#!/usr/bin/env python3
"""
Program to read astronomical observation data and convert observation dates to Julian Day.
Uses astropy Table for simple and efficient data handling.
Authors: Tõnis Eenmäe and Claude.ai
"""

import sys
from astropy.table import Table
from astropy.time import Time
from astropy.io import ascii
import astropy.units as u

def convert_observations_to_jd(input_file, output_file=None):
    """
    Read observation data and convert dates to Julian Day.
    
    Parameters:
    -----------
    input_file : str
        Path to input file containing observation data
    output_file : str, optional
        Path to output file. If None, prints to stdout
    """
    
    # Read the table (astropy automatically handles the parsing)
    table = ascii.read(input_file, names=['Object', 'Date', 'Time', 'Mag', 'Error', 'Band', 'OID'],
                       data_start=1)

    # Print the input for debug, comment out when not needed
    print("Input table is:")
    print(table)

    # Combine date and time columns into datetime strings
    datetime_strings = [f"{date} {time}" for date, time in zip(table['Date'], table['Time'])]
    
    # Convert to Time objects (in UTC) and extract Julian Day
    times = Time(datetime_strings, format='iso', scale='utc')

    table['JD'] = times.jd
    
    # Create output table with desired columns (comment corresponding line out when not needed)
    output_table = Table()
    output_table['Object'] = table['Object']
    output_table['JD'] = table['JD']
    #output_table['Date'] = table['Date']
    #output_table['Time'] = table['Time']
    output_table['Mag'] = table['Mag']
    output_table['Error'] = table['Error']
    output_table['Band'] = table['Band']
    output_table['OID'] = table['OID']
    
    # Limit JD in the table to 5 decimals, change the number between . and f when needed
    output_table['JD'].format = '.5f'

    # Write or print the output, to change field delimiter, change to ' ' for space
    if output_file:
        output_table.write(output_file, format='ascii', delimiter=',', overwrite=True)
        print(f"Output written to {output_file}")
    else:
        print("Output table is:")
        output_table.pprint_all()
    
    return


def main():
    if len(sys.argv) < 2:
        print("Usage: python convert_to_jd_simple.py <input_file> [output_file]")
        print("\nExample:")
        print("  python convert_to_jd_simple.py observations.txt")
        print("  python convert_to_jd_simple.py observations.txt output.txt")
        sys.exit(1)
    
    input_file = sys.argv[1]
    output_file = sys.argv[2] if len(sys.argv) > 2 else None
    
    convert_observations_to_jd(input_file, output_file)


if __name__ == "__main__":
    main()