#!/usr/bin/env python3

import os
import json
import argparse


def create_hardlinks(json_file, source_dir, target_dir, dry_run: bool = False):
    """
    Reads the JSON file and creates hardlinks based on the mapping of source and target files.

    Args:
        json_file (str): Path to the JSON file containing the mapping.
        source_dir (str): Base path of the source directory.
        target_dir (str): Base path of the target directory.
        dry_run (bool): If True, no changes will be made; actions will be printed instead.
    """
    try:
        with open(json_file, 'r') as f:
            file_mappings = json.load(f)
    except Exception as e:
        print(f"Failed to read JSON file {json_file}: {e}")
        return

    for source_file, target_file in file_mappings:
        source_path = os.path.join(source_dir, source_file)
        target_path = os.path.join(target_dir, target_file)

        # Ensure the source file exists
        if not os.path.exists(source_path):
            print(f"Source file does not exist: {source_path}. Skipping...")
            continue

        # Ensure the target directory exists
        target_dir_path = os.path.dirname(target_path)
        if not os.path.exists(target_dir_path):
            if dry_run:
                print(f"[DRY-RUN] Would create directory: {target_dir_path}")
            else:
                print(f"Creating directory: {target_dir_path}")
                os.makedirs(target_dir_path, exist_ok=True)

        # Create the hard link if the target does not already exist
        if not os.path.exists(target_path):
            if dry_run:
                print(f"[DRY-RUN] Would create hard link: {source_path} -> {target_path}")
            else:
                print(f"Creating hard link: {source_path} -> {target_path}")
                try:
                    os.link(source_path, target_path)
                except OSError as e:
                    print(f"Failed to create hard link for {target_path}: {e}")
        else:
            print(f"Target file already exists, skipping: {target_path}")


def main():
    parser = argparse.ArgumentParser(description="Create hardlinks based on JSON output from the first script.")
    parser.add_argument('json_file', help="Path to the JSON file containing source-target mappings.")
    parser.add_argument('source_dir', help="Path to the source directory.")
    parser.add_argument('target_dir', help="Path to the target directory.")
    parser.add_argument(
        '--dry-run', '-n', 
        action='store_true', 
        help="Perform a dry run; only print actions without making changes."
    )
    args = parser.parse_args()

    create_hardlinks(args.json_file, args.source_dir, args.target_dir, args.dry_run)


if __name__ == "__main__":
    main()