package containerd

import (
	"context"
	"encoding/json"
	"strings"
	"time"

	"github.com/containerd/containerd/content"
	cerrdefs "github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/images"
	"github.com/containerd/containerd/labels"
	"github.com/docker/distribution/reference"
	"github.com/docker/docker/api/types"
	"github.com/docker/docker/api/types/filters"
	timetypes "github.com/docker/docker/api/types/time"
	"github.com/opencontainers/go-digest"
	"github.com/opencontainers/image-spec/identity"
	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

var acceptedImageFilterTags = map[string]bool{
	"dangling":  true,
	"label":     true,
	"label!":    true,
	"before":    true,
	"since":     true,
	"reference": true,
	"until":     true,
}

// Images returns a filtered list of images.
//
// TODO(thaJeztah): sort the results by created (descending); see https://github.com/moby/moby/issues/43848
// TODO(thaJeztah): implement opts.ContainerCount (used for docker system df); see https://github.com/moby/moby/issues/43853
// TODO(thaJeztah): add labels to results; see https://github.com/moby/moby/issues/43852
// TODO(thaJeztah): verify behavior of `RepoDigests` and `RepoTags` for images without (untagged) or multiple tags; see https://github.com/moby/moby/issues/43861
// TODO(thaJeztah): verify "Size" vs "VirtualSize" in images; see https://github.com/moby/moby/issues/43862
func (i *ImageService) Images(ctx context.Context, opts types.ImageListOptions) ([]*types.ImageSummary, error) {
	if err := opts.Filters.Validate(acceptedImageFilterTags); err != nil {
		return nil, err
	}

	listFilters, filter, err := i.setupFilters(ctx, opts.Filters)
	if err != nil {
		return nil, err
	}

	imgs, err := i.client.ImageService().List(ctx, listFilters...)
	if err != nil {
		return nil, err
	}

	// TODO(thaJeztah): do we need to take multiple snapshotters into account? See https://github.com/moby/moby/issues/45273
	snapshotter := i.client.SnapshotService(i.snapshotter)
	sizeCache := make(map[digest.Digest]int64)
	snapshotSizeFn := func(d digest.Digest) (int64, error) {
		if s, ok := sizeCache[d]; ok {
			return s, nil
		}
		usage, err := snapshotter.Usage(ctx, d.String())
		if err != nil {
			return 0, err
		}
		sizeCache[d] = usage.Size
		return usage.Size, nil
	}

	var (
		summaries = make([]*types.ImageSummary, 0, len(imgs))
		root      []*[]digest.Digest
		layers    map[digest.Digest]int
	)
	if opts.SharedSize {
		root = make([]*[]digest.Digest, 0, len(imgs))
		layers = make(map[digest.Digest]int)
	}

	contentStore := i.client.ContentStore()
	for _, img := range imgs {
		if !filter(img) {
			continue
		}

		err := i.walkImageManifests(ctx, img, func(img *ImageManifest) error {
			if isPseudo, err := img.IsPseudoImage(ctx); isPseudo || err != nil {
				return err
			}

			available, err := img.CheckContentAvailable(ctx)
			if err != nil {
				logrus.WithFields(logrus.Fields{
					logrus.ErrorKey: err,
					"manifest":      img.Target(),
					"image":         img.Name(),
				}).Warn("checking availability of platform specific manifest failed")
				return nil
			}

			if !available {
				return nil
			}

			image, chainIDs, err := i.singlePlatformImage(ctx, contentStore, img)
			if err != nil {
				return err
			}

			summaries = append(summaries, image)

			if opts.SharedSize {
				root = append(root, &chainIDs)
				for _, id := range chainIDs {
					layers[id] = layers[id] + 1
				}
			}

			return nil
		})

		if err != nil {
			return nil, err
		}

	}

	if opts.SharedSize {
		for n, chainIDs := range root {
			sharedSize, err := computeSharedSize(*chainIDs, layers, snapshotSizeFn)
			if err != nil {
				return nil, err
			}
			summaries[n].SharedSize = sharedSize
		}
	}

	return summaries, nil
}

func (i *ImageService) singlePlatformImage(ctx context.Context, contentStore content.Store, image *ImageManifest) (*types.ImageSummary, []digest.Digest, error) {
	diffIDs, err := image.RootFS(ctx)
	if err != nil {
		return nil, nil, err
	}
	chainIDs := identity.ChainIDs(diffIDs)

	size, err := image.Size(ctx)
	if err != nil {
		return nil, nil, err
	}

	// TODO(thaJeztah): do we need to take multiple snapshotters into account? See https://github.com/moby/moby/issues/45273
	snapshotter := i.client.SnapshotService(i.snapshotter)
	sizeCache := make(map[digest.Digest]int64)

	snapshotSizeFn := func(d digest.Digest) (int64, error) {
		if s, ok := sizeCache[d]; ok {
			return s, nil
		}
		usage, err := snapshotter.Usage(ctx, d.String())
		if err != nil {
			if cerrdefs.IsNotFound(err) {
				return 0, nil
			}
			return 0, err
		}
		sizeCache[d] = usage.Size
		return usage.Size, nil
	}
	snapshotSize, err := computeSnapshotSize(chainIDs, snapshotSizeFn)
	if err != nil {
		return nil, nil, err
	}

	// totalSize is the size of the image's packed layers and snapshots
	// (unpacked layers) combined.
	totalSize := size + snapshotSize

	var repoTags, repoDigests []string
	rawImg := image.Metadata()
	target := rawImg.Target.Digest

	logger := logrus.WithFields(logrus.Fields{
		"name":   rawImg.Name,
		"digest": target,
	})

	ref, err := reference.ParseNamed(rawImg.Name)
	if err != nil {
		// If the image has unexpected name format (not a Named reference or a dangling image)
		// add the offending name to RepoTags but also log an error to make it clear to the
		// administrator that this is unexpected.
		// TODO: Reconsider when containerd is more strict on image names, see:
		//       https://github.com/containerd/containerd/issues/7986
		if !isDanglingImage(rawImg) {
			logger.WithError(err).Error("failed to parse image name as reference")
			repoTags = append(repoTags, rawImg.Name)
		}
	} else {
		repoTags = append(repoTags, reference.TagNameOnly(ref).String())

		digested, err := reference.WithDigest(reference.TrimNamed(ref), target)
		if err != nil {
			logger.WithError(err).Error("failed to create digested reference")
		} else {
			repoDigests = append(repoDigests, digested.String())
		}
	}

	summary := &types.ImageSummary{
		ParentID:    "",
		ID:          target.String(),
		Created:     rawImg.CreatedAt.Unix(),
		RepoDigests: repoDigests,
		RepoTags:    repoTags,
		Size:        totalSize,
		VirtualSize: totalSize, //nolint:staticcheck // ignore SA1019: field is deprecated, but still set on API < v1.44.
		// -1 indicates that the value has not been set (avoids ambiguity
		// between 0 (default) and "not set". We cannot use a pointer (nil)
		// for this, as the JSON representation uses "omitempty", which would
		// consider both "0" and "nil" to be "empty".
		SharedSize: -1,
		Containers: -1,
	}

	return summary, chainIDs, nil
}

type imageFilterFunc func(image images.Image) bool

// setupFilters constructs an imageFilterFunc from the given imageFilters.
//
// containerdListFilters is a slice of filters which should be passed to ImageService.List()
// filterFunc is a function that checks whether given image matches the filters.
// TODO(thaJeztah): reimplement filters using containerd filters: see https://github.com/moby/moby/issues/43845
func (i *ImageService) setupFilters(ctx context.Context, imageFilters filters.Args) (
	containerdListFilters []string, filterFunc imageFilterFunc, outErr error) {

	var fltrs []imageFilterFunc
	err := imageFilters.WalkValues("before", func(value string) error {
		ref, err := reference.ParseDockerRef(value)
		if err != nil {
			return err
		}
		img, err := i.client.GetImage(ctx, ref.String())
		if img != nil {
			t := img.Metadata().CreatedAt
			fltrs = append(fltrs, func(image images.Image) bool {
				created := image.CreatedAt
				return created.Equal(t) || created.After(t)
			})
		}
		return err
	})
	if err != nil {
		return nil, nil, err
	}

	err = imageFilters.WalkValues("since", func(value string) error {
		ref, err := reference.ParseDockerRef(value)
		if err != nil {
			return err
		}
		img, err := i.client.GetImage(ctx, ref.String())
		if img != nil {
			t := img.Metadata().CreatedAt
			fltrs = append(fltrs, func(image images.Image) bool {
				created := image.CreatedAt
				return created.Equal(t) || created.Before(t)
			})
		}
		return err
	})
	if err != nil {
		return nil, nil, err
	}

	err = imageFilters.WalkValues("until", func(value string) error {
		ts, err := timetypes.GetTimestamp(value, time.Now())
		if err != nil {
			return err
		}
		seconds, nanoseconds, err := timetypes.ParseTimestamps(ts, 0)
		if err != nil {
			return err
		}
		until := time.Unix(seconds, nanoseconds)

		fltrs = append(fltrs, func(image images.Image) bool {
			created := image.CreatedAt
			return created.Before(until)
		})
		return err
	})
	if err != nil {
		return nil, nil, err
	}

	labelFn, err := setupLabelFilter(i.client.ContentStore(), imageFilters)
	if err != nil {
		return nil, nil, err
	}
	if labelFn != nil {
		fltrs = append(fltrs, labelFn)
	}

	if imageFilters.Contains("dangling") {
		danglingValue, err := imageFilters.GetBoolOrDefault("dangling", false)
		if err != nil {
			return nil, nil, err
		}
		fltrs = append(fltrs, func(image images.Image) bool {
			return danglingValue == isDanglingImage(image)
		})
	}

	var listFilters []string
	err = imageFilters.WalkValues("reference", func(value string) error {
		ref, err := reference.ParseNormalizedNamed(value)
		if err != nil {
			return err
		}
		ref = reference.TagNameOnly(ref)
		listFilters = append(listFilters, "name=="+ref.String())
		return nil
	})
	if err != nil {
		return nil, nil, err
	}

	return listFilters, func(image images.Image) bool {
		for _, filter := range fltrs {
			if !filter(image) {
				return false
			}
		}
		return true
	}, nil
}

// setupLabelFilter parses filter args for "label" and "label!" and returns a
// filter func which will check if any image config from the given image has
// labels that match given predicates.
func setupLabelFilter(store content.Store, fltrs filters.Args) (func(image images.Image) bool, error) {
	type labelCheck struct {
		key        string
		value      string
		onlyExists bool
		negate     bool
	}

	var checks []labelCheck
	for _, fltrName := range []string{"label", "label!"} {
		for _, l := range fltrs.Get(fltrName) {
			k, v, found := strings.Cut(l, "=")
			err := labels.Validate(k, v)
			if err != nil {
				return nil, err
			}

			negate := strings.HasSuffix(fltrName, "!")

			// If filter value is key!=value then flip the above.
			if strings.HasSuffix(k, "!") {
				k = strings.TrimSuffix(k, "!")
				negate = !negate
			}

			checks = append(checks, labelCheck{
				key:        k,
				value:      v,
				onlyExists: !found,
				negate:     negate,
			})
		}
	}

	return func(image images.Image) bool {
		ctx := context.TODO()

		// This is not an error, but a signal to Dispatch that it should stop
		// processing more content (otherwise it will run for all children).
		// It will be returned once a matching config is found.
		errFoundConfig := errors.New("success, found matching config")
		err := images.Dispatch(ctx, presentChildrenHandler(store, images.HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) (subdescs []ocispec.Descriptor, err error) {
			if !images.IsConfigType(desc.MediaType) {
				return nil, nil
			}
			// Subset of ocispec.Image that only contains Labels
			var cfg struct {
				Config struct {
					Labels map[string]string `json:"Labels,omitempty"`
				} `json:"Config,omitempty"`
			}
			if err := readConfig(ctx, store, desc, &cfg); err != nil {
				return nil, err
			}

			for _, check := range checks {
				value, exists := cfg.Config.Labels[check.key]

				if check.onlyExists {
					// label! given without value, check if doesn't exist
					if check.negate {
						// Label exists, config doesn't match
						if exists {
							return nil, nil
						}
					} else {
						// Label should exist
						if !exists {
							// Label doesn't exist, config doesn't match
							return nil, nil
						}
					}
					continue
				} else if !exists {
					// We are checking value and label doesn't exist.
					return nil, nil
				}

				valueEquals := value == check.value
				if valueEquals == check.negate {
					return nil, nil
				}
			}

			// This config matches the filter so we need to shop this image, stop dispatch.
			return nil, errFoundConfig
		})), nil, image.Target)

		if err == errFoundConfig {
			return true
		}
		if err != nil {
			logrus.WithFields(logrus.Fields{
				logrus.ErrorKey: err,
				"image":         image.Name,
				"checks":        checks,
			}).Error("failed to check image labels")
		}

		return false
	}, nil
}

// computeSnapshotSize calculates the total size consumed by the snapshots
// for the given chainIDs.
func computeSnapshotSize(chainIDs []digest.Digest, sizeFn func(d digest.Digest) (int64, error)) (int64, error) {
	var totalSize int64
	for _, chainID := range chainIDs {
		size, err := sizeFn(chainID)
		if err != nil {
			return totalSize, err
		}
		totalSize += size
	}
	return totalSize, nil
}

func computeSharedSize(chainIDs []digest.Digest, layers map[digest.Digest]int, sizeFn func(d digest.Digest) (int64, error)) (int64, error) {
	var sharedSize int64
	for _, chainID := range chainIDs {
		if layers[chainID] == 1 {
			continue
		}
		size, err := sizeFn(chainID)
		if err != nil {
			return 0, err
		}
		sharedSize += size
	}
	return sharedSize, nil
}

// readConfig reads content pointed by the descriptor and unmarshals it into a specified output.
func readConfig(ctx context.Context, store content.Provider, desc ocispec.Descriptor, out interface{}) error {
	data, err := content.ReadBlob(ctx, store, desc)
	if err != nil {
		return errors.Wrapf(err, "failed to read config content")
	}
	err = json.Unmarshal(data, out)
	if err != nil {
		return errors.Wrapf(err, "could not deserialize image config")
	}

	return nil
}
