autotask.rb

#!/usr/bin/env ruby

require 'rake'

module FileWatchHandler
  def execute
    EM.stop_event_loop
  end
  alias :file_modified :execute
  alias :file_moved :execute
  alias :file_deleted :execute
end

def autotask(*args)
  def resolve_dependency(tasknames)
    files = []
    tasks = []
    tasknames.each do |taskname|
      if Rake::Task.task_defined?(taskname)
        task = Rake::Task[taskname]
        files << task.name if task.is_a? Rake::FileTask
        tasks << task.name
        dep_files, dep_tasks = resolve_dependency(task.prerequisites)
        files += dep_files
        tasks += dep_tasks
      else
        files << taskname
      end
    end
    return files, tasks
  end

  fail "Task Argument Error" if args.size != 1
  hash = args.pop
  fail "Task Argument Error" if hash.size != 1
  key, value = hash.map { |k, v| [k,v] }.first

  require 'eventmachine'
  EM.kqueue = true if EM.kqueue?

  value = [value] if !value.is_a?(Array)
  task key => value do
    loop do
      files, tasks = resolve_dependency(value)
      EM.run do
        files.each {|v| EM.watch_file(v, FileWatchHandler)}
      end
      tasks.each do |taskname|
        Rake::Task[taskname].reenable
      end
      value.each do |taskname|
        Rake::Task[taskname].invoke
      end
    end
  end
end