blob: 66f28da45941a874e01e99c697a33b2facc14f8a [file] [log] [blame]
// Copyright 2018 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ui
import (
"context"
"crypto/sha256"
"encoding/base64"
"time"
"go.chromium.org/gae/service/memcache"
"go.chromium.org/luci/common/logging"
)
type cursorKind string
const instancesListing cursorKind = "v1:instances"
// cursorKey is a memcache key for items that link cursor to a previous page.
func (k cursorKind) cursorKey(pkg, cursor string) string {
blob := sha256.Sum224([]byte(pkg + ":" + cursor))
return string(k) + ":" + base64.RawStdEncoding.EncodeToString(blob[:])
}
// storePrevCursor stores mapping cursor => prev, so that prev can be fetched
// later by fetchPrevCursor.
//
// Logs and ignores errors. Cursor mapping is non-essential functionality.
func (k cursorKind) storePrevCursor(c context.Context, pkg, cursor, prev string) {
itm := memcache.NewItem(c, k.cursorKey(pkg, cursor))
itm.SetValue([]byte(prev))
itm.SetExpiration(24 * time.Hour)
if err := memcache.Set(c, itm); err != nil {
logging.WithError(err).Errorf(c, "Failed to store prev cursor %q in memcache", k)
}
}
// fetchPrevCursor returns a cursor stored by storePrevCursor.
//
// Logs and ignores errors. Cursor mapping is non-essential functionality.
func (k cursorKind) fetchPrevCursor(c context.Context, pkg, cursor string) string {
itm, err := memcache.GetKey(c, k.cursorKey(pkg, cursor))
if err != nil {
if err != memcache.ErrCacheMiss {
logging.WithError(err).Errorf(c, "Failed to fetch prev cursor %q from memcache", k)
}
return ""
}
return string(itm.Value())
}