cue2flac

#!/bin/bash

if [[ $# -ne 1 ]] ; then
  echo 'Usage:'
  echo -n "$(basename ${BASH_SOURCE[0]}) <path to CUE file>"
  exit 1
fi

if ! which flac >/dev/null
then
  echo 'flac was not found' >&2
  exit 1
fi

set -e

readonly CUE="$1"


GENRE=                                                                                                                                                                                                                                                                     
YEAR=                                                                                                                                                                                                                                                                      
PERFORMER=
ALBUM=
FILE=
TRACKNUMBER=
TRACKTITLE=
INDEX=


READ_TRACK=
READ_PERFORMER=
READ_TITLE=
READ_FROM=
READ_UNTIL=


## function accepts 2 arguments:
##   1) prefix to be trimmed from the line;
##   2) the line read from the cue file;
## performs following operations:
##   1) cuts the prefix from the beginning of the line,
##      including any whitespaces;
##   2) cuts all the trailing whitespaces;
##   3) if the remainder of the string starts with quotes
##      then everything outside quotes is dropped and the
##      content between the quotes is printed to stdout;
##   4) if the remainder of the string does NOT start with quotes
##      then only first part of the string, to first space,
##      is printed to stdout.
function sedTheLine {
  local prefix="$1"
  local line="$2"
  line="$( echo "$line" | sed -e "s/^ *${prefix} *//" -e 's/ *$//' )"
  if [[ $line == '"'* ]] ; then
    echo "$line" | sed -e 's/^"//' -e 's/".*$//'
  else
    echo "$line" | awk '{ print $1 }'
  fi
}

function resolveFile {
  local input="$1"
  case "${input,,}" in
    *'.wav')
      FILE="$input"
    ;;
    *'.flac')
      flac -d -f "$input" 1>/dev/null
      FILE="$( echo "$input" | sed 's/.flac$/.wav/' )"
    ;;
    *)
      FILE="$( echo "$input" | sed 's/\.[^\.]*$/.wav/' )"
      if [[ -f "$FILE" ]] ; then
        rm -f "$FILE"
      fi
      if ! ffmpeg -i "$input" "$FILE" </dev/null
      then
        echo 'ffmpeg failed to decode the input file into wav' >&2
        exit 1
      fi
    ;;
  esac
}

function cueTimeToFlacTime {
  local input="$1"
  local frame
  local fraction
  frame="$( echo "$input" | sed -e 's/^.*://' -e 's/^0//' )"
  fraction=$(( $frame * 4 / 3 ))
  if [[ $fraction -gt 99 ]] ; then
    fraction=99
  elif [[ $fraction -lt 10 ]] ; then
    fraction="0$fraction"
  fi
  echo "${input:0:5}.$fraction"
}

function validate {
  if [[ "$READ_TITLE" == *'"'* ]] || [[ "$READ_PERFORMER" == *'"'* ]] || [[ "$ALBUM" == *'"'* ]] ; then
    echo 'Some of the titles contain double quotes, that is not yet supported' >&2
    exit 1
  fi
}

function encodeTrack {

  validate

  local command='flac -f --best'
  ## dropping illegal filename characters from title:
  command="$command --output-name=\"$READ_TRACK - $( echo "$READ_TITLE" | tr -d "\`\!#\$%^&*{}<>;:?/'\"|=+\\\\" ).flac\""
  ## adding must-exist tags:
  command="$command --tag=TRACKNUMBER=\"$READ_TRACK\" --tag=ARTIST=\"$READ_PERFORMER\" --tag=PERFORMER=\"$READ_PERFORMER\" --tag=TITLE=\"$READ_TITLE\" --tag=ALBUM=\"$ALBUM\""
  ## checking and adding optional tags:
  if [[ -n "$GENRE" ]] ; then
    command="$command --tag=GENRE=\"$GENRE\""
  fi
  if [[ -n "$YEAR" ]] ; then
    command="$command --tag=DATE=\"$YEAR\""
  fi
  ## adding skip:
  command="$command --skip=\"$( cueTimeToFlacTime "$READ_FROM" )\""
  ## adding until if we have one:
  if [[ -n "$READ_UNTIL" ]] ; then
    command="$command --until=\"$( cueTimeToFlacTime "$READ_UNTIL" )\""
  fi
  ## adding input file:
  command="$command \"$FILE\""
  
  echo -n "executing: '$command'"
  eval "$command" 1>/dev/null
 
  READ_TRACK=''
  READ_TITLE=''
  READ_PERFORMER=''
  READ_FROM=''
  READ_UNTIL=''
}


while read -r cueline || [[ -n "$cueline" ]] ; do
  line="$( echo "$cueline" | tr -d '\r\n' )"
  if [[ -z $line ]] ; then
    continue
  fi
  case "$line" in
    'REM'*)
      case "$( echo "$line" | awk '{ print $2 }' )" in
        'GENRE')
          GENRE="$( sedTheLine 'REM *GENRE' "$line" )"
        ;;
        'DATE')
          YEAR="$( sedTheLine 'REM *DATE' "$line" )"
        ;;
      esac
    ;;
    'PERFORMER'*)
      PERFORMER="$( sedTheLine 'PERFORMER' "$line" )"
    ;;
    'TITLE'*)
      if [[ -z $TRACKNUMBER ]] ; then
        ALBUM="$( sedTheLine 'TITLE' "$line" )"
      else
        TRACKTITLE="$( sedTheLine 'TITLE' "$line" )"
      fi
    ;;
    'FILE'*)
      resolveFile "$( sedTheLine 'FILE' "$line" )"
    ;;
    'TRACK'*)
      TRACKNUMBER="$( sedTheLine 'TRACK' "$line" )"
    ;;
    'INDEX'*)
      case "$( echo "$line" | awk '{ print $2 }' )" in
        '00')
          if [[ -n "$READ_TITLE" ]] ; then
            READ_UNTIL="$( sedTheLine 'INDEX *00' "$line" )"
            encodeTrack
          fi
        ;;
        '01')
          if [[ -n "$READ_TITLE" ]] ; then
            READ_UNTIL="$( sedTheLine 'INDEX *01' "$line" )"
            encodeTrack
          fi
          READ_PERFORMER="$PERFORMER"
          READ_TITLE="$TRACKTITLE"
          READ_TRACK="$TRACKNUMBER"
          READ_FROM="$( sedTheLine 'INDEX *01' "$line" )"
        ;;
      esac
    ;;
  esac
done < "$CUE"

## one last track left to encode:
encodeTrack