class ReeMapper::Mapper

def self.build(strategies, type = nil)
  if type
    strategies.each do |strategy|
      method = strategy.method
      next if type.respond_to?(method)
      raise ReeMapper::UnsupportedTypeError, "type #{type.name} should implement method `#{method}`"
    end
  end
  klass = Class.new(self)
  klass.instance_eval do
    strategies.each do |strategy|
      method = strategy.method
      if type
        class_eval(<<~RUBY, __FILE__, __LINE__ + 1)
          def #{method}(obj, name: nil, role: nil)
            @type.#{method}(obj, name: name, role: role)
          end
        RUBY
      else
        class_eval(<<~RUBY, __FILE__, __LINE__ + 1)
          def #{method}(obj, name: nil, role: nil)
            @fields.each_with_object(@#{method}_strategy.build_object) do |(_, field), acc|
              next unless field.has_role?(role)
              nested_name = name ? "\#{name}[\#{field.name_as_str}]" : field.name_as_str
              if @#{method}_strategy.has_value?(obj, field)
                value = @#{method}_strategy.get_value(obj, field)
                unless value.nil? && field.null
                  value = field.type.#{method}(value, name: nested_name, role: role)
                end
                @#{method}_strategy.assign_value(acc, field, value)
              elsif field.optional || @#{method}_strategy.always_optional
                if field.has_default?
                  value = field.default
                  unless value.nil? && field.null
                    value = field.type.#{method}(value, name: nested_name, role: role)
                  end
                  @#{method}_strategy.assign_value(acc, field, value)
                end
              else
                raise ReeMapper::TypeError, "Missing required field `\#{field.from_as_str}` for `\#{name || 'root'}`"
              end
            end
          end
        RUBY
      end
    end
  end
  klass.new(strategies, type)
end

def add_field(type, name, **opts)
  @fields[name] = ReeMapper::Field.new(type, name, **opts)
  nil
end

def initialize(strategies, type)
  @fields = {}
  @type = type
  @strategies = strategies
  @strategy_methods = strategies.map(&:method)
  strategies.each do |strategy|
    method = strategy.method
    instance_variable_set(:"@#{method}_strategy", strategy)
  end
end

def name
  @name
end

def name=(name)
  @name = name
end