class Grape::Middleware::Versioner::Header

def accept_header
  env[Grape::Http::Headers::HTTP_ACCEPT]
end

def accept_header_check!
  return if accept_header.present?
  invalid_accept_header!('Accept header must be set.')
end

def available_media_types
  [].tap do |available_media_types|
    base_media_type = "application/vnd.#{vendor}"
    content_types.each_key do |extension|
      versions&.reverse_each do |version|
        available_media_types << "#{base_media_type}-#{version}+#{extension}"
        available_media_types << "#{base_media_type}-#{version}"
      end
      available_media_types << "#{base_media_type}+#{extension}"
    end
    available_media_types << base_media_type
    available_media_types.concat(content_types.values.flatten)
  end
end

def before
  match_best_quality_media_type! do |media_type|
    env.update(
      Grape::Env::API_TYPE => media_type.type,
      Grape::Env::API_SUBTYPE => media_type.subtype,
      Grape::Env::API_VENDOR => media_type.vendor,
      Grape::Env::API_VERSION => media_type.version,
      Grape::Env::API_FORMAT => media_type.format
    )
  end
end

def fail!
  return if env[Grape::Env::GRAPE_ALLOWED_METHODS].present?
  media_types = q_values_mime_types.map { |mime_type| Grape::Util::MediaType.parse(mime_type) }
  vendor_not_found!(media_types) || version_not_found!(media_types)
end

def invalid_accept_header!(message)
  raise Grape::Exceptions::InvalidAcceptHeader.new(message, error_headers)
end

def invalid_version_header!(message)
  raise Grape::Exceptions::InvalidVersionHeader.new(message, error_headers)
end

def match_best_quality_media_type!
  return unless vendor
  strict_header_checks!
  media_type = Grape::Util::MediaType.best_quality(accept_header, available_media_types)
  if media_type
    yield media_type
  else
    fail!
  end
end

def q_values_mime_types
  @q_values_mime_types ||= Rack::Utils.q_values(accept_header).map(&:first)
end

def strict_header_checks!
  return unless strict?
  accept_header_check!
  version_and_vendor_check!
end

def vendor_not_found!(media_types)
  return unless media_types.all? { |media_type| media_type&.vendor && media_type.vendor != vendor }
  invalid_accept_header!('API vendor not found.')
end

def version_and_vendor?
  q_values_mime_types.any? { |mime_type| Grape::Util::MediaType.match?(mime_type) }
end

def version_and_vendor_check!
  return if versions.blank? || version_and_vendor?
  invalid_accept_header!('API vendor or version not found.')
end

def version_not_found!(media_types)
  return unless media_types.all? { |media_type| media_type&.version && versions&.exclude?(media_type.version) }
  invalid_version_header!('API version not found.')
end