class Aws::S3::Presigner

def expires_in(params)
  if expires_in = params.delete(:expires_in)
    if expires_in > ONE_WEEK
      msg = "expires_in value of #{expires_in} exceeds one-week maximum"
      raise ArgumentError, msg
    end
    expires_in
  else
    FIFTEEN_MINUTES
  end
end

def http_scheme(params, virtual_host)
  if params.delete(:secure) == false || virtual_host
    'http'
  else
    @client.config.endpoint.scheme
  end
end

def initialize(options = {})
  @client = options[:client] || Aws::S3::Client.new
end

def presigned_url(method, params = {})
  if params[:key].nil? or params[:key] == ''
    raise ArgumentError, ":key must not be blank"
  end
  virtual_host = !!params.delete(:virtual_host)
  scheme = http_scheme(params, virtual_host)
  req = @client.build_request(method, params)
  use_bucket_as_hostname(req) if virtual_host
  sign_but_dont_send(req, expires_in(params), scheme)
  req.send_request.data
end

def sign_but_dont_send(req, expires_in, scheme)
  req.handlers.remove(Plugins::S3RequestSigner::SigningHandler)
  req.handlers.remove(Seahorse::Client::Plugins::ContentLength::Handler)
  req.handle(step: :send) do |context|
    if scheme != context.http_request.endpoint.scheme
      endpoint = context.http_request.endpoint.dup
      endpoint.scheme = scheme
      endpoint.port = (scheme == 'http' ? 80 : 443)
      context.http_request.endpoint = URI.parse(endpoint.to_s)
    end
    signer = Signers::V4.new(
      context.config.credentials, 's3',
      context.config.region
    )
    url = signer.presigned_url(
      context.http_request,
      expires_in: expires_in,
      body_digest: "UNSIGNED-PAYLOAD"
    )
    Seahorse::Client::Response.new(context: context, data: url)
  end
end

def use_bucket_as_hostname(req)
  req.handlers.remove(Plugins::S3BucketDns::Handler)
  req.handle do |context|
    uri = context.http_request.endpoint
    uri.host = context.params[:bucket]
    uri.path.sub!("/#{context.params[:bucket]}", '')
    uri.scheme = 'http'
    uri.port = 80
    @handler.call(context)
  end
end