module Baurets

  class Optionsful  

    def initialize(app)  
      @app = app  
    end  

    def call(env) 
      unless env["REQUEST_METHOD"] == "OPTIONS"
        @app.call(env)
      else
        extract_options_information(env)
      end
    end

    private

    def extract_options_information(env)
      [204, {"Allow" => extract_allowed_methods(env), "Link" => build_help_link}, ""]  
    end

    def extract_allowed_methods(env)
      # do routing introspection:
      routes = do_routing_introspection
      # do request path investigation
      route_guess = guess_route(routes, env["PATH_INFO"])
      allows = ""
      # do the matches:
      routes.each do |route|
        if route.first == route_guess
          allows += route[1].to_s.upcase! + "|" 
        end
      end
      allows = allows.split("|").join(", ")
    end

    def build_help_link
      #PENDING
      "<http://baurets.net/api/resources>; type=text/html; rel=help"
    end

    def guess_route(routes, path)
      parts = prepare_request_path(path)
      guess = []
      index = 0
      parts.each do |part|
        if is_part_static?(routes, index, part)
          guess << part
        else
          guess << :dynamic
        end
        index += 1
      end
      guess
    end

    def is_part_static?(routes, index, value)
      routes.each do |route|
        if route[0][index] == value
          return true
        end
      end
      return false
    end

    def do_routing_introspection
      routes = []
      ActionController::Routing::Routes.routes.each do |route|
        static_path = []
        route.segments.each do |segment|
          if segment.kind_of?(ActionController::Routing::StaticSegment)
            static_path << segment.value if (segment.respond_to?(:value) && segment.value != "/")
          elsif segment.kind_of?(ActionController::Routing::DynamicSegment)
            #TODO ignoring (.:format), think about it:
            static_path << :dynamic unless (segment.respond_to?(:key) && segment.key == :format)   
          end
        end
        routes << [static_path, route.conditions[:method]] unless route.conditions[:method].nil?
      end
      routes
    end

    def prepare_request_path(path)
      path = path[0..(path.rindex('.')-1)] if path.include?('.') #TODO ignoring (.:format), think about it
      path_parts = path.split("/")
      path_parts.delete("")
      path_parts
    end

  end

end