#!/bin/bash
# I, Ian Kelling, follow the GNU license recommendations at
# https://www.gnu.org/licenses/license-recommendations.en.html. They
# recommend that small programs, < 300 lines, be licensed under the
# Apache License 2.0. This file contains or is part of one or more small
# programs. If a small program grows beyond 300 lines, I plan to switch
# its license to GPL.

# Copyright 2024 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
--ifexists: add to path only if directory exists"
  local found x y ifexists end loop newpath
  ifexists=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" = --ifexists ]; then
          ifexists=true
        elif [ "$1" = --help ]; then
          echo "$help"
          return
        fi
        shift
        ;;
      *)
        loop=false
        ;;
    esac
  done
  # if we arent passed a PATH, just return 0 for convenience
  if ! test "$1"; then
    return 0
  fi
  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 ! $ifexists || [ -d "$x" ]; then
      if [ ! "$PATH" ]; then
        PATH="$x"
      elif $end; then
        PATH="$PATH:$x"
      else
        PATH="$x:$PATH"
      fi
    fi
  done
}