Move registry package into handler package

The goal is to free up the distribution/registry package to include common
registry types. This moves the webapp definitions out of the way to allow for
this change in the future.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

docs/handlers/context.go

@@ -0,0 +1,90 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/docker/distribution/api/v2"
+	ctxu "github.com/docker/distribution/context"
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/storage"
+	"golang.org/x/net/context"
+)
+
+// Context should contain the request specific context for use in across
+// handlers. Resources that don't need to be shared across handlers should not
+// be on this object.
+type Context struct {
+	// App points to the application structure that created this context.
+	*App
+	context.Context
+
+	// Repository is the repository for the current request. All requests
+	// should be scoped to a single repository. This field may be nil.
+	Repository storage.Repository
+
+	// Errors is a collection of errors encountered during the request to be
+	// returned to the client API. If errors are added to the collection, the
+	// handler *must not* start the response via http.ResponseWriter.
+	Errors v2.Errors
+
+	urlBuilder *v2.URLBuilder
+
+	// TODO(stevvooe): The goal is too completely factor this context and
+	// dispatching out of the web application. Ideally, we should lean on
+	// context.Context for injection of these resources.
+}
+
+// Value overrides context.Context.Value to ensure that calls are routed to
+// correct context.
+func (ctx *Context) Value(key interface{}) interface{} {
+	return ctx.Context.Value(key)
+}
+
+func getName(ctx context.Context) (name string) {
+	return ctxu.GetStringValue(ctx, "vars.name")
+}
+
+func getTag(ctx context.Context) (tag string) {
+	return ctxu.GetStringValue(ctx, "vars.tag")
+}
+
+var errDigestNotAvailable = fmt.Errorf("digest not available in context")
+
+func getDigest(ctx context.Context) (dgst digest.Digest, err error) {
+	dgstStr := ctxu.GetStringValue(ctx, "vars.digest")
+
+	if dgstStr == "" {
+		ctxu.GetLogger(ctx).Errorf("digest not available")
+		return "", errDigestNotAvailable
+	}
+
+	d, err := digest.ParseDigest(dgstStr)
+	if err != nil {
+		ctxu.GetLogger(ctx).Errorf("error parsing digest=%q: %v", dgstStr, err)
+		return "", err
+	}
+
+	return d, nil
+}
+
+func getUploadUUID(ctx context.Context) (uuid string) {
+	return ctxu.GetStringValue(ctx, "vars.uuid")
+}
+
+// getUserName attempts to resolve a username from the context and request. If
+// a username cannot be resolved, the empty string is returned.
+func getUserName(ctx context.Context, r *http.Request) string {
+	username := ctxu.GetStringValue(ctx, "auth.user.name")
+
+	// Fallback to request user with basic auth
+	if username == "" {
+		var ok bool
+		uname, _, ok := basicAuth(r)
+		if ok {
+			username = uname
+		}
+	}
+
+	return username
+}