Fix #897 and shuffle directory around (#1054)

* Fix #897 and shuffle directory around

* Update find-lint

* goimports

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

internal/keydb/cache/keydb.go

@@ -0,0 +1,69 @@
+package cache
+
+import (
+	"context"
+	"errors"
+
+	"github.com/matrix-org/dendrite/internal/caching"
+	"github.com/matrix-org/dendrite/internal/keydb"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// A Database implements gomatrixserverlib.KeyDatabase and is used to store
+// the public keys for other matrix servers.
+type KeyDatabase struct {
+	inner keydb.Database
+	cache caching.ImmutableCache
+}
+
+func NewKeyDatabase(inner keydb.Database, cache caching.ImmutableCache) (*KeyDatabase, error) {
+	if inner == nil {
+		return nil, errors.New("inner database can't be nil")
+	}
+	if cache == nil {
+		return nil, errors.New("cache can't be nil")
+	}
+	return &KeyDatabase{
+		inner: inner,
+		cache: cache,
+	}, nil
+}
+
+// FetcherName implements KeyFetcher
+func (d KeyDatabase) FetcherName() string {
+	return "InMemoryKeyCache"
+}
+
+// FetchKeys implements gomatrixserverlib.KeyDatabase
+func (d *KeyDatabase) FetchKeys(
+	ctx context.Context,
+	requests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
+) (map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult, error) {
+	results := make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult)
+	for req := range requests {
+		if res, cached := d.cache.GetServerKey(req); cached {
+			results[req] = res
+			delete(requests, req)
+		}
+	}
+	fromDB, err := d.inner.FetchKeys(ctx, requests)
+	if err != nil {
+		return results, err
+	}
+	for req, res := range fromDB {
+		results[req] = res
+		d.cache.StoreServerKey(req, res)
+	}
+	return results, nil
+}
+
+// StoreKeys implements gomatrixserverlib.KeyDatabase
+func (d *KeyDatabase) StoreKeys(
+	ctx context.Context,
+	keyMap map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult,
+) error {
+	for req, res := range keyMap {
+		d.cache.StoreServerKey(req, res)
+	}
+	return d.inner.StoreKeys(ctx, keyMap)
+}