#!/usr/bin/env python3
import pwd, sys, os, shutil, time, subprocess, datetime, signal
"""
    Program ners_to_eop inquires the Network Earth Rotation Server,
    retrieves the EOP series and converts them into erp format
    used by Calc and Solve.
"""

prog_name = "ners_to_erp v 1.0 2019.01.09"

ners_host_name = "alt.earthrotation.net"
eop_start_date = "1980.01.01"

if ( sys.version[:3] < "3.0" ): print ( "This script cannot run under Python-2" ); exit ( 1 )
if ( sys.version[:3] < "3.2" ): print ( "This script cannot run under Python older than 3.2. Please upgrade" ); exit ( 1 )

#
# ------------------------------------------------------------------------
#
def ners_exe ( command, verb=0 ):
    global ners_child_pid
    """
    Auxilliary routine ners_exe spawns a subprocess, executes command in 
    the context of the subprocess, waits for its completion and return 
    the completion code and the results as ( returncode, out ). 
    out is a list of strings without trailing "\n". If verb >= 2, 
    the command to be executed is also printed in stdout.

    Requires  sys, os, subprocess, signal, datetime
    """

    if ( verb >= 2 ): 
         date_str = datetime.now().strftime("%Y.%m.%d_%H:%M:%S.%f")[0:23]
         print ( date_str, "execute:", command )
         sys.stdout.flush()
         
#
# --- Launch the subprocess
#
    proc = subprocess.Popen ( command, \
                              stdout=subprocess.PIPE, \
                              stderr=subprocess.STDOUT, \
                              shell=True )
#
# --- Catch the output in list out
#
    out = []
    for line in proc.stdout:
        out.append ( str(line, encoding="utf-8").split("\n")[0] )
#
# --- wait for completion of the child process
#
    proc.wait()
#
# --- Return the runcode and the output that was caught
#
    return ( proc.returncode, out )
#
# ------------------------------------------------------------------------
#

ners_file = "/tmp/eop_ners.txt"

#
# --- Command line for getting the EOP series from the NERS server
#
com_line = "wget -q -O - 'http://" + ners_host_name + "/cgi-bin/eop_series.py?start_date=" + \
            eop_start_date + "&stop_date=now&time_step=86400.0&eop_group=polu&service=series&submit=Submit'"

#
# --- Get the EOP
#
(ret, ners_buf) = ners_exe ( com_line )
if ( ret != 0 ):
     for line in ners_buf:
         print ( line.strip("\n") )

     print ( "Failure to get EOP from NERS server" )
     exit ( 1 ) 

#
# --- The first pass: learn the number of EOP entries, 
# --- dates of the first and the last entires
#

num_rec = 0
for line in ners_buf:
    if ( line[0:1] == '#' or \
         line[0:1] == '<' or \
         len(line.split()) < 6 ):
         continue
    if ( num_rec == 0 ):
         tim_sec_first = float(line.replace("D","E").split()[1])
         first_date = line.split()[2]
    num_rec = num_rec + 1    
    last_date = line.split()[2]

#
# --- Print the header
#
jd_first = 2451544.50 + tim_sec_first/86400.0
print ( "EOP-MOD Ver 2.0  %9.1f   1.0  %5d  UT1-TAI   UNDEF                   " % \
         ( jd_first, num_rec ) )
print ( "%-72s" % "# " )
print ( "%-72s" % ( "# Generated by " + prog_name ) )
print ( "%-72s" % "# EOP are generated by the Nethwork Earth Rotation Service" )
print ( "%-72s" % "# " )
print ( "%-72s" % ( "# First date: " + first_date ) )
print ( "%-72s" % ( "# Last  date: " + last_date  ) )
print ( "%-72s" % "# " )

#
# --- Parse the EOP file
#
for line in ners_buf:
    if ( line[0:1] == '#' or \
         line[0:1] == '<' or \
         len(line.split()) < 6 ):
         continue
#
    tim_sec = float(line.replace("D","E").split()[1])
    xpol    = float(line.replace("D","E").split()[4])
    ypol    = float(line.replace("D","E").split()[5])
    ut1     = float(line.replace("D","E").split()[6])
    jd = 2451544.50 + tim_sec/86400.0
#
# --- Print re-formatted line
#
    print ( "%9.1f %7.4f %7.4f %9d 0.0    0.0         0. 0.000 0.000 0.000" % \
             ( jd, 10.*xpol, 10.*ypol, int(ut1*1.e6) ) )