# Copyright (c) 2019-2020, RTE (https://www.rte-france.com)
# See AUTHORS.txt
# This Source Code Form is subject to the terms of the Mozilla Public License, version 2.0.
# If a copy of the Mozilla Public License, version 2.0 was not distributed with this file,
# you can obtain one at http://mozilla.org/MPL/2.0/.
# SPDX-License-Identifier: MPL-2.0
# This file is part of Grid2Op, Grid2Op a testbed platform to model sequential decision making in power systems.

import numpy as np
from grid2op.Reward.baseReward import BaseReward
from grid2op.dtypes import dt_float


class DistanceReward(BaseReward):
    """
    This reward computes a penalty based on the distance of the current grid to the grid at time 0 where
    everything is connected to bus 1.

    Examples
    ---------
    You can use this reward in any environment with:

    .. code-block:

        import grid2op
        from grid2op.Reward import DistanceReward

        # then you create your environment with it:
        NAME_OF_THE_ENVIRONMENT = "rte_case14_realistic"
        env = grid2op.make(NAME_OF_THE_ENVIRONMENT,reward_class=DistanceReward)
        # and do a step with a "do nothing" action
        obs = env.reset()
        obs, reward, done, info = env.step(env.action_space())
        # the reward is computed with the DistanceReward class

    """

    def __init__(self, logger=None):
        BaseReward.__init__(self, logger=logger)
        self.reward_min = dt_float(0.0)
        self.reward_max = dt_float(1.0)

    def __call__(self, action, env, has_error, is_done, is_illegal, is_ambiguous):
        if has_error or is_illegal or is_ambiguous:
            return self.reward_min

        # Get topo from env
        obs = env.get_obs()
        topo = obs.topo_vect

        idx = 0
        diff = dt_float(0.0)
        for n_elems_on_sub in obs.sub_info:
            # Find this substation elements range in topology vect
            sub_start = idx
            sub_end = idx + n_elems_on_sub
            current_sub_topo = topo[sub_start:sub_end]

            # Count number of elements not on bus 1
            # Because at the initial state, all elements are on bus 1
            diff += dt_float(1.0) * np.count_nonzero(current_sub_topo != 1)

            # Set index to next sub station
            idx += n_elems_on_sub

        r = np.interp(
            diff,
            [dt_float(0.0), len(topo) * dt_float(1.0)],
            [self.reward_max, self.reward_min],
        )
        return r
