#  Phusion Passenger - http://www.modrails.com/
#  Copyright (C) 2008  Phusion
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; version 2 of the License.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License along
#  with this program; if not, write to the Free Software Foundation, Inc.,
#  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
require 'rubygems'
require 'socket'
require 'etc'
require 'passenger/abstract_server'
require 'passenger/application'
require 'passenger/utils'
require 'passenger/request_handler'
 
begin
  # Preload MySQL if possible. We want to preload it and we need
  # its exception classes.
  require 'mysql'
rescue LoadError
end
begin
  # Preload SQLite 3 if possible. Rails 2.0 apps use it by default.
  require 'sqlite3'
rescue LoadError
end
 
module Passenger
 
# An abstract base class for AppInitError and FrameworkInitError. This represents
# the failure when initializing something.
class InitializationError < StandardError
  # The exception that caused initialization to fail. This may be nil.
  attr_accessor :child_exception
 
  # Create a new InitializationError. +message+ is the error message,
  # and +child_exception+ is the exception that caused initialization
  # to fail.
  def initialize(message, child_exception = nil)
    super(message)
    @child_exception = child_exception
  end
end
 
# Raised when ApplicationSpawner, FrameworkSpawner or SpawnManager was unable
# spawn a Ruby on Rails application, because the application either threw an
# exception or called exit.
#
# If the +child_exception+ attribute is nil, then it means that the application
# called exit.
class AppInitError < InitializationError
end
 
# This class is capable of spawns instances of a single Ruby on Rails application.
# It does so by preloading as much of the application's code as possible, then creating
# instances of the application using what is already preloaded. This makes it spawning
# application instances very fast, except for the first spawn.
#
# Use multiple instances of ApplicationSpawner if you need to spawn multiple different
# Ruby on Rails applications.
#
# *Note*: ApplicationSpawner may only be started asynchronously with AbstractServer#start.
# Starting it synchronously with AbstractServer#start_synchronously has not been tested.
class ApplicationSpawner < AbstractServer
  include Utils
  
  # This exception means that the ApplicationSpawner server process exited unexpectedly.
  class Error < AbstractServer::ServerError
  end
  
  # The user ID of the root user.
  ROOT_UID = 0
  # The group ID of the root user.
  ROOT_GID = 0
  
  # An attribute, used internally. This should not be used outside Passenger.
  attr_accessor :time
  # The application root of this spawner.
  attr_reader :app_root
 
  # +app_root+ is the root directory of this application, i.e. the directory
  # that contains 'app/', 'public/', etc. If given an invalid directory,
  # or a directory that doesn't appear to be a Rails application root directory,
  # then an ArgumentError will be raised.
  #
  # If +lower_privilege+ is true, then ApplicationSpawner will attempt to
  # switch to the user who owns the application's <tt>config/environment.rb</tt>,
  # and to the default group of that user.
  #
  # If that user doesn't exist on the system, or if that user is root,
  # then ApplicationSpawner will attempt to switch to the username given by
  # +lowest_user+ (and to the default group of that user).
  # If +lowest_user+ doesn't exist either, or if switching user failed
  # (because the current process does not have the privilege to do so),
  # then ApplicationSpawner will continue without reporting an error.
  def initialize(app_root, lower_privilege = true, lowest_user = "nobody")
    super()
    begin
      @app_root = normalize_path(app_root)
    rescue SystemCallError => e
      raise ArgumentError, e.message
    rescue ArgumentError
      raise
    end
    @lower_privilege = lower_privilege
    @lowest_user = lowest_user
    self.time = Time.now
    assert_valid_app_root(@app_root)
    define_message_handler(:spawn_application, :handle_spawn_application)
  end
  
  # Spawn an instance of the RoR application. When successful, an Application object
  # will be returned, which represents the spawned RoR application.
  #
  # Raises:
  # - AbstractServer::ServerNotStarted: The ApplicationSpawner server hasn't already been started.
  # - ApplicationSpawner::Error: The ApplicationSpawner server exited unexpectedly.
  def spawn_application
    server.write("spawn_application")
    pid, socket_name, using_abstract_namespace = server.read
    if pid.nil?
      raise IOError, "Connection closed"
    end
    owner_pipe = server.recv_io
    return Application.new(@app_root, pid, socket_name,
      using_abstract_namespace == "true", owner_pipe)
  rescue SystemCallError, IOError, SocketError => e
    raise Error, "The application spawner server exited unexpectedly"
  end
  
  # Overrided from AbstractServer#start.
  #
  # May raise these additional exceptions:
  # - AppInitError: The Ruby on Rails application raised an exception
  #   or called exit() during startup.
  # - ApplicationSpawner::Error: The ApplicationSpawner server exited unexpectedly.
  def start
    super
    begin
      status = server.read[0]
      if status == 'exception'
        child_exception = unmarshal_exception(server.read_scalar)
        stop
        raise AppInitError.new(
          "Application '#{@app_root}' raised an exception: " <<
          "#{child_exception.class} (#{child_exception.message})",
          child_exception)
      elsif status == 'exit'
        stop
        raise AppInitError.new("Application '#{@app_root}' exited during startup")
      end
    rescue IOError, SystemCallError, SocketError
      stop
      raise Error, "The application spawner server exited unexpectedly"
    end
  end
 
protected
  # Overrided method.
  def before_fork # :nodoc:
    if GC.copy_on_write_friendly?
      # Garbage collect now so that the child process doesn't have to
      # do that (to prevent making pages dirty).
      GC.start
    end
  end
  
  # Overrided method.
  def initialize_server # :nodoc:
    begin
      $0 = "Passenger ApplicationSpawner: #{@app_root}"
      Dir.chdir(@app_root)
      lower_privilege! if @lower_privilege
      preload_application
    rescue StandardError, ScriptError, NoMemoryError => e
      if ENV['TESTING_PASSENGER'] == '1'
        print_exception(self.class.to_s, e)
      end
      client.write('exception')
      client.write_scalar(marshal_exception(e))
      return
    rescue SystemExit
      client.write('exit')
      raise
    end
    client.write('success')
  end
  
private
  def lower_privilege!
    stat = File.stat("config/environment.rb")
    begin
      if !switch_to_user(stat.uid)
        switch_to_user(@lowest_user)
      end
    rescue Errno::EPERM
      # No problem if we were unable to switch user.
    end
  end
 
  def switch_to_user(user)
    begin
      if user.is_a?(String)
        pw = Etc.getpwnam(user)
        username = user
        uid = pw.uid
        gid = pw.gid
      else
        pw = Etc.getpwuid(user)
        username = pw.name
        uid = user
        gid = pw.gid
      end
    rescue
      return false
    end
    if uid == ROOT_UID
      return false
    else
      Process.groups = Process.initgroups(username, gid)
      Process::Sys.setgid(gid)
      Process::Sys.setuid(uid)
      return true
    end
  end
 
  def preload_application
    Object.const_set(:RAILS_ROOT, @app_root)
    if defined?(Rails::Initializer)
      Rails::Initializer.run(:set_load_path)
      
      # The Rails framework is loaded at the moment.
      # environment.rb may set ENV['RAILS_ENV']. So we re-initialize
      # RAILS_ENV in Rails::Initializer.load_environment.
      Rails::Initializer.class_eval do
        def load_environment_with_passenger
          if defined?(::RAILS_ENV)
            Object.send(:remove_const, :RAILS_ENV)
          end
          Object.const_set(:RAILS_ENV, (ENV['RAILS_ENV'] || 'development').dup)
          load_environment_without_passenger
        end
        
        alias_method :load_environment_without_passenger, :load_environment
        alias_method :load_environment, :load_environment_with_feature
      end
    end
    require 'config/environment'
    if ActionController::Base.page_cache_directory.blank?
      ActionController::Base.page_cache_directory = "#{RAILS_ROOT}/public"
    end
    if defined?(ActionController::Dispatcher) \
       && ActionController::Dispatcher.respond_to?(:error_file_path)
      ActionController::Dispatcher.error_file_path = "#{RAILS_ROOT}/public"
    end
    if !defined?(Dispatcher)
      require 'dispatcher'
    end
    require_dependency 'application'
    if GC.copy_on_write_friendly?
      Dir.glob('app/{models,controllers,helpers}/*.rb').each do |file|
        require_dependency normalize_path(file)
      end
    end
  end
 
  def handle_spawn_application
    # Double fork to prevent zombie processes.
    pid = fork do
      begin
        pid = fork do
          begin
            start_request_handler
          rescue SignalException => signal
            if e.message != RequestHandler::HARD_TERMINATION_SIGNAL &&
               e.message != RequestHandler::SOFT_TERMINATION_SIGNAL
              print_exception('application', e)
            end
          rescue Exception => e
            print_exception('application', e)
          ensure
            exit!
          end
        end
      rescue Exception => e
        print_exception(self.class.to_s, e)
      ensure
        exit!
      end
    end
    Process.waitpid(pid)
  end
  
  def start_request_handler
    $0 = "Rails: #{@app_root}"
    reader, writer = IO.pipe
    begin
      # Re-establish connection if a connection was established
      # in environment.rb. This prevents us from concurrently
      # accessing the same MySQL connection handle.
      if defined?(::ActiveRecord::Base) && ::ActiveRecord::Base.connected?
        ::ActiveRecord::Base.establish_connection
      end
      
      handler = RequestHandler.new(reader)
      client.write(Process.pid, handler.socket_name,
        handler.using_abstract_namespace?)
      client.send_io(writer)
      writer.close
      client.close
      handler.main_loop
    ensure
      client.close rescue nil
      writer.close rescue nil
      handler.cleanup rescue nil
    end
  end
end
 
end # module Passenger