require 'moneta'
require 'rack/session/abstract/id'
require 'thread'

module Rack
  module Session
    # Rack::Session::Moneta stores sessions in a Moneta store.
    #
    # Example:
    #
    # use Rack::Session::Moneta, key: 'rack.session',
    # domain: 'foo.com',
    # path: '/',
    # expire_after: 2592000,
    # store: Moneta.new(...)
    #
    # You can use all options supported by `Rack::Session::Abstract::ID`.
    #
    # @api public
    class Moneta < Abstract::ID
      attr_reader :mutex, :pool

      def initialize(app, options = {}, &block)
        super
        if block
          raise ArgumentError, 'Use either block or option :store' if options[:store]
          @pool = ::Moneta.build(&block)
        else
          raise ArgumentError, 'Block or option :store is required' unless @pool = options[:store]
          @pool = ::Moneta.new(@pool, expires: true) if Symbol === @pool
        end
        @pool = ::Moneta::WeakCreate.new(@pool) unless @pool.supports?(:create)
        @mutex = ::Mutex.new
      end

      def generate_sid
        loop do
          sid = super
          break sid unless @pool.key?(sid)
        end
      end

      def get_session(env, sid)
        with_lock(env) do
          unless sid && session = @pool[sid]
            session = {}
            begin
              sid = generate_sid
            end until @pool.create(sid, session)
          end
          [sid, session]
        end
      end

      def set_session(env, session_id, new_session, options)
        with_lock(env) do
          @pool.store(session_id, new_session,
                      options[:expire_after] ? { expires: options[:expire_after] } : {})
          session_id
        end
      end

      def destroy_session(env, session_id, options)
        with_lock(env) do
          @pool.delete(session_id)
          generate_sid unless options[:drop]
        end
      end

      def with_lock(env)
        @mutex.lock if env['rack.multithread']
        yield
      ensure
        @mutex.unlock if @mutex.locked?
      end
    end
  end
end