require 'yaml'
 
module Thin
  # Error raised that will abort the process and print not backtrace.
  class RunnerError < RuntimeError; end
  
  # Raised when a mandatory option is missing to run a command.
  class OptionRequired < RunnerError
    def initialize(option)
      super("#{option} option required")
    end
  end
  
  # Raised when an option is not valid.
  class InvalidOption < RunnerError; end
  
  # Build and control Thin servers.
  # Hey Controller pattern is not only for web apps yo!
  module Controllers  
    # Controls one Thin server.
    # Allow to start, stop, restart and configure a single thin server.
    class Controller
      include Logging
    
      # Command line options passed to the thin script
      attr_accessor :options
    
      def initialize(options)
        @options = options
        
        if @options[:socket]
          @options.delete(:address)
          @options.delete(:port)
        end
      end
    
      def start
        # Constantize backend class
        @options[:backend] = eval(@options[:backend], TOPLEVEL_BINDING) if @options[:backend]
        
        server = Server.new(@options[:socket] || @options[:address], # Server detects kind of socket
                            @options[:port],                         # Port ignored on UNIX socket
                            @options)
        
        # Set options
        server.pid_file                       = @options[:pid]
        server.log_file                       = @options[:log]
        server.timeout                        = @options[:timeout]
        server.maximum_connections            = @options[:max_conns]
        server.maximum_persistent_connections = @options[:max_persistent_conns]
        server.threaded                       = @options[:threaded]
 
        # Detach the process, after this line the current process returns
        server.daemonize if @options[:daemonize]
 
        # +config+ must be called before changing privileges since it might require superuser power.
        server.config
        
        server.change_privilege @options[:user], @options[:group] if @options[:user] && @options[:group]
 
        # If a Rack config file is specified we eval it inside a Rack::Builder block to create
        # a Rack adapter from it. Or else we guess which adapter to use and load it.
        if @options[:rackup]
          server.app = load_rackup_config
        else
          server.app = load_adapter
        end
 
        # If a prefix is required, wrap in Rack URL mapper
        server.app = Rack::URLMap.new(@options[:prefix] => server.app) if @options[:prefix]
 
        # If a stats URL is specified, wrap in Stats adapter
        server.app = Stats::Adapter.new(server.app, @options[:stats]) if @options[:stats]
 
        # Register restart procedure which just start another process with same options,
        # so that's why this is done here.
        server.on_restart { Command.run(:start, @options) }
 
        server.start
      end
    
      def stop
        raise OptionRequired, :pid unless @options[:pid]
      
        tail_log(@options[:log]) do
          Server.kill(@options[:pid], @options[:timeout] || 60)
          wait_for_file :deletion, @options[:pid]
        end
      end
    
      def restart
        raise OptionRequired, :pid unless @options[:pid]
      
        tail_log(@options[:log]) do
          Server.restart(@options[:pid])
          wait_for_file :creation, @options[:pid]
        end
      end
    
      def config
        config_file = @options.delete(:config) || raise(OptionRequired, :config)
 
        # Stringify keys
        @options.keys.each { |o| @options[o.to_s] = @options.delete(o) }
 
        File.open(config_file, 'w') { |f| f << @options.to_yaml }
        log ">> Wrote configuration to #{config_file}"
      end
      
      protected
        # Wait for a pid file to either be created or deleted.
        def wait_for_file(state, file)
          case state
          when :creation then sleep 0.1 until File.exist?(file)
          when :deletion then sleep 0.1 while File.exist?(file)
          end
        end
        
        # Tail the log file of server +number+ during the execution of the block.        
        def tail_log(log_file)
          if log_file
            tail_thread = tail(log_file)
            yield
            tail_thread.kill
          else
            yield
          end
        end
        
        # Acts like GNU tail command. Taken from Rails.
        def tail(file)
          cursor = File.exist?(file) ? File.size(file) : 0
          last_checked = Time.now
          tail_thread = Thread.new do
            Thread.pass until File.exist?(file)
            File.open(file, 'r') do |f|
              loop do
                f.seek cursor
                if f.mtime > last_checked
                  last_checked = f.mtime
                  contents = f.read
                  cursor += contents.length
                  print contents
                  STDOUT.flush
                end
                sleep 0.1
              end
            end
          end
          sleep 1 if File.exist?(file) # HACK Give the thread a little time to open the file
          tail_thread
        end
 
      private
        def load_adapter
          adapter = @options[:adapter] || Rack::Adapter.guess(@options[:chdir])
          log ">> Using #{adapter} adapter"
          Rack::Adapter.for(adapter, @options)
        rescue Rack::AdapterNotFound => e
          raise InvalidOption, e.message
        end
        
        def load_rackup_config
          rackup_code = File.read(@options[:rackup])
          eval("Rack::Builder.new {( #{rackup_code}\n )}.to_app", TOPLEVEL_BINDING, @options[:rackup])
        end
    end
  end
end