require 'rbconfig'

module Guard

  autoload :Darwin,  'guard/listeners/darwin'
  autoload :Linux,   'guard/listeners/linux'
  autoload :Windows, 'guard/listeners/windows'
  autoload :Polling, 'guard/listeners/polling'

  class Listener
    attr_reader :last_event

    def self.select_and_init
      if mac? && Darwin.usable?
        Darwin.new
      elsif linux? && Linux.usable?
        Linux.new
      elsif windows? && Windows.usable?
        Windows.new
      else
        UI.info "Using polling (Please help us to support your system better than that.)"
        Polling.new
      end
    end

    def initialize
      update_last_event
    end

    def update_last_event
      @last_event = Time.now
    end

    def modified_files(dirs, options = {})
      files = potentially_modified_files(dirs, options).select { |path| File.file?(path) && recent_file?(path) }
      files.map! { |file| file.gsub("#{Dir.pwd}/", '') }
    end

  private

    def potentially_modified_files(dirs, options = {})
      match = options[:all] ? "**/*" : "*"
      Dir.glob(dirs.map { |dir| "#{dir}#{match}" })
    end

    def recent_file?(file)
      File.mtime(file) >= last_event
    rescue
      false
    end

    def self.mac?
      Config::CONFIG['target_os'] =~ /darwin/i
    end

    def self.linux?
      Config::CONFIG['target_os'] =~ /linux/i
    end

    def self.windows?
      Config::CONFIG['target_os'] =~ /mswin|mingw/i
    end

  end
end