mac: watch home dir via fsevents and set encoding attr and reveal extension for txt and rb files

ftff-events.rb

#!/usr/bin/ruby
# encoding: UTF-8

require 'rubygems'
require 'fsevent'
require 'shellwords'

class Time
  def age_in_seconds(now = Time.now)
    now - self
  end
end

class FTFFEvents < FSEvent
  WATCH_PATH       = ENV['HOME']
  WATCH_EXTENSIONS = %w[ txt rb ]
  ACTIONS          = %w[ set_enconding_xattr reveal_extension ]
  LATENCY          = 1.0
  CHANGE_HISTORY   = []

  def self.start
    new.start
  end

  def start
    self.latency = LATENCY
    self.watch_directories WATCH_PATH
    super
  end

  def on_change(directories)
    now = Time.now
    candidate_paths = directories.map { |d| Dir[File.join(d, "*.{#{WATCH_EXTENSIONS.join(',')}}")] }.flatten\
      .select { |path| File.file?(path) }\
      .select { |path| File.mtime(path).age_in_seconds(now) <= LATENCY * 2 }

    CHANGE_HISTORY.reject! { |path, time_of_change| time_of_change.age_in_seconds(now) > LATENCY * 2 }
    candidate_paths -= CHANGE_HISTORY.map(&:first)
    CHANGE_HISTORY.concat(candidate_paths.map { |path| [path, now] })

    return if candidate_paths.empty?
    ACTIONS.each { |m| send(m, candidate_paths) }
  end


  private

  def set_enconding_xattr(candidate_paths)
    target_paths = candidate_paths\
      .select { |path| `file -b --mime-encoding #{escape_args(path)}` =~ /ascii|utf-8/i }\
      .reject { |path| system("xattr -p com.apple.TextEncoding #{escape_args(path)} >/dev/null 2>&1") }

    system("xattr -w com.apple.TextEncoding 'UTF-8;134217984' #{escape_args(target_paths)}")
  end

  def reveal_extension(target_paths)
    system("/Developer/usr/bin/SetFile -a e #{escape_args(target_paths)}")
  end
  
  def escape_args(*a)
    a.flatten.map(&:shellescape).join(" ")
  end

end

FTFFEvents.start