todo

#!/bin/sh

# todo: minimal command-line todo list.
#       this is actually a reimplementation of an hello world program I wrote in
#       go and in c before, but i figured a shell script is more than enough for
#       my needs. highly inspired by https://github.com/sjl/t

list="$HOME/.todo"

trim() {
        echo "$@" | awk '{
            for (i = 1; i <= NF; i++) {
                gsub(/^[[:space:]]+|[[:space:]]+$/, "", $i);
                printf "%s%s", $i, (i == NF ? "" : OFS);
            }
        }'
}

validate() {
        echo "$@" | awk '{
            for (i = 1; i <= NF; i++)
                if ($i !~ /^[0-9]+$/ || $i <= 0)
                    exit 1;
        }'
}

die() {
        echo "error:" "$@" >&2
        exit 1
}

[ -f "$list" ] || touch "$list"

case "$1" in
"-h" | "--help")
        echo "usage: todo [-x|-e|-n] [id...] [-|desc...]"
        ;;
"")
        awk '{ printf "%2d ", NR; print }' "$list"
        ;;
"-x")
        shift
        ids="$(trim "$@")"
        # shellcheck disable=SC2015
        [ -n "$ids" ] && validate "$ids" || die "invalid or missing todo id(s)"
        sed -n "$(echo "$ids" | sed -e 's/[[:space:]]\+/p;/g' -e 's/$/p;/')" "$list" >> "$list.x"
        tail "$list.x" > "$list.x.$$.tmp" && mv "$list.x.$$.tmp" "$(readlink -f "$list.x")"
        sed "$(echo "$ids" | sed -e 's/[[:space:]]\+/d;/g' -e 's/$/d;/')" "$list" > "$list.$$.tmp" && mv "$list.$$.tmp" "$(readlink -f "$list")"
        ;;
"-e")
        id="$(trim "$2")"
        validate "$id" || die "invalid todo id"
        vim "+$id" "$list" # +[num] is vim specific, that's why the editor is hardcoded here.
        ;;
"-n")
        shift
        ids="$(trim "$@")"
        validate "$ids" || die "invalid todo id(s)"
        sed -n "$(echo "$ids" | sed -e 's/[[:space:]]\+/p;/g' -e 's/$/p;/')" "$list"
        ;;
"-")
        cat >> "$list"
        ;;
*)
        echo "$@" >> "$list"
        ;;
esac