#!/usr/bin/ruby

# This script watches modifications on the given directory, using the new # FSEvents API in Leopard.

require 'osx/foundation'
OSX.require_framework '/System/Library/Frameworks/CoreServices.framework/Frameworks/CarbonCore.framework'
include OSX
require 'set'
require 'optparse'
require 'ostruct'

$COMMAND = File.basename($0)
$USAGE = "Usage: #{$COMMAND} [OPTIONS] <command> [<args> ...]"
def die(s)
  $stderr.puts s
  exit 1
end

options = OpenStruct.new
options.directoriesOnly = false
options.outputFile = "-"

opts = OptionParser.new do |opts|
  opts.banner = $USAGE
  opts.separator ""
  opts.separator "Specific options:"

  opts.on("-d", "--dir-only", "Only display directories") do
    options.directoriesOnly = true
  end
  
  opts.on("-o", "--output FILE", "Write output to a file") do |fileName|
    options.outputFile = fileName
  end
  
  opts.on_tail("-h", "--help", "Show this message") do
    puts opts
    exit
  end
end
opts.parse!(ARGV)

die $USAGE unless ARGV.size >= 1

if options.outputFile == "-"
  outputHandle = $stdout.clone
else
  outputHandle = File.open(options.outputFile, "w")
end

path = "/"

startId = FSEventsGetCurrentEventId()
# Used to compare with mtime, which only has second accuracy
startTime = Time.now.to_i

fork do
  begin
    exec(*ARGV)
  rescue SystemCallError  => e
    puts e.message
    exit 127
  end
end
pid = Process.wait
returnCode = $? >> 8

sleep(0.1)

allPaths = Set.new

fsevents_cb = proc do |stream, ctx, numEvents, paths, marks, eventIDs|
  paths.regard_as('*')
  numEvents.times do |n|
    allPaths.add(paths[n])
  end
end

stream = FSEventStreamCreate(
  KCFAllocatorDefault,
  fsevents_cb,
  nil,
  [path],
  startId,
  1.0,
  KFSEventStreamCreateFlagNoDefer)

die "Failed to create the FSEventStream" unless stream

FSEventStreamScheduleWithRunLoop(
  stream,
  CFRunLoopGetCurrent(),
  KCFRunLoopDefaultMode)

ok = FSEventStreamStart(stream)
die "Failed to start the FSEventStream" unless ok

FSEventStreamFlushSync(stream)
allPaths.sort.each do |path|
  if File.exists?(path)
    outputHandle.puts path
    if (!options.directoriesOnly)
      Dir.foreach(path) do |file|
        fullPath = File.join(path, file)
        stat = File.stat(fullPath)
        if (stat.mtime.to_i >= startTime)
          outputHandle.puts "  #{file}"
        end
      end
    end
  else
    outputHandle.puts "#{path} !"
  end
end

FSEventStreamStop(stream)
FSEventStreamInvalidate(stream)
FSEventStreamRelease(stream)


outputHandle.flush

exit(returnCode)