module Rack
  class AdapterNotFound < RuntimeError; end
  
  # Mapping used to guess which adapter to use in <tt>Adapter.for</tt>.
  # Framework <name> => <file unique to this framework> in order they will
  # be tested.
  # +nil+ for value to never guess.
  # NOTE: If a framework has a file that is not unique, make sure to place
  # it at the end.
  ADAPTERS = [
    [:rack,    'config.ru'],
    [:rails,   'config/environment.rb'],
    [:ramaze,  'start.rb'],
    [:merb,    'config/init.rb'],
    [:file,    nil]
  ]
  
  module Adapter
    # Guess which adapter to use based on the directory structure
    # or file content.
    # Returns a symbol representing the name of the adapter to use
    # to load the application under <tt>dir/</tt>.
    def self.guess(dir)
      ADAPTERS.each do |adapter, file|
        return adapter if file && ::File.exist?(::File.join(dir, file))
      end
      raise AdapterNotFound, "No adapter found for #{dir}"
    end
    
    # Load a Rack application from a Rack config file (.ru).
    def self.load(config)
      rackup_code = ::File.read(config)
      eval("Rack::Builder.new {( #{rackup_code}\n )}.to_app", TOPLEVEL_BINDING, config)
    end
    
    # Loads an adapter identified by +name+ using +options+ hash.
    def self.for(name, options={})
      ENV['RACK_ENV'] = options[:environment]
      
      case name.to_sym
      when :rack
        return load(::File.join(options[:chdir], "config.ru"))
        
      when :rails
        return Rails.new(options.merge(:root => options[:chdir]))
      
      when :ramaze
        require "#{options[:chdir]}/start"
        
        Ramaze.trait[:essentials].delete Ramaze::Adapter
        Ramaze.start :force => true
        
        return Ramaze::Adapter::Base
        
      when :merb
        require 'merb-core'
        
        Merb::Config.setup(:merb_root   => options[:chdir],
                           :environment => options[:environment])
        Merb.environment = Merb::Config[:environment]
        Merb.root = Merb::Config[:merb_root]
        Merb::BootLoader.run
        
        return Merb::Rack::Application.new
        
      when :file
        return Rack::Files.new(options[:chdir])
        
      else
        raise AdapterNotFound, "Adapter not found: #{name}"
        
      end
    end
  end
end