require 'openssl'
require 'path-builder'
require 'active_support/core_ext/string/inflections'

module SecondStep
  def self.register_orm_adapter(**opts)
    if @registered_orm_adapters
      @registered_orm_adapters.merge! opts
    else
      @registered_orm_adapters = opts
    end
  end

  SecondStep.register_orm_adapter active_record: 'second_step/active_record_adapter',
                                  memory: 'second_step/memory_adapter'

  def self.use_orm(orm)
    return :none if orm == :none
    include @registered_orm_adapters[orm].to_s.camelcase.constantize
  end

  class Config
    def initialize(&block)
      self.instance_eval(&block)
    end

    class<< self
      private
      # A dry way of specifing config options.
      def config_option(name, default_value=nil, setter: nil, before_set: nil,
                        after_set: nil, getter: nil, &default)
        instance_eval { define_method name do |new_value=nil|
          var = "@#{name}"
          value = if new_value
            new_value = instance_exec(new_value, &setter) if setter
            instance_exec new_value, &before_set if before_set
            new_value = instance_variable_set var, new_value
            instance_exec new_value, &after_set if after_set
            new_value
          else
            instance_variable_get var
          end
          value ||= default ? instance_eval(&default) : instance_variable_set(var, default_value)  # For some reason, removing instance_eval on Ruby 2.3.0 causes a segfault when api_path is accessed.
          (value && getter) ? getter.call(value) : value
        end }
      end
    end

    def path(*args)
      PathBuilder.new(*args)
    end

    config_option :secondstep_uri, 'https://getsecondstep.com/', after_set: -> (uri) {
      @base_path = nil
    }
    config_option :secondstep_aud, "SecondStep Authentication - Env: production - Host: https://getsecondstep.com - Tech Edge Advisors, LLC."
    config_option(:api_path,
      setter: -> (path) { path.save! },
      getter: -> (path) { path.new },
      after_set: -> (uri) { @base_path = nil }){
        path.api(:version).save![version]
      }
    config_option :application_id
    config_option :client_id
    config_option :client_secret
    config_option :redirect_uri, 'urn:ietf:wg:oauth:2.0:oob'
    config_option :version, 'v1'
    config_option :rsa_key
    config_option :orm_adapter, before_set: -> (orm) {
      raise ORMAlreadySetError if @orm_adapter
    }, after_set: -> (orm) { SecondStep.use_orm orm }
    config_option :secret_string_length
    config_option :word_list_path, '/usr/share/dict/words', after_set: -> (_) {
      @word_list_count = nil
      @phrase_possibility_count = nil
      @phrase_entropy = nil
    }
    config_option :phrase_generator_min_entropy, 92
    config_option :phrase_generator_length, 5, after_set: -> (_) {
      @phrase_possibility_count = nil
      @phrase_entropy = nil
    }
    config_option :phrase_delimiters, %{., -:;_+~*=}.split(''), after_set: -> (delimiters) {
      @phrase_possibility_count = nil
      @phrase_entropy = nil
    }
    config_option :secret_qr_length, 50
    config_option :jwt_leeway, 0
    config_option :jwt_hmac_algorithm, 'HS512'
    config_option :jwt_rsa_algorithm, 'RS512'

    def word_list_count
      @word_list_count ||= `sed -n '$=' #{word_list_path}`.chomp.to_i
    end
    def phrase_possibility_count
      @phrase_possibility_count ||= (word_list_count ** phrase_generator_length) * phrase_delimiters.length
    end
    def phrase_entropy
      @phrase_entropy ||= Math.log2 phrase_possibility_count
    end
    def secondstep_path
      path self.secondstep_uri
    end
    def base_path
      (@base_path ||= (secondstep_path + api_path).save!).new
    end
    def public_key
      rsa_key.public_key
    end
  end
  def self.config(&block)
    block ? @config = Config.new(&block) : @config
  end
end