}/{filename}"  # Default path
        success = add_file(user_id=user_id, file_name=filename, file_path=file_path)
        if success:
            file_id = get_file_id_by_name(user_id=user_id, file_name=filename)
            return file_id
        return -1
    except Exception as e:
        log.error(f"Error adding file '{filename}': {e}")
        return -1


# Modified add_embedding to match sq_db signature
def add_embedding_compat(file_id: int, vector_id: str) -> bool:
    """
    Add embedding with file_id and vector_id (sq_db.py compatibility).
    """
    try:
        with get_db() as db:
            file = db.query(UserFile).filter(UserFile.id == file_id).first()
            if not file:
                log.warning(f"File ID {file_id} not found.")
                return False
            
            user_id = file.user_id
            return add_embedding(user_id=user_id, qdrant_doc_id=vector_id, source=file.file_name)
    except Exception as e:
        log.error(f"Error adding embedding for file ID {file_id}: {e}")
        return False


# Modified get_user_files to return list of strings (filenames only)
def get_user_files_compat(user_id: str) -> List[str]:
    """
    Get user files as list of filenames (sq_db.py compatibility).
    """
    files_data = get_user_files(user_id=user_id)
    return [f['file_name'] for f in files_data]


# Initialize database on module import
init_database()