docker_tag_pusher.rb

require "json"
require "net/http"
require "uri"

class DockerTagPusher
  REGISTRY = "https://registry-1.docker.io".freeze
  MEDIA_TYPE = "application/vnd.docker.distribution.manifest.v2+json".freeze

  attr_reader :username, :password
  private :username, :password

  def initialize(username, password)
    @username = username
    @password = password
  end

  def has_repo?(repo)
    request = Net::HTTP::Get.new(
      "#{REGISTRY}/v2/#{repo}/tags/list?n=1",
      "Authorization" => "Bearer #{token(repo)}",
    )
    response = registry_client.request(request)
    raise "Error (#{response.code}) checking repo exists: #{response.body}" unless %w[200 404].include?(response.code)

    response.code == "200"
  end

  def get_manifest(repo, tag)
    request = Net::HTTP::Get.new(
      "#{REGISTRY}/v2/#{repo}/manifests/#{tag}",
      "Authorization" => "Bearer #{token(repo)}",
      "Accept" => MEDIA_TYPE,
    )
    response = registry_client.request(request)

    raise "Image or tag not found" if response.code == "404"
    raise "Error (#{response.code}) while fetching manifest: #{response.body}" if response.code != "200"
    raise "Remote image not in correct format (must be #{MEDIA_TYPE})" if response["Content-Type"] != MEDIA_TYPE

    response.body
  end

  def put_manifest(repo, manifest, tag)
    request = Net::HTTP::Put.new(
      "#{REGISTRY}/v2/#{repo}/manifests/#{tag}",
      "Authorization" => "Bearer #{token(repo)}",
      "Content-Type" => MEDIA_TYPE,
    )
    request.body = manifest
    response = registry_client.request(request)

    raise "Server error while putting manifest: #{response.body}" if response.code != "201"
  end

private

  def token(repo)
    uri = URI.parse("https://auth.docker.io/token?service=registry.docker.io&scope=repository:#{repo}:pull,push")

    Net::HTTP.start(uri.host, uri.port, use_ssl: true) do |http|
      request = Net::HTTP::Get.new uri
      request.basic_auth username, password
      response = http.request request
      JSON.parse(response.body)["token"]
    end
  end

  def registry_client
    @registry_client ||= begin
      uri = URI.parse(REGISTRY)
      Net::HTTP.new(uri.host, uri.port).tap do |client|
        client.use_ssl = uri.scheme == "https"
      end
    end
  end
end