#!/bin/bash

usage() {
        echo "usage: ${0} database target_directory"
        exit 127
}

database="${1}"
if [ -z "${database}" ]; then
        usage
fi

target_directory="${2}"
if [ -z "${target_directory}" ] || [ ! -d "${target_directory}" ]; then
        echo "target directory does not exist."
        exit 1
fi

jsfile="$( mktemp )"

cat << EOF > $jsfile
use ${database};
show collections;

EOF

collections=$( mongo --quiet "${database}" < $jsfile | tail -n+2 )
if [ "$?" != "0" ]; then
        echo "failed to get collections: $!"
        exit 1
fi

for collection in $collections; do
        mongoexport --db "${database}" --collection "${collection}" --out "${target_directory}/${collection}.json"
done