import logging
import os
from collections.abc import Generator
from contextlib import contextmanager
from typing import Any

import mlflow
import mlflow.sklearn
import pandas as pd

from model_manager.sientia.exceptions import SientiaMlException


class ModelServing:
    """
    MLflow model serving wrapper.

    Thread-safety note: This class modifies global state (MLflow tracking URI and
    environment variables) during initialization. In multi-threaded environments,
    ensure that:
    1. Instances are created with the same tracking_uri/credentials, OR
    2. Instance creation is synchronized (e.g., using a lock), OR
    3. Create a single instance and share it across threads

    The MLflow operations themselves (log_param, log_metric, etc.) are thread-safe
    when operating on different runs.
    """

    def __init__(
        self,
        tracking_uri: str,
        username: str | None = None,
        password: str | None = None,
    ):
        """
        Initialize ModelServing client.

        WARNING: This modifies global state (MLflow config and environment variables).
        Not thread-safe during initialization if different credentials are used.

        Args:
            tracking_uri: MLflow tracking server URI
            username: Optional MLflow username
            password: Optional MLflow password
            logger: Optional logger (currently unused)
        """
        # Set tracking URI (modifies global MLflow state)
        mlflow.set_tracking_uri(tracking_uri)

        # Set credentials in environment variables (global state)
        if username is not None:
            os.environ['MLFLOW_TRACKING_USERNAME'] = username
        if password is not None:
            os.environ['MLFLOW_TRACKING_PASSWORD'] = password

    # Function to list runs for a given experiment
    def search_runs_by_name(
        self, experiment_names: list[str], order_by: None | list[str] = None
    ) -> pd.DataFrame | list:
        """
        List runs for a specified MLflow experiment.

        Args:
            experiment_names (list[str]): List with experiment_names to retrieve runs from.

        Returns:
            Union[pd.DataFrame, list]: A DataFrame or list containing run information.

        Raises:
            SientiaMlException: If unable to search runs.
        """
        try:
            runs = mlflow.search_runs(experiment_names=experiment_names, order_by=order_by)
        except SientiaMlException as e:
            logging.error(e)
            raise SientiaMlException(str(e)) from e
        return runs

    def set_experiment(self, experiment_identifier: str) -> None:
        """
        Set the given experiment as the active experiment.

        Args:
            experiment_identifier (str): name or id of the experiment to be setted

        Raises:
            Exception: If setting the experiment fails.
        """
        mlflow.set_experiment(experiment_identifier)

    def log_model(self, sk_model: Any, artifact_path: Any, **kwargs) -> None:
        """
        Log a sklearn model.

        Args:
            sk_model: scikit-learn model to be saved.
            artifact_path: Run-relative artifact path.

        Returns:
            None

        Security Warning:
            The GitHub token is hardcoded. Consider moving to environment variable
            or using a secure secret management solution (e.g., K8s secrets).

        Raises:
            Exception: If logging the model fails.
        """
        mlflow.sklearn.log_model(
            sk_model,
            artifact_path,
            extra_pip_requirements=[os.getenv('EXTRA_PIP_REQUIREMENTS')],
            **kwargs,
        )

    def log_param(self, key: str, value: Any) -> None:
        """
        Log a param in the active run.

        Args:
            key (str): Param name
            value (any): Param value

        Returns:
            None

        Raises:
            Exception: If logging the parameter fails.
        """
        mlflow.log_param(key, value)

    def log_metric(self, key: str, value: Any) -> None:
        """
        Log a metric in the active run.

        Args:
            key (str): Metric name
            value (any): Metric value

        Returns:
            None

        Raises:
            Exception: If logging the metric fails.
        """
        mlflow.log_metric(key, value)

    def log_artifact(
        self, local_path: str, artifact_path: str | None = None, run_id: str | None = None
    ) -> None:
        """
        Log an artifact.

        Args:
            local_path: Local path of the artifact to log.
            artifact_path: If provided, the directory in artifact_uri to write to.
            run_id: optional id of current run

        Returns:
            None

        Raises:
            Exception: If logging the artifact fails.
        """
        mlflow.log_artifact(local_path=local_path, artifact_path=artifact_path, run_id=run_id)

    @contextmanager
    def save_experiment(
        self,
        run_id: str | None = None,
        experiment_id: str | None = None,
        run_name: str | None = None,
        nested: bool = False,
        tags: dict[str, Any] | None = None,
        description: str | None = None,
        log_system_metrics: bool | None = None,
    ) -> Generator[mlflow.ActiveRun, None, None]:
        """
        Context manager to save an experiment, ensuring the run is properly closed.

        This prevents memory leaks by guaranteeing that MLflow runs are always ended,
        even if an exception occurs. Thread-safe when used with proper MLflow configuration.

        Args:
            run_id: If specified, get the run with the specified UUID and log parameters and metrics under that run.
            experiment_id: ID of the experiment under which to create the current run (applicable only when run_id is not specified).
            run_name: Name of new run. Used only when run_id is unspecified.
            nested: Controls whether run is nested in parent run. True creates a nested run.
            tags: An optional dictionary of string keys and values to set as tags on the run. If a run is being resumed, these tags are set on the resumed run. If a new run is being created, these tags are set on the new run.
            description: An optional string that populates the description box of the run.
            log_system_metrics: If True, system metrics will be logged. If None, we will check environment variable

        Yields:
            ActiveRun: object that acts as a context manager wrapping the run's state.

        Raises:
            Exception: If starting or ending the MLflow run fails.
        """
        run = mlflow.start_run(
            run_id=run_id,
            experiment_id=experiment_id,
            run_name=run_name,
            nested=nested,
            tags=tags,
            description=description,
            log_system_metrics=log_system_metrics,
        )
        try:
            yield run
        finally:
            # Ensure run is always ended, preventing resource leaks
            mlflow.end_run()