#!/bin/sh

[ "$(id -u)" = "0" ] && echo "This script should not be run as root" >&2 && exit 1

find . -type d -path '*/.*' -prune -o -print0 | xargs -0 -n1 -P10 -I{} sh -c '
    generate_unique_name() {
        base_name="$1"; ext="$2"; dest_path="$3"; count=1
        [ -z "$ext" ] && new_name="$base_name" || new_name="${base_name}.${ext}"
        while [ -e "${dest_path}/${new_name}" ]; do
            [ -z "$ext" ] && new_name="${base_name}_${count}" || new_name="${base_name}_${count}.${ext}"
            count=$(( count + 1 ))
        done
        echo "$new_name"
    }
    process_item() {
        item_path="$1"; 
        [ "$item_path" = "." ] && return
        dir_name=$(dirname "$item_path"); base_name=$(basename "$item_path")
        [ -d "$item_path" ] && {
            new_name=$(echo "$base_name" | sed -E "s/[^a-zA-Z0-9 _.-]+//g; s/[ .-]+/_/g; s/_+/_/g; s/^_//; s/_$//; s/(.*)/\L\1/")
            [ -z "$new_name" ] && new_name="untitled"
        } || {
            file_ext="${base_name##*.}"
            base_name_no_ext="${base_name%.*}"
            new_base_name_no_ext=$(echo "$base_name_no_ext" | sed -E "s/[^a-zA-Z0-9 _.-]+//g; s/[ .-]+/_/g; s/_+/_/g; s/^_//; s/_$//; s/(.*)/\L\1/")
            [ -z "$new_base_name_no_ext" ] && new_base_name_no_ext="untitled"
            [ -z "$file_ext" ] || [ "$file_ext" = "$base_name_no_ext" ] && new_name="$new_base_name_no_ext" || new_name="${new_base_name_no_ext}.${file_ext}"
        }
        [ "$base_name" != "$new_name" ] && {
            [ -e "${dir_name}/${new_name}" ] && new_name=$(generate_unique_name "${new_name%.*}" "${new_name##*.}" "$dir_name")
            mv "$item_path" "${dir_name}/${new_name}" 2>/dev/null || true
        }
    }
    process_item "{}"
' 2>/dev/null