beets-setup/scripts/utility/split-flac

#!/usr/bin/env bash
set -euo pipefail

usage() {
  cat >&2 <<'EOF'
Usage:
  split-cue-flac.sh /path/to/album-folder [--keep-originals]

Behavior:
  - Finds one .cue file in the folder.
  - Finds the matching single .flac file.
  - Splits into a temporary directory inside the album folder.
  - Tags the generated tracks from the CUE.
  - Verifies generated FLACs.
  - Moves split tracks back into the album folder.
  - Deletes the original single FLAC and CUE unless --keep-originals is passed.
EOF
  exit 2
}

die() {
  echo "ERROR: $*" >&2
  exit 1
}

need_cmd() {
  command -v "$1" >/dev/null 2>&1 || die "Missing required command: $1"
}

[[ $# -ge 1 && $# -le 2 ]] || usage

album_dir="${1%/}"
keep_originals=0

if [[ "${2:-}" == "--keep-originals" ]]; then
  keep_originals=1
elif [[ $# -eq 2 ]]; then
  usage
fi

[[ -d "$album_dir" ]] || die "Not a directory: $album_dir"

need_cmd find
need_cmd shnsplit
need_cmd flac

if command -v cuetag.sh >/dev/null 2>&1; then
  CUETAG_CMD="cuetag.sh"
elif command -v cuetag >/dev/null 2>&1; then
  CUETAG_CMD="cuetag"
else
  die "Missing required command: cuetag.sh or cuetag"
fi

# Optional but useful validation.
HAS_CUEPRINT=0
if command -v cueprint >/dev/null 2>&1; then
  HAS_CUEPRINT=1
fi

mapfile -d '' cue_files < <(
  find "$album_dir" -maxdepth 1 -type f -iname '*.cue' -print0 | sort -z
)

[[ ${#cue_files[@]} -eq 1 ]] || die "Expected exactly one .cue file, found ${#cue_files[@]}"

cue_file="${cue_files[0]}"

mapfile -d '' flac_files < <(
  find "$album_dir" -maxdepth 1 -type f -iname '*.flac' -print0 | sort -z
)

[[ ${#flac_files[@]} -ge 1 ]] || die "No .flac files found in $album_dir"

# Try to identify the source FLAC.
# First, if there is exactly one FLAC, use it.
# Otherwise, try to match the CUE FILE line by basename/stem.
flac_file=""

if [[ ${#flac_files[@]} -eq 1 ]]; then
  flac_file="${flac_files[0]}"
else
  cue_ref="$(
    awk '
      BEGIN { IGNORECASE=1 }
      /^[[:space:]]*FILE[[:space:]]+/ {
        line=$0
        sub(/^[[:space:]]*FILE[[:space:]]+/, "", line)
        if (line ~ /^"/) {
          sub(/^"/, "", line)
          sub(/"[[:space:]]+[A-Za-z0-9_]+[[:space:]]*$/, "", line)
          print line
          exit
        } else {
          print $2
          exit
        }
      }
    ' "$cue_file"
  )"

  if [[ -n "$cue_ref" ]]; then
    cue_ref_base="$(basename "$cue_ref")"
    cue_ref_stem="${cue_ref_base%.*}"

    matches=()

    for f in "${flac_files[@]}"; do
      f_base="$(basename "$f")"
      f_stem="${f_base%.*}"

      if [[ "$f_base" == "$cue_ref_base" || "$f_stem" == "$cue_ref_stem" ]]; then
        matches+=("$f")
      fi
    done

    if [[ ${#matches[@]} -eq 1 ]]; then
      flac_file="${matches[0]}"
    fi
  fi

  [[ -n "$flac_file" ]] || die "Multiple .flac files found and could not determine which one matches the CUE"
fi

echo "Album dir: $album_dir"
echo "CUE:       $(basename "$cue_file")"
echo "Source:    $(basename "$flac_file")"

# Validate source FLAC before doing anything.
echo "Verifying source FLAC..."
flac -t --silent "$flac_file"

if [[ "$HAS_CUEPRINT" -eq 1 ]]; then
  echo "Validating CUE syntax..."
  cueprint "$cue_file" >/dev/null
fi

tmp_dir="$(mktemp -d "$album_dir/.cue-split.tmp.XXXXXXXX")"
cleanup() {
  if [[ -d "$tmp_dir" ]]; then
    rm -rf -- "$tmp_dir"
  fi
}
trap cleanup EXIT

split_dir="$tmp_dir/split"
original_dir="$tmp_dir/originals"

mkdir -p "$split_dir" "$original_dir"

echo "Splitting into temporary directory..."
shnsplit \
  -f "$cue_file" \
  -o flac \
  -t "%n - %t" \
  -d "$split_dir" \
  "$flac_file"

mapfile -d '' split_files < <(
  find "$split_dir" -maxdepth 1 -type f -iname '*.flac' -print0 | sort -z
)

[[ ${#split_files[@]} -gt 0 ]] || die "No split FLAC files were produced"

echo "Tagging split tracks from CUE..."
"$CUETAG_CMD" "$cue_file" "${split_files[@]}"

echo "Verifying split FLAC files..."
flac -t --silent "${split_files[@]}"

echo "Checking for filename collisions in album directory..."
for f in "${split_files[@]}"; do
  dest="$album_dir/$(basename "$f")"

  if [[ -e "$dest" ]]; then
    die "Refusing to overwrite existing file: $dest"
  fi
done

echo "Moving original files aside..."
mv -- "$flac_file" "$original_dir/"
mv -- "$cue_file" "$original_dir/"

echo "Moving split tracks into album directory..."
for f in "${split_files[@]}"; do
  mv -- "$f" "$album_dir/"
done

if [[ "$keep_originals" -eq 1 ]]; then
  keep_dir="$album_dir/.cue-split-originals"
  mkdir -p "$keep_dir"

  echo "Keeping originals in: $keep_dir"
  mv -- "$original_dir/"* "$keep_dir/"
else
  echo "Deleting original single FLAC and CUE..."
  rm -rf -- "$original_dir"
fi

echo "Done."