require 'logger'

def load_path_candidates_for(filename)
  $LOAD_PATH.select { |path| File.exist?(File.join(path, filename)) }
end

def pick_first(candidates, *regexps)
  for r in regexps
    match = candidates.find { |c| c =~ r }
    return match if match
  end
  nil
end

candidate_paths = load_path_candidates_for('dispatcher.rb')

built_in_dispatcher_path = pick_first(candidate_paths, /vendor/, /gems/)

if built_in_dispatcher_path
  RAILS_DEFAULT_LOGGER.debug "Using pre-dispatcher from\n  #{File.expand_path(__FILE__)})"
  RAILS_DEFAULT_LOGGER.debug "Loading built-in dispatcher from\n  #{built_in_dispatcher_path}"
  Kernel.load File.join(built_in_dispatcher_path, 'dispatcher.rb')

  class Dispatcher
    class << self
      alias_method :original_dispatch, :dispatch

      def dispatch(cgi = nil, session_options = ActionController::CgiRequest::DEFAULT_SESSION_OPTIONS, output = $stdout)
        begin
          ActiveRecord::Base.connection
        rescue Exception => e
          RAILS_DEFAULT_LOGGER.debug \
           "Pre-Dispatcher (#{__FILE__}) trapped exception: #{e.class} -- #{e}"
          if cgi ||= new_cgi(output)
            request  = ActionController::CgiRequest.new(cgi, session_options)
            response = ActionController::CgiResponse.new(cgi)
            request.parameters[:error] = e
            begin
              DatabaseExceptionController.process(request, response).out(output)
            rescue Exception => f
              RAILS_DEFAULT_LOGGER.debug \
                "Pre-Dispatcher (#{__FILE__}) trap failed with: #{f}"
            end
          end
        else
          original_dispatch(cgi, session_options, output)
        end
      end

    end
  end
end