#!/usr/bin/env bash

# Source the script 'common-functions.sh'.
SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)
ROOT_DIR=$(grep --only-matching "^.*scripts[^/]*" <<<"$SCRIPT_DIR")
source "$ROOT_DIR/common-functions.sh"

_main() {
    local input_files=""
    local output_dir=""

    # Execute initial checks.
    _check_dependencies "command=mp3gain"
    _display_wait_box "2"
    input_files=$(_get_files "par_type=file; par_recursive=true; par_select_mime=audio/mpeg; par_skip_extension=bak")

    # Execute the function '_main_task' for each file in parallel.
    _run_task_parallel "$input_files" "$output_dir"
    _display_result_box ""
}

_main_task() {
    local input_file=$1
    local output_dir=$2
    local output_file=""
    local std_output=""
    local temp_file=""

    # Work on a temporary file.
    temp_file=$(_get_temp_file)
    std_output=$(cp --archive -- "$input_file" "$temp_file" 2>&1)
    _check_output "$?" "$std_output" "$input_file" "" || return 1

    # Run the main process.
    std_output=$(mp3gain -q -r -s s -c "$temp_file" 2>&1)
    _check_output "$?" "$std_output" "$input_file" "" || return 1

    # Move the temporary file to the output.
    output_file=$input_file
    _move_temp_file_to_output "$input_file" "$temp_file" "$output_file"

    # Remove the temporary files on each iteration (if not removed before).
    rm -f -- "$temp_file"
}

_main "$@"