require 'osx/foundation'
OSX.require_framework '/System/Library/Frameworks/CoreServices.framework/Frameworks/CarbonCore.framework'

module RSpactor
  # based on http://rails.aizatto.com/2007/11/28/taming-the-autotest-beast-with-fsevents/
  class Listener
    attr_reader :last_check, :callback, :valid_extensions

    def initialize(valid_extensions = nil)
      @valid_extensions = valid_extensions
      timestamp_checked

      @callback = lambda do |stream, ctx, num_events, paths, marks, event_ids|
        changed_files = extract_changed_files_from_paths(split_paths(paths, num_events))
        timestamp_checked
        yield changed_files unless changed_files.empty?
      end
    end

    def run(directories)
      dirs = Array(directories)
      stream = OSX::FSEventStreamCreate(OSX::KCFAllocatorDefault, callback, nil, dirs, OSX::KFSEventStreamEventIdSinceNow, 0.5, 0)
      unless stream
        $stderr.puts "Failed to create stream"
        exit(1)
      end

      OSX::FSEventStreamScheduleWithRunLoop(stream, OSX::CFRunLoopGetCurrent(), OSX::KCFRunLoopDefaultMode)
      unless OSX::FSEventStreamStart(stream)
        $stderr.puts "Failed to start stream"
        exit(1)
      end

      begin
        OSX::CFRunLoopRun()
      rescue Interrupt
        OSX::FSEventStreamStop(stream)
        OSX::FSEventStreamInvalidate(stream)
        OSX::FSEventStreamRelease(stream)
      end
    end

    def timestamp_checked
      @last_check = Time.now
    end

    def split_paths(paths, num_events)
      paths.regard_as('*')
      rpaths = []
      num_events.times { |i| rpaths << paths[i] }
      rpaths
    end

    def extract_changed_files_from_paths(paths)
      changed_files = []
      paths.each do |path|
        next if ignore_path?(path)
        Dir.glob(path + "*").each do |file|
          next if ignore_file?(file)
          changed_files << file if file_changed?(file)
        end
      end
      changed_files
    end

    def file_changed?(file)
      File.stat(file).mtime > last_check
    rescue Errno::ENOENT
      false
    end

    def ignore_path?(path)
      path =~ /(?:^|\/)\.(git|svn)/
    end

    def ignore_file?(file)
      File.basename(file).index('.') == 0 or not valid_extension?(file)
    end

    def file_extension(file)
      file =~ /\.(\w+)$/ and $1
    end

    def valid_extension?(file)
      valid_extensions.nil? or valid_extensions.include?(file_extension(file))
    end
  end
end