"""
Copyright (C) 2014 John Evans

This example code illustrates how to access and visualize an NSIDC/ICESat/GLAS
L2 HDF5 file in Python.

If you have any questions, suggestions, or comments on this example, please use
the HDF-EOS Forum (http://hdfeos.org/forums).  If you would like to see an
example of any other NASA HDF/HDF-EOS data product that is not listed in the
HDF-EOS Comprehensive Examples page (http://hdfeos.org/zoo), feel free to
contact us at eoshelp@hdfgroup.org or post it at the HDF-EOS Forum
(http://hdfeos.org/forums).

Usage:  save this script and run

    python GLAH13_633_2103_001_1317_0_01_0001_a.py

The HDF file must either be in your current working directory or in a directory
specified by the environment variable HDFEOS_ZOO_DIR.
"""

import os

import matplotlib as mpl
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap
import numpy as np

# Can do this using either netCDF4 or h5py.
USE_NETCDF4 = False

def run(FILE_NAME):
    if USE_NETCDF4:
    
        from netCDF4 import Dataset
    
        nc = Dataset(FILE_NAME)

        latvar = nc.groups['Data_1HZ'].groups['Geolocation'].variables['d_lat']
        latitude = latvar[:]
        lat_vr = [latvar.valid_min, latvar.valid_max]

        lonvar = nc.groups['Data_1HZ'].groups['Geolocation'].variables['d_lon']
        longitude = lonvar[:]
        lon_vr = [lonvar.valid_min, lonvar.valid_max]

        tempvar = nc.groups['Data_1HZ'].groups['Atmosphere'].variables['d_Surface_temp']
        temp = tempvar[:]
        temp_vr = [tempvar.valid_min, tempvar.valid_max]
        units = tempvar.units
        longname = tempvar.long_name

        timevar = nc.groups['Data_1HZ'].groups['Time'].variables['d_UTCTime_1']
        time = timevar[:]

    else:
    
        import h5py
    
        with h5py.File(FILE_NAME, mode='r') as f:
    
            latvar = f['/Data_1HZ/Geolocation/d_lat']
            latitude = latvar[:]
            lat_vr = [latvar.attrs['valid_min'], latvar.attrs['valid_max']]
    
            lonvar = f['/Data_1HZ/Geolocation/d_lon']
            longitude = lonvar[:]
            lon_vr = [lonvar.attrs['valid_min'], lonvar.attrs['valid_max']]
    
            tempvar = f['/Data_1HZ/Atmosphere/d_Surface_temp']
            temp = tempvar[:]
            temp_vr = [tempvar.attrs['valid_min'], tempvar.attrs['valid_max']]
            units = tempvar.attrs['units']
            longname = tempvar.attrs['long_name']
    
            time = f['/Data_1HZ/Time/d_UTCTime_1'][:]
    
    # Apply attribute restrictions.
    latitude[latitude < lat_vr[0]] = np.nan
    latitude[latitude > lat_vr[1]] = np.nan
    longitude[longitude < lon_vr[0]] = np.nan
    longitude[longitude > lon_vr[1]] = np.nan
    temp[temp < temp_vr[0]] = np.nan
    temp[temp > temp_vr[1]] = np.nan

    # Just use a small subset.
    idx = slice(0, 600)

    # Make a split window plot.  First plot is time vs. temperature.
    fig = plt.figure(figsize = (15, 6))
    ax1 = plt.subplot(1, 2, 1)
    elapsed_time = (time - time[0])/60
    ax1.plot(elapsed_time[idx], temp[idx], 'b-')
    ax1.set_xlabel('Elapsed Time (minutes)')
    ax1.set_ylabel(units)

    basename = os.path.basename(FILE_NAME)
    ax1.set_title('{0}\n{1}'.format(basename, longname))

    # The 2nd plot is the trajectory.
    # Use a north polar azimuthal equal area projection.
    ax2 = plt.subplot(1, 2, 2)
    m = Basemap(projection='nplaea', resolution='l',
                boundinglat=52, lon_0=0)
    m.drawcoastlines(linewidth=0.5)
    m.drawparallels(np.arange(0., 91., 10.), labels=[0, 0, 0, 1])
    m.drawmeridians(np.arange(-180, 180., 30.), labels=[0, 1, 0, 0])
    m.plot(longitude[idx], latitude[idx], linestyle='None', marker='.',
           color='blue', latlon=True)
    plt.title('Trajectory of Flight Path')

    fig = plt.gcf()
    # plt.show()
    pngfile = "{0}.a.py.png".format(basename)
    fig.savefig(pngfile)

if __name__ == "__main__":

    # If a certain environment variable is set, look there for the input
    # file, otherwise look in the current directory.
    hdffile = 'GLAH13_633_2103_001_1317_0_01_0001.h5'

    try:
        hdffile = os.path.join(os.environ['HDFEOS_ZOO_DIR'], hdffile)
    except KeyError:
        pass

    run(hdffile)