import zmq
from breezyslam.algorithms import RMHC_SLAM
from breezyslam.sensors import RPLidarA1 as LaserModel
from rplidar import RPLidar as Lidar
from .SlamController_pb2 import SlamScan, SlamLocation


# Left here as was used in the example, configure as necessary.
# MAP_SIZE_PIXELS         = 500
# MAP_SIZE_METERS         = 10
# LIDAR_DEVICE            = '/dev/ttyUSB0'
    
class SlamStreamer:
    can_scan = False

    def __init__(self, map_pixels = None, map_meters = None, lidar_connection = None, port = None):
        self._map_pixels = map_pixels
        self._map_meters = map_meters
        self._lidar_connection = lidar_connection
        self._port = port
        self._socket = self._start_socket(self._create_tcp_pub_socket(), port)

    def start(self):
        '''
        Does scanning and constructs the slam map,
        and pushes to subscribers through a zmq pub socket.
        This is done on the main thread, so you'll need
        to run this method on a separate thread yourself.

        All constructor parameters must be set prior
        to calling this method, and changing those values after
        calling this method will have no effect.
        '''
        
        # Block until user opens zmq.
        self._socket.recv()

        # Adapted from BreezySLAM rpslam example.
        # Connect to Lidar unit
        lidar = Lidar(self._lidar_connection)

        # Create an RMHC SLAM object with a laser model and optional robot model
        slam = RMHC_SLAM(LaserModel(), self._map_pixels, self._map_meters)

        # Initialize empty map
        mapbytes = bytearray(self.map_pixels * self.map_pixels)

        # Create an iterator to collect scan data from the RPLidar
        iterator = lidar.iter_scans()

        # First scan is crap, so ignore it
        next(iterator)

        while self.can_scan:
            # Extract (quality, angle, distance) triples from current scan
            items = [item for item in next(iterator)]

            # Extract distances and angles from triples
            distances = [item[2] for item in items]
            angles    = [item[1] for item in items]

            # Update SLAM with current Lidar scan and scan angles
            slam.update(distances, scan_angles_degrees=angles)

            self._push_map(slam.getmap(mapbytes), slam.getpos())

    def _push_map(self, mapbytes, location):
        '''
        Pushes a scan over zmq using protocol buffers.
        map should be the result of slam.getmap.
        location should be a tuple, the result of slam.getpos()
        ''' 
        protoScan = SlamScan(map = bytes(mapbytes), \
            location = SlamLocation(x = location[0], y = location[1], theta = location[3]))
        self._socket.send(protoScan.SerializeToString())

    def stop_scanning(self):
        self.can_scan = False

    def _create_context(self):
        return zmq.Context.instance()

    def _create_tcp_pub_socket(self):
        return self._create_context().socket(zmq.PAIR)

    def _start_socket(self, socket, port):
        socket.bind('tcp://*:' + str(self._port))
        return socket

    # Properties
    @property
    def map_pixels(self):
        return self._map_pixels

    @map_pixels.setter
    def map_pixels(self, value):
        self._map_pixels = value

    @property
    def map_meters(self):
        return self._map_meters

    @map_meters.setter
    def map_meters(self, value):
        self._map_meters = value

    @property
    def lidar_connection(self):
        return self._lidar_connection

    @lidar_connection.setter
    def lidar_connection(self, value):
        self._lidar_connection = value

    @property
    def port(self):
        return self._port

    @port.setter
    def port(self, value):
        self._port = value