sudo=                       # empty is false, non-empty is true
editor=${EDITOR:-vi}

# prints a question and returns 0 (true) if the user said "y", 1 (false) otherwise
confirm()
{
    printf "%s? [y/n]" "$1" 1>&2
    if test -t 0 && test -t 2; then
        read -n 1
        printf "\n"
        case $REPLY in
        y|Y)
            return 0
            ;;
        n|N)
            return 1
            ;;
        *)
            printf "Expected y or n.  Saying n to be safe." 1>&2
            return 1
            ;;
        esac
    else
        printf "You are not on a terminal.  Saying n to be safe." 1>&2
        return 1
    fi
}

if test ! -w "$1"; then
    ls -l "$1"
    if test -t 0 && test -t 2; then
        if confirm "You don't have permission to edit $1.  Edit with sudo"; then
            sudo=true
        else
            printf "Canceling edit." 1>&2
            exit 1
        fi
    else
        printf "You don't have permission to edit %s.  Fix the permissions or run \"view\" instead." "$1" 1>&2
        exit 1
    fi
fi

${sudo:+sudo} "$editor" "$1"