json formater in posix shell and just sed command

jq-lite.sh

#!/bin/sh
i=0
sed  \
"
s/^ *//g
s/^\t*//g
s/,/,\n/g
s/{/\n&\n/g
s/}/\n&/g
s/\[/&\n/g
s/\]/\n&\n/g
" |while read line ; do
    case "$line" in
        "{")
            i=$(expr $i + 1)
            ;;
    esac
    if [ $i -gt 1 ] ; then
        j=0
        while [ $j -lt $i ] ; do
            echo -n "  "
            j=$(expr $j + 1)
        done
    fi
    case "$line" in
        "}")
            i=$(expr $i - 1)
            ;;
    esac
    echo $line
done | sed "/^$/d"