# This Python module lists the scan numbers and observed object names from
# all of the files under /home/gbtdata for the specified project ID and
# device.  The default device is the spectral processor.  The default
# output is stdout, but the output may be directed to a file named in the
# third argument.

# To run from the Python prompt:
# >>> import list_scans
# >>> list_scans.list_scans('AGBT02A_069_01')
# or
# >>> from list_scans import *
# >>> list_scans('AGBT02A_069_01')

import os, string
from fitsio import cfitsio

def list_scans ( project, device='SpectralProcessor', out_file='' ) :
    # assemble the directory path name and get a list of file names
    path = '/home/gbtdata/' + project + '/' + device
    ls = os.listdir(path)
    if len(ls) < 1 :
        return
    file_num = 0
    # if file output has been requested, open the file
    if out_file != '' :
        fd = open(out_file, 'w')
    # step through every file in the list
    for fn in ls :
        sfn = string.split(fn, '.')
        # if it's not a FITS file, skip it
        if sfn[-1] == 'fits' :
            file_num += 1
            fpn = path + '/' + fn
            # open the file to the cfitsio access module for reading
            status, fits = cfitsio.fits_open_file(fpn, cfitsio.READONLY)
            # retrieve the SCAN and OBJECT keyword values in the main header
            status, scan, comment = cfitsio.fits_read_key_lng(fits, 'SCAN')
            status, object, comment = cfitsio.fits_read_key_str(fits, 'OBJECT')

            # if it's a spectral pocessor FITS file, skip to the second and
            # fourth HDU's, and pick up the number of receivers and number
            # of records (integrations) in the data table
            if device == 'SpectralProcessor' :
                q, qq = cfitsio.fits_movabs_hdu(fits, 2)
                status, num_rcvrs, comment = \
                                cfitsio.fits_read_key_str(fits, 'NAXIS2')
                q, qq = cfitsio.fits_movabs_hdu(fits, 4)
                status, num_records, comment = \
                                cfitsio.fits_read_key_str(fits, 'NAXIS2')
                # assemble the output string
                line = ('Scan ' + str(scan) + ' ' + object + ' - ' +
                        str(num_rcvrs) + ' receivers ' + str(num_records) +
                        ' records')
            else :
                line = 'Scan ' + str(scan) + object
            # print or write the output line
            if out_file == '' :
                print line
            else :
                fd.write(line + '\n')
            # close the cfitsio access for this file
            cfitsio.fits_close_file(fits)
            # and repeat until no more files

    # Tell how many FITS files and files of all sort were found in this
    # directory
    print file_num, 'FITS files in this directory'
    print 'Total number of files:', len(ls)

    # if necessary, close the output file
    if out_file != '' :
        fd.close()
    return

# To test uncover one of the list_scans calls below and, from the Python
# prompt, execute either
# import list_scans
#     or
# reload(list_scans)
# list_scans('AGBT02A_069_01')
# list_scans('AGBT02A_069_01', 'Antenna')
# list_scans('AGBT02A_069_01', out_file='testlist')