"""
NCL_proj_3.py
=============

This script illustrates the following concepts:
   - Drawing filled contours over an orthographic map
   - Changing the center latitude and longitude for an orthographic projection
   - Turning off map fill

See following URLs to see the reproduced NCL plot & script:
    - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/proj_3.ncl
    - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/proj_3_lg.png
"""
###############################################################################
# Import packages:
import numpy as np
import xarray as xr
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import geocat.datafiles as gdf
from geocat.viz import util as gvutil

###############################################################################
# Read in data:

# Open a netCDF data file using xarray default engine and load the data into xarrays
ds = xr.open_dataset(gdf.get("netcdf_files/atmos.nc"), decode_times=False)
t = ds.TS.isel(time=0)

###############################################################################
# Fix the artifact of not-shown-data around 0 and 360-degree longitudes
wrap_t = gvutil.xr_add_cyclic_longitudes(t, "lon")

###############################################################################
#Plot:

# Generate figure (set its size (width, height) in inches)
fig = plt.figure(figsize=(10, 10))

# Generate axes using Cartopy and draw coastlines with
ax = plt.axes(
    projection=ccrs.Orthographic(central_longitude=-120, central_latitude=50))

# Set extent to include latitudes between 0 and 90, and longitude between
# 0 and -180 only
ax.set_extent([0, -180, 0, 90], ccrs.PlateCarree())
ax.set_global()
ax.coastlines(linewidths=0.5)

# Plot data and add a colorbar
temp = wrap_t.plot.contourf(
    ax=ax,
    transform=ccrs.PlateCarree(),
    levels=11,
    cmap='coolwarm',
    add_colorbar=False)

cbar_ticks = np.arange(210, 311, 10)
cbar = plt.colorbar(temp, 
                    orientation='horizontal', 
                    shrink=0.75, 
                    pad=0.05, 
                    extendrect=True,
                    ticks=cbar_ticks)

cbar.ax.tick_params(labelsize=10)

# Use geocat.viz.util convenience function to add titles to left and right
# of the plot axis.
gvutil.set_titles_and_labels(ax,
                             maintitle="Example of Orthogonal Projection",
                             lefttitle="Surface Temperature",
                             righttitle="K")

# Show the plot
plt.show()