package autoupdate

import (
	"context"
	"os"
	"sort"

	"github.com/containers/image/v5/docker"
	"github.com/containers/image/v5/docker/reference"
	"github.com/containers/image/v5/manifest"
	"github.com/containers/image/v5/transports/alltransports"
	"github.com/containers/libpod/libpod"
	"github.com/containers/libpod/libpod/define"
	"github.com/containers/libpod/libpod/image"
	"github.com/containers/libpod/pkg/systemd"
	systemdGen "github.com/containers/libpod/pkg/systemd/generate"
	"github.com/containers/libpod/pkg/util"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// Label denotes the container/pod label key to specify auto-update policies in
// container labels.
const Label = "io.containers.autoupdate"

// Policy represents an auto-update policy.
type Policy string

const (
	// PolicyDefault is the default policy denoting no auto updates.
	PolicyDefault Policy = "disabled"
	// PolicyNewImage is the policy to update as soon as there's a new image found.
	PolicyNewImage = "image"
)

// Map for easy lookups of supported policies.
var supportedPolicies = map[string]Policy{
	"":         PolicyDefault,
	"disabled": PolicyDefault,
	"image":    PolicyNewImage,
}

// LookupPolicy looksup the corresponding Policy for the specified
// string. If none is found, an errors is returned including the list of
// supported policies.
//
// Note that an empty string resolved to PolicyDefault.
func LookupPolicy(s string) (Policy, error) {
	policy, exists := supportedPolicies[s]
	if exists {
		return policy, nil
	}

	// Sort the keys first as maps are non-deterministic.
	keys := []string{}
	for k := range supportedPolicies {
		if k != "" {
			keys = append(keys, k)
		}
	}
	sort.Strings(keys)

	return "", errors.Errorf("invalid auto-update policy %q: valid policies are %+q", s, keys)
}

// ValidateImageReference checks if the specified imageName is a fully-qualified
// image reference to the docker transport (without digest).  Such a reference
// includes a domain, name and tag (e.g., quay.io/podman/stable:latest).  The
// reference may also be prefixed with "docker://" explicitly indicating that
// it's a reference to the docker transport.
func ValidateImageReference(imageName string) error {
	// Make sure the input image is a docker.
	imageRef, err := alltransports.ParseImageName(imageName)
	if err == nil && imageRef.Transport().Name() != docker.Transport.Name() {
		return errors.Errorf("auto updates require the docker image transport but image is of transport %q", imageRef.Transport().Name())
	} else if err != nil {
		repo, err := reference.Parse(imageName)
		if err != nil {
			return errors.Wrap(err, "error enforcing fully-qualified docker transport reference for auto updates")
		}
		if _, ok := repo.(reference.NamedTagged); !ok {
			return errors.Errorf("auto updates require fully-qualified image references (no tag): %q", imageName)
		}
		if _, ok := repo.(reference.Digested); ok {
			return errors.Errorf("auto updates require fully-qualified image references without digest: %q", imageName)
		}
	}
	return nil
}

// AutoUpdate looks up containers with a specified auto-update policy and acts
// accordingly.  If the policy is set to PolicyNewImage, it checks if the image
// on the remote registry is different than the local one. If the image digests
// differ, it pulls the remote image and restarts the systemd unit running the
// container.
//
// It returns a slice of successfully restarted systemd units and a slice of
// errors encountered during auto update.
func AutoUpdate(runtime *libpod.Runtime) ([]string, []error) {
	// Create a map from `image ID -> []*Container`.
	containerMap, errs := imageContainersMap(runtime)
	if len(containerMap) == 0 {
		return nil, errs
	}

	// Create a map from `image ID -> *image.Image` for image lookups.
	imagesSlice, err := runtime.ImageRuntime().GetImages()
	if err != nil {
		return nil, []error{err}
	}
	imageMap := make(map[string]*image.Image)
	for i := range imagesSlice {
		imageMap[imagesSlice[i].ID()] = imagesSlice[i]
	}

	// Connect to DBUS.
	conn, err := systemd.ConnectToDBUS()
	if err != nil {
		logrus.Errorf(err.Error())
		return nil, []error{err}
	}
	defer conn.Close()

	// Update images.
	containersToRestart := []*libpod.Container{}
	updatedRawImages := make(map[string]bool)
	for imageID, containers := range containerMap {
		image, exists := imageMap[imageID]
		if !exists {
			errs = append(errs, errors.Errorf("container image ID %q not found in local storage", imageID))
			return nil, errs
		}
		// Now we have to check if the image of any containers must be updated.
		// Note that the image ID is NOT enough for this check as a given image
		// may have multiple tags.
		for i, ctr := range containers {
			rawImageName := ctr.RawImageName()
			if rawImageName == "" {
				errs = append(errs, errors.Errorf("error auto-updating container %q: raw-image name is empty", ctr.ID()))
			}
			needsUpdate, err := newerImageAvailable(runtime, image, rawImageName)
			if err != nil {
				errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: image check for %q failed", ctr.ID(), rawImageName))
				continue
			}
			if !needsUpdate {
				continue
			}
			logrus.Infof("Auto-updating container %q using image %q", ctr.ID(), rawImageName)
			if _, updated := updatedRawImages[rawImageName]; !updated {
				_, err = updateImage(runtime, rawImageName)
				if err != nil {
					errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: image update for %q failed", ctr.ID(), rawImageName))
					continue
				}
				updatedRawImages[rawImageName] = true
			}
			containersToRestart = append(containersToRestart, containers[i])
		}
	}

	// Restart containers.
	updatedUnits := []string{}
	for _, ctr := range containersToRestart {
		labels := ctr.Labels()
		unit, exists := labels[systemdGen.EnvVariable]
		if !exists {
			// Shouldn't happen but let's be sure of it.
			errs = append(errs, errors.Errorf("error auto-updating container %q: no %s label found", ctr.ID(), systemdGen.EnvVariable))
			continue
		}
		_, err := conn.RestartUnit(unit, "replace", nil)
		if err != nil {
			errs = append(errs, errors.Wrapf(err, "error auto-updating container %q: restarting systemd unit %q failed", ctr.ID(), unit))
			continue
		}
		logrus.Infof("Successfully restarted systemd unit %q", unit)
		updatedUnits = append(updatedUnits, unit)
	}

	return updatedUnits, errs
}

// imageContainersMap generates a map[image ID] -> [containers using the image]
// of all containers with a valid auto-update policy.
func imageContainersMap(runtime *libpod.Runtime) (map[string][]*libpod.Container, []error) {
	allContainers, err := runtime.GetAllContainers()
	if err != nil {
		return nil, []error{err}
	}

	errors := []error{}
	imageMap := make(map[string][]*libpod.Container)
	for i, ctr := range allContainers {
		state, err := ctr.State()
		if err != nil {
			errors = append(errors, err)
			continue
		}
		// Only update running containers.
		if state != define.ContainerStateRunning {
			continue
		}

		// Only update containers with the specific label/policy set.
		labels := ctr.Labels()
		value, exists := labels[Label]
		if !exists {
			continue
		}

		policy, err := LookupPolicy(value)
		if err != nil {
			errors = append(errors, err)
			continue
		}

		// Skip non-image labels (could be explicitly disabled).
		if policy != PolicyNewImage {
			continue
		}

		// Now we know that `ctr` is configured for auto updates.
		id, _ := ctr.Image()
		imageMap[id] = append(imageMap[id], allContainers[i])
	}

	return imageMap, errors
}

// newerImageAvailable returns true if there corresponding image on the remote
// registry is newer.
func newerImageAvailable(runtime *libpod.Runtime, img *image.Image, origName string) (bool, error) {
	remoteRef, err := docker.ParseReference("//" + origName)
	if err != nil {
		return false, err
	}

	remoteImg, err := remoteRef.NewImage(context.Background(), runtime.SystemContext())
	if err != nil {
		return false, err
	}

	rawManifest, _, err := remoteImg.Manifest(context.Background())
	if err != nil {
		return false, err
	}

	remoteDigest, err := manifest.Digest(rawManifest)
	if err != nil {
		return false, err
	}

	return img.Digest().String() != remoteDigest.String(), nil
}

// updateImage pulls the specified image.
func updateImage(runtime *libpod.Runtime, name string) (*image.Image, error) {
	sys := runtime.SystemContext()
	registryOpts := image.DockerRegistryOptions{}
	signaturePolicyPath := ""
	authFilePath := ""

	if sys != nil {
		registryOpts.OSChoice = sys.OSChoice
		registryOpts.ArchitectureChoice = sys.OSChoice
		registryOpts.DockerCertPath = sys.DockerCertPath

		signaturePolicyPath = sys.SignaturePolicyPath
		authFilePath = sys.AuthFilePath
	}

	newImage, err := runtime.ImageRuntime().New(context.Background(),
		docker.Transport.Name()+"://"+name,
		signaturePolicyPath,
		authFilePath,
		os.Stderr,
		&registryOpts,
		image.SigningOptions{},
		nil,
		util.PullImageAlways,
	)
	if err != nil {
		return nil, err
	}
	return newImage, nil
}