# This code is part of Qiskit.
#
# (C) Copyright IBM 2021.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

"""Backend REST adapter."""

from typing import Dict, Optional, Any, List
from datetime import datetime

from .base import RestAdapterBase
from ..session import RetrySession


class Backend(RestAdapterBase):
    """Rest adapter for backend related endpoints."""

    URL_MAP = {
        "properties": "/properties",
        "pulse_defaults": "/defaults",
        "status": "/status",
        "configuration": "/configuration",
    }

    def __init__(
        self, session: RetrySession, backend_name: str = "", url_prefix: str = ""
    ) -> None:
        """Backend constructor.

        Args:
            session: Session to be used in the adaptor.
            backend_name: Name of the backend.
            url_prefix: Base URL.
        """
        self.backend_name = backend_name
        super().__init__(session, "{}/backends/{}".format(url_prefix, backend_name))

    def backends(self, hgp: str) -> List[str]:
        """Return a list of backends.

        Args:
            hgp: hub, group, and project.

        Returns:
            The list of backends from the given hgp.
        """
        payload = {"provider": hgp}
        return self.session.get(self.prefix_url, params=payload).json()["devices"]

    def properties(self, datetime: Optional[datetime] = None) -> Dict[str, Any]:
        """Return backend properties.

        Args:
            datetime: Date and time used for additional filtering passed to the query.

        Returns:
            JSON response of backend properties.
        """
        # pylint: disable=redefined-outer-name
        url = self.get_url("properties")

        params = {}
        if datetime:
            params["updated_before"] = datetime.isoformat()

        response = self.session.get(url, params=params).json()

        # Adjust name of the backend.
        if response:
            response["backend_name"] = self.backend_name

        return response

    def pulse_defaults(self) -> Dict[str, Any]:
        """Return backend pulse defaults.

        Returns:
            JSON response of pulse defaults.
        """
        url = self.get_url("pulse_defaults")
        return self.session.get(url).json()

    def status(self) -> Dict[str, Any]:
        """Return backend status.

        Returns:
            JSON response of backend status.
        """
        url = self.get_url("status")
        response = self.session.get(url).json()

        # Adjust fields according to the specs (BackendStatus).
        ret = {
            "backend_name": self.backend_name,
            "backend_version": response.get("backend_version", "0.0.0"),
            "status_msg": response.get("status", ""),
            "operational": bool(response.get("state", False)),
        }

        # 'pending_jobs' is required, and should be >= 0.
        if "length_queue" in response:
            ret["pending_jobs"] = max(response["length_queue"], 0)
        else:
            ret["pending_jobs"] = 0

        return ret

    def configuration(self) -> Dict[str, Any]:
        """Return backend configuration.

        Returns:
            JSON response of backend configuration.
        """
        url = self.get_url("configuration")
        return self.session.get(url).json()