#!/usr/bin/env bash
set -x
set -eufo pipefail

# CONSTANTS
declare -r m4b-tool="nix run github:sandreas/m4b-tool#m4b-tool-libfdk -- "
declare -r script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# VARS
LEADING_ZEROES=2
MAIN_SRC="${SRC:${script_dir}/src}"
MAIN_OUT="${OUT:${script_dir}/out}"

# FUNCTIONS
parse-vars() {
  # TODO implement parsing the directory structure of the passed directory, to fill in missing vars and return them
  # Series structure: ${SRC}/<author>/<series>/Book <part> - <year> - <book> {<narrator>}/
  # Standalone structure: ${SRC}/<author>/<year> - <book> {<narrator>}/
  # Return the <part> wihh leading zeros based on the LEADING_ZEROES variable
}

get-book-directories() {
  # TODO implemet getting the book directoris based on the ${SRC} path
  # find the directories that contains the books files and return them as an array
  # Example book directory:
  # /path/to/src/Author/Series/Book Part - Year - Book {Narrator}/
  # /path/to/src/Author/Year - Book {Narrator}/
}

m4b-merge() {
  local output_file="${1}"
  local source_dir="${2}"
  local author="${3}"
  local narrator="${4}"
  local title="${5}"
  local year="${6}"
  local series="${7}"
  local series_index=${8}

  mkdir -p "$(dirname "${output_file}")"
  "${m4b-tool}" \
    merge \
      -v \
      --jobs=6 \
      --audio-samplerate=44100 \
      --audio-quality=100 \
      --writer="${author}" \
      --artist="${narrator}" \
      --title="${title}" \
      --year="${year}" \
      --album="${series}" \
      --album-sort="${series_index}" \
      --output-file="${output_file}/" \
      -- "${source_dir}"
}

main() {

}

main "$@"