class PhusionPassenger::AdminTools::ServerInstance

def initialize(path)
	raise ArgumentError, "Path may not be nil." if path.nil?
	@path = path
	
	if File.exist?("#{path}/control_process.pid")
		data = File.read("#{path}/control_process.pid").strip
		@pid = data.to_i
	else
		path =~ /passenger\.\d+\.\d+\.(\d+)\Z/
		@pid = $1.to_i
	end
	
	generations = Dir["#{path}/generation-*"]
	if generations.empty?
		raise GenerationsAbsentError, "There are no generation subdirectories in this instance directory."
	end
	highest_generation_number = 0
	generations.each do |generation|
		File.basename(generation) =~ /(\d+)/
		generation_number = $1.to_i
		if generation_number > highest_generation_number
			highest_generation_number = generation_number
		end
	end
	@generation_path = "#{path}/generation-#{highest_generation_number}"
	
	if !File.exist?("#{@generation_path}/structure_version.txt")
		raise CorruptedDirectoryError, "The generation directory doesn't contain a structure version specification file."
	end
	version_data = File.read("#{@generation_path}/structure_version.txt").strip
	major, minor = version_data.split(".", 2)
	if major.nil? || minor.nil? || major !~ /\A\d+\Z/ || minor !~ /\A\d+\Z/
		raise CorruptedDirectoryError, "The generation directory doesn't contain a valid structure version specification file."
	end
	major = major.to_i
	minor = minor.to_i
	if major != PhusionPassenger::SERVER_INSTANCE_DIR_GENERATION_STRUCTURE_MAJOR_VERSION ||
	   minor > PhusionPassenger::SERVER_INSTANCE_DIR_GENERATION_STRUCTURE_MINOR_VERSION
		raise UnsupportedGenerationStructureVersionError, "Unsupported generation directory structure version."
	end
	
	if @pid == 0
		raise CorruptedDirectoryError, "Instance directory contains corrupted control_process.pid file."
	elsif !AdminTools.process_is_alive?(@pid)
		raise StaleDirectoryError, "There is no instance with PID #{@pid}."
	end
end