/*
 * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
 *
 * 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 cmd

import (
	"context"
	"errors"
	"time"

	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/color"
	"github.com/minio/minio/pkg/console"
	"github.com/minio/minio/pkg/madmin"
)

const (
	bgHealingUUID = "0000-0000-0000-0000"
)

// NewBgHealSequence creates a background healing sequence
// operation which crawls all objects and heal them.
func newBgHealSequence() *healSequence {
	reqInfo := &logger.ReqInfo{API: "BackgroundHeal"}
	ctx, cancelCtx := context.WithCancel(logger.SetReqInfo(GlobalContext, reqInfo))

	hs := madmin.HealOpts{
		// Remove objects that do not have read-quorum
		Remove:   true,
		ScanMode: madmin.HealNormalScan,
	}

	return &healSequence{
		sourceCh:    make(chan healSource),
		respCh:      make(chan healResult),
		startTime:   UTCNow(),
		clientToken: bgHealingUUID,
		// run-background heal with reserved bucket
		bucket:   minioReservedBucket,
		settings: hs,
		currentStatus: healSequenceStatus{
			Summary:      healNotStartedStatus,
			HealSettings: hs,
		},
		cancelCtx:          cancelCtx,
		ctx:                ctx,
		reportProgress:     false,
		scannedItemsMap:    make(map[madmin.HealItemType]int64),
		healedItemsMap:     make(map[madmin.HealItemType]int64),
		healFailedItemsMap: make(map[string]int64),
	}
}

func getLocalBackgroundHealStatus() (madmin.BgHealState, bool) {
	if globalBackgroundHealState == nil {
		return madmin.BgHealState{}, false
	}

	bgSeq, ok := globalBackgroundHealState.getHealSequenceByToken(bgHealingUUID)
	if !ok {
		return madmin.BgHealState{}, false
	}

	var healDisksMap = map[string]struct{}{}
	for _, ep := range getLocalDisksToHeal() {
		healDisksMap[ep.String()] = struct{}{}
	}

	for _, ep := range globalBackgroundHealState.getHealLocalDisks() {
		if _, ok := healDisksMap[ep.String()]; !ok {
			healDisksMap[ep.String()] = struct{}{}
		}
	}

	var healDisks []string
	for disk := range healDisksMap {
		healDisks = append(healDisks, disk)
	}

	return madmin.BgHealState{
		ScannedItemsCount: bgSeq.getScannedItemsCount(),
		LastHealActivity:  bgSeq.lastHealActivity,
		HealDisks:         healDisks,
		NextHealRound:     UTCNow(),
	}, true
}

func mustGetHealSequence(ctx context.Context) *healSequence {
	// Get background heal sequence to send elements to heal
	for {
		globalHealStateLK.RLock()
		hstate := globalBackgroundHealState
		globalHealStateLK.RUnlock()

		if hstate == nil {
			time.Sleep(time.Second)
			continue
		}

		bgSeq, ok := hstate.getHealSequenceByToken(bgHealingUUID)
		if !ok {
			time.Sleep(time.Second)
			continue
		}
		return bgSeq
	}
}

// healErasureSet lists and heals all objects in a specific erasure set
func (er *erasureObjects) healErasureSet(ctx context.Context, buckets []BucketInfo) error {
	bgSeq := mustGetHealSequence(ctx)
	buckets = append(buckets, BucketInfo{
		Name: pathJoin(minioMetaBucket, minioConfigPrefix),
	})

	// Try to pro-actively heal backend-encrypted file.
	if _, err := er.HealObject(ctx, minioMetaBucket, backendEncryptedFile, "", madmin.HealOpts{}); err != nil {
		if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) {
			logger.LogIf(ctx, err)
		}
	}

	// Heal all buckets with all objects
	for _, bucket := range buckets {
		// Heal current bucket
		if _, err := er.HealBucket(ctx, bucket.Name, madmin.HealOpts{}); err != nil {
			if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) {
				logger.LogIf(ctx, err)
			}
		}

		if serverDebugLog {
			console.Debugf(color.Green("healDisk:")+" healing bucket %s content on erasure set %d\n", bucket.Name, er.setNumber+1)
		}

		disks, _ := er.getOnlineDisksWithHealing()
		if len(disks) == 0 {
			return errors.New("healErasureSet: No non-healing disks found")
		}
		// Limit listing to 3 drives.
		if len(disks) > 3 {
			disks = disks[:3]
		}
		healEntry := func(entry metaCacheEntry) {
			if entry.isDir() {
				return
			}
			fivs, err := entry.fileInfoVersions(bucket.Name)
			if err != nil {
				logger.LogIf(ctx, err)
				return
			}
			waitForLowHTTPReq(globalHealConfig.IOCount, globalHealConfig.Sleep)
			for _, version := range fivs.Versions {
				if _, err := er.HealObject(ctx, bucket.Name, version.Name, version.VersionID, madmin.HealOpts{ScanMode: madmin.HealNormalScan, Remove: healDeleteDangling}); err != nil {
					if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) {
						logger.LogIf(ctx, err)
					}
				}
				bgSeq.logHeal(madmin.HealItemObject)
			}
		}
		err := listPathRaw(ctx, listPathRawOptions{
			disks:          disks,
			bucket:         bucket.Name,
			recursive:      true,
			forwardTo:      "", //TODO(klauspost): Set this to last known offset when resuming.
			minDisks:       1,
			reportNotFound: false,
			agreed:         healEntry,
			partial: func(entries metaCacheEntries, nAgreed int, errs []error) {
				entry, _ := entries.firstFound()
				if entry != nil && !entry.isDir() {
					healEntry(*entry)
				}
			},
			finished: nil,
		})
		logger.LogIf(ctx, err)
	}

	return nil
}

// healObject heals given object path in deep to fix bitrot.
func healObject(bucket, object, versionID string, scan madmin.HealScanMode) {
	// Get background heal sequence to send elements to heal
	bgSeq, ok := globalBackgroundHealState.getHealSequenceByToken(bgHealingUUID)
	if ok {
		bgSeq.sourceCh <- healSource{
			bucket:    bucket,
			object:    object,
			versionID: versionID,
			opts: &madmin.HealOpts{
				Remove:   true, // if found dangling purge it.
				ScanMode: scan,
			},
		}
	}
}