#  Phusion Passenger - http://www.modrails.com/
#  Copyright (c) 2008, 2009 Phusion
#
#  "Phusion Passenger" is a trademark of Hongli Lai & Ninh Bui.
#
#  Permission is hereby granted, free of charge, to any person obtaining a copy
#  of this software and associated documentation files (the "Software"), to deal
#  in the Software without restriction, including without limitation the rights
#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#  copies of the Software, and to permit persons to whom the Software is
#  furnished to do so, subject to the following conditions:
#
#  The above copyright notice and this permission notice shall be included in
#  all copies or substantial portions of the Software.
#
#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#  THE SOFTWARE.

require 'phusion_passenger/abstract_server'
require 'phusion_passenger/abstract_server_collection'
require 'phusion_passenger/constants'
require 'phusion_passenger/utils'

# Define a constant with a name that's unlikely to clash with anything the
# application defines, so that they can detect whether they're running under
# Phusion Passenger.
IN_PHUSION_PASSENGER = true

module PhusionPassenger

# The spawn manager is capable of spawning Ruby on Rails or Rack application
# instances. It acts like a simple fascade for the rest of the spawn manager
# system.
#
# *Note*: SpawnManager may only be started synchronously with
# AbstractServer#start_synchronously. Starting asynchronously has not been
# tested. Don't forget to call cleanup after the server's main loop has
# finished.
#
# == Ruby on Rails optimizations
#
# Spawning a Ruby on Rails application is usually slow. But SpawnManager
# will preload and cache Ruby on Rails frameworks, as well as application
# code, so subsequent spawns will be very fast.
#
# Internally, SpawnManager uses Railz::FrameworkSpawner to preload and cache
# Ruby on Rails frameworks. Railz::FrameworkSpawner, in turn, uses
# Railz::ApplicationSpawner to preload and cache application code.
#
# In case you're wondering why the namespace is "Railz" and not "Rails":
# it's to work around an obscure bug in ActiveSupport's Dispatcher.
class SpawnManager < AbstractServer
	include Utils
	
	def initialize
		super()
		@spawners = AbstractServerCollection.new
		define_message_handler(:spawn_application, :handle_spawn_application)
		define_message_handler(:reload, :handle_reload)
		define_signal_handler('SIGHUP', :reload)
		
		# Start garbage collector in order to free up some existing
		# heap slots. This prevents the heap from growing unnecessarily
		# during the startup phase.
		GC.start
		if GC.copy_on_write_friendly?
			# Preload libraries for copy-on-write semantics.
			require 'base64'
			require 'phusion_passenger/application'
			require 'phusion_passenger/railz/framework_spawner'
			require 'phusion_passenger/railz/application_spawner'
			require 'phusion_passenger/rack/application_spawner'
			require 'phusion_passenger/html_template'
			require 'phusion_passenger/platform_info'
			require 'phusion_passenger/exceptions'
			
			# Commonly used libraries.
			['mysql', 'sqlite3'].each do |lib|
				begin
					require lib
				rescue LoadError
					# Do nothing; ignore if not present.
				end
			end
		end
	end
	
	# Spawn an application with the given spawn options. When successful, an
	# Application object will be returned, which represents the spawned application.
	# At least one option must be given: +app_root+. This is the application's root
	# folder.
	#
	# Other options are:
	#
	# ['lower_privilege', 'lowest_user', 'environment', 'environment_variables', 'base_uri' and 'print_exceptions']
	#   See Railz::ApplicationSpawner.new for an explanation of these options.
	# 
	# ['app_type']
	#   What kind of application is being spawned. Either "rails" (default), "rack" or "wsgi".
	# 
	# ['spawn_method']
	#   May be one of "smart", "smart-lv2" or "conservative". When "smart" is specified,
	#   SpawnManager will internally cache the code of Rails applications, in
	#   order to speed up future spawning attempts. This implies that, if you've changed
	#   the application's
	#   code, you must do one of these things:
	#   - Restart this SpawnManager by calling AbstractServer#stop, then AbstractServer#start.
	#   - Reload the application by calling reload with the correct app_root argument.
	#   
	#   "smart" caches the Rails framework code in a framework spawner server, and application
	#   code in an application spawner server. Sometimes it is desirable to skip the
	#   framework spawning and going directly for the application spawner instead. The
	#   "smart-lv2" method allows you to do that.
	#   
	#   Caching however can be incompatible with some applications. The "conservative"
	#   spawning method does not involve any caching at all. Spawning will be slower,
	#   but is guaranteed to be compatible with all applications.
	#   
	#   The default spawn method is "smart-lv2".
	# 
	# ['framework_spawner_timeout' and 'app_spawner_timeout']
	#   These options allow you to specify the maximum idle timeout, in seconds, of the
	#   framework spawner servers and application spawner servers that will be started under
	#   the hood. These options are only used if +app_type+ equals "rails".
	#   
	#   A timeout of 0 means that the spawner server should never idle timeout. A timeout of
	#   -1 means that the default timeout value should be used. The default value is -1.
	#
	# <b>Exceptions:</b>
	# - InvalidPath: +app_root+ doesn't appear to be a valid Ruby on Rails application root.
	# - VersionNotFound: The Ruby on Rails framework version that the given application requires
	#   is not installed.
	# - AbstractServer::ServerError: One of the server processes exited unexpectedly.
	# - FrameworkInitError: The Ruby on Rails framework that the application requires could not be loaded.
	# - AppInitError: The application raised an exception or called exit() during startup.
	def spawn_application(options)
		if !options["app_root"]
			raise ArgumentError, "The 'app_root' option must be given."
		end
		options = sanitize_spawn_options(options)
		
		if options["app_type"] == "rails"
			if !defined?(Railz::FrameworkSpawner)
				require 'phusion_passenger/application'
				require 'phusion_passenger/railz/framework_spawner'
				require 'phusion_passenger/railz/application_spawner'
			end
			return spawn_rails_application(options)
		elsif options["app_type"] == "rack"
			if !defined?(Rack::ApplicationSpawner)
				require 'phusion_passenger/rack/application_spawner'
			end
			return Rack::ApplicationSpawner.spawn_application(
				options["app_root"], options
			)
		elsif options["app_type"] == "wsgi"
			require 'phusion_passenger/wsgi/application_spawner'
			return WSGI::ApplicationSpawner.spawn_application(
				options["app_root"],
				options["lower_privilege"],
				options["lowest_user"],
				options["environment"]
			)
		else
			raise ArgumentError, "Unknown 'app_type' value '#{options["app_type"]}'."
		end
	end
	
	# Remove the cached application instances at the given application root.
	# If nil is specified as application root, then all cached application
	# instances will be removed, no matter the application root.
	#
	# <b>Long description:</b>
	# Application code might be cached in memory. But once it a while, it will
	# be necessary to reload the code for an application, such as after
	# deploying a new version of the application. This method makes sure that
	# any cached application code is removed, so that the next time an
	# application instance is spawned, the application code will be freshly
	# loaded into memory.
	#
	# Raises AbstractServer::SpawnError if something went wrong.
	def reload(app_root = nil)
		@spawners.synchronize do
			if app_root
				# Delete associated ApplicationSpawner.
				@spawners.delete("app:#{app_root}")
			else
				# Delete all ApplicationSpawners.
				keys_to_delete = []
				@spawners.each_pair do |key, spawner|
					if spawner.is_a?(Railz::ApplicationSpawner)
						keys_to_delete << key
					end
				end
				keys_to_delete.each do |key|
					@spawners.delete(key)
				end
			end
			@spawners.each do |spawner|
				# Reload all FrameworkSpawners.
				if spawner.respond_to?(:reload)
					spawner.reload(app_root)
				end
			end
		end
	end
	
	# Cleanup resources. Should be called when this SpawnManager is no longer needed.
	def cleanup
		@spawners.cleanup
	end

private
	def spawn_rails_application(options)
		spawn_method = options["spawn_method"]
		app_root     = options["app_root"]
		
		if [nil, "", "smart", "smart-lv2"].include?(spawn_method)
			spawner_must_be_started = true
			if spawn_method != "smart-lv2"
				framework_version = Application.detect_framework_version(app_root)
			end
			if framework_version.nil? || framework_version == :vendor
				key = "app:#{app_root}"
				create_spawner = proc do
					Railz::ApplicationSpawner.new(app_root, options)
				end
				spawner_timeout = options["app_spawner_timeout"]
			else
				key = "version:#{framework_version}"
				create_spawner = proc do
					framework_options = { :version => framework_version }
					if options.has_key?(:print_framework_loading_exceptions)
						framework_options[:print_framework_loading_exceptions] = options[:print_framework_loading_exceptions]
					end
					Railz::FrameworkSpawner.new(framework_options)
				end
				spawner_timeout = options["framework_spawner_timeout"]
			end
		else
			key = "app:#{app_root}"
			create_spawner = proc do
				Railz::ApplicationSpawner.new(app_root, options)
			end
			spawner_timeout = options["app_spawner_timeout"]
			spawner_must_be_started = false
		end
		
		@spawners.synchronize do
			spawner = @spawners.lookup_or_add(key) do
				spawner = create_spawner.call
				if spawner_timeout != -1
					spawner.max_idle_time = spawner_timeout
				end
				if spawner_must_be_started
					spawner.start
				end
				spawner
			end
			begin
				if spawner.is_a?(Railz::FrameworkSpawner)
					return spawner.spawn_application(app_root, options)
				elsif spawner.started?
					return spawner.spawn_application
				else
					return spawner.spawn_application!
				end
			rescue AbstractServer::ServerError
				@spawners.delete(key)
				raise
			end
		end
	end
	
	def handle_spawn_application(*options)
		options = sanitize_spawn_options(Hash[*options])
		app = nil
		app_root = options["app_root"]
		app_type = options["app_type"]
		begin
			app = spawn_application(options)
		rescue InvalidPath => e
			send_error_page(client, 'invalid_app_root', :error => e, :app_root => app_root)
		rescue AbstractServer::ServerError => e
			send_error_page(client, 'general_error', :error => e)
		rescue VersionNotFound => e
			send_error_page(client, 'version_not_found', :error => e, :app_root => app_root)
		rescue AppInitError => e
			if database_error?(e)
				send_error_page(client, 'database_error', :error => e,
					:app_root => app_root, :app_name => app_name(app_type),
					:app_type => app_type)
			elsif load_error?(e)
				# A source file failed to load, maybe because of a
				# missing gem. If that's the case then the sysadmin
				# will install probably the gem. So we clear RubyGems's
				# cache so that it can detect new gems.
				Gem.clear_paths
				send_error_page(client, 'load_error', :error => e, :app_root => app_root,
					:app_name => app_name(app_type))
			elsif e.child_exception.is_a?(SystemExit)
				send_error_page(client, 'app_exited_during_initialization', :error => e,
					:app_root => app_root, :app_name => app_name(app_type))
			else
				send_error_page(client, 'app_init_error', :error => e,
					:app_root => app_root, :app_name => app_name(app_type))
			end
		rescue FrameworkInitError => e
			send_error_page(client, 'framework_init_error', :error => e)
		end
		if app
			begin
				client.write('ok')
				client.write(app.pid, app.listen_socket_name,
					app.listen_socket_type)
				client.send_io(app.owner_pipe)
			rescue Errno::EPIPE
				# The Apache module may be interrupted during a spawn command,
				# in which case it will close the connection. We ignore this error.
			ensure
				app.close
			end
		end
	end
	
	def handle_reload(app_root)
		reload(app_root)
	end
	
	def send_error_page(channel, template_name, options = {})
		require 'phusion_passenger/html_template' unless defined?(HTMLTemplate)
		require 'phusion_passenger/platform_info' unless defined?(PlatformInfo)
		options["enterprisey"] = File.exist?("#{File.dirname(__FILE__)}/../../enterprisey.txt") ||
			File.exist?("/etc/passenger_enterprisey.txt")
		data = HTMLTemplate.new(template_name, options).result
		channel.write('error_page')
		channel.write_scalar(data)
	end
	
	def database_error?(e)
		return ( defined?(Mysql::Error) && e.child_exception.is_a?(Mysql::Error) ) ||
		       ( e.child_exception.is_a?(UnknownError) &&
		           (
		               e.child_exception.real_class_name =~ /^ActiveRecord/ ||
		               e.child_exception.real_class_name =~ /^Mysql::/
		           )
		       )
	end
	
	def load_error?(e)
		return e.child_exception.is_a?(LoadError) || (
		           e.child_exception.is_a?(UnknownError) &&
		           e.child_exception.real_class_name == "MissingSourceFile"
		)
	end
	
	def app_name(app_type)
		if app_type == "rails"
			return "Ruby on Rails"
		else
			return "Ruby (Rack)"
		end
	end
end

end # module PhusionPassenger