import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap # Import the Basemap toolkit
import xarray as xr
import sys
import matplotlib.colors as colors

file = sys.argv[1:]
dset = xr.open_dataset(str(file[0]))
lon_min = np.asscalar(np.min(dset['lon']))
lon_max = np.asscalar(np.max(dset['lon']))
lat_min = np.asscalar(np.min(dset['lat']))
lat_max = np.asscalar(np.max(dset['lat']))
print('Longitude min. %7.4f, max. %7.4f' % (lon_min, lon_max) )
print('Latitude min. %7.4f, max. %7.4f' % (lat_min,lat_max) )

def get_projection(dset):
    x, y = dset['lon'].values, dset['lat'].values
    m = Basemap(projection='mill', llcrnrlon=dset['lon'].min()-1., llcrnrlat=dset['lat'].min()-1.,
                 urcrnrlon=dset['lon'].max()+1., urcrnrlat=dset['lat'].max()+1., resolution='i')
    m.drawcountries(linewidth=0.5, color='black')
    m.shadedrelief()
    m.drawcoastlines()
    m.drawparallels(np.arange(-90.0, 90.0, 5.), linewidth=0.5, color='white',
        labels=[True, False, False, True], fontsize=7)
    m.drawmeridians(np.arange(0.0, 360.0, 5.), linewidth=0.5, color='white',
        labels=[True, False, False, True], fontsize=7)
    x, y = m(x, y)
    return(m, x, y)

def truncate_colormap(cmap, minval=0.0, maxval=1.0, n=256):
    """Truncate a colormap by specifying the start and endpoint."""
    new_cmap = colors.LinearSegmentedColormap.from_list(
        'trunc({n},{a:.2f},{b:.2f})'.format(n=cmap.name, a=minval, b=maxval),
        cmap(np.linspace(minval, maxval, n)))
    return(new_cmap)

fig = plt.figure(figsize=(10,10))
m, x, y = get_projection(dset)

cmap = truncate_colormap(plt.get_cmap('terrain'), 0.2, 1.)

m.contourf(x, y, dset['topography_c'], tri=True, cmap=cmap, levels=np.arange(-100., 3000., 10.))

plt.show(block=True)