#!/usr/bin/env python
# -*- coding: utf-8 -*-

from flatland.core.env import RailEnv
from flatland.core.transitions import Grid4Transitions
from flatland.core.transitionmap import GridTransitionMap
import numpy as np

"""Tests for `flatland` package."""


def test_rail_environment_single_agent():

    cells = [int('0000000000000000', 2),  # empty cell - Case 0
             int('1000000000100000', 2),  # Case 1 - straight
             int('1001001000100000', 2),  # Case 2 - simple switch
             int('1000010000100001', 2),  # Case 3 - diamond drossing
             int('1001011000100001', 2),  # Case 4 - single slip switch
             int('1100110000110011', 2),  # Case 5 - double slip switch
             int('0101001000000010', 2),  # Case 6 - symmetrical switch
             int('0010000000000000', 2)]  # Case 7 - dead end

    # We instantiate the following map on a 3x3 grid
    #  _  _
    # / \/ \
    # | |  |
    # \_/\_/

    transitions = Grid4Transitions([])
    vertical_line = cells[1]
    south_symmetrical_switch = cells[6]
    north_symmetrical_switch = transitions.rotate_transition(
                                south_symmetrical_switch, 180)
    # Simple turn not in the base transitions ?
    south_east_turn = int('0100000000000010', 2)
    south_west_turn = transitions.rotate_transition(south_east_turn, 90)
    # print(bytes(south_west_turn))
    north_east_turn = transitions.rotate_transition(south_east_turn, 270)
    north_west_turn = transitions.rotate_transition(south_east_turn, 180)

    rail_map = np.array([[south_east_turn, south_symmetrical_switch,
                          south_west_turn],
                         [vertical_line, vertical_line, vertical_line],
                         [north_east_turn, north_symmetrical_switch,
                          north_west_turn]],
                        dtype=np.uint16)

    rail = GridTransitionMap(width=3, height=3, transitions=transitions)
    rail.grid = rail_map
    rail_env = RailEnv(rail, number_of_agents=1)
    for _ in range(200):
        _ = rail_env.reset()

        # We do not care about target for the moment
        rail_env.agents_target[0] = [-1, -1]

        # Check that trains are always initialized at a consistent position
        # or direction.
        # They should always be able to go somewhere.
        assert(transitions.get_transitions(
            rail_map[rail_env.agents_position[0]],
            rail_env.agents_direction[0]) != (0, 0, 0, 0))

        initial_pos = rail_env.agents_position[0]

        valid_active_actions_done = 0
        pos = initial_pos
        while valid_active_actions_done < 6:
            # We randomly select an action
            action = np.random.randint(4)

            _, _, _, _ = rail_env.step({0: action})

            prev_pos = pos
            pos = rail_env.agents_position[0]
            if prev_pos != pos:
                valid_active_actions_done += 1

        # After 6 movements on this railway network, the train should be back
        # to its original position.
        assert(initial_pos[0] == rail_env.agents_position[0][0])

        # We check that the train always attains its target after some time
        for _ in range(10):
            _ = rail_env.reset()

            done = False
            while not done:
                # We randomly select an action
                action = np.random.randint(4)

                _, _, dones, _ = rail_env.step({0: action})

                done = dones['__all__']