package storage

import (
	"errors"
	"fmt"
	"net/url"

	"encoding/json"

	"github.com/docker/distribution"
	"github.com/docker/distribution/context"
	"github.com/docker/distribution/digest"
	"github.com/docker/distribution/manifest/schema2"
)

var (
	errUnexpectedURL = errors.New("unexpected URL on layer")
	errMissingURL    = errors.New("missing URL on layer")
	errInvalidURL    = errors.New("invalid URL on layer")
)

//schema2ManifestHandler is a ManifestHandler that covers schema2 manifests.
type schema2ManifestHandler struct {
	repository distribution.Repository
	blobStore  distribution.BlobStore
	ctx        context.Context
}

var _ ManifestHandler = &schema2ManifestHandler{}

func (ms *schema2ManifestHandler) Unmarshal(ctx context.Context, dgst digest.Digest, content []byte) (distribution.Manifest, error) {
	context.GetLogger(ms.ctx).Debug("(*schema2ManifestHandler).Unmarshal")

	var m schema2.DeserializedManifest
	if err := json.Unmarshal(content, &m); err != nil {
		return nil, err
	}

	return &m, nil
}

func (ms *schema2ManifestHandler) Put(ctx context.Context, manifest distribution.Manifest, skipDependencyVerification bool) (digest.Digest, error) {
	context.GetLogger(ms.ctx).Debug("(*schema2ManifestHandler).Put")

	m, ok := manifest.(*schema2.DeserializedManifest)
	if !ok {
		return "", fmt.Errorf("non-schema2 manifest put to schema2ManifestHandler: %T", manifest)
	}

	if err := ms.verifyManifest(ms.ctx, *m, skipDependencyVerification); err != nil {
		return "", err
	}

	mt, payload, err := m.Payload()
	if err != nil {
		return "", err
	}

	revision, err := ms.blobStore.Put(ctx, mt, payload)
	if err != nil {
		context.GetLogger(ctx).Errorf("error putting payload into blobstore: %v", err)
		return "", err
	}

	return revision.Digest, nil
}

// verifyManifest ensures that the manifest content is valid from the
// perspective of the registry. As a policy, the registry only tries to store
// valid content, leaving trust policies of that content up to consumers.
func (ms *schema2ManifestHandler) verifyManifest(ctx context.Context, mnfst schema2.DeserializedManifest, skipDependencyVerification bool) error {
	var errs distribution.ErrManifestVerification

	if !skipDependencyVerification {
		target := mnfst.Target()
		_, err := ms.repository.Blobs(ctx).Stat(ctx, target.Digest)
		if err != nil {
			if err != distribution.ErrBlobUnknown {
				errs = append(errs, err)
			}

			// On error here, we always append unknown blob errors.
			errs = append(errs, distribution.ErrManifestBlobUnknown{Digest: target.Digest})
		}

		for _, fsLayer := range mnfst.References() {
			var err error
			if fsLayer.MediaType != schema2.MediaTypeForeignLayer {
				if len(fsLayer.URLs) == 0 {
					_, err = ms.repository.Blobs(ctx).Stat(ctx, fsLayer.Digest)
				} else {
					err = errUnexpectedURL
				}
			} else {
				// Clients download this layer from an external URL, so do not check for
				// its presense.
				if len(fsLayer.URLs) == 0 {
					err = errMissingURL
				}
				for _, u := range fsLayer.URLs {
					var pu *url.URL
					pu, err = url.Parse(u)
					if err != nil || (pu.Scheme != "http" && pu.Scheme != "https") || pu.Fragment != "" {
						err = errInvalidURL
					}
				}
			}
			if err != nil {
				if err != distribution.ErrBlobUnknown {
					errs = append(errs, err)
				}

				// On error here, we always append unknown blob errors.
				errs = append(errs, distribution.ErrManifestBlobUnknown{Digest: fsLayer.Digest})
			}
		}
	}
	if len(errs) != 0 {
		return errs
	}

	return nil
}