// Copyright 2021 The etcd 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 storage

import (
	"sync"

	"go.uber.org/zap"

	"go.etcd.io/etcd/server/v3/etcdserver/cindex"
	"go.etcd.io/etcd/server/v3/storage/backend"
	"go.etcd.io/etcd/server/v3/storage/schema"
	"go.etcd.io/raft/v3/raftpb"
)

type BackendHooks struct {
	indexer cindex.ConsistentIndexer
	lg      *zap.Logger

	// confState to Be written in the next submitted Backend transaction (if dirty)
	confState raftpb.ConfState
	// first write changes it to 'dirty'. false by default, so
	// not initialized `confState` is meaningless.
	confStateDirty bool
	confStateLock  sync.Mutex
}

func NewBackendHooks(lg *zap.Logger, indexer cindex.ConsistentIndexer) *BackendHooks {
	return &BackendHooks{lg: lg, indexer: indexer}
}

func (bh *BackendHooks) OnPreCommitUnsafe(tx backend.UnsafeReadWriter) {
	bh.indexer.UnsafeSave(tx)
	bh.confStateLock.Lock()
	defer bh.confStateLock.Unlock()
	if bh.confStateDirty {
		schema.MustUnsafeSaveConfStateToBackend(bh.lg, tx, &bh.confState)
		// save bh.confState
		bh.confStateDirty = false
	}
}

func (bh *BackendHooks) SetConfState(confState *raftpb.ConfState) {
	bh.confStateLock.Lock()
	defer bh.confStateLock.Unlock()
	bh.confState = *confState
	bh.confStateDirty = true
}