#! /bin/bash

set -e
: ${JBDIR=/mnt/jb}

zero_start=0 trim_end=0 offset=0
while getopts flF:L:o:b:a: opt; do
  case "$opt" in
    f) zero_start=$((588 * 5 - 1)) ;;
    l) trim_end=$((588 * 5)) ;;
    F) zero_start=$OPTARG ;;
    L) trim_end=$OPTARG ;;
    o) offset=$OPTARG ;;
    b) before=$OPTARG ;;
    a) after=$OPTARG ;;
    *) exit 1 ;;
  esac
done

shift $((OPTIND - 1))
case $# in
  1) ;;
  *) echo >&2 "missing file argument" ;;
esac
file=$1

len=$(metaflac --show-total-samples "$file")

if ((offset < 0)); then
  start=0
  stop=$((stop + offset))
elif ((offset >= 0)); then
  start=$offset
  stop=$len
fi

{
  if ((offset < 0)); then
    if [ "${before+set}" ]; then
      n=$(metaflac --show-total-samples "$before")
      flac -d -s -o- --force-raw-format --sign=signed --endian=little \
	--skip=$((n + offset)) --until=$n \
	"$before"
    else
      $JBDIR/bin/cat-prefix $((4 * -offset)) </dev/zero
    fi
  fi

  flac -d -s -o- --force-raw-format --sign=signed --endian=little \
    --skip=$start --until=$stop \
    "$file"

  if ((offset > 0)); then
    if [ "${after+set}" ]; then
      flac -d -s -o- --force-raw-format --sign=signed --endian=little \
	--skip=0 --until=$offset \
	"$after"
    else
      $JBDIR/bin/cat-prefix $((4 * offset)) </dev/zero
    fi
  fi
} | {
  if ((zero_start > 0)); then
    $JBDIR/bin/cat-prefix $((4 * zero_start)) </dev/zero
    $JBDIR/bin/cat-prefix $((4 * zero_start)) >/dev/null
    len=$((len - zero_start))
  fi
  if ((trim_end > 0)); then
    $JBDIR/bin/cat-prefix $((4 * (len - trim_end)))
    $JBDIR/bin/cat-prefix $((4 * trim_end)) </dev/zero
    cat >/dev/null
  else
    cat
  fi
}