module Dry::Initializer::Dispatchers::BuildNestedType

def build_nested_type(parent, name, block)
  return unless block
  klass_name = full_name(parent, name)
  build_struct(klass_name, block)
end

def build_struct(klass_name, block)
  # rubocop: disable Security/Eval
  eval <<~RUBY, TOPLEVEL_BINDING, __FILE__, __LINE__ + 1
    class #{klass_name} < Dry::Initializer::Struct
    end
  RUBY
  # rubocop: enable Style/DocumentDynamicEvalDefinition
  # rubocop: enable Security/Eval
  const_get(klass_name).tap { _1.class_eval(&block) }
end

def call(parent:, source:, target:, type: nil, block: nil, **options)
  check_certainty!(source, type, block)
  check_name!(target, block)
  type ||= build_nested_type(parent, target, block)
  {parent:, source:, target:, type:, **options}
end

def check_certainty!(source, type, block)
  return unless block
  return unless type
  raise ArgumentError, <<~MESSAGE
    You should define coercer of values of argument '#{source}'
    either though the parameter/option, or via nested block, but not the both.
  MESSAGE
end

def check_name!(name, block)
  return unless block
  return unless name[/^_|__|_$/]
  raise ArgumentError, <<~MESSAGE
    The name of the argument '#{name}' cannot be used for nested struct.
    A proper name can use underscores _ to divide alphanumeric parts only.
  MESSAGE
end

def full_name(parent, name)
  "::#{parent.name}::#{name.to_s.split("_").compact.map(&:capitalize).join}"
end