#!/bin/bash

# Remove all occurrences of $1 from the path on stdin, and add
# it to the front.
function move_to_front {
    # First, give each element its own leading and trailing colon:
    # foo:bar -> :foo::bar:.  Then remove all instances of $1, add one
    # to the front, and put back in normal path form.
    sed \
        -e "s|:|::|g" \
        -e "s|..*|:&:|" \
        -e "s|:$1:||g" \
        -e "s|^|:$1:|" \
        -e "s|^:||" \
        -e "s|:$||" \
        -e "s|::*|:|g"
}

# Remove all occurrences of $1 from the path on stdin, and add
# it to the end.
function move_to_back {
    sed \
        -e "s|:|::|g" \
        -e "s|..*|:&:|" \
        -e "s|:$1:||g" \
        -e "s|\$|:$1:|" \
        -e "s|^:||" \
        -e "s|:$||" \
        -e "s|::*|:|g"
}

function prepend {
    eval "export $1=\"\$(echo \"\$$1\" | move_to_front '$2')\""
}

function postpend {
  eval "export $1=\"\$(echo \"\$$1\" | move_to_back '$2')\""
}

function prepend-if-dir {
  if [ -d $2 ]; then
    prepend $1 $2
  fi
}

function postpend-if-dir {
  if [ -d $2 ]; then
    postpend $1 $2
  fi
}

function add-path {
  prepend-if-dir PATH $1
}

function add-path-after {
  postpend-if-dir PATH $1
}

function add-bin-man {
    prepend-if-dir PATH $1/bin
    prepend-if-dir INFOPATH $1/info
    prepend-if-dir LD_LIBRARY_PATH $1/lib

    # You might think we should set MANPATH here too, but Linux man
    # automatically checks for a 'man' subdirectory associated with
    # each directory in PATH, so we don't need to do the equivalent
    # here.  And setting MANPATH at all overrides that automatically
    # generated search list; since MANPATH is initially unset, but
    # PATH isn't, setting MANPATH can actually *reduce* the set of
    # directories man will search.
}

function add-bin-man-after {
    postpend-if-dir PATH $1/bin
    postpend-if-dir INFOPATH $1/info
    postpend-if-dir LD_LIBRARY_PATH $1/lib
}  

function add-library-path {
  case ":$LD_LIBRARY_PATH:" in
    *":$1:"* ) ;;
    * )
      if [ -d $1 ]; then
        postpend LD_LIBRARY_PATH $1 
      fi
    ;;
  esac
}