package handlers

import (
	"bytes"
	"fmt"
	"net/http"

	"github.com/docker/distribution"
	ctxu "github.com/docker/distribution/context"
	"github.com/docker/distribution/digest"
	"github.com/docker/distribution/registry/api/errcode"
	"github.com/docker/distribution/registry/api/v2"
	"github.com/gorilla/handlers"
)

// imageManifestDispatcher takes the request context and builds the
// appropriate handler for handling image manifest requests.
func imageManifestDispatcher(ctx *Context, r *http.Request) http.Handler {
	imageManifestHandler := &imageManifestHandler{
		Context: ctx,
	}
	reference := getReference(ctx)
	dgst, err := digest.ParseDigest(reference)
	if err != nil {
		// We just have a tag
		imageManifestHandler.Tag = reference
	} else {
		imageManifestHandler.Digest = dgst
	}

	mhandler := handlers.MethodHandler{
		"GET":  http.HandlerFunc(imageManifestHandler.GetImageManifest),
		"HEAD": http.HandlerFunc(imageManifestHandler.GetImageManifest),
	}

	if !ctx.readOnly {
		mhandler["PUT"] = http.HandlerFunc(imageManifestHandler.PutImageManifest)
		mhandler["DELETE"] = http.HandlerFunc(imageManifestHandler.DeleteImageManifest)
	}

	return mhandler
}

// imageManifestHandler handles http operations on image manifests.
type imageManifestHandler struct {
	*Context

	// One of tag or digest gets set, depending on what is present in context.
	Tag    string
	Digest digest.Digest
}

// GetImageManifest fetches the image manifest from the storage backend, if it exists.
// todo(richardscothern): this assumes v2 schema 1 manifests for now but in the future
// get the version from the Accept HTTP header
func (imh *imageManifestHandler) GetImageManifest(w http.ResponseWriter, r *http.Request) {
	ctxu.GetLogger(imh).Debug("GetImageManifest")
	manifests, err := imh.Repository.Manifests(imh)
	if err != nil {
		imh.Errors = append(imh.Errors, err)
		return
	}

	var manifest distribution.Manifest
	if imh.Tag != "" {
		tags := imh.Repository.Tags(imh)
		desc, err := tags.Get(imh, imh.Tag)
		if err != nil {
			imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnknown.WithDetail(err))
			return
		}
		imh.Digest = desc.Digest
	}

	if etagMatch(r, imh.Digest.String()) {
		w.WriteHeader(http.StatusNotModified)
		return
	}

	manifest, err = manifests.Get(imh, imh.Digest)
	if err != nil {
		imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnknown.WithDetail(err))
		return
	}

	ct, p, err := manifest.Payload()
	if err != nil {
		return
	}

	w.Header().Set("Content-Type", ct)
	w.Header().Set("Content-Length", fmt.Sprint(len(p)))
	w.Header().Set("Docker-Content-Digest", imh.Digest.String())
	w.Header().Set("Etag", fmt.Sprintf(`"%s"`, imh.Digest))
	w.Write(p)
}

func etagMatch(r *http.Request, etag string) bool {
	for _, headerVal := range r.Header["If-None-Match"] {
		if headerVal == etag || headerVal == fmt.Sprintf(`"%s"`, etag) { // allow quoted or unquoted
			return true
		}
	}
	return false
}

// PutImageManifest validates and stores an image in the registry.
func (imh *imageManifestHandler) PutImageManifest(w http.ResponseWriter, r *http.Request) {
	ctxu.GetLogger(imh).Debug("PutImageManifest")
	manifests, err := imh.Repository.Manifests(imh)
	if err != nil {
		imh.Errors = append(imh.Errors, err)
		return
	}

	var jsonBuf bytes.Buffer
	if err := copyFullPayload(w, r, &jsonBuf, imh, "image manifest PUT", &imh.Errors); err != nil {
		// copyFullPayload reports the error if necessary
		return
	}

	mediaType := r.Header.Get("Content-Type")
	manifest, desc, err := distribution.UnmarshalManifest(mediaType, jsonBuf.Bytes())
	if err != nil {
		imh.Errors = append(imh.Errors, v2.ErrorCodeManifestInvalid.WithDetail(err))
		return
	}

	if imh.Digest != "" {
		if desc.Digest != imh.Digest {
			ctxu.GetLogger(imh).Errorf("payload digest does match: %q != %q", desc.Digest, imh.Digest)
			imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid)
			return
		}
	} else if imh.Tag != "" {
		imh.Digest = desc.Digest
	} else {
		imh.Errors = append(imh.Errors, v2.ErrorCodeTagInvalid.WithDetail("no tag or digest specified"))
		return
	}

	_, err = manifests.Put(imh, manifest)
	if err != nil {
		// TODO(stevvooe): These error handling switches really need to be
		// handled by an app global mapper.
		if err == distribution.ErrUnsupported {
			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnsupported)
			return
		}
		switch err := err.(type) {
		case distribution.ErrManifestVerification:
			for _, verificationError := range err {
				switch verificationError := verificationError.(type) {
				case distribution.ErrManifestBlobUnknown:
					imh.Errors = append(imh.Errors, v2.ErrorCodeManifestBlobUnknown.WithDetail(verificationError.Digest))
				case distribution.ErrManifestNameInvalid:
					imh.Errors = append(imh.Errors, v2.ErrorCodeNameInvalid.WithDetail(err))
				case distribution.ErrManifestUnverified:
					imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnverified)
				default:
					if verificationError == digest.ErrDigestInvalidFormat {
						imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid)
					} else {
						imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown, verificationError)
					}
				}
			}
		default:
			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
		}

		return
	}

	// Tag this manifest
	if imh.Tag != "" {
		tags := imh.Repository.Tags(imh)
		err = tags.Tag(imh, imh.Tag, desc)
		if err != nil {
			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
			return
		}

	}

	// Construct a canonical url for the uploaded manifest.
	location, err := imh.urlBuilder.BuildManifestURL(imh.Repository.Name(), imh.Digest.String())
	if err != nil {
		// NOTE(stevvooe): Given the behavior above, this absurdly unlikely to
		// happen. We'll log the error here but proceed as if it worked. Worst
		// case, we set an empty location header.
		ctxu.GetLogger(imh).Errorf("error building manifest url from digest: %v", err)
	}

	w.Header().Set("Location", location)
	w.Header().Set("Docker-Content-Digest", imh.Digest.String())
	w.WriteHeader(http.StatusCreated)
}

// DeleteImageManifest removes the manifest with the given digest from the registry.
func (imh *imageManifestHandler) DeleteImageManifest(w http.ResponseWriter, r *http.Request) {
	ctxu.GetLogger(imh).Debug("DeleteImageManifest")

	manifests, err := imh.Repository.Manifests(imh)
	if err != nil {
		imh.Errors = append(imh.Errors, err)
		return
	}

	err = manifests.Delete(imh, imh.Digest)
	if err != nil {
		switch err {
		case digest.ErrDigestUnsupported:
		case digest.ErrDigestInvalidFormat:
			imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid)
			return
		case distribution.ErrBlobUnknown:
			imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnknown)
			return
		case distribution.ErrUnsupported:
			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnsupported)
			return
		default:
			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown)
			return
		}
	}

	w.WriteHeader(http.StatusAccepted)
}