#!/bin/bash
# Copyright (C) 2016 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# avoiding bashisms so it can be used in edge cases where I don't have bash,
# however, I'm not super confident that I've avoided them all
#
path_add() {
    local help="usage: path_add [options] PATH
--help:     print this
--end:      adds to end of path, which will give it lowest priority
--force:    add to path even if directory does not exist"
    local found x y z ifexists end loop newpath
    force=false
    end=false
    loop=true
    # portable substring matching is ugly http://mywiki.wooledge.org/BashFAQ/041
    while $loop; do
        case $1 in
            --*)
                if [ "$1" = --end ]; then
                    end=true
                elif [ "$1" = --force ]; then
                    force=true
                elif [ "$1" = --help ]; then
                    echo "$help"
                    return
                fi
                shift
                ;;
            *)
                loop=false
                ;;
        esac
    done
    IFS=:
    # build up the path without the components we want to add
    for y in $PATH; do
        for x in "$@"; do
            if [ "$x" = "$y" ]; then
                found=true
            else
                found=false
            fi
        done
        if ! $found; then
            if [ ! "$newpath" ]; then
                newpath="$y"
            else
                newpath="$newpath:$y"
            fi
        fi
    done

    unset IFS
    PATH="$newpath"
    for x in "$@"; do
        if $force || [ -d "$x" ]; then
            if [ ! "$PATH" ]; then
                PATH="$x"
            elif $end; then
                PATH="$PATH:$x"
            else
                PATH="$x:$PATH"
            fi
        fi
    done
}