// Licensed to the LF AI & Data foundation under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 datacoord

import (
	"context"
	"path"
	"sync"
	"time"

	"github.com/milvus-io/milvus/internal/log"
	"github.com/milvus-io/milvus/internal/proto/commonpb"
	"github.com/milvus-io/milvus/internal/proto/datapb"
	"github.com/minio/minio-go/v7"
	"go.uber.org/zap"
)

const (
	//TODO silverxia change to configuration
	insertLogPrefix = `insert_log`
	statsLogPrefix  = `stats_log`
	deltaLogPrefix  = `delta_log`
)

// GcOption garbage collection options
type GcOption struct {
	cli              *minio.Client // OSS client
	enabled          bool          // enable switch
	checkInterval    time.Duration // each interval
	missingTolerance time.Duration // key missing in meta tolerace time
	dropTolerance    time.Duration // dropped segment related key tolerance time
	bucketName       string
	rootPath         string
}

// garbageCollector handles garbage files in object storage
// which could be dropped collection remanent or data node failure traces
type garbageCollector struct {
	option GcOption
	meta   *meta

	startOnce sync.Once
	stopOnce  sync.Once
	wg        sync.WaitGroup
	closeCh   chan struct{}
}

// newGarbageCollector create garbage collector with meta and option
func newGarbageCollector(meta *meta, opt GcOption) *garbageCollector {
	log.Info("GC with option", zap.Bool("enabled", opt.enabled), zap.Duration("interval", opt.checkInterval),
		zap.Duration("missingTolerance", opt.missingTolerance), zap.Duration("dropTolerance", opt.dropTolerance))
	return &garbageCollector{
		meta:    meta,
		option:  opt,
		closeCh: make(chan struct{}),
	}
}

// start a goroutine and perform gc check every `checkInterval`
func (gc *garbageCollector) start() {
	if gc.option.enabled {
		if gc.option.cli == nil {
			log.Warn("DataCoord gc enabled, but SSO client is not provided")
			return
		}
		gc.startOnce.Do(func() {
			gc.wg.Add(1)
			go gc.work()
		})
	}
}

// work contains actual looping check logic
func (gc *garbageCollector) work() {
	defer gc.wg.Done()
	ticker := time.Tick(gc.option.checkInterval)
	for {
		select {
		case <-ticker:
			gc.clearEtcd()
			gc.scan()
		case <-gc.closeCh:
			log.Warn("garbage collector quit")
			return
		}
	}
}

func (gc *garbageCollector) close() {
	gc.stopOnce.Do(func() {
		close(gc.closeCh)
		gc.wg.Wait()
	})
}

// scan load meta file info and compares OSS keys
// if missing found, performs gc cleanup
func (gc *garbageCollector) scan() {
	var v, m, e int
	valid := gc.meta.ListSegmentFiles()
	vm := make(map[string]struct{})
	for _, k := range valid {
		vm[k.GetLogPath()] = struct{}{}
	}

	// walk only data cluster related prefixes
	prefixes := make([]string, 0, 3)
	prefixes = append(prefixes, path.Join(gc.option.rootPath, insertLogPrefix))
	prefixes = append(prefixes, path.Join(gc.option.rootPath, statsLogPrefix))
	prefixes = append(prefixes, path.Join(gc.option.rootPath, deltaLogPrefix))

	for _, prefix := range prefixes {
		for info := range gc.option.cli.ListObjects(context.TODO(), gc.option.bucketName, minio.ListObjectsOptions{
			Prefix:    prefix,
			Recursive: true,
		}) {
			_, has := vm[info.Key]
			if has {
				v++
				continue
			}
			m++
			// not found in meta, check last modified time exceeds tolerance duration
			if time.Since(info.LastModified) > gc.option.missingTolerance {
				e++
				// ignore error since it could be cleaned up next time
				_ = gc.option.cli.RemoveObject(context.TODO(), gc.option.bucketName, info.Key, minio.RemoveObjectOptions{})
			}
		}
	}
	log.Warn("scan result", zap.Int("valid", v), zap.Int("missing", m), zap.Int("removed", e))
}

func (gc *garbageCollector) clearEtcd() {
	drops := gc.meta.SelectSegments(func(segment *SegmentInfo) bool {
		return segment.GetState() == commonpb.SegmentState_Dropped
	})

	for _, sinfo := range drops {
		if !gc.isExpire(sinfo.GetDroppedAt()) {
			continue
		}
		logs := getLogs(sinfo)
		if gc.removeLogs(logs) {
			_ = gc.meta.DropSegment(sinfo.GetID())
		}
	}
}

func (gc *garbageCollector) isExpire(dropts Timestamp) bool {
	droptime := time.Unix(0, int64(dropts))
	return time.Since(droptime) > gc.option.dropTolerance
}

func getLogs(sinfo *SegmentInfo) []*datapb.Binlog {
	var logs []*datapb.Binlog
	for _, flog := range sinfo.GetBinlogs() {
		logs = append(logs, flog.GetBinlogs()...)
	}

	for _, flog := range sinfo.GetStatslogs() {
		logs = append(logs, flog.GetBinlogs()...)
	}

	for _, flog := range sinfo.GetDeltalogs() {
		logs = append(logs, flog.GetBinlogs()...)
	}
	return logs
}

func (gc *garbageCollector) removeLogs(logs []*datapb.Binlog) bool {
	delFlag := true
	for _, l := range logs {
		err := gc.option.cli.RemoveObject(context.TODO(), gc.option.bucketName, l.GetLogPath(), minio.RemoveObjectOptions{})
		errResp := minio.ToErrorResponse(err)
		if errResp.Code != "" && errResp.Code != "NoSuchKey" {
			delFlag = false
		}
	}
	return delFlag
}