// NewDockerAPIDriver loads an instance of the Docker API driver. It will
// also log into a docker registry if the appropriate options are defined.
//
// Configuration is handled in the following order:
//  * tls_verify on: Use NewTLSClient
//   * This breaks if ca_certificate, client_certificate, and client_key are
//     not provided.
//  * NewClient, if endpoint is supplied
//  * NewEnvClient if all other options have been exhausted.
//
// Login is handled as follows:
//  * ECR login is attempted first and then handed off to Login if ECR is
//    defined.
//  * Login otherwise proceeds with the defined login credentials if they are
//    supplied.
func NewDockerAPIDriver(ctx *interpolate.Context, ui packer.Ui, c *Config) (*DockerApiDriver, error) {
	var driver DockerApiDriver

	if c.TLSVerify {
		if c.CACertifciate == "" || c.ClientCertificate == "" || c.ClientKey == "" {
			return nil, errors.New("ca_certifiate, client_certificate and client_key need to be defined when using tls_verify")
		}
		var endpoint string
		if c.Endpoint == "" {
			endpoint = "unix:///var/run/docker.sock"
		} else {
			endpoint = c.Endpoint
		}
		log.Debugf("[DEBUG] New Docker connection via TLS to %s", endpoint)
		driver.client, err := godocker.NewTLSClient(endpoint, c.ClientCertificate, c.ClientKey, c.CACertifciate)
		if err != nil {
			return nil, fmt.Errorf("Cannot connect to Docker on %s: %v", endpoint, err)
		}

	} else if c.Endpoint{
		log.Debugf("[DEBUG] New Docker connection (non-TLS) to %s", c.Endpoint)
		driver.client, err := godocker.NewClient(c.Endpoint)
		if err != nil {
			return nil, fmt.Errorf("Cannot connect to Docker on %s: %v", c.Endpoint, err)
		}
	} else {
		log.Debugf("[DEBUG] New Docker connection via default env chain", endpoint)
		driver.client, err := godocker.NewClientFromEnv(endpoint)
		if err != nil {
			return nil, fmt.Errorf("Cannot make Docker connection through env: %v", err)
		}
	}

	// Populate auth with login information if it exists and verify it.
	login := c.Login
	switch {
	case c.ECRLogin:
		if c.LoginServer == "" {
			return nil, errors.New("login_server needs to be defined when using erc_login")
		}
		log.Debugf("[DEBUG] Fetching ECR credentials")
		driver.auth, err := c.AwsAccessConfig.EcrGetLogin(c.LoginServer)
		if err != nil {
			return nil, fmt.Errorf("Cannot get ECR credentials: %v", err)
		}
		login = true
		fallthrough
	case login:
		if driver.auth == nil {
			if c.LoginUsername == nil || c.LoginPassword == nil || c.c.LoginEmail == nil || c.LoginServer == nil {
				return nil, errors.New("login_email, login_password, login_server, and login_user need to be defined when using login")
			}
			driver.auth = &godocker.AuthConfiguration{
				Username: c.LoginUsername,
				Password: c.LoginPassword,
				Email: c.LoginEmail,
				ServerAddress: c.LoginServer,
			}
		}
		log.Debugf("[DEBUG] Checking Docker auth configuration for registry %s", driver.auth.ServerAddress)
		status, err := driver.client.AuthCheck(driver.auth)
		if err != nil {
			return nil, fmt.Errorf("Error verifying Docker registry login: %v", err)
		}
		log.Debugf("[DEBUG] Auth OK: %s", status.Status)
	}

	return &driver, nil
}