// New initializes a new engine managing the directory specified at `root`.
// `root` is used to store containers and any other state private to the engine.
// Changing the contents of the root without executing a job will cause unspecified
// behavior.
func New(root string) (*Engine, error) {
	// Check for unsupported architectures
	if runtime.GOARCH != "amd64" {
		return nil, fmt.Errorf("The docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
	}
	// Check for unsupported kernel versions
	// FIXME: it would be cleaner to not test for specific versions, but rather
	// test for specific functionalities.
	// Unfortunately we can't test for the feature "does not cause a kernel panic"
	// without actually causing a kernel panic, so we need this workaround until
	// the circumstances of pre-3.8 crashes are clearer.
	// For details see http://github.com/dotcloud/docker/issues/407
	if k, err := utils.GetKernelVersion(); err != nil {
		log.Printf("WARNING: %s\n", err)
	} else {
		if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
		}
	}
	if err := os.MkdirAll(root, 0700); err != nil && !os.IsExist(err) {
		return nil, err
	}
	eng := &Engine{
		root:     root,
		handlers: globalHandlers,
	}
	return eng, nil
}

// New initializes a new engine managing the directory specified at `root`.
// `root` is used to store containers and any other state private to the engine.
// Changing the contents of the root without executing a job will cause unspecified
// behavior.
func New(root string) (*Engine, error) {
	// Check for unsupported architectures
	if runtime.GOARCH != "amd64" {
		return nil, fmt.Errorf("The docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
	}
	// Check for unsupported kernel versions
	// FIXME: it would be cleaner to not test for specific versions, but rather
	// test for specific functionalities.
	// Unfortunately we can't test for the feature "does not cause a kernel panic"
	// without actually causing a kernel panic, so we need this workaround until
	// the circumstances of pre-3.8 crashes are clearer.
	// For details see http://github.com/dotcloud/docker/issues/407
	if k, err := utils.GetKernelVersion(); err != nil {
		log.Printf("WARNING: %s\n", err)
	} else {
		if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
				log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
			}
		}
	}

	if err := os.MkdirAll(root, 0700); err != nil && !os.IsExist(err) {
		return nil, err
	}

	// Docker makes some assumptions about the "absoluteness" of root
	// ... so let's make sure it has no symlinks
	if p, err := filepath.Abs(root); err != nil {
		log.Fatalf("Unable to get absolute root (%s): %s", root, err)
	} else {
		root = p
	}
	if p, err := filepath.EvalSymlinks(root); err != nil {
		log.Fatalf("Unable to canonicalize root (%s): %s", root, err)
	} else {
		root = p
	}

	eng := &Engine{
		root:     root,
		handlers: make(map[string]Handler),
		id:       utils.RandomString(),
		Stdout:   os.Stdout,
		Stderr:   os.Stderr,
		Stdin:    os.Stdin,
	}
	eng.Register("commands", func(job *Job) Status {
		for _, name := range eng.commands() {
			job.Printf("%s\n", name)
		}
		return StatusOK
	})
	// Copy existing global handlers
	for k, v := range globalHandlers {
		eng.handlers[k] = v
	}
	return eng, nil
}

// FIXME: harmonize with NewGraph()
func NewRuntime(config *DaemonConfig) (*Runtime, error) {
	runtime, err := NewRuntimeFromDirectory(config)
	if err != nil {
		return nil, err
	}

	if k, err := utils.GetKernelVersion(); err != nil {
		log.Printf("WARNING: %s\n", err)
	} else {
		if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
		}
	}
	runtime.UpdateCapabilities(false)
	return runtime, nil
}

// FIXME: harmonize with NewGraph()
func NewRuntime(flGraphPath string, autoRestart bool, dns []string) (*Runtime, error) {
	runtime, err := NewRuntimeFromDirectory(flGraphPath, autoRestart)
	if err != nil {
		return nil, err
	}
	runtime.Dns = dns

	if k, err := utils.GetKernelVersion(); err != nil {
		log.Printf("WARNING: %s\n", err)
	} else {
		runtime.kernelVersion = k
		if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
		}
	}
	runtime.UpdateCapabilities(false)
	return runtime, nil
}

func checkKernelAndArch() error {
	// Check for unsupported architectures
	if runtime.GOARCH != "amd64" {
		return fmt.Errorf("The Docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
	}
	// Check for unsupported kernel versions
	// FIXME: it would be cleaner to not test for specific versions, but rather
	// test for specific functionalities.
	// Unfortunately we can't test for the feature "does not cause a kernel panic"
	// without actually causing a kernel panic, so we need this workaround until
	// the circumstances of pre-3.8 crashes are clearer.
	// For details see http://github.com/dotcloud/docker/issues/407
	if k, err := utils.GetKernelVersion(); err != nil {
		log.Printf("WARNING: %s\n", err)
	} else {
		if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
				log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
			}
		}
	}
	return nil
}