#!/bin/bash
# Copyright (C) 2014 Ian Kelling
# This program is under GPL v. 3 or later, see <http://www.gnu.org/licenses/>

lnf() {
    local help="lnf - Create symlinks conveniently and forcefully.
Usage:
       lnf -T TARGET LINK_NAME     (1st form)
       lnf TARGET                  (2nd form)
       lnf TARGET... DIRECTORY     (3rd form)

Remove existing file in the using trash-put or rm -rf if it is not available.
Create directory if needed. Slightly more restrictive arguments than ln.

In the 1st form, create a link to TARGET with the name LINK_NAME.  In the 2nd
form, create a link to TARGET in the current directory.  In the 3rd form, create
links to each TARGET in DIRECTORY."
    
    if [[ $1 == --help || $# -eq 0 ]]; then
        echo "$help"
        return 0
    fi

    local nodir
    if [[ $1 == -T ]]; then
        nodir=-T
        shift
        if (( $# != 2 )); then
            echo "lnf error: expected 2 arguments with -T flag. Got $#"
            return 1
        fi
    fi
    
    local reset_extglob=false
    ! shopt extglob >/dev/null && reset_extglob=true
    shopt -s extglob

    
    local remove x
    if type -P trash-put >/dev/null; then
        remove=trash-put
    else
        remove="rm -rf"
    fi
    
    if [[ $nodir ]]; then
        if [[ -e "$2" || -L "$2" ]]; then
            $remove "$2"
        elif ! mkdir -p "$(dirname "$2")"; then
            echo "lnf error: failed to make directory $(dirname "$2")"
            return 1
        fi
    elif (( $# >= 2 )); then
        if [[ -d ${!#} ]]; then
            local oldcwd=$PWD
            cd "${!#}" # last arg
            for x in "${@:1:$(( $# - 1 ))}"; do # all but last arg
                # remove any trailing slashes, uses extglob
                x="${x%%+(/)}"
                # remove any leading directory components
                x="${x##*/}"
                [[ -e "$x" || -L "$x" ]] && $remove "$x"
            done
            cd "$oldcwd"
        else
            if ! mkdir -p "${!#}"; then
                echo "lnf error: failed to make directory ${!#}"
                return 1
            fi
        fi
    elif  [[ $# -eq 1 ]]; then
        [[ -e "${1##*/}" || -L "${1##*/}" ]] && $remove "${1##*/}"
    fi

    $reset_extglob && shopt -u extglob 
    ln -s $nodir -- "$@"
}