autofocus

#!/bin/sh

TARGET=$1
if [ -z "${TARGET}" ]
then
    echo "Please give a target file."
    exit 1
fi
shift

ACTION=$1
if [ -z "${ACTION}" ]
then
    ACTION="ls"
else
    shift
fi

strikeGrep='^~.*~$'

strikeP () {
    echo "$@" | grep -q -E "${strikeGrep}"
}

trimEmptyLines () {
    sed -i "/^$/d" "$1"
}

case ${ACTION} in
    ls|show)
        i=0
        while read -r p; do
            echo "${i} - ${p}";
            i=$((i + 1))
        done <"${TARGET}"
        ;;
    add)
        echo "$@" >> "${TARGET}"
        ;;
    strike)
        targetLine=$1
        targetLine=$((targetLine + 1))
        echo "${targetLine}"
        lineText=$(sed "${targetLine}q;d" "${TARGET}")
        echo "${lineText}"
        if strikeP "${lineText}"
        then
            sed -i "${targetLine} s/^~\(.*\)~$/\1/" "${TARGET}"
        else
            sed -i "${targetLine} s/^.*$/~\0~/" "${TARGET}"
        fi
        ;;
    sink)
        strikeLines=$(grep -E "${strikeGrep}" "${TARGET}")
        noStrikeLines=$(grep -v -E "${strikeGrep}" "${TARGET}")
        echo "${noStrikeLines}" > "${TARGET}"
        echo "${strikeLines}" >> "${TARGET}"
        trimEmptyLines "${TARGET}"
        ;;
    *)
        echo "Unknown action"
        ;;
esac