#!/usr/bin/python3
import os
import sys
import argparse


def split_lines(input_file, chunk_size_mb=500):
    """
    Splits a file into chunks of size chunk_size_mb but preserves lines.

    Args:
      input_file (str): Path to the file that will be splitted into chunks.
      chunk_size_mb (int, optional): Size of each chunk in MB. Defaults to 500.
    """
    chunk_size_bytes = chunk_size_mb * 1024 * 1024 # Convert to MB to bytes
    current_chunk = 1
    current_size = 0
    output_file = None
    # Try to extract original extension
    file_extension = os.path.splitext(input_file)
    if len(file_extension) == 2:
        file_extension = file_extension[1]
    else:
        file_extension = ''

    # Open the file and split it into chunks
    with open(input_file, 'r') as infile:
        for line in infile:
            # Open new file if none exists or next line exceeds chunk size
            if output_file is None or ((current_size + len(line.encode('utf-8'))) > chunk_size_bytes):
                if output_file:
                    output_file.close()
                output_filename = f"{os.path.splitext(input_file)[0]}_chunk{current_chunk:03d}{file_extension}"
                print(f"Created {output_filename}")
                output_file = open(output_filename, 'w')
                current_chunk += 1
                current_size = 0
            output_file.write(line)
            current_size += len(line.encode('utf-8'))
        
        if output_file:
            output_file.close()

def parse_arguments():
    """
    Parses command line arguments.

    Returns:
    argparse.Namespace: The arguments passed to the command line.
    """
    parser = argparse.ArgumentParser(description='Split a text file into smaller chunks but keep lines intakt.')
    parser.add_argument('input_file', type=str, help='The path to the input file to be split.')
    parser.add_argument('--chunk_size_mb', type=int, default=500, help='Maximum chunk size in MB (default: 500).')
    return parser.parse_args()

def main():
    args = parse_arguments()
    split_lines(args.input_file, args.chunk_size_mb)

if __name__ == '__main__':
    main()