cgar_csv2table

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

"""
cgar_csv2table

Reads a CVS file created by `cgar_log2csv` and prints the data as table to stdout.


Ideas/ToDos:
-----------
    - Implement filtering by start and end time.


Changelog:
----------
    08.02.2023      v0.1            - first release
    09.02.2023      v0.2            - code cleaning
                                    - table can now splitted into two lines (cgroup and attribute)
                                      to save space and increase readability
"""

import argparse
import datetime
import os
import sys


__version__ = '0.2'


def argument_parse():
    """Evaluates the command line arguments."""

    # All supported attributes (with and without their sub keys).
    
    parser = argparse. ArgumentParser(prog=os.path.basename(sys.argv[0]), 
                       description='Reads a CVS file created by `cgar_log2csv` and prints the data as table to stdout.',
                       add_help=True,
                       epilog=f'v{__version__}')

    # Global flags and arguments.   
    # parser.add_argument('--start-time',
    #                     metavar='TIME',
    #                     dest='start_time',
    #                     type=str,
    #                     action='store',
    #                     required=False,
    #                     help='only print data from this time forward (no timezone info)')   
    # parser.add_argument('--end-time',
    #                     metavar='TIME',
    #                     dest='end_time',
    #                     type=str,
    #                     action='store',
    #                     required=False,
    #                     help='only print data to this time (no timezone info)')  
    parser.add_argument('-s', '--separator',
                        dest='separator',
                        type=str,
                        action='store',
                        default=',',
                        required=False,
                        help='separator used in the CSV file (default: ,)')  
    parser.add_argument('-l', '--remove-level',
                        dest='remove_level',
                        action='store',
                        type=int,
                        choices=range(0,10),
                        default=0,
                        required=False,
                        help='amount of directory levels removed from cgroup path for output (default: 0)')                          
    parser.add_argument('csvfile', 
                        metavar='CSVFILE',
                        type=str,
                        help='the CSV file'),

    args = parser.parse_args()

    # Convert times into datetime objects
    # try:
    #     args.time_range = (
    #         datetime.datetime.strptime(args.start_time, '%Y-%m-%dT%H:%M:%S') if args.start_time else None,
    #         datetime.datetime.strptime(args.end_time, '%Y-%m-%dT%H:%M:%S') if args.end_time else None)
    # except Exception as err:
    #     print(f'Error in time range: {err}')
    #     sys.exit(1)  

    # Check if the CSV file is available.
    if not os.path.isfile(args.csvfile) and os.access(args.csvfile, os.R_OK):
        print(f'Logfile "{args.csvfile}" does not exists!')
        sys.exit(0)     

    return args


def get_csv_line(filename: str) -> str:
    """Generator to walk through the given file."""
    
    try: 
        with open(filename, 'r') as f:
            for line in f:
                yield line           
    except Exception as err:
        print(f'Error reading the CSV file: {err}')
        sys.exit(2)  


def split_csv_line(line: str, separator: str) -> list:
    """Splits a CSV line into a list of cleaned fields."""

    return [x.strip('\n\t "') for x in line.split(separator)]


def length_of_line(line: str, separator: str) -> list:
    """Gets a CSV line and returns a list with the length of each field."""

    return [len(col) for col in split_csv_line(line ,separator)]

def print_table_line(fields: list, alignment:str, widths: list) -> None:
        """Prints the line formatted on stdout."""
        for ix, col in enumerate(fields):
            print(f'''{col:{alignment}{widths[ix]}} ''',end='')
        print()

def main():

    # Parse command line arguments.
    arguments = argument_parse()    

    try:

        # The generator for pre-reading the CSV file.
        csv_file = get_csv_line(arguments.csvfile)

        # Do a pre-parsing of the CSV file to get the width of each column.
        # We also build the header, which gets transformed into two lines (cgroup and attribute)
        # to save space and increase readability.
        header = [[],[]]
        for field in split_csv_line(next(csv_file), arguments.separator):
            if '/' in field:
                level = min(arguments.remove_level, field.count('/'))
                field =  '/'.join(field.split('/')[level:])
            if '::' in field:
                one, two = field.split('::', maxsplit=1)
                header[0].append(one)
                header[1].append(two)
            else:
                header[0].append(field)
                header[1].append('')

        column_width = [max(x) for x in zip([len(col) for col in header[0]], [len(col) for col in header[1]])]
        for line in csv_file:
            for ix, length in enumerate(length_of_line(line, arguments.separator)):
                try:
                    column_width[ix] = max(column_width[ix], length)
                except IndexError:
                    column_width.append(length)

        # Print the prepared header first.
        print_table_line(header[0], '^', column_width)
        print_table_line(header[1], '^', column_width)
        print(' '.join(['-' * l for l in column_width]))

        # Walk trough the CSV file and print each line nicely.
        # The first line we drop, because we have printed the header already. 
        csv_file = get_csv_line(arguments.csvfile)
        next(csv_file)
        for line in csv_file:
            print_table_line(split_csv_line(line, arguments.separator), '>', column_width)

    except (BrokenPipeError, IOError):
        # Handle BrokenPipe issue: https://docs.python.org/3/library/signal.html#note-on-sigpipe
        devnull = os.open(os.devnull, os.O_WRONLY)
        os.dup2(devnull, sys.stdout.fileno())
        sys.exit(0)

    except Exception as err:
        print(f'Sadly a runtime error ocurred: {err}')
        sys.exit(3)  

    # Bye.        
    sys.exit(0)


if __name__ == "__main__":
    main()