strands.rb

require 'sinatra/base'
require 'fiber'

module Sinatra
  module Strands
    REQUEST_METHODS = [:get,:put,:post,:delete]
    class Strand
      def initialize *args, &block
        @secure_id = object_id    # TODO: not actually secure
        @fiber = Fiber.new do
          @route_context.instance_exec *args, &block
        end
      end
      attr_reader :secure_id

      def yield response
        raise ServerError.new "Internal error: tried to yield from outside a strand" unless @fiber == Fiber.current
        Fiber.yield response
      end

      def uri qs={}
        s = "/_strand/#{@secure_id}"
        unless qs.empty?
          s << (qs.map do |k,v|
            k = Rack::Utils.escape(k)
            if v.is_a? Enumerable
              v.map {|v| "#{k}=#{Rack::Utils.escape v}" }.join('&')
            else
              "#{k}=#{Rack::Utils.escape v}"
            end
          end)
        end
        return s
      end

      def resume route_context
        @route_context = route_context
        @fiber.resume route_context
      end
      attr_reader :route_context

      def alive?
        @fiber && @fiber.alive?
      end
    end # Strand

    module Helpers
      def _strand_resume sid, route_context
        strands = Sinatra::Strands.all_strands
        $stderr.puts "\e[1;33mresuming strand \e[1;35m#{sid} \e[1;34m(#{strands.size} total)\e[0m"
        # $stderr.puts "all strands: #{strands.inspect}"
        raise NotFound.new "Strand #{sid} doesn't exist" unless strands and @_strand = strands[sid]
        raise NotFound.new "Strand #{sid} is dead" unless @_strand.alive?
        page = @_strand.resume route_context
        strands.delete sid unless @_strand.alive?
        page
      end

      def strand_uri qs={}
        @_strand.uri qs
      end

      def show response
        @_strand.yield response
      end
    end # Helpers

    class << self
      attr_reader :all_strands

      def registered app
        # Sinatra passes us Default which is no good because
        # Application doesn't inherit Default's routes
        # This might be fixed in edge
        app = Sinatra::Application

        app.helpers Helpers

        app.configure do
          Sinatra::Strands.instance_eval { @all_strands = {} }
        end

        REQUEST_METHODS.each do |meth|
          app.send meth, %r{/_strand/(\d+)} do |sid|
            _strand_resume sid.to_i, self
          end
        end
      end # Strands.registered

    end # << self

    def strand_route meth, path, opts={}, &block
      raise ServerError.new "Can't handle request method '#{meth}' with a strand" unless REQUEST_METHODS.include? meth

      send meth, path, opts do |*args|
        strands = Sinatra::Strands.all_strands
        @_strand = Strand.new *args, &block
        sid = @_strand.secure_id
        strands[sid] = @_strand
        $stderr.puts "\e[1;32mstarted strand \e[1;35m#{sid} \e[1;34m(#{strands.size} total)\e[0m"
        # $stderr.puts "all strands: #{strands.inspect}"
        page = @_strand.resume self
        strands.delete sid unless @_strand.alive?
        page
      end
    end

    REQUEST_METHODS.each do |meth|
      define_method "strand_#{meth}" do |path, opts={}, &block|
        strand_route meth, path, opts, &block
      end
    end

  end # Strands

  register Strands
end # Sinatra