#!/usr/bin/env bash
set -euo pipefail
shopt -s dotglob
IFS=$'\n\t'

VERSION=2.0.1

VERBOSE=0
RECURSIVE=0
NOACTION=0
SYNC=1
FLAC_LEVEL=5 # Default FLAC compression level

SELF="$(readlink -f "$0")"
OPTS=$(getopt -o 012345678hnrsvV \
              -l best,fast,help,no-action,no-sync,recursive,verbose,version \
              -n reflac -- "$@")
TMPDIR="$(mktemp --tmpdir -d reflac.XXXXXXXXXX)"

eval set -- "$OPTS"

trap "exit 1" INT

cleanup()
{
    rmdir "$TMPDIR"
    exit "$1"
}

usage()
{
    cat <<EOF
‘reflac’ recompresses FLAC files while maintaining tags and file names.

Usage: reflac [OPTION]... [--] DIRECTORY...

 -h --help       Displays this help text
 -0 --fast       Use the fastest, but worst, compression possible.
 -1..-7          Adjust FLAC compression between these standard ranges.
                 The default is -5, the same as for flac itself.
 -8 --best       Use the slowest, but best, compression possible.
 -n --no-action  Do not recompress.  With --verbose, displays a list of
                 files that would be processed.
 -r --recursive  Recurse into directories.
 -s --no-sync    Do not synchronize file data.  Will return faster, with
                 the potential danger to lose your files in a system crash.
 -v --verbose    Increases the verbosity.  Use once to display the FLACs
                 currently being processed, use twice for the full ‘flac’
                 output.
 -V --version    Displays the version of this program

DIRECTORY should point ‘reflac’ to somewhere that contains *.flac
files. Optionally terminate the argument list with -- so that any
possible directory names don’t get misinterpreted as arguments.
EOF
    cleanup 0
}

recompress()
{
    for flac in *.flac; do
        if [ $VERBOSE -eq 1 ]; then
            echo "  $flac"
        fi

        if [ $NOACTION -eq 0 ]; then
            if [ $VERBOSE -gt 1 ]; then
                flac -$FLAC_LEVEL \
                     --output-name="${TMPDIR}/$(basename -- "$flac")" \
                     --verify -- \
                     "$flac"
            else
                flac --silent -$FLAC_LEVEL \
                     --output-name="${TMPDIR}/$(basename -- "$flac")" \
                     --verify -- \
                     "$flac"
            fi

            mv -f -- "$TMPDIR/$flac" "$flac.new"
            if [ $SYNC -eq 1 ]; then
                sync "$flac.new"
                mv -f "$flac.new" "$flac"
                sync "$flac"
            else
                mv -f "$flac.new" "$flac"
            fi
        fi
    done
}

while true ; do
    case "$1" in
        -0|-1|-2|-3|-4|-5|-6|-7|-8)
            FLAC_LEVEL=${1#-}
            shift ;;
        --fast)
            FLAC_LEVEL=0
            shift ;;
        --best)
            FLAC_LEVEL=8
            shift ;;
        -h|--help)
            usage ;;
        -n|--no-action)
            NOACTION=1
            shift ;;
        -r|--recursive)
            RECURSIVE=1
            shift ;;
        -s|--no-sync)
            SYNC=0
            shift ;;
        -v|--verbose)
            VERBOSE=$((VERBOSE+1))
            shift ;;
        -V|--version)
            echo "reflac version $VERSION"
            cleanup 0 ;;
        --) shift; break ;;
        *) echo "$0: This should never happen!" >&2; cleanup 1 ;;
    esac
done

if [ -z "$*" ]; then
    usage
fi

if [ $VERBOSE -eq 0 ] && [ $NOACTION -eq 1 ]; then
    cleanup 0
fi

for dir; do
    REFLAC_OPTS="${FLAC_LEVEL}"

    if [ $SYNC -eq 0 ]; then
        REFLAC_OPTS="${REFLAC_OPTS}s"
    fi

    if [ $RECURSIVE -eq 1 ] && [ $NOACTION -eq 1 ]; then
        find "$(readlink -f -- "$dir")" -type d -execdir "$SELF" -nv {} \;
    elif [ $RECURSIVE -eq 1 ]; then
        if [ $VERBOSE -eq 1 ]; then
            find "$(readlink -f -- "$dir")" -type d \
                 -execdir "$SELF" -v"$REFLAC_OPTS" {} \;
        elif [ $VERBOSE -ge 2 ]; then
            find "$(readlink -f -- "$dir")" -type d \
                 -execdir "$SELF" -vv"$REFLAC_OPTS" {} \;
        else
            find "$(readlink -f -- "$dir")" -type d \
                 -execdir "$SELF" -"$REFLAC_OPTS" {} \;
        fi
    else
        pushd -- "$dir" >/dev/null || cleanup $?
        if [ $VERBOSE -gt 0 ]; then readlink -f .; fi
        if [ -n "$(ls -- *.flac 2>/dev/null)" ]; then
            recompress
        fi
        popd >/dev/null
    fi
done

rmdir "$TMPDIR"