module Guard

  autoload :UI,           'guard/ui'
  autoload :Dsl,          'guard/dsl'
  autoload :DslDescriber, 'guard/dsl_describer'
  autoload :Interactor,   'guard/interactor'
  autoload :Listener,     'guard/listener'
  autoload :Watcher,      'guard/watcher'
  autoload :Notifier,     'guard/notifier'
  autoload :Hook,         'guard/hook'

  class << self
    attr_accessor :options, :guards, :groups, :listener

    # initialize this singleton
    def setup(options = {})
      @options  = options
      @listener = Listener.select_and_init(@options[:watchdir] ? File.expand_path(@options[:watchdir]) : Dir.pwd)
      @groups   = [:default]
      @guards   = []

      @options[:notify] && ENV["GUARD_NOTIFY"] != 'false' ? Notifier.turn_on : Notifier.turn_off

      UI.clear if @options[:clear]
      debug_command_execution if @options[:debug]

      self
    end

    def start(options = {})
      Interactor.init_signal_traps

      setup(options)

      Dsl.evaluate_guardfile(options)

      listener.on_change do |files|
        Dsl.reevaluate_guardfile if Watcher.match_guardfile?(files)

        run { run_on_change_for_all_guards(files) } if Watcher.match_files?(guards, files)
      end

      UI.info "Guard is now watching at '#{listener.directory}'"
      guards.each { |guard| supervised_task(guard, :start) }
      listener.start
    end

    def run_on_change_for_all_guards(files)
      guards.each do |guard|
        paths = Watcher.match_files(guard, files)
        unless paths.empty?
          UI.debug "#{guard.class.name}#run_on_change with #{paths.inspect}"
          supervised_task(guard, :run_on_change, paths)
        end
      end

      # Reparse the whole directory to catch new files modified during the guards run
      new_modified_files = listener.modified_files([listener.directory], :all => true)
      if !new_modified_files.empty? && Watcher.match_files?(guards, new_modified_files)
        run { run_on_change_for_all_guards(new_modified_files) }
      end
    end

    # Let a guard execute its task but
    # fire it if his work leads to a system failure
    def supervised_task(guard, task_to_supervise, *args)
      guard.hook("#{task_to_supervise}_begin", *args)
      result = guard.send(task_to_supervise, *args)
      guard.hook("#{task_to_supervise}_end", result)
      result
    rescue Exception => ex
      UI.error("#{guard.class.name} failed to achieve its <#{task_to_supervise.to_s}>, exception was:" +
      "\n#{ex.class}: #{ex.message}\n#{ex.backtrace.join("\n")}")
      guards.delete guard
      UI.info("\n#{guard.class.name} has just been fired")
      return ex
    end

    def run
      listener.stop
      UI.clear if options[:clear]
      begin
        yield
      rescue Interrupt
      end
      listener.start
    end

    def add_guard(name, watchers = [], callbacks = [], options = {})
      if name.to_sym == :ego
        UI.deprecation("Guard::Ego is now part of Guard. You can remove it from your Guardfile.")
      else
        guard_class = get_guard_class(name)
        callbacks.each { |callback| ::Guard::Hook.add_callback(callback[:listener], guard_class, callback[:events]) }
        @guards << guard_class.new(watchers, options)
      end
    end

    def add_group(name)
      @groups << name.to_sym unless name.nil?
    end

    def get_guard_class(name)
      name        = name.to_s
      try_require = false
      const_name  = name.downcase.gsub('-', '')
      begin
        require "guard/#{name.downcase}" if try_require
        self.const_get(self.constants.find { |c| c.to_s.downcase == const_name })
      rescue TypeError
        unless try_require
          try_require = true
          retry
        else
          UI.error "Could not find class Guard::#{const_name.capitalize}"
        end
      rescue LoadError => loadError
        UI.error "Could not load 'guard/#{name.downcase}' or find class Guard::#{const_name.capitalize}"
        UI.error loadError.to_s
      end
    end

    def locate_guard(name)
      if Gem::Version.create(Gem::VERSION) >= Gem::Version.create('1.8.0')
        Gem::Specification.find_by_name("guard-#{name}").full_gem_path
      else
        Gem.source_index.find_name("guard-#{name}").last.full_gem_path
      end
    rescue
      UI.error "Could not find 'guard-#{name}' gem path."
    end

    ##
    # Returns a list of guard Gem names installed locally.
    def guard_gem_names
      if Gem::Version.create(Gem::VERSION) >= Gem::Version.create('1.8.0')
        Gem::Specification.find_all.select { |x| x.name =~ /^guard-/ }
      else
        Gem.source_index.find_name(/^guard-/)
      end.map { |x| x.name.sub /^guard-/, '' }
    end

    def debug_command_execution
      Kernel.send(:alias_method, :original_system, :system)
      Kernel.send(:define_method, :system) do |command, *args|
        ::Guard::UI.debug "Command execution: #{command} #{args.join(' ')}"
        original_system command, *args
      end

      Kernel.send(:alias_method, :original_backtick, :"`")
      Kernel.send(:define_method, :"`") do |command|
        ::Guard::UI.debug "Command execution: #{command}"
        original_backtick command
      end
    end

  end
end