#!/bin/bash

# Directory containing PNG files
directory="restart/basic/img/"

# Function to pad filename with initial zeros
pad_filename() {
    filename="$1"
    if [[ $filename =~ ^([0-9]+)(-?[0-9]*)\.png$ ]]; then
        prefix="${BASH_REMATCH[1]}"
        suffix="${BASH_REMATCH[2]}"
        padded_prefix=$(printf "%04d" "$prefix")
        padded_filename="$padded_prefix$suffix.png"
        echo "$padded_filename"
    else
        echo "Invalid filename: $filename"
    fi
}

# Iterate over PNG files in the directory
cd "$directory" || exit
for file in *.png; do
    new_filename=$(pad_filename "$file")
    if [[ -n $new_filename ]]; then
        mv "$file" "$new_filename"
        echo "Renamed $file to $new_filename"
    fi
done