#!/bin/bash

# =========================================================
# Script for resampling audio files to cd resolution
# and automatically adjusting the peak level
#
# Dependencies: SoX, flac, bash, awk
# =========================================================

function printHelp() {
  echo 'Usage: cmd [OPTION]... FILES'
  echo 'Options:'
  echo '  --help (-h): Print this page'
  echo '  --no-gain-adjustment (-ng): Disable gain adjustment, no peak level changes'
  #echo '        '
  #echo '        '
  #echo '        '
}

cmd=sox_ng
iterations=2
gainAdjustment=true
destination='resampled'
gain='0.00'
safeGuard='0.00'
targetLevel='0.01' # -0.01 dB
files=()

if [[ -z "${*}" ]]; then
  echo 'No arguments given.'
  printHelp
  exit
fi

for argument in "${@}"; do
  if [[ "${argument}" == '-h' ]] || [[ "${argument}" == '--help' ]]; then
    printHelp
    exit
  elif [[ "${argument}" == '--no-gain-adjustment' ]] || [[ "${argument}" == '-ng' ]]; then
    echo 'Disabling gain adjustment...'
    iterations=1
    gainAdjustment=false
  elif [[ ! -r "${argument}" ]]; then
    echo "The argument or filepath provided \`${argument}\` does not exist, quitting..."
    exit
  else
    files+=("${argument}")
  fi
done

mkdir -vp "${destination}"

for (( i = 0 ; i < iterations ; i++ )); do
  for file in "${files[@]}"; do
    cmdOutput="$("${cmd}" -DV4 "${file}" -b 16 -t flac "resampled/${file}" gain "${safeGuard}" rate -u -L -d 33 -b 96 44100 gain "${gain}" 2>&1)"
    clipping="$(echo "${cmdOutput}" | grep -i 'clipped')"

    echo "${cmdOutput}"
    if [[ -n "${clipping// /}" ]]; then
      echo 'Audio clipped, resetting...'

      safeGuard="$(echo "${safeGuard} 0.30" | awk '{ print $1 - $2 }')"
      gain='0.00'
      i=-1
      break
    fi
  done

  if [[ "${gainAdjustment}" == true ]] && [[ "${i}" != -1 ]]; then
    peakLevel="$(cd "${destination}" && "${cmd}" "${files[@]}" -n stats 2>&1 | grep 'Pk lev' | awk '{ print $4 }')"
    if [[ -z "${peakLevel// /}" ]]; then
      echo 'Error invoking SoX, check dependencies and audio files'
      exit
    fi
    echo -e "\nTracks peak level: ${peakLevel} dB"

    gain="$(echo "${targetLevel} ${peakLevel} ${gain}" | awk '{ print $3 + (($1 + $2) * -1) }')"
    echo "Applied gain: ${gain} dB"
  fi
done