rbfu

#!/usr/bin/env bash

# Useful methods. \o/
#
set_variable () { export $1="$2"; }
unset_variable () { unset $1; }

path_append ()  { path_remove $1; set_variable PATH "$PATH:$1"; }
path_prepend () { path_remove $1; set_variable PATH "$1:$PATH"; }
path_remove ()  { set_variable PATH `echo $PATH | awk -v RS=: -v ORS=: '$0 != "'$1'"' | sed 's/:$//'`; }

command_exists () { type "$1" &> /dev/null; }

warn () { echo -e "$1" >&2; }
info () { warn "$1"; }

deactivate_previous_ruby_version () {
  if [ $RBFU_RUBY_VERSION ]; then
    path_remove "$RUBIES_ROOT/$RBFU_RUBY_VERSION/bin"
    path_remove "$RUBIES_ROOT/$RBFU_RUBY_VERSION/lib/ruby/gems/bin"
    unset_variable GEM_PATH
    unset_variable GEM_HOME
    unset_variable RBFU_RUBY_VERSION
  fi
}

_rbfu_activate () {
  local VERSION COMMAND MSG SOURCE
  local RBFU_ROOT="$HOME/.rbfu"
  local RUBIES_ROOT="$RBFU_ROOT/rubies"

  # Run-time configuration
  #
  if [[ $1 =~ ^@ ]]; then
    VERSION=$1; shift
    VERSION=${VERSION:1}
  fi
  COMMAND="$@"
  SOURCE="from command line"

  # fall back to $PWD/.rbfu-version and $HOME/.rbfu-version if no version is given
  read_version_from_file () { if [ -f "$1" ]; then SOURCE="from $1"; VERSION=`head -n 1 $1`; fi; }
  [ -n "$VERSION" ] || read_version_from_file "$PWD/.rbfu-version"
  [ -n "$VERSION" ] || read_version_from_file "$PWD/.ruby-version"
  [ -n "$VERSION" ] || read_version_from_file "$HOME/.rbfu-version"
  [ -n "$VERSION" ] || read_version_from_file "$HOME/.ruby-version"

  # sanity checks
  [ ! "$VERSION" ] && warn "Please specify the Ruby version to activate." && return

  if [[ "$VERSION" == "system" ]]; then
    deactivate_previous_ruby_version
    MSG="Activated system Ruby."
  else
    # additional sanity checks
    RUBY_ROOT="$RUBIES_ROOT/$VERSION"
    if [ ! -e $RUBY_ROOT ]; then
      warn "Ruby $VERSION was requested, but is not installed. ($SOURCE)"
      warn "If you have ruby-build installed, you can install the requested version like this:"
      warn "\nruby-build $VERSION \$HOME/.rbfu/rubies/$VERSION"
      return 1
    fi

    deactivate_previous_ruby_version

    # activate requested version
    path_prepend "$RUBY_ROOT/lib/ruby/gems/bin"
    path_prepend "$RUBY_ROOT/bin"
    set_variable "RBFU_RUBY_VERSION" "$VERSION"
    set_variable "GEM_PATH" "$RUBY_ROOT/lib/ruby/gems"
    set_variable "GEM_HOME" "$RUBY_ROOT/lib/ruby/gems"

    MSG="Activated Ruby $RBFU_RUBY_VERSION."
  fi

  info "$MSG ($SOURCE)"

  # execute command, if given
  [ -n "$COMMAND" ] && eval $COMMAND
}


# check for our favorite command line options!
#
if [ "$1" = "--help" ]; then
  cat <<EOD
rbfu [@<version>] [command]
EOD
  exit 0

# initialization code (run from shell startup script)
#
elif [ "$1" = "--init" ]; then
  cat <<EOD
alias rbfu-env="source rbfu"

# enable tab completion for bash and zsh
if command -v complete >/dev/null 2>&1; then
  _rbfu_complete_version() {
    if [ -d "$HOME/.rbfu/rubies" ]; then
      cur="\${COMP_WORDS[COMP_CWORD]}"
      opts=\$(\\ls -1 $HOME/.rbfu/rubies | sed -e "s/^/@/")

      if [[ \$COMP_CWORD == 1 ]]; then
        COMPREPLY=( \$(compgen -W "\${opts} @system" -- \${cur}) )
        return 0
      fi
    fi
  }
  complete -o nospace -F _rbfu_complete_version rbfu
  complete -o nospace -F _rbfu_complete_version rbfu-env

elif command -v compdef >/dev/null 2>&1; then
  _rbfu() {
    local curcontext="\$curcontext" state line _rubies ret=1
    _arguments -w -S '(-)--help[show usage and exit]: :->noargs' '1: :->versions' '*::: :->args' && ret=0

    case \$state in
      versions)
        _rubies=( \$(\\ls -1 "$HOME/.rbfu/rubies" 2>/dev/null | sed -e "s/^/@/") "@system" )
        _values 'rubies' \$_rubies && ret=0
        ;;
      args)
        _normal && ret=0
        ;;
    esac
    return \$ret
  }
  compdef _rbfu rbfu rbfu-env
fi
EOD

  # optional automatic mode
  #
  if [ "$2" = "--auto" ]; then
    cat <<EOD
function _rbfu_auto() {
  ([ -f "\$PWD/.rbfu-version" ] || [ -f "\$PWD/.ruby-version" ]) && source rbfu true
  return 0
}

if [ -n "\$ZSH_VERSION" ]; then
  chpwd_functions=(\${chpwd_functions[@]} "_rbfu_auto")
else
  function cd() {
    builtin cd "\$@" && _rbfu_auto
  }
fi
_rbfu_auto
EOD
  fi

  exit 0

# normal operation
#
else
  _rbfu_activate $@
fi