import threading
from datetime import datetime
from pathlib import Path
from typing import Optional

from loguru import logger
from sqlalchemy import exc, func, inspect, text
from sqlmodel import Session, SQLModel, and_, create_engine, select

from ..datamodel import LinkTypes, Response
from .schema_manager import SchemaManager

# from .dbutils import init_db_samples


class DatabaseManager:
    _init_lock = threading.Lock()

    def __init__(self, engine_uri: str, base_dir: Optional[Path] = None):
        """
        Initialize DatabaseManager with database connection settings.
        Does not perform any database operations.

        Args:
            engine_uri: Database connection URI (e.g. sqlite:///db.sqlite3)
            base_dir: Base directory for migration files. If None, uses current directory
        """
        connection_args = {"check_same_thread": True} if "sqlite" in engine_uri else {}

        self.engine = create_engine(engine_uri, connect_args=connection_args)
        self.schema_manager = SchemaManager(
            engine=self.engine,
            base_dir=base_dir,
        )

    def initialize_database(self, auto_upgrade: bool = False, force_init_alembic: bool = True) -> Response:
        """
        Initialize database and migrations in the correct order.

        Args:
            auto_upgrade: If True, automatically generate and apply migrations for schema changes
            force_init_alembic: If True, reinitialize alembic configuration even if it exists
        """
        if not self._init_lock.acquire(blocking=False):
            return Response(message="Database initialization already in progress", status=False)

        try:
            inspector = inspect(self.engine)
            tables_exist = inspector.get_table_names()

            if not tables_exist:
                # Fresh install - create tables and initialize migrations
                logger.info("Creating database tables...")
                SQLModel.metadata.create_all(self.engine)

                if self.schema_manager.initialize_migrations(force=force_init_alembic):
                    return Response(message="Database initialized successfully", status=True)
                return Response(message="Failed to initialize migrations", status=False)

            # Handle existing database
            if auto_upgrade:
                logger.info("Checking database schema...")
                if self.schema_manager.ensure_schema_up_to_date():  # <-- Use this instead
                    return Response(message="Database schema is up to date", status=True)
                return Response(message="Database upgrade failed", status=False)

            return Response(message="Database is ready", status=True)

        except Exception as e:
            error_msg = f"Database initialization failed: {str(e)}"
            logger.error(error_msg)
            return Response(message=error_msg, status=False)
        finally:
            self._init_lock.release()

    def reset_db(self, recreate_tables: bool = True):
        """
        Reset the database by dropping all tables and optionally recreating them.

        Args:
            recreate_tables (bool): If True, recreates the tables after dropping them.
                                Set to False if you want to call create_db_and_tables() separately.
        """
        if not self._init_lock.acquire(blocking=False):
            logger.warning("Database reset already in progress")
            return Response(message="Database reset already in progress", status=False, data=None)

        try:
            # Dispose existing connections
            self.engine.dispose()
            with Session(self.engine) as session:
                try:
                    # Disable foreign key checks for SQLite
                    if "sqlite" in str(self.engine.url):
                        session.exec(text("PRAGMA foreign_keys=OFF"))

                    # Drop all tables
                    SQLModel.metadata.drop_all(self.engine)
                    logger.info("All tables dropped successfully")

                    # Re-enable foreign key checks for SQLite
                    if "sqlite" in str(self.engine.url):
                        session.exec(text("PRAGMA foreign_keys=ON"))

                    session.commit()

                except Exception as e:
                    session.rollback()
                    raise e
                finally:
                    session.close()
                    self._init_lock.release()

            if recreate_tables:
                logger.info("Recreating tables...")
                self.initialize_database(auto_upgrade=False, force_init_alembic=True)

            return Response(
                message="Database reset successfully" if recreate_tables else "Database tables dropped successfully",
                status=True,
                data=None,
            )

        except Exception as e:
            error_msg = f"Error while resetting database: {str(e)}"
            logger.error(error_msg)
            return Response(message=error_msg, status=False, data=None)
        finally:
            if self._init_lock.locked():
                self._init_lock.release()
                logger.info("Database reset lock released")

    def upsert(self, model: SQLModel, return_json: bool = True):
        """Create or update an entity

        Args:
            model (SQLModel): The model instance to create or update
            return_json (bool, optional): If True, returns the model as a dictionary.
                If False, returns the SQLModel instance. Defaults to True.

        Returns:
            Response: Contains status, message and data (either dict or SQLModel based on return_json)
        """
        status = True
        model_class = type(model)
        existing_model = None

        with Session(self.engine) as session:
            try:
                existing_model = session.exec(select(model_class).where(model_class.id == model.id)).first()
                if existing_model:
                    model.updated_at = datetime.now()
                    for key, value in model.model_dump().items():
                        setattr(existing_model, key, value)
                    model = existing_model  # Use the updated existing model
                    session.add(model)
                else:
                    session.add(model)
                session.commit()
                session.refresh(model)
            except Exception as e:
                session.rollback()
                logger.error("Error while updating/creating " + str(model_class.__name__) + ": " + str(e))
                status = False

        return Response(
            message=(
                f"{model_class.__name__} Updated Successfully"
                if existing_model
                else f"{model_class.__name__} Created Successfully"
            ),
            status=status,
            data=model.model_dump() if return_json else model,
        )

    def _model_to_dict(self, model_obj):
        return {col.name: getattr(model_obj, col.name) for col in model_obj.__table__.columns}

    def get(
        self,
        model_class: SQLModel,
        filters: dict = None,
        return_json: bool = False,
        order: str = "desc",
    ):
        """List entities"""
        with Session(self.engine) as session:
            result = []
            status = True
            status_message = ""

            try:
                statement = select(model_class)
                if filters:
                    conditions = [getattr(model_class, col) == value for col, value in filters.items()]
                    statement = statement.where(and_(*conditions))

                if hasattr(model_class, "created_at") and order:
                    order_by_clause = getattr(model_class.created_at, order)()  # Dynamically apply asc/desc
                    statement = statement.order_by(order_by_clause)

                items = session.exec(statement).all()
                result = [self._model_to_dict(item) if return_json else item for item in items]
                status_message = f"{model_class.__name__} Retrieved Successfully"
            except Exception as e:
                session.rollback()
                status = False
                status_message = f"Error while fetching {model_class.__name__}"
                logger.error("Error while getting items: " + str(model_class.__name__) + " " + str(e))

            return Response(message=status_message, status=status, data=result)

    def delete(self, model_class: SQLModel, filters: dict = None):
        """Delete an entity"""
        status_message = ""
        status = True

        with Session(self.engine) as session:
            try:
                statement = select(model_class)
                if filters:
                    conditions = [getattr(model_class, col) == value for col, value in filters.items()]
                    statement = statement.where(and_(*conditions))

                rows = session.exec(statement).all()

                if rows:
                    for row in rows:
                        session.delete(row)
                    session.commit()
                    status_message = f"{model_class.__name__} Deleted Successfully"
                else:
                    status_message = "Row not found"
                    logger.info(f"Row with filters {filters} not found")

            except exc.IntegrityError as e:
                session.rollback()
                status = False
                status_message = f"Integrity error: The {model_class.__name__} is linked to another entity and cannot be deleted. {e}"
                # Log the specific integrity error
                logger.error(status_message)
            except Exception as e:
                session.rollback()
                status = False
                status_message = f"Error while deleting: {e}"
                logger.error(status_message)

        return Response(message=status_message, status=status, data=None)

    def link(
        self,
        link_type: LinkTypes,
        primary_id: int,
        secondary_id: int,
        sequence: Optional[int] = None,
    ):
        """Link two entities with automatic sequence handling."""
        with Session(self.engine) as session:
            try:
                # Get classes from LinkTypes
                primary_class = link_type.primary_class
                secondary_class = link_type.secondary_class
                link_table = link_type.link_table

                # Get entities
                primary_entity = session.get(primary_class, primary_id)
                secondary_entity = session.get(secondary_class, secondary_id)

                if not primary_entity or not secondary_entity:
                    return Response(message="One or both entities do not exist", status=False)

                # Get field names
                primary_id_field = f"{primary_class.__name__.lower()}_id"
                secondary_id_field = f"{secondary_class.__name__.lower()}_id"

                # Check for existing link
                existing_link = session.exec(
                    select(link_table).where(
                        and_(
                            getattr(link_table, primary_id_field) == primary_id,
                            getattr(link_table, secondary_id_field) == secondary_id,
                        )
                    )
                ).first()

                if existing_link:
                    return Response(message="Link already exists", status=False)

                # Get the next sequence number if not provided
                if sequence is None:
                    max_seq_result = session.exec(
                        select(func.max(link_table.sequence)).where(getattr(link_table, primary_id_field) == primary_id)
                    ).first()
                    sequence = 0 if max_seq_result is None else max_seq_result + 1

                # Create new link
                new_link = link_table(
                    **{primary_id_field: primary_id, secondary_id_field: secondary_id, "sequence": sequence}
                )
                session.add(new_link)
                session.commit()

                return Response(message=f"Entities linked successfully with sequence {sequence}", status=True)

            except Exception as e:
                session.rollback()
                return Response(message=f"Error linking entities: {str(e)}", status=False)

    def unlink(self, link_type: LinkTypes, primary_id: int, secondary_id: int, sequence: Optional[int] = None):
        """Unlink two entities and reorder sequences if needed."""
        with Session(self.engine) as session:
            try:
                # Get classes from LinkTypes
                primary_class = link_type.primary_class
                secondary_class = link_type.secondary_class
                link_table = link_type.link_table

                # Get field names
                primary_id_field = f"{primary_class.__name__.lower()}_id"
                secondary_id_field = f"{secondary_class.__name__.lower()}_id"

                # Find existing link
                statement = select(link_table).where(
                    and_(
                        getattr(link_table, primary_id_field) == primary_id,
                        getattr(link_table, secondary_id_field) == secondary_id,
                    )
                )

                if sequence is not None:
                    statement = statement.where(link_table.sequence == sequence)

                existing_link = session.exec(statement).first()

                if not existing_link:
                    return Response(message="Link does not exist", status=False)

                deleted_sequence = existing_link.sequence
                session.delete(existing_link)

                # Reorder sequences for remaining links
                remaining_links = session.exec(
                    select(link_table)
                    .where(getattr(link_table, primary_id_field) == primary_id)
                    .where(link_table.sequence > deleted_sequence)
                    .order_by(link_table.sequence)
                ).all()

                # Decrease sequence numbers to fill the gap
                for link in remaining_links:
                    link.sequence -= 1

                session.commit()

                return Response(message="Entities unlinked successfully and sequences reordered", status=True)

            except Exception as e:
                session.rollback()
                return Response(message=f"Error unlinking entities: {str(e)}", status=False)

    def get_linked_entities(
        self,
        link_type: LinkTypes,
        primary_id: int,
        return_json: bool = False,
    ):
        """Get linked entities based on link type and primary ID, ordered by sequence."""
        with Session(self.engine) as session:
            try:
                # Get classes from LinkTypes
                primary_class = link_type.primary_class
                secondary_class = link_type.secondary_class
                link_table = link_type.link_table

                # Get field names
                primary_id_field = f"{primary_class.__name__.lower()}_id"
                secondary_id_field = f"{secondary_class.__name__.lower()}_id"

                # Query both link and entity, ordered by sequence
                items = session.exec(
                    select(secondary_class)
                    .join(link_table, getattr(link_table, secondary_id_field) == secondary_class.id)
                    .where(getattr(link_table, primary_id_field) == primary_id)
                    .order_by(link_table.sequence)
                ).all()

                result = [item.model_dump() if return_json else item for item in items]

                return Response(message="Linked entities retrieved successfully", status=True, data=result)

            except Exception as e:
                logger.error(f"Error getting linked entities: {str(e)}")
                return Response(message=f"Error getting linked entities: {str(e)}", status=False, data=[])

    # Add new close method

    async def close(self):
        """Close database connections and cleanup resources"""
        logger.info("Closing database connections...")
        try:
            # Dispose of the SQLAlchemy engine
            self.engine.dispose()
            logger.info("Database connections closed successfully")
        except Exception as e:
            logger.error(f"Error closing database connections: {str(e)}")
            raise