#!/bin/sh

set -e
#set -x

INDIR=
OUTDIR=
PRESERVE_OUTPUT=0

error() {
    >&2 echo "error: $*"
}

warning() {
    >&2 echo "warning: $*"
}

die() {
    error "$*"
    exit 1
}

usage() {
    code="$1"
    [ -z "$code" ] && code=0
    cat <<EOF
usage: $PROGNAME [OPTIONS]

Options:
    -o  output directory
    -i  input directory
    -p  preserve output directory (don't clear it)
    -h  show this help
EOF
    exit "$code"
}

input_args() {
    [ -z "$1" ] && usage
    while [ $# -gt 0 ]; do
        case $1 in
            -o) OUTDIR="$2"; shift ;;
            -i) INDIR="$2"; shift ;;
            -p) PRESERVE_OUTPUT=1 ;;
            -h) usage ;;
            *) die "unexpected argument: $1" ;;
        esac
        shift
    done
}

check_args() {
    [ -z "$OUTDIR" ] && {
        error "output directory not specified"
        usage 1
    }
    [ -z "$INDIR" ] && {
        error "input directory not specified"
        usage 1
    }
    if [ ! -d "$OUTDIR" ]; then
        mkdir "$OUTDIR"
    elif [ "$PRESERVE_OUTPUT" -eq 0 ]; then
        find "$OUTDIR" -mindepth 1 -delete
    fi
}