module Figleaf
  class Settings
    InvalidYAML = Class.new(RuntimeError)
    InvalidRb = Class.new(RuntimeError)

    class_attribute :auto_define
    self.auto_define = false

    class << self
      # Public - configure pre-defined attributes
      #
      def configure
        auto_define.tap do |cached_auto_define|
          self.auto_define = false
          yield self
          self.auto_define = cached_auto_define
        end
      end

      # Public - configure auto defined settings attributes
      # and load yaml settings from confing/settings directory
      #
      def configure!(&)
        load_settings
        configure_with_auto_define(&)
      end

      def configure_with_auto_define
        auto_define.tap do |cached_auto_define|
          self.auto_define = true
          yield self
          self.auto_define = cached_auto_define
        end
      end

      # Load all files in config/settings and set their contents as first level
      # citizen of Settings:
      # config/settings/some_service.yml contains
      # production:
      #   foo: bar
      # --> Settings.some_service.foo = bar
      def load_settings(file_pattern = default_file_pattern, env_to_load = env)
        configure_with_auto_define do
          Dir.glob(file_pattern).each do |file|
            property_name, property = load_file(file, env_to_load)

            next if property.nil?

            if respond_to?(property_name) &&
                send(property_name).respond_to?(:merge) &&
                property.respond_to?(:merge)
              property = send(property_name).merge(property)
            end

            send(:"#{property_name}=", property)
          end
        end
      end

      def load_file(file, env_to_load = env)
        if file.end_with?(".rb")
          property_name = File.basename(file, ".rb")
          config = load_rb_file(file) or return nil
        else
          property_name = File.basename(file, ".yml")
          config = load_yaml_file(file) or return nil
        end

        return if config.nil?

        default = config["default"]
        property = config[env_to_load]
        property = default.merge(property || {}) if !default.nil?

        [property_name, use_hashie_if_hash(property)]
      end

      def load_rb_file(file_path, env = nil)
        contents = File.read(file_path)
        block = ->(*) { eval contents }
        Config.new.call(&block)
      rescue SyntaxError => e
        raise InvalidRb, "#{file_path} has invalid Ruby\n" + e.message
      end

      def load_yaml_file(file_path)
        YAML.safe_load(ERB.new(IO.read(file_path)).result, aliases: true)
      rescue Psych::SyntaxError => e
        raise InvalidYAML, "#{file_path} has invalid YAML\n" + e.message
      end

      def root
        return Rails.root if defined?(Rails)
        Pathname.new(".")
      end

      def default_file_pattern
        [root.join("config/settings/*.yml"), root.join("config/settings/*.rb")]
      end

      def env
        return Rails.env if defined?(Rails)
        ENV["ENVIRONMENT"]
      end

      def use_hashie_if_hash(property)
        return Figleaf::Fighash.new(property) if property.is_a?(Hash)
        property
      end

      def override_with_local!(local_file)
        # this file (i.e. test.local.rb) is an optional place to put settings
        local_file.tap do |local_settings_path|
          eval(IO.read(local_settings_path), binding) if File.exist?(local_settings_path)
        end
      end

      def method_missing(method_name, *args)
        getter_name, modifier = extract_getter_name_and_modifier(method_name)

        if auto_define && modifier == "=" && args.length == 1
          define_cattr_methods(getter_name)
          send(method_name, args.shift)
        elsif modifier == "?" && args.empty?
          send(getter_name).present?
        else
          super
        end
      end

      def extract_getter_name_and_modifier(method_name)
        match = method_name.to_s.match(/(?<name>.*?)(?<modifier>[?=]?)$/)
        [match[:name], match[:modifier]]
      end

      def define_cattr_methods(getter_name)
        cattr_writer getter_name
        define_singleton_method(getter_name) do
          result = class_variable_get :"@@#{getter_name}"
          result.respond_to?(:call) ? result.call : result
        end
      end
    end
  end
end