"""
    kartograph - a svg mapping library
    Copyright (C) 2011,2012  Gregor Aisch

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""

from azimuthal import Azimuthal
import math


class EquidistantAzimuthal(Azimuthal):
    """
    Equidistant Azimuthal projection

    implementation taken from
    Snyder, Map projections - A working manual
    """
    def __init__(self, lat0=0.0, lon0=0.0):
        Azimuthal.__init__(self, lat0, lon0)

    def project(self, lon, lat):
        from math import radians as rad, cos, sin

        phi = rad(lat)
        lam = rad(lon)

        cos_c = sin(self.phi0) * sin(phi) + cos(self.phi0) * cos(phi) * cos(lam - self.lam0)
        c = math.acos(cos_c)
        sin_c = sin(c)
        if sin_c == 0:
            k = 1
        else:
            k = 0.325 * c / sin(c)

        xo = self.r * k * cos(phi) * sin(lam - self.lam0)
        yo = -self.r * k * (cos(self.phi0) * sin(phi) - sin(self.phi0) * cos(phi) * cos(lam - self.lam0))

        x = self.r + xo
        y = self.r + yo

        return (x, y)

    def _visible(self, lon, lat):
        return True