require 'rbconfig'

module Guard
  
  autoload :Darwin,  'guard/listeners/darwin'
  autoload :Linux,   'guard/listeners/linux'
  autoload :Polling, 'guard/listeners/polling'
  
  class Listener
    attr_accessor :last_event, :changed_files
    
    def self.select_and_init
      if mac? && Darwin.usable?
        Darwin.new
      elsif linux? && Linux.usable?
        Linux.new
      else
        UI.info "Using polling (Please help us to support your system better than that.)"
        Polling.new
      end
    end
    
    def initialize
      @changed_files = []
      update_last_event
    end
    
    def get_and_clear_changed_files
      files = changed_files.dup
      changed_files.clear
      files.uniq
    end
    
  private
    
    def find_changed_files(dirs, options = {})
      files = potentially_changed_files(dirs, options).select { |path| File.file?(path) && changed_file?(path) }
      files.map! { |file| file.gsub("#{Dir.pwd}/", '') }
    end
    
    def potentially_changed_files(dirs, options = {})
      match = options[:all] ? "**/*" : "*"
      Dir.glob(dirs.map { |dir| "#{dir}#{match}" })
    end
    
    def changed_file?(file)
      File.mtime(file) >= last_event
    rescue
      false
    end
    
    def update_last_event
      @last_event = Time.now
    end
    
    def self.mac?
      Config::CONFIG['target_os'] =~ /darwin/i
    end
    
    def self.linux?
      Config::CONFIG['target_os'] =~ /linux/i
    end
    
  end
end