#!/bin/bash

# Directory to clean (current directory)
DIR="."

cd "$DIR" || exit

for f in *; do
    # Skip if not a file
    [ -f "$f" ] || continue

    # Convert to lowercase
    new=$(echo "$f" | tr '[:upper:]' '[:lower:]')

    # Replace spaces with underscore
    new=$(echo "$new" | tr ' ' '_')

    # Remove ALL special characters except: letters numbers _ .
    new=$(echo "$new" | sed 's/[^a-z0-9._-]/_/g')

    # Collapse multiple underscores to one
    new=$(echo "$new" | sed 's/_\+/_/g')

    # Remove underscore before extension
    new=$(echo "$new" | sed 's/_\./\./g')

    # If filename changed, rename it
    if [[ "$f" != "$new" ]]; then
        echo "Renaming: $f  →  $new"
        mv -i "$f" "$new"
    fi
done