#!/usr/bin/env bash
# Sync and transcode music files to a destination directory
set -e

SRC="${1:?Source directory required}"
DST="${2:?Destination directory required}"
JOBS="${3:-12}"

command -v opusenc >/dev/null || { echo "ERROR: opusenc not found" >&2; exit 1; }

mkdir -p "$DST"

echo "Syncing music from $SRC to $DST (using $JOBS parallel jobs)"

# Process source files in parallel
process_file() {
  local src="$1"
  local rel="${src#"$SRC/"}"
  local dst="$DST/$rel"
  
  case "${src,,}" in
    *.flac)
      dst="${dst%.*}.opus"
      if [[ ! -f "$dst" || "$src" -nt "$dst" ]]; then
        echo "Converting: $rel"
        mkdir -p "$(dirname "$dst")"
        opusenc --quiet --bitrate 160 --vbr "$src" "$dst"
      fi
      ;;
    *.mp3)
      if [[ ! -f "$dst" || "$src" -nt "$dst" ]]; then
        echo "Copying: $rel"
        mkdir -p "$(dirname "$dst")"
        cp -p "$src" "$dst"
      fi
      ;;
  esac
}

export -f process_file
export SRC DST

find -L "$SRC" -type f \( -iname "*.flac" -o -iname "*.mp3" \) -print0 | \
  xargs -0 -P "$JOBS" -I {} bash -c 'process_file "$@"' _ {}

# Remove stray files
while IFS= read -r -d '' dst; do
  rel="${dst#"$DST/"}"
  base="${rel%.*}"
  
  case "${dst,,}" in
    *.opus)
      [[ -f "$SRC/$base.flac" || -f "$SRC/$base.FLAC" ]] && continue
      echo "Removing: $rel"
      rm -f "$dst"
      ;;
    *.mp3)
      [[ -f "$SRC/$rel" ]] && continue
      echo "Removing: $rel"
      rm -f "$dst"
      ;;
  esac
done < <(find -L "$DST" -type f \( -iname "*.opus" -o -iname "*.mp3" \) -print0)

# Clean empty directories
find "$DST" -type d -empty -delete 2>/dev/null || true

echo "Done"