// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"context"
	"errors"
	"fmt"
	"sort"
	"time"

	"github.com/minio/madmin-go"
	"github.com/minio/minio/internal/color"
	"github.com/minio/minio/internal/logger"
	"github.com/minio/pkg/console"
	"github.com/minio/pkg/wildcard"
)

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

// NewBgHealSequence creates a background healing sequence
// operation which scans 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),
	}
}

// getBackgroundHealStatus will return the
func getBackgroundHealStatus(ctx context.Context, o ObjectLayer) (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{}{}
	}
	status := madmin.BgHealState{
		ScannedItemsCount: bgSeq.getScannedItemsCount(),
	}

	if o == nil {
		healing := globalBackgroundHealState.getLocalHealingDisks()
		for _, disk := range healing {
			status.HealDisks = append(status.HealDisks, disk.Endpoint)
		}

		return status, true
	}

	// ignores any errors here.
	si, _ := o.StorageInfo(ctx)

	indexed := make(map[string][]madmin.Disk)
	for _, disk := range si.Disks {
		setIdx := fmt.Sprintf("%d-%d", disk.PoolIndex, disk.SetIndex)
		indexed[setIdx] = append(indexed[setIdx], disk)
	}

	for id, disks := range indexed {
		ss := madmin.SetStatus{
			ID:        id,
			SetIndex:  disks[0].SetIndex,
			PoolIndex: disks[0].PoolIndex,
		}
		for _, disk := range disks {
			ss.Disks = append(ss.Disks, disk)
			if disk.Healing {
				ss.HealStatus = "Healing"
				ss.HealPriority = "high"
				status.HealDisks = append(status.HealDisks, disk.Endpoint)
			}
		}
		sortDisks(ss.Disks)
		status.Sets = append(status.Sets, ss)
	}
	sort.Slice(status.Sets, func(i, j int) bool {
		return status.Sets[i].ID < status.Sets[j].ID
	})

	return status, 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, tracker *healingTracker) error {
	bgSeq := mustGetHealSequence(ctx)
	buckets = append(buckets, BucketInfo{
		Name: pathJoin(minioMetaBucket, minioConfigPrefix),
	})

	// Heal all buckets with all objects
	for _, bucket := range buckets {
		if tracker.isHealed(bucket.Name) {
			continue
		}
		var forwardTo string
		// If we resume to the same bucket, forward to last known item.
		if tracker.Bucket != "" {
			if tracker.Bucket == bucket.Name {
				forwardTo = tracker.Bucket
			} else {
				// Reset to where last bucket ended if resuming.
				tracker.resume()
			}
		}
		tracker.Object = ""
		tracker.Bucket = bucket.Name
		// 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, tracker.SetIndex+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
			}
			// We might land at .metacache, .trash, .multipart
			// no need to heal them skip, only when bucket
			// is '.minio.sys'
			if bucket.Name == minioMetaBucket {
				if wildcard.Match("buckets/*/.metacache/*", entry.name) {
					return
				}
				if wildcard.Match("tmp/.trash/*", entry.name) {
					return
				}
				if wildcard.Match("multipart/*", entry.name) {
					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) {
						// If not deleted, assume they failed.
						tracker.ObjectsFailed++
						tracker.BytesFailed += uint64(version.Size)
						logger.LogIf(ctx, err)
					}
				} else {
					tracker.ObjectsHealed++
					tracker.BytesDone += uint64(version.Size)
				}
				bgSeq.logHeal(madmin.HealItemObject)
			}
			tracker.Object = entry.name
			if time.Since(tracker.LastUpdate) > time.Minute {
				logger.LogIf(ctx, tracker.update(ctx))
			}
		}

		// How to resolve partial results.
		resolver := metadataResolutionParams{
			dirQuorum: 1,
			objQuorum: 1,
			bucket:    bucket.Name,
		}

		err := listPathRaw(ctx, listPathRawOptions{
			disks:          disks,
			bucket:         bucket.Name,
			recursive:      true,
			forwardTo:      forwardTo,
			minDisks:       1,
			reportNotFound: false,
			agreed:         healEntry,
			partial: func(entries metaCacheEntries, nAgreed int, errs []error) {
				entry, ok := entries.resolve(&resolver)
				if ok {
					healEntry(*entry)
				}
			},
			finished: nil,
		})

		select {
		// If context is canceled don't mark as done...
		case <-ctx.Done():
			return ctx.Err()
		default:
			logger.LogIf(ctx, err)
			tracker.bucketDone(bucket.Name)
			logger.LogIf(ctx, tracker.update(ctx))
		}
	}
	tracker.Object = ""
	tracker.Bucket = ""

	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,
			},
		}
	}
}