"""
location.py: definition of CoreLocation class that is a member of the
Session object. Provides conversions between Cartesian and geographic coordinate
systems. Depends on utm contributed module, from
https://pypi.python.org/pypi/utm (version 0.3.0).
"""

from core import logger
from core.enumerations import RegisterTlvs
from core.misc import utm


class CoreLocation(object):
    """
    Member of session class for handling global location data. This keeps
    track of a latitude/longitude/altitude reference point and scale in
    order to convert between X,Y and geo coordinates.
    """
    name = "location"
    config_type = RegisterTlvs.UTILITY.value

    def __init__(self):
        """
        Creates a MobilityManager instance.

        :return: nothing
        """
        # ConfigurableManager.__init__(self)
        self.reset()
        self.zonemap = {}
        self.refxyz = (0.0, 0.0, 0.0)
        self.refscale = 1.0
        self.zoneshifts = {}
        self.refgeo = (0.0, 0.0, 0.0)
        for n, l in utm.ZONE_LETTERS:
            self.zonemap[l] = n

    def reset(self):
        """
        Reset to initial state.
        """
        # (x, y, z) coordinates of the point given by self.refgeo
        self.refxyz = (0.0, 0.0, 0.0)
        # decimal latitude, longitude, and altitude at the point (x, y, z)
        self.setrefgeo(0.0, 0.0, 0.0)
        # 100 pixels equals this many meters
        self.refscale = 1.0
        # cached distance to refpt in other zones
        self.zoneshifts = {}

    def px2m(self, val):
        """
        Convert the specified value in pixels to meters using the
        configured scale. The scale is given as s, where
        100 pixels = s meters.

        :param val: value to use in converting to meters
        :return: value converted to meters
        """
        return (val / 100.0) * self.refscale

    def m2px(self, val):
        """
        Convert the specified value in meters to pixels using the
        configured scale. The scale is given as s, where
        100 pixels = s meters.

        :param val: value to convert to pixels
        :return: value converted to pixels
        """
        if self.refscale == 0.0:
            return 0.0
        return 100.0 * (val / self.refscale)

    def setrefgeo(self, lat, lon, alt):
        """
        Record the geographical reference point decimal (lat, lon, alt)
        and convert and store its UTM equivalent for later use.

        :param lat: latitude
        :param lon: longitude
        :param alt: altitude
        :return: nothing
        """
        self.refgeo = (lat, lon, alt)
        # easting, northing, zone
        e, n, zonen, zonel = utm.from_latlon(lat, lon)
        self.refutm = ((zonen, zonel), e, n, alt)

    def getgeo(self, x, y, z):
        """
        Given (x, y, z) Cartesian coordinates, convert them to latitude,
        longitude, and altitude based on the configured reference point
        and scale.

        :param x: x value
        :param y: y value
        :param z: z value
        :return: lat, lon, alt values for provided coordinates
        :rtype: tuple
        """
        # shift (x,y,z) over to reference point (x,y,z)
        x -= self.refxyz[0]
        y = -(y - self.refxyz[1])
        if z is None:
            z = self.refxyz[2]
        else:
            z -= self.refxyz[2]
        # use UTM coordinates since unit is meters
        zone = self.refutm[0]
        if zone == "":
            raise ValueError("reference point not configured")
        e = self.refutm[1] + self.px2m(x)
        n = self.refutm[2] + self.px2m(y)
        alt = self.refutm[3] + self.px2m(z)
        (e, n, zone) = self.getutmzoneshift(e, n)
        try:
            lat, lon = utm.to_latlon(e, n, zone[0], zone[1])
        except utm.OutOfRangeError:
            logger.exception("UTM out of range error for n=%s zone=%s xyz=(%s,%s,%s)", n, zone, x, y, z)
            lat, lon = self.refgeo[:2]
        # self.info("getgeo(%s,%s,%s) e=%s n=%s zone=%s  lat,lon,alt=" \
        #          "%.3f,%.3f,%.3f" % (x, y, z, e, n, zone, lat, lon, alt))
        return lat, lon, alt

    def getxyz(self, lat, lon, alt):
        """
        Given latitude, longitude, and altitude location data, convert them
        to (x, y, z) Cartesian coordinates based on the configured
        reference point and scale. Lat/lon is converted to UTM meter
        coordinates, UTM zones are accounted for, and the scale turns
        meters to pixels.

        :param lat: latitude
        :param lon: longitude
        :param alt: altitude
        :return: converted x, y, z coordinates
        :rtype: tuple
        """
        # convert lat/lon to UTM coordinates in meters
        e, n, zonen, zonel = utm.from_latlon(lat, lon)
        rlat, rlon, ralt = self.refgeo
        xshift = self.geteastingshift(zonen, zonel)
        if xshift is None:
            xm = e - self.refutm[1]
        else:
            xm = e + xshift
        yshift = self.getnorthingshift(zonen, zonel)
        if yshift is None:
            ym = n - self.refutm[2]
        else:
            ym = n + yshift
        zm = alt - ralt

        # shift (x,y,z) over to reference point (x,y,z)
        x = self.m2px(xm) + self.refxyz[0]
        y = -(self.m2px(ym) + self.refxyz[1])
        z = self.m2px(zm) + self.refxyz[2]
        return x, y, z

    def geteastingshift(self, zonen, zonel):
        """
        If the lat, lon coordinates being converted are located in a
        different UTM zone than the canvas reference point, the UTM meters
        may need to be shifted.
        This picks a reference point in the same longitudinal band
        (UTM zone number) as the provided zone, to calculate the shift in
        meters for the x coordinate.

        :param zonen: zonen
        :param zonel: zone1
        :return: the x shift value
        """
        rzonen = int(self.refutm[0][0])
        # same zone number, no x shift required
        if zonen == rzonen:
            return None
        z = (zonen, zonel)
        # x shift already calculated, cached
        if z in self.zoneshifts and self.zoneshifts[z][0] is not None:
            return self.zoneshifts[z][0]

        rlat, rlon, ralt = self.refgeo
        # ea. zone is 6deg band
        lon2 = rlon + 6 * (zonen - rzonen)
        # ignore northing
        e2, n2, zonen2, zonel2 = utm.from_latlon(rlat, lon2)
        # NOTE: great circle distance used here, not reference ellipsoid!
        xshift = utm.haversine(rlon, rlat, lon2, rlat) - e2
        # cache the return value
        yshift = None
        if z in self.zoneshifts:
            yshift = self.zoneshifts[z][1]
        self.zoneshifts[z] = (xshift, yshift)
        return xshift

    def getnorthingshift(self, zonen, zonel):
        """
        If the lat, lon coordinates being converted are located in a
        different UTM zone than the canvas reference point, the UTM meters
        may need to be shifted.
        This picks a reference point in the same latitude band (UTM zone letter)
        as the provided zone, to calculate the shift in meters for the
        y coordinate.

        :param zonen: zonen
        :param zonel:  zone1
        :return: calculated y shift
        """
        rzonel = self.refutm[0][1]
        # same zone letter, no y shift required
        if zonel == rzonel:
            return None
        z = (zonen, zonel)
        # y shift already calculated, cached
        if z in self.zoneshifts and self.zoneshifts[z][1] is not None:
            return self.zoneshifts[z][1]

        rlat, rlon, ralt = self.refgeo
        # zonemap is used to calculate degrees difference between zone letters
        latshift = self.zonemap[zonel] - self.zonemap[rzonel]
        # ea. latitude band is 8deg high
        lat2 = rlat + latshift
        e2, n2, zonen2, zonel2 = utm.from_latlon(lat2, rlon)
        # NOTE: great circle distance used here, not reference ellipsoid
        yshift = -(utm.haversine(rlon, rlat, rlon, lat2) + n2)
        # cache the return value
        xshift = None
        if z in self.zoneshifts:
            xshift = self.zoneshifts[z][0]
        self.zoneshifts[z] = (xshift, yshift)
        return yshift

    def getutmzoneshift(self, e, n):
        """
        Given UTM easting and northing values, check if they fall outside
        the reference point's zone boundary. Return the UTM coordinates in a
        different zone and the new zone if they do. Zone lettering is only
        changed when the reference point is in the opposite hemisphere.

        :param e: easting value
        :param n: northing value
        :return: modified easting, northing, and zone values
        :rtype: tuple
        """
        zone = self.refutm[0]
        rlat, rlon, ralt = self.refgeo
        if e > 834000 or e < 166000:
            num_zones = (int(e) - 166000) / (utm.R / 10)
            # estimate number of zones to shift, E (positive) or W (negative)
            rlon2 = self.refgeo[1] + (num_zones * 6)
            e2, n2, zonen2, zonel2 = utm.from_latlon(rlat, rlon2)
            xshift = utm.haversine(rlon, rlat, rlon2, rlat)
            # after >3 zones away from refpt, the above estimate won't work
            # (the above estimate could be improved)
            if not 100000 <= (e - xshift) < 1000000:
                # move one more zone away
                num_zones = (abs(num_zones) + 1) * (abs(num_zones) / num_zones)
                rlon2 = self.refgeo[1] + (num_zones * 6)
                e2, n2, zonen2, zonel2 = utm.from_latlon(rlat, rlon2)
                xshift = utm.haversine(rlon, rlat, rlon2, rlat)
            e = e - xshift
            zone = (zonen2, zonel2)
        if n < 0:
            # refpt in northern hemisphere and we crossed south of equator
            n += 10000000
            zone = (zone[0], 'M')
        elif n > 10000000:
            # refpt in southern hemisphere and we crossed north of equator
            n -= 10000000
            zone = (zone[0], 'N')
        return e, n, zone
