#! /usr/bin/env python
# ==========================================================================
# Show a spectrum in PHA format.
#
# Copyright (C) 2013-2016 Juergen Knoedlseder
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# ==========================================================================
import sys
import math
import gammalib
try:
    import matplotlib.pyplot as plt
    plt.figure()
    plt.close()
except:
    print('This script needs the "matplotlib" module')
    sys.exit()


# ================= #
# Show PHA spectrum #
# ================= #
def show_pha(pha, plotfile=''):
    """
    Show PHA spectrum

    Parameters
    ----------
    spectrum : `~gammalib.GPha`
        PHA file
    plotfile : str, optional
        Plot file name
    """
    # Create figure
    plt.figure(1)
    plt.title('PHA spectrum (' + pha.filename() + ')')

    # Generate energy vector
    energy   = []
    channels = False
    if pha.ebounds().size() > 0:
        for i in range(pha.ebounds().size()):
            energy.append(pha.ebounds().elogmean(i).TeV())
    else:
        for i in range(pha.size()):
            energy.append(float(i+1))
            channels = True

    # Generate data and error vector
    counts = [0.0 for i in range(pha.size())]
    for i in range(pha.size()):
        counts[i] = pha[i]
    error = [math.sqrt(c) for c in counts]

    # Plot data
    if channels:
        plt.semilogy(energy, counts, 'ro')
    else:
        plt.loglog(energy, counts, 'ro')
    plt.errorbar(energy, counts, error, fmt='ro', ecolor='r')

    # Set axes
    if channels:
        plt.xlabel('Channels')
    else:
        plt.xlabel('Energy (TeV)')
    plt.ylabel('Counts')

    # Show spectrum or save it into file
    if len(plotfile) > 0:
        plt.savefig(plotfile)
    else:
        plt.show()

    # Return
    return


# ======================== #
# Main routine entry point #
# ======================== #
if __name__ == '__main__':

    # Print usage information
    usage = 'Usage: show_pha.py filename [file]'
    if len(sys.argv) < 2:
        print(usage)
        sys.exit()

    # Check if plotting in file is requested
    plotfile = ''
    if len(sys.argv) == 3:
        plotfile = sys.argv[2]

    # Extract parameters
    filename = sys.argv[1]

    # Load PHA spectrum
    pha = gammalib.GPha(filename)

    # Show PHA spectrum
    show_pha(pha, plotfile=plotfile)