from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import six

import math

import numpy as np
import numpy.ma as ma

import matplotlib
rcParams = matplotlib.rcParams
from matplotlib.axes import Axes
from matplotlib import cbook
from matplotlib.patches import Circle
from matplotlib.path import Path
import matplotlib.spines as mspines
import matplotlib.axis as maxis
from matplotlib.ticker import Formatter, Locator, NullLocator, FixedLocator, NullFormatter
from matplotlib.transforms import Affine2D, Affine2DBase, Bbox, \
    BboxTransformTo, IdentityTransform, Transform, TransformWrapper

class GeoAxes(Axes):
    """
    An abstract base class for geographic projections
    """
    class ThetaFormatter(Formatter):
        """
        Used to format the theta tick labels.  Converts the native
        unit of radians into degrees and adds a degree symbol.
        """
        def __init__(self, round_to=1.0):
            self._round_to = round_to

        def __call__(self, x, pos=None):
            degrees = (x / np.pi) * 180.0
            degrees = round(degrees / self._round_to) * self._round_to
            if rcParams['text.usetex'] and not rcParams['text.latex.unicode']:
                return r"$%0.0f^\circ$" % degrees
            else:
                return "%0.0f\u00b0" % degrees

    RESOLUTION = 75

    def _init_axis(self):
        self.xaxis = maxis.XAxis(self)
        self.yaxis = maxis.YAxis(self)
        # Do not register xaxis or yaxis with spines -- as done in
        # Axes._init_axis() -- until GeoAxes.xaxis.cla() works.
        # self.spines['geo'].register_axis(self.yaxis)
        self._update_transScale()

    def cla(self):
        Axes.cla(self)

        self.set_longitude_grid(30)
        self.set_latitude_grid(15)
        self.set_longitude_grid_ends(75)
        self.xaxis.set_minor_locator(NullLocator())
        self.yaxis.set_minor_locator(NullLocator())
        self.xaxis.set_ticks_position('none')
        self.yaxis.set_ticks_position('none')
        self.yaxis.set_tick_params(label1On=True)
        # Why do we need to turn on yaxis tick labels, but
        # xaxis tick labels are already on?

        self.grid(rcParams['axes.grid'])

        Axes.set_xlim(self, -np.pi, np.pi)
        Axes.set_ylim(self, -np.pi / 2.0, np.pi / 2.0)

    def _set_lim_and_transforms(self):
        # A (possibly non-linear) projection on the (already scaled) data
        self.transProjection = self._get_core_transform(self.RESOLUTION)

        self.transAffine = self._get_affine_transform()

        self.transAxes = BboxTransformTo(self.bbox)

        # The complete data transformation stack -- from data all the
        # way to display coordinates
        self.transData = \
            self.transProjection + \
            self.transAffine + \
            self.transAxes

        # This is the transform for longitude ticks.
        self._xaxis_pretransform = \
            Affine2D() \
            .scale(1.0, self._longitude_cap * 2.0) \
            .translate(0.0, -self._longitude_cap)
        self._xaxis_transform = \
            self._xaxis_pretransform + \
            self.transData
        self._xaxis_text1_transform = \
            Affine2D().scale(1.0, 0.0) + \
            self.transData + \
            Affine2D().translate(0.0, 4.0)
        self._xaxis_text2_transform = \
            Affine2D().scale(1.0, 0.0) + \
            self.transData + \
            Affine2D().translate(0.0, -4.0)

        # This is the transform for latitude ticks.
        yaxis_stretch = Affine2D().scale(np.pi * 2.0, 1.0).translate(-np.pi, 0.0)
        yaxis_space = Affine2D().scale(1.0, 1.1)
        self._yaxis_transform = \
            yaxis_stretch + \
            self.transData
        yaxis_text_base = \
            yaxis_stretch + \
            self.transProjection + \
            (yaxis_space + \
             self.transAffine + \
             self.transAxes)
        self._yaxis_text1_transform = \
            yaxis_text_base + \
            Affine2D().translate(-8.0, 0.0)
        self._yaxis_text2_transform = \
            yaxis_text_base + \
            Affine2D().translate(8.0, 0.0)

    def _get_affine_transform(self):
        transform = self._get_core_transform(1)
        xscale, _ = transform.transform_point((np.pi, 0))
        _, yscale = transform.transform_point((0, np.pi / 2.0))
        return Affine2D() \
            .scale(0.5 / xscale, 0.5 / yscale) \
            .translate(0.5, 0.5)

    def get_xaxis_transform(self,which='grid'):
        assert which in ['tick1','tick2','grid']
        return self._xaxis_transform

    def get_xaxis_text1_transform(self, pad):
        return self._xaxis_text1_transform, 'bottom', 'center'

    def get_xaxis_text2_transform(self, pad):
        return self._xaxis_text2_transform, 'top', 'center'

    def get_yaxis_transform(self,which='grid'):
        assert which in ['tick1','tick2','grid']
        return self._yaxis_transform

    def get_yaxis_text1_transform(self, pad):
        return self._yaxis_text1_transform, 'center', 'right'

    def get_yaxis_text2_transform(self, pad):
        return self._yaxis_text2_transform, 'center', 'left'

    def _gen_axes_patch(self):
        return Circle((0.5, 0.5), 0.5)

    def _gen_axes_spines(self):
        return {'geo':mspines.Spine.circular_spine(self,
                                                   (0.5, 0.5), 0.5)}

    def set_yscale(self, *args, **kwargs):
        if args[0] != 'linear':
            raise NotImplementedError

    set_xscale = set_yscale

    def set_xlim(self, *args, **kwargs):
        raise TypeError("It is not possible to change axes limits "
                        "for geographic projections. Please consider "
                        "using Basemap or Cartopy.")

    set_ylim = set_xlim

    def format_coord(self, lon, lat):
        'return a format string formatting the coordinate'
        lon = lon * (180.0 / np.pi)
        lat = lat * (180.0 / np.pi)
        if lat >= 0.0:
            ns = 'N'
        else:
            ns = 'S'
        if lon >= 0.0:
            ew = 'E'
        else:
            ew = 'W'
        return '%f\u00b0%s, %f\u00b0%s' % (abs(lat), ns, abs(lon), ew)

    def set_longitude_grid(self, degrees):
        """
        Set the number of degrees between each longitude grid.
        """
        number = (360.0 / degrees) + 1
        self.xaxis.set_major_locator(
            FixedLocator(
                np.linspace(-np.pi, np.pi, number, True)[1:-1]))
        self._logitude_degrees = degrees
        self.xaxis.set_major_formatter(self.ThetaFormatter(degrees))

    def set_latitude_grid(self, degrees):
        """
        Set the number of degrees between each longitude grid.
        """
        number = (180.0 / degrees) + 1
        self.yaxis.set_major_locator(
            FixedLocator(
                np.linspace(-np.pi / 2.0, np.pi / 2.0, number, True)[1:-1]))
        self._latitude_degrees = degrees
        self.yaxis.set_major_formatter(self.ThetaFormatter(degrees))

    def set_longitude_grid_ends(self, degrees):
        """
        Set the latitude(s) at which to stop drawing the longitude grids.
        """
        self._longitude_cap = degrees * (np.pi / 180.0)
        self._xaxis_pretransform \
            .clear() \
            .scale(1.0, self._longitude_cap * 2.0) \
            .translate(0.0, -self._longitude_cap)

    def get_data_ratio(self):
        '''
        Return the aspect ratio of the data itself.
        '''
        return 1.0

    ### Interactive panning

    def can_zoom(self):
        """
        Return *True* if this axes supports the zoom box button functionality.

        This axes object does not support interactive zoom box.
        """
        return False

    def can_pan(self) :
        """
        Return *True* if this axes supports the pan/zoom button functionality.

        This axes object does not support interactive pan/zoom.
        """
        return False

    def start_pan(self, x, y, button):
        pass

    def end_pan(self):
        pass

    def drag_pan(self, button, key, x, y):
        pass


class AitoffAxes(GeoAxes):
    name = 'aitoff'

    class AitoffTransform(Transform):
        """
        The base Aitoff transform.
        """
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            """
            Create a new Aitoff transform.  Resolution is the number of steps
            to interpolate between each input line segment to approximate its
            path in curved Aitoff space.
            """
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, ll):
            longitude = ll[:, 0:1]
            latitude  = ll[:, 1:2]

            # Pre-compute some values
            half_long = longitude / 2.0
            cos_latitude = np.cos(latitude)

            alpha = np.arccos(cos_latitude * np.cos(half_long))
            # Mask this array or we'll get divide-by-zero errors
            alpha = ma.masked_where(alpha == 0.0, alpha)
            # The numerators also need to be masked so that masked
            # division will be invoked.
            # We want unnormalized sinc.  numpy.sinc gives us normalized
            sinc_alpha = ma.sin(alpha) / alpha

            x = (cos_latitude * ma.sin(half_long)) / sinc_alpha
            y = (ma.sin(latitude) / sinc_alpha)
            return np.concatenate((x.filled(0), y.filled(0)), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def transform_path_non_affine(self, path):
            vertices = path.vertices
            ipath = path.interpolated(self._resolution)
            return Path(self.transform(ipath.vertices), ipath.codes)
        transform_path_non_affine.__doc__ = Transform.transform_path_non_affine.__doc__

        def inverted(self):
            return AitoffAxes.InvertedAitoffTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    class InvertedAitoffTransform(Transform):
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, xy):
            # MGDTODO: Math is hard ;(
            return xy
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def inverted(self):
            return AitoffAxes.AitoffTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    def __init__(self, *args, **kwargs):
        self._longitude_cap = np.pi / 2.0
        GeoAxes.__init__(self, *args, **kwargs)
        self.set_aspect(0.5, adjustable='box', anchor='C')
        self.cla()

    def _get_core_transform(self, resolution):
        return self.AitoffTransform(resolution)


class HammerAxes(GeoAxes):
    name = 'hammer'

    class HammerTransform(Transform):
        """
        The base Hammer transform.
        """
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            """
            Create a new Hammer transform.  Resolution is the number of steps
            to interpolate between each input line segment to approximate its
            path in curved Hammer space.
            """
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, ll):
            longitude = ll[:, 0:1]
            latitude  = ll[:, 1:2]

            # Pre-compute some values
            half_long = longitude / 2.0
            cos_latitude = np.cos(latitude)
            sqrt2 = np.sqrt(2.0)

            alpha = np.sqrt(1.0 + cos_latitude * np.cos(half_long))
            x = (2.0 * sqrt2) * (cos_latitude * np.sin(half_long)) / alpha
            y = (sqrt2 * np.sin(latitude)) / alpha
            return np.concatenate((x, y), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def transform_path_non_affine(self, path):
            vertices = path.vertices
            ipath = path.interpolated(self._resolution)
            return Path(self.transform(ipath.vertices), ipath.codes)
        transform_path_non_affine.__doc__ = Transform.transform_path_non_affine.__doc__

        def inverted(self):
            return HammerAxes.InvertedHammerTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    class InvertedHammerTransform(Transform):
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, xy):
            x = xy[:, 0:1]
            y = xy[:, 1:2]

            quarter_x = 0.25 * x
            half_y = 0.5 * y
            z = np.sqrt(1.0 - quarter_x*quarter_x - half_y*half_y)
            longitude = 2 * np.arctan((z*x) / (2.0 * (2.0*z*z - 1.0)))
            latitude = np.arcsin(y*z)
            return np.concatenate((longitude, latitude), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def inverted(self):
            return HammerAxes.HammerTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    def __init__(self, *args, **kwargs):
        self._longitude_cap = np.pi / 2.0
        GeoAxes.__init__(self, *args, **kwargs)
        self.set_aspect(0.5, adjustable='box', anchor='C')
        self.cla()

    def _get_core_transform(self, resolution):
        return self.HammerTransform(resolution)


class MollweideAxes(GeoAxes):
    name = 'mollweide'

    class MollweideTransform(Transform):
        """
        The base Mollweide transform.
        """
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            """
            Create a new Mollweide transform.  Resolution is the number of steps
            to interpolate between each input line segment to approximate its
            path in curved Mollweide space.
            """
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, ll):
            def d(theta):
                delta = -(theta + np.sin(theta) - pi_sin_l) / (1 + np.cos(theta))
                return delta, np.abs(delta) > 0.001

            longitude = ll[:, 0]
            latitude  = ll[:, 1]

            clat = np.pi/2 - np.abs(latitude)
            ihigh = clat < 0.087 # within 5 degrees of the poles
            ilow = ~ihigh
            aux = np.empty(latitude.shape, dtype=np.float)

            if ilow.any():  # Newton-Raphson iteration
                pi_sin_l = np.pi * np.sin(latitude[ilow])
                theta = 2.0 * latitude[ilow]
                delta, large_delta = d(theta)
                while np.any(large_delta):
                    theta[large_delta] += delta[large_delta]
                    delta, large_delta = d(theta)
                aux[ilow] = theta / 2

            if ihigh.any(): # Taylor series-based approx. solution
                e = clat[ihigh]
                d = 0.5 * (3 * np.pi * e**2) ** (1.0/3)
                aux[ihigh] = (np.pi/2 - d) * np.sign(latitude[ihigh])

            xy = np.empty(ll.shape, dtype=np.float)
            xy[:,0] = (2.0 * np.sqrt(2.0) / np.pi) * longitude * np.cos(aux)
            xy[:,1] = np.sqrt(2.0) * np.sin(aux)

            return xy
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def transform_path_non_affine(self, path):
            vertices = path.vertices
            ipath = path.interpolated(self._resolution)
            return Path(self.transform(ipath.vertices), ipath.codes)
        transform_path_non_affine.__doc__ = Transform.transform_path_non_affine.__doc__

        def inverted(self):
            return MollweideAxes.InvertedMollweideTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    class InvertedMollweideTransform(Transform):
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, resolution):
            Transform.__init__(self)
            self._resolution = resolution

        def transform_non_affine(self, xy):
            x = xy[:, 0:1]
            y = xy[:, 1:2]

            # from Equations (7, 8) of
            # http://mathworld.wolfram.com/MollweideProjection.html
            theta = np.arcsin(y / np.sqrt(2))
            lon = (np.pi / (2 * np.sqrt(2))) * x / np.cos(theta)
            lat = np.arcsin((2 * theta + np.sin(2 * theta)) / np.pi)

            return np.concatenate((lon, lat), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def inverted(self):
            return MollweideAxes.MollweideTransform(self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    def __init__(self, *args, **kwargs):
        self._longitude_cap = np.pi / 2.0
        GeoAxes.__init__(self, *args, **kwargs)
        self.set_aspect(0.5, adjustable='box', anchor='C')
        self.cla()

    def _get_core_transform(self, resolution):
        return self.MollweideTransform(resolution)


class LambertAxes(GeoAxes):
    name = 'lambert'

    class LambertTransform(Transform):
        """
        The base Lambert transform.
        """
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, center_longitude, center_latitude, resolution):
            """
            Create a new Lambert transform.  Resolution is the number of steps
            to interpolate between each input line segment to approximate its
            path in curved Lambert space.
            """
            Transform.__init__(self)
            self._resolution = resolution
            self._center_longitude = center_longitude
            self._center_latitude = center_latitude

        def transform_non_affine(self, ll):
            longitude = ll[:, 0:1]
            latitude  = ll[:, 1:2]
            clong = self._center_longitude
            clat = self._center_latitude
            cos_lat = np.cos(latitude)
            sin_lat = np.sin(latitude)
            diff_long = longitude - clong
            cos_diff_long = np.cos(diff_long)

            inner_k = (1.0 +
                       np.sin(clat)*sin_lat +
                       np.cos(clat)*cos_lat*cos_diff_long)
            # Prevent divide-by-zero problems
            inner_k = np.where(inner_k == 0.0, 1e-15, inner_k)
            k = np.sqrt(2.0 / inner_k)
            x = k*cos_lat*np.sin(diff_long)
            y = k*(np.cos(clat)*sin_lat -
                   np.sin(clat)*cos_lat*cos_diff_long)

            return np.concatenate((x, y), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def transform_path_non_affine(self, path):
            vertices = path.vertices
            ipath = path.interpolated(self._resolution)
            return Path(self.transform(ipath.vertices), ipath.codes)
        transform_path_non_affine.__doc__ = Transform.transform_path_non_affine.__doc__

        def inverted(self):
            return LambertAxes.InvertedLambertTransform(
                self._center_longitude,
                self._center_latitude,
                self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    class InvertedLambertTransform(Transform):
        input_dims = 2
        output_dims = 2
        is_separable = False

        def __init__(self, center_longitude, center_latitude, resolution):
            Transform.__init__(self)
            self._resolution = resolution
            self._center_longitude = center_longitude
            self._center_latitude = center_latitude

        def transform_non_affine(self, xy):
            x = xy[:, 0:1]
            y = xy[:, 1:2]
            clong = self._center_longitude
            clat = self._center_latitude
            p = np.sqrt(x*x + y*y)
            p = np.where(p == 0.0, 1e-9, p)
            c = 2.0 * np.arcsin(0.5 * p)
            sin_c = np.sin(c)
            cos_c = np.cos(c)

            lat = np.arcsin(cos_c*np.sin(clat) +
                             ((y*sin_c*np.cos(clat)) / p))
            lon = clong + np.arctan(
                (x*sin_c) / (p*np.cos(clat)*cos_c - y*np.sin(clat)*sin_c))

            return np.concatenate((lon, lat), 1)
        transform_non_affine.__doc__ = Transform.transform_non_affine.__doc__

        def inverted(self):
            return LambertAxes.LambertTransform(
                self._center_longitude,
                self._center_latitude,
                self._resolution)
        inverted.__doc__ = Transform.inverted.__doc__

    def __init__(self, *args, **kwargs):
        self._longitude_cap = np.pi / 2.0
        self._center_longitude = kwargs.pop("center_longitude", 0.0)
        self._center_latitude = kwargs.pop("center_latitude", 0.0)
        GeoAxes.__init__(self, *args, **kwargs)
        self.set_aspect('equal', adjustable='box', anchor='C')
        self.cla()

    def cla(self):
        GeoAxes.cla(self)
        self.yaxis.set_major_formatter(NullFormatter())

    def _get_core_transform(self, resolution):
        return self.LambertTransform(
            self._center_longitude,
            self._center_latitude,
            resolution)

    def _get_affine_transform(self):
        return Affine2D() \
            .scale(0.25) \
            .translate(0.5, 0.5)
