#
# Whimsy pubsub support: watches for updates to the whimsy repository,
# fetches the changes and deploys them.
#
# For usage instructions, try
#
#   ruby pubsub.rb --help
#

require 'optparse'
require 'ostruct'
require 'etc'
require 'net/http'
require 'json'
require 'fileutils'

# extract script name
script = File.basename(__FILE__, '.rb')

#
### option parsing
#

options = OpenStruct.new
options.remote = 'https://gitbox.apache.org/repos/asf/whimsy.git'
options.local = '/srv/whimsy'
options.pidfile = "/var/run/#{script}.pid"
options.streamURL = 'http://pubsub.apache.org:2069/git/'
options.puppet = false

optionparser = OptionParser.new do |opts|
  opts.on '-u', '--user id', "Optional user to run #{script} as" do |user|
    options.user = user
  end

  opts.on '-g', '--group id', "Optional group to run #{script} as" do |group|
    options.group = group
  end

  opts.on '-p', '--pidfile path', "Optional pid file location" do |path|
    options.pidfile = path
  end

  opts.on '-d', '--daemonize', "Run as daemon" do
    options.daemonize = true
  end

  opts.on '--puppet', "Use puppet agent to update" do
    options.puppet = true
  end

  opts.on '-s', '--stream', "StreamURL" do |url|
    options.streamURL = url
  end

  opts.on '-r', '--remote', "Git Clone URL" do |url|
    options.streamURL = url
  end

  opts.on '-c', '--clone', "Git Clone Directory" do |path|
    options.local = path
  end

  opts.on '--stop', "Kill the currently running #{script} process" do
    options.kill = true
  end
end

optionparser.parse!

# Check for required tools

if options.puppet and `which puppet 2>/dev/null`.empty?
  STDERR.puts 'puppet not found in path; exiting'
  exit 1
end

%w(git rake).each do |tool|
  if `which #{tool} 2>/dev/null`.empty?
    STDERR.puts "#{tool} not found in path; exiting"
    exit 1
  end
end

#
### process management
#

# Either kill old process, or start a new one
if options.kill
  if File.exist? options.pidfile
    Process.kill 'TERM', File.read(options.pidfile).to_i
    File.delete options.pidfile if File.exist? options.pidfile
    exit 0
  end
else
  # optionally daemonize
  Process.daemon if options.daemonize

  # Determine if pidfile is writable
  if File.exist? options.pidfile
    writable = File.writable? options.pidfile
  else
    writable = File.writable? File.dirname(options.pidfile)
  end

  # PID file management
  if writable
    File.write options.pidfile, Process.pid.to_s
    at_exit { File.delete options.pidfile if File.exist? options.pidfile }
  else
    STDERR.puts "EACCES: Skipping creation of pidfile #{options.pidfile}"
  end
end

# Optionally change user/group
if Process.uid == 0
  Process::Sys.setgid Etc.getgrnam(options.group).gid if options.group
  Process::Sys.setuid Etc.getpwnam(options.user).uid if options.user
end

# Perform initial clone
if not Dir.exist? options.local
  FileUtils.mkdir_p File.basename(options.local)
  system('git', 'clone', options.remote, options.local)
end

#
# Monitor PubSub endpoint (see https://infra.apache.org/pypubsub.html)
#

PROJECT = File.basename(options.remote, '.git')

# prime the pump
restartable = false
notification_queue = Queue.new
notification_queue.push 'project' => PROJECT

ps_thread = Thread.new do
  begin
    uri = URI.parse(options.streamURL)

    Net::HTTP.start(uri.host, uri.port) do |http|
      request = Net::HTTP::Get.new uri.request_uri

      http.request request do |response|
        body = ''
        response.read_body do |chunk|
          # Looks like the service only sends \n terminators now
          if chunk =~ /\r?\n$|\0$/
            notification = JSON.parse(body + chunk.chomp("\0"))
            body = ''

            if notification['stillalive']
              restartable = true
            elsif notification['push']
              notification_queue << notification['push']
            elsif notification['commit']
              notification_queue << notification['commit']
            elsif notification['svnpubsub']
              next
            else
              STDERR.puts '*** unexpected notification ***'
              STDERR.puts notification.inspect
            end
          else
            body += chunk
          end
        end
      end
    end
  rescue Errno::ECONNREFUSED => e
    restartable = true
    STDERR.puts e
    sleep 3
  rescue Exception => e
    STDERR.puts e
    STDERR.puts e.backtrace
  end
end

#
# Process queued requests
#

begin
  mtime = File.mtime(__FILE__)
  while ps_thread.alive?
    notification = notification_queue.pop
    next unless notification['project'] == PROJECT
    notification_queue.clear

    if options.puppet
      # Update using puppet.  If puppet fails, it may be due to puppet already
      # running; in which case it may not have picked up this update.  So try
      # again in 30, 60, 90, and 120 seconds, for a total of five minutes.
      4.times do |i|
        break if system('puppet', 'agent', '-t')
        sleep 30 * (i+1)
      end
    else
      # update git directories in the foreground
      Dir.chdir(options.local) do
        before = `git log --oneline -1`
        system('git', 'fetch', 'origin')
        system('git', 'clean', '-df')
        system('git', 'reset', '--hard', 'origin/master')
        if File.exist? 'Rakefile' and `git log --oneline -1` != before
          system('rake', 'update')
        end
      end
    end
    break if mtime != File.mtime(__FILE__)
  end
rescue SignalException => e
  STDERR.puts e
  restartable = false
rescue Exception => e
  if ps_thread.alive?
    STDERR.puts e
    STDERR.puts e.backtrace
    restartable = false
  end
end

#
# restart
#

if restartable
  STDERR.puts 'restarting'

  # relaunch script after a one second delay
  sleep 1
  exec RbConfig.ruby, __FILE__, *ARGV
end