"""
rename_lower - Rename files to lowercase

Usage: rename_lower FILE [FILE...]

This script renames files by converting their filenames to lowercase.
It performs validation to ensure files exist and that the target lowercase
filename doesn't already exist before renaming.

Examples:
  rename_lower MyFile.TXT
  rename_lower *.JPG
  rename_lower Document.PDF Image.PNG
"""

import sys
from pathlib import Path


def usage():
    """Show usage information"""
    print("""Usage: ,rename_lower FILE [FILE...]

Rename files to lowercase filenames.

This script converts filenames to lowercase. It validates that files
exist and checks for conflicts before renaming.

Arguments:
  FILE    One or more files to rename

Options:
  -h, --help    Show this help message

Examples:
  ,rename_lower MyFile.TXT
  ,rename_lower *.JPG
  ,rename_lower Document.PDF Image.PNG

Exit codes:
  0    Success - all files renamed (or already lowercase)
  1    Error - invalid arguments, missing files, or conflicts
""")


def rename_to_lowercase(filepath: str) -> bool:
    """
    Rename a single file to lowercase.

    Arguments:
        filepath: Path to the file to rename

    Returns:
        True on success, False on error
    """
    # Convert to Path object for easier manipulation
    original = Path(filepath)

    # Validate that the file exists
    if not original.exists():
        print(f"Error: File not found: {filepath}", file=sys.stderr)
        return False

    # Get the directory and filename components
    directory = original.parent
    original_name = original.name
    lowercase_name = original_name.lower()

    # Check if the filename is already lowercase
    if original_name == lowercase_name:
        # Already lowercase, nothing to do
        return True

    # Construct the target path
    target = directory / lowercase_name

    # Check if target already exists
    if target.exists():
        print(f"Error: Target file already exists: {target}", file=sys.stderr)
        print(f"  Cannot rename: {filepath}", file=sys.stderr)
        return False

    # Perform the rename
    try:
        original.rename(target)
        print(f"Renamed: {original_name} -> {lowercase_name}")
        return True
    except OSError as e:
        print(f"Error: Failed to rename {filepath}: {e}", file=sys.stderr)
        return False


def main():
    """Main script logic"""
    # Handle help flag or no arguments
    if len(sys.argv) == 1 or sys.argv[1] in ("-h", "--help"):
        usage()
        return 0 if len(sys.argv) > 1 else 1

    success = True

    # Process each file argument
    for filepath in sys.argv[1:]:
        if not rename_to_lowercase(filepath):
            success = False
            # Continue processing other files even if one fails

    return 0 if success else 1


if __name__ == "__main__":
    sys.exit(main())