module Moneta
  # Shares a store between processes
  #
  # @example Share a store
  #   Moneta.build do
  #     use :Transformer, key: :marshal, value: :marshal
  #     use :Shared do
  #       adapter :GDBM, file: 'shared.db'
  #     end
  #   end
  #
  # @api public
  class Shared < Wrapper
    # @param [Hash] options
    # @option options [Integer] :port (9000) TCP port
    # @option options [String] :host Server hostname
    # @option options [String] :socket Unix socket file name
    def initialize(options = {}, &block)
      @options = options
      @builder = Builder.new(&block)
      @connect_lock = ::Mutex.new
    end

    # (see Proxy#close)
    def close
      if server?
        @server.stop
        @thread.join
        @server = @thread = nil
      end
      if @adapter
        @adapter.close
        @adapter = nil
      end
    end

    # Returns true if this wrapper is running as the server
    #
    # @return [Boolean] wrapper is a server
    def server?
      @server != nil
    end

    protected

    def wrap(*args)
      connect
      yield
    rescue Errno::ECONNRESET, Errno::EPIPE, IOError, SystemCallError
      @connect_lock.synchronize { close unless server? }
      tries ||= 0
      (tries += 1) < 3 ? retry : raise
    end

    def connect
      return if @adapter
      @connect_lock.synchronize do
        @adapter ||= Adapters::Client.new(@options)
      end
    rescue Errno::ECONNREFUSED, Errno::ENOENT, IOError => ex
      start_server
      tries ||= 0
      warn "Moneta::Shared - Failed to connect: #{ex.message}" if tries > 0
      (tries += 1) < 10 ? retry : raise
    end

    # TODO: Implement this using forking (MRI) and threading (JRuby)
    # to get maximal performance
    def start_server
      @connect_lock.synchronize do
        return if server?
        begin
          raise "Adapter already set" if @adapter
          @adapter = Lock.new(@builder.build.last)
          raise "Server already set" if server?
          @server = Server.new(@adapter, @options)
          @thread = Thread.new { @server.run }
          sleep 0.1 until @server.running?
        rescue => ex
          @adapter.close if @adapter
          @adapter = nil
          @server = nil
          @thread = nil
          warn "Moneta::Shared - Failed to start server: #{ex.message}"
        end
      end
    end
  end
end