import os
from datetime import datetime

def merge_files(file_paths):
    # Dictionary to hold file contents by extension
    files_by_extension = {}

    # Read each file and group contents by extension
    for file_path in file_paths:
        _, ext = os.path.splitext(file_path)
        if ext not in files_by_extension:
            files_by_extension[ext] = []
        with open(file_path, 'r') as file:
            files_by_extension[ext].append(file.read())

    # Ensure the .old directory exists
    old_dir = '.old'
    if not os.path.exists(old_dir):
        os.makedirs(old_dir)

    # Write merged contents to new files
    for ext, contents in files_by_extension.items():
        current_date = datetime.now().strftime("%Y-%m-%d")
        merged_file_path = f'{current_date}{ext}'

        # Move existing merged file to .old directory
        if os.path.exists(merged_file_path):
            os.rename(merged_file_path, os.path.join(old_dir, f'{current_date}{ext}'))

        with open(merged_file_path, 'w') as merged_file:
            for content in contents:
                merged_file.write(content)

if __name__ == "__main__":
    # Example usage: specify the file paths you want to merge
    file_paths = [
        '/test/first.csv',
        '/test/second.csv',
        '/test/third.csv'
    ]
    merge_files(file_paths)