// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package satellitedb

import (
	"context"
	"database/sql"
	"strings"
	"time"

	"github.com/golang/protobuf/ptypes"
	"github.com/zeebo/errs"
	monkit "gopkg.in/spacemonkeygo/monkit.v2"

	"storj.io/storj/internal/version"
	"storj.io/storj/pkg/overlay"
	"storj.io/storj/pkg/pb"
	"storj.io/storj/pkg/storj"
	dbx "storj.io/storj/satellite/satellitedb/dbx"
	"storj.io/storj/storage"
)

var (
	mon             = monkit.Package()
	errAuditSuccess = errs.Class("overlay audit success error")
	errUptime       = errs.Class("overlay uptime error")
)

var _ overlay.DB = (*overlaycache)(nil)

type overlaycache struct {
	db *dbx.DB
}

func (cache *overlaycache) SelectStorageNodes(ctx context.Context, count int, criteria *overlay.NodeCriteria) ([]*pb.Node, error) {
	nodeType := int(pb.NodeType_STORAGE)

	safeQuery := `
		WHERE type = ? AND free_bandwidth >= ? AND free_disk >= ?
		  AND total_audit_count >= ?
		  AND audit_success_ratio >= ?
		  AND total_uptime_count >= ?
		  AND uptime_ratio >= ?
		  AND last_contact_success > ?
		  AND last_contact_success > last_contact_failure`
	args := append(make([]interface{}, 0, 13),
		nodeType, criteria.FreeBandwidth, criteria.FreeDisk,
		criteria.AuditCount, criteria.AuditSuccessRatio, criteria.UptimeCount, criteria.UptimeSuccessRatio,
		time.Now().Add(-overlay.OnlineWindow))

	if criteria.MinimumVersion != "" {
		v, err := version.NewSemVer(criteria.MinimumVersion)
		if err != nil {
			return nil, Error.New("invalid node selection criteria version: %v", err)
		}
		safeQuery += `
			AND major > ? OR (major = ? AND (minor > ? OR (minor = ? AND patch >= ?)))
			AND release`
		args = append(args, v.Major, v.Major, v.Minor, v.Minor, v.Patch)
	}

	return cache.queryFilteredNodes(ctx, criteria.Excluded, count, safeQuery, args...)
}

func (cache *overlaycache) SelectNewStorageNodes(ctx context.Context, count int, criteria *overlay.NewNodeCriteria) ([]*pb.Node, error) {
	nodeType := int(pb.NodeType_STORAGE)

	safeQuery := `
		WHERE type = ? AND free_bandwidth >= ? AND free_disk >= ?
		  AND total_audit_count < ?
		  AND last_contact_success > ?
		  AND last_contact_success > last_contact_failure`
	args := append(make([]interface{}, 0, 10),
		nodeType, criteria.FreeBandwidth, criteria.FreeDisk, criteria.AuditThreshold, time.Now().Add(-overlay.OnlineWindow))

	if criteria.MinimumVersion != "" {
		v, err := version.NewSemVer(criteria.MinimumVersion)
		if err != nil {
			return nil, Error.New("invalid node selection criteria version: %v", err)
		}
		safeQuery += `
			AND major > ? OR (major = ? AND (minor > ? OR (minor = ? AND patch >= ?)))
			AND release`
		args = append(args, v.Major, v.Major, v.Minor, v.Minor, v.Patch)
	}

	return cache.queryFilteredNodes(ctx, criteria.Excluded, count, safeQuery, args...)
}

func (cache *overlaycache) queryFilteredNodes(ctx context.Context, excluded []storj.NodeID, count int, safeQuery string, args ...interface{}) (_ []*pb.Node, err error) {
	if count == 0 {
		return nil, nil
	}

	safeExcludeNodes := ""
	if len(excluded) > 0 {
		safeExcludeNodes = ` AND id NOT IN (?` + strings.Repeat(", ?", len(excluded)-1) + `)`
	}
	for _, id := range excluded {
		args = append(args, id.Bytes())
	}
	args = append(args, count)

	rows, err := cache.db.Query(cache.db.Rebind(`SELECT id,
		type, address, free_bandwidth, free_disk, audit_success_ratio,
		uptime_ratio, total_audit_count, audit_success_count, total_uptime_count,
		uptime_success_count
		FROM nodes
		`+safeQuery+safeExcludeNodes+`
		ORDER BY RANDOM()
		LIMIT ?`), args...)
	if err != nil {
		return nil, err
	}
	defer func() { err = errs.Combine(err, rows.Close()) }()

	var nodes []*pb.Node
	for rows.Next() {
		dbNode := &dbx.Node{}
		err = rows.Scan(&dbNode.Id, &dbNode.Type,
			&dbNode.Address, &dbNode.FreeBandwidth, &dbNode.FreeDisk,
			&dbNode.AuditSuccessRatio, &dbNode.UptimeRatio,
			&dbNode.TotalAuditCount, &dbNode.AuditSuccessCount,
			&dbNode.TotalUptimeCount, &dbNode.UptimeSuccessCount)
		if err != nil {
			return nil, err
		}

		dossier, err := convertDBNode(dbNode)
		if err != nil {
			return nil, err
		}
		nodes = append(nodes, &dossier.Node)
	}

	return nodes, rows.Err()
}

// Get looks up the node by nodeID
func (cache *overlaycache) Get(ctx context.Context, id storj.NodeID) (*overlay.NodeDossier, error) {
	if id.IsZero() {
		return nil, overlay.ErrEmptyNode
	}

	node, err := cache.db.Get_Node_By_Id(ctx, dbx.Node_Id(id.Bytes()))
	if err == sql.ErrNoRows {
		return nil, overlay.ErrNodeNotFound.New(id.String())
	}
	if err != nil {
		return nil, err
	}

	return convertDBNode(node)
}

// GetAll looks up nodes based on the ids from the overlay cache
func (cache *overlaycache) GetAll(ctx context.Context, ids storj.NodeIDList) ([]*overlay.NodeDossier, error) {
	infos := make([]*overlay.NodeDossier, len(ids))
	for i, id := range ids {
		// TODO: abort on canceled context
		info, err := cache.Get(ctx, id)
		if err != nil {
			continue
		}
		infos[i] = info
	}
	return infos, nil
}

// List lists nodes starting from cursor
func (cache *overlaycache) List(ctx context.Context, cursor storj.NodeID, limit int) ([]*overlay.NodeDossier, error) {
	// TODO: handle this nicer
	if limit <= 0 || limit > storage.LookupLimit {
		limit = storage.LookupLimit
	}

	dbxInfos, err := cache.db.Limited_Node_By_Id_GreaterOrEqual_OrderBy_Asc_Id(ctx, dbx.Node_Id(cursor.Bytes()), limit, 0)
	if err != nil {
		return nil, err
	}

	infos := make([]*overlay.NodeDossier, len(dbxInfos))
	for i, dbxInfo := range dbxInfos {
		infos[i], err = convertDBNode(dbxInfo)
		if err != nil {
			return nil, err
		}
	}
	return infos, nil
}

// Paginate will run through
func (cache *overlaycache) Paginate(ctx context.Context, offset int64, limit int) ([]*overlay.NodeDossier, bool, error) {
	cursor := storj.NodeID{}

	// more represents end of table. If there are more rows in the database, more will be true.
	more := true

	if limit <= 0 || limit > storage.LookupLimit {
		limit = storage.LookupLimit
	}

	dbxInfos, err := cache.db.Limited_Node_By_Id_GreaterOrEqual_OrderBy_Asc_Id(ctx, dbx.Node_Id(cursor.Bytes()), limit, offset)
	if err != nil {
		return nil, false, err
	}

	if len(dbxInfos) < limit {
		more = false
	}

	infos := make([]*overlay.NodeDossier, len(dbxInfos))
	for i, dbxInfo := range dbxInfos {
		infos[i], err = convertDBNode(dbxInfo)
		if err != nil {
			return nil, false, err
		}
	}
	return infos, more, nil
}

// Update updates node address
func (cache *overlaycache) UpdateAddress(ctx context.Context, info *pb.Node) (err error) {
	if info == nil || info.Id.IsZero() {
		return overlay.ErrEmptyNode
	}

	tx, err := cache.db.Open(ctx)
	if err != nil {
		return Error.Wrap(err)
	}
	// TODO: use upsert
	_, err = tx.Get_Node_By_Id(ctx, dbx.Node_Id(info.Id.Bytes()))

	address := info.Address
	if address == nil {
		address = &pb.NodeAddress{}
	}

	if err != nil {
		// add the node to DB for first time
		_, err = tx.Create_Node(
			ctx,
			dbx.Node_Id(info.Id.Bytes()),
			dbx.Node_Address(address.Address),
			dbx.Node_Protocol(int(address.Transport)),
			dbx.Node_Type(int(pb.NodeType_INVALID)),
			dbx.Node_Email(""),
			dbx.Node_Wallet(""),
			dbx.Node_FreeBandwidth(-1),
			dbx.Node_FreeDisk(-1),
			dbx.Node_Major(0),
			dbx.Node_Minor(0),
			dbx.Node_Patch(0),
			dbx.Node_Hash(""),
			dbx.Node_Timestamp(time.Time{}),
			dbx.Node_Release(false),
			dbx.Node_Latency90(0),
			dbx.Node_AuditSuccessCount(0),
			dbx.Node_TotalAuditCount(0),
			dbx.Node_AuditSuccessRatio(0),
			dbx.Node_UptimeSuccessCount(0),
			dbx.Node_TotalUptimeCount(0),
			dbx.Node_UptimeRatio(0),
			dbx.Node_LastContactSuccess(time.Now()),
			dbx.Node_LastContactFailure(time.Time{}),
		)
		if err != nil {
			return Error.Wrap(errs.Combine(err, tx.Rollback()))
		}
	} else {
		update := dbx.Node_Update_Fields{
			Address:  dbx.Node_Address(address.Address),
			Protocol: dbx.Node_Protocol(int(address.Transport)),
		}

		_, err := tx.Update_Node_By_Id(ctx, dbx.Node_Id(info.Id.Bytes()), update)
		if err != nil {
			return Error.Wrap(errs.Combine(err, tx.Rollback()))
		}
	}

	return Error.Wrap(tx.Commit())
}

// CreateStats initializes the stats the provided storagenode
func (cache *overlaycache) CreateStats(ctx context.Context, nodeID storj.NodeID, startingStats *overlay.NodeStats) (stats *overlay.NodeStats, err error) {
	defer mon.Task()(&ctx)(&err)

	tx, err := cache.db.Open(ctx)
	if err != nil {
		return nil, Error.Wrap(err)
	}
	dbNode, err := tx.Get_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()))
	if err != nil {
		return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
	}

	if startingStats != nil {
		auditSuccessRatio, err := checkRatioVars(startingStats.AuditSuccessCount, startingStats.AuditCount)
		if err != nil {
			return nil, errAuditSuccess.Wrap(errs.Combine(err, tx.Rollback()))
		}

		uptimeRatio, err := checkRatioVars(startingStats.UptimeSuccessCount, startingStats.UptimeCount)
		if err != nil {
			return nil, errUptime.Wrap(errs.Combine(err, tx.Rollback()))
		}

		updateFields := dbx.Node_Update_Fields{
			AuditSuccessCount:  dbx.Node_AuditSuccessCount(startingStats.AuditSuccessCount),
			TotalAuditCount:    dbx.Node_TotalAuditCount(startingStats.AuditCount),
			AuditSuccessRatio:  dbx.Node_AuditSuccessRatio(auditSuccessRatio),
			UptimeSuccessCount: dbx.Node_UptimeSuccessCount(startingStats.UptimeSuccessCount),
			TotalUptimeCount:   dbx.Node_TotalUptimeCount(startingStats.UptimeCount),
			UptimeRatio:        dbx.Node_UptimeRatio(uptimeRatio),
		}

		dbNode, err = tx.Update_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()), updateFields)
		if err != nil {
			return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
		}
	}

	// TODO: Allegedly tx.Get_Node_By_Id and tx.Update_Node_By_Id should never return a nil value for dbNode,
	// however we've seen from some crashes that it does. We need to track down the cause of these crashes
	// but for now we're adding a nil check to prevent a panic.
	if dbNode == nil {
		return nil, Error.Wrap(errs.New("unable to get node by ID: %s", nodeID.String()))
	}
	return getNodeStats(dbNode), Error.Wrap(tx.Commit())
}

// FindInvalidNodes finds a subset of storagenodes that fail to meet minimum reputation requirements
func (cache *overlaycache) FindInvalidNodes(ctx context.Context, nodeIDs storj.NodeIDList, maxStats *overlay.NodeStats) (invalidIDs storj.NodeIDList, err error) {
	defer mon.Task()(&ctx)(&err)

	var invalidIds storj.NodeIDList

	maxAuditSuccess := maxStats.AuditSuccessRatio
	maxUptime := maxStats.UptimeRatio

	rows, err := cache.findInvalidNodesQuery(nodeIDs, maxAuditSuccess, maxUptime)

	if err != nil {
		return nil, err
	}
	defer func() {
		err = errs.Combine(err, rows.Close())
	}()

	for rows.Next() {
		node := &dbx.Node{}
		err = rows.Scan(&node.Id, &node.TotalAuditCount, &node.TotalUptimeCount, &node.AuditSuccessRatio, &node.UptimeRatio)
		if err != nil {
			return nil, err
		}
		id, err := storj.NodeIDFromBytes(node.Id)
		if err != nil {
			return nil, err
		}
		invalidIds = append(invalidIds, id)
	}

	return invalidIds, nil
}

func (cache *overlaycache) findInvalidNodesQuery(nodeIds storj.NodeIDList, auditSuccess, uptime float64) (*sql.Rows, error) {
	args := make([]interface{}, len(nodeIds))
	for i, id := range nodeIds {
		args[i] = id.Bytes()
	}
	args = append(args, auditSuccess, uptime)

	rows, err := cache.db.Query(cache.db.Rebind(`SELECT nodes.id, nodes.total_audit_count,
		nodes.total_uptime_count, nodes.audit_success_ratio,
		nodes.uptime_ratio
		FROM nodes
		WHERE nodes.id IN (?`+strings.Repeat(", ?", len(nodeIds)-1)+`)
		AND nodes.total_audit_count > 0
		AND nodes.total_uptime_count > 0
		AND (
			nodes.audit_success_ratio < ?
			OR nodes.uptime_ratio < ?
		)`), args...)

	return rows, err
}

// UpdateStats a single storagenode's stats in the db
func (cache *overlaycache) UpdateStats(ctx context.Context, updateReq *overlay.UpdateRequest) (stats *overlay.NodeStats, err error) {
	defer mon.Task()(&ctx)(&err)

	nodeID := updateReq.NodeID

	tx, err := cache.db.Open(ctx)
	if err != nil {
		return nil, Error.Wrap(err)
	}
	dbNode, err := tx.Get_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()))
	if err != nil {
		return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
	}

	auditSuccessCount := dbNode.AuditSuccessCount
	totalAuditCount := dbNode.TotalAuditCount
	var auditSuccessRatio float64
	uptimeSuccessCount := dbNode.UptimeSuccessCount
	totalUptimeCount := dbNode.TotalUptimeCount
	var uptimeRatio float64

	auditSuccessCount, totalAuditCount, auditSuccessRatio = updateRatioVars(
		updateReq.AuditSuccess,
		auditSuccessCount,
		totalAuditCount,
	)

	uptimeSuccessCount, totalUptimeCount, uptimeRatio = updateRatioVars(
		updateReq.IsUp,
		uptimeSuccessCount,
		totalUptimeCount,
	)

	updateFields := dbx.Node_Update_Fields{
		AuditSuccessCount:  dbx.Node_AuditSuccessCount(auditSuccessCount),
		TotalAuditCount:    dbx.Node_TotalAuditCount(totalAuditCount),
		AuditSuccessRatio:  dbx.Node_AuditSuccessRatio(auditSuccessRatio),
		UptimeSuccessCount: dbx.Node_UptimeSuccessCount(uptimeSuccessCount),
		TotalUptimeCount:   dbx.Node_TotalUptimeCount(totalUptimeCount),
		UptimeRatio:        dbx.Node_UptimeRatio(uptimeRatio),
	}

	if updateReq.IsUp {
		updateFields.LastContactSuccess = dbx.Node_LastContactSuccess(time.Now())
	} else {
		updateFields.LastContactFailure = dbx.Node_LastContactFailure(time.Now())
	}

	dbNode, err = tx.Update_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()), updateFields)
	if err != nil {
		return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
	}

	// TODO: Allegedly tx.Get_Node_By_Id and tx.Update_Node_By_Id should never return a nil value for dbNode,
	// however we've seen from some crashes that it does. We need to track down the cause of these crashes
	// but for now we're adding a nil check to prevent a panic.
	if dbNode == nil {
		return nil, Error.Wrap(errs.New("unable to get node by ID: %s", nodeID.String()))
	}

	return getNodeStats(dbNode), Error.Wrap(tx.Commit())
}

// UpdateNodeInfo updates the email and wallet for a given node ID for satellite payments.
func (cache *overlaycache) UpdateNodeInfo(ctx context.Context, nodeID storj.NodeID, nodeInfo *pb.InfoResponse) (stats *overlay.NodeDossier, err error) {
	defer mon.Task()(&ctx)(&err)

	var updateFields dbx.Node_Update_Fields
	if nodeInfo != nil {
		if nodeInfo.GetType() != pb.NodeType_INVALID {
			updateFields.Type = dbx.Node_Type(int(nodeInfo.GetType()))
		}
		if nodeInfo.GetOperator() != nil {
			updateFields.Wallet = dbx.Node_Wallet(nodeInfo.GetOperator().GetWallet())
			updateFields.Email = dbx.Node_Email(nodeInfo.GetOperator().GetEmail())
		}
		if nodeInfo.GetCapacity() != nil {
			updateFields.FreeDisk = dbx.Node_FreeDisk(nodeInfo.GetCapacity().GetFreeDisk())
			updateFields.FreeBandwidth = dbx.Node_FreeBandwidth(nodeInfo.GetCapacity().GetFreeBandwidth())
		}
		if nodeInfo.GetVersion() != nil {
			semVer, err := version.NewSemVer(nodeInfo.GetVersion().GetVersion())
			if err != nil {
				return nil, errs.New("unable to convert version to semVer")
			}
			pbts, err := ptypes.Timestamp(nodeInfo.GetVersion().GetTimestamp())
			if err != nil {
				return nil, errs.New("unable to convert version timestamp")
			}
			updateFields.Major = dbx.Node_Major(semVer.Major)
			updateFields.Minor = dbx.Node_Minor(semVer.Minor)
			updateFields.Patch = dbx.Node_Patch(semVer.Patch)
			updateFields.Hash = dbx.Node_Hash(nodeInfo.GetVersion().GetCommitHash())
			updateFields.Timestamp = dbx.Node_Timestamp(pbts)
			updateFields.Release = dbx.Node_Release(nodeInfo.GetVersion().GetRelease())
		}
	}

	updatedDBNode, err := cache.db.Update_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()), updateFields)
	if err != nil {
		return nil, Error.Wrap(err)
	}

	return convertDBNode(updatedDBNode)
}

// UpdateUptime updates a single storagenode's uptime stats in the db
func (cache *overlaycache) UpdateUptime(ctx context.Context, nodeID storj.NodeID, isUp bool) (stats *overlay.NodeStats, err error) {
	defer mon.Task()(&ctx)(&err)

	tx, err := cache.db.Open(ctx)
	if err != nil {
		return nil, Error.Wrap(err)
	}
	dbNode, err := tx.Get_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()))
	if err != nil {
		return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
	}

	uptimeSuccessCount := dbNode.UptimeSuccessCount
	totalUptimeCount := dbNode.TotalUptimeCount
	var uptimeRatio float64

	updateFields := dbx.Node_Update_Fields{}

	uptimeSuccessCount, totalUptimeCount, uptimeRatio = updateRatioVars(
		isUp,
		uptimeSuccessCount,
		totalUptimeCount,
	)

	updateFields.UptimeSuccessCount = dbx.Node_UptimeSuccessCount(uptimeSuccessCount)
	updateFields.TotalUptimeCount = dbx.Node_TotalUptimeCount(totalUptimeCount)
	updateFields.UptimeRatio = dbx.Node_UptimeRatio(uptimeRatio)

	if isUp {
		updateFields.LastContactSuccess = dbx.Node_LastContactSuccess(time.Now())
	} else {
		updateFields.LastContactFailure = dbx.Node_LastContactFailure(time.Now())
	}

	dbNode, err = tx.Update_Node_By_Id(ctx, dbx.Node_Id(nodeID.Bytes()), updateFields)
	if err != nil {
		return nil, Error.Wrap(errs.Combine(err, tx.Rollback()))
	}
	// TODO: Allegedly tx.Get_Node_By_Id and tx.Update_Node_By_Id should never return a nil value for dbNode,
	// however we've seen from some crashes that it does. We need to track down the cause of these crashes
	// but for now we're adding a nil check to prevent a panic.
	if dbNode == nil {
		return nil, Error.Wrap(errs.New("unable to get node by ID: %s", nodeID.String()))
	}

	return getNodeStats(dbNode), Error.Wrap(tx.Commit())
}

func convertDBNode(info *dbx.Node) (*overlay.NodeDossier, error) {
	if info == nil {
		return nil, Error.New("missing info")
	}

	id, err := storj.NodeIDFromBytes(info.Id)
	if err != nil {
		return nil, err
	}
	ver := &version.SemVer{
		Major: info.Major,
		Minor: info.Minor,
		Patch: info.Patch,
	}

	pbts, err := ptypes.TimestampProto(info.Timestamp)
	if err != nil {
		return nil, err
	}

	node := &overlay.NodeDossier{
		Node: pb.Node{
			Id: id,
			Address: &pb.NodeAddress{
				Address:   info.Address,
				Transport: pb.NodeTransport(info.Protocol),
			},
		},
		Type: pb.NodeType(info.Type),
		Operator: pb.NodeOperator{
			Email:  info.Email,
			Wallet: info.Wallet,
		},
		Capacity: pb.NodeCapacity{
			FreeBandwidth: info.FreeBandwidth,
			FreeDisk:      info.FreeDisk,
		},
		Reputation: overlay.NodeStats{
			Latency90:          info.Latency90,
			AuditSuccessRatio:  info.AuditSuccessRatio,
			UptimeRatio:        info.UptimeRatio,
			AuditCount:         info.TotalAuditCount,
			AuditSuccessCount:  info.AuditSuccessCount,
			UptimeCount:        info.TotalUptimeCount,
			UptimeSuccessCount: info.UptimeSuccessCount,
			LastContactSuccess: info.LastContactSuccess,
			LastContactFailure: info.LastContactFailure,
		},
		Version: pb.NodeVersion{
			Version:    ver.String(),
			CommitHash: info.Hash,
			Timestamp:  pbts,
			Release:    info.Release,
		},
	}

	return node, nil
}

func getNodeStats(dbNode *dbx.Node) *overlay.NodeStats {
	nodeStats := &overlay.NodeStats{
		Latency90:          dbNode.Latency90,
		AuditSuccessRatio:  dbNode.AuditSuccessRatio,
		AuditSuccessCount:  dbNode.AuditSuccessCount,
		AuditCount:         dbNode.TotalAuditCount,
		UptimeRatio:        dbNode.UptimeRatio,
		UptimeSuccessCount: dbNode.UptimeSuccessCount,
		UptimeCount:        dbNode.TotalUptimeCount,
		LastContactSuccess: dbNode.LastContactSuccess,
		LastContactFailure: dbNode.LastContactFailure,
	}
	return nodeStats
}

func updateRatioVars(newStatus bool, successCount, totalCount int64) (int64, int64, float64) {
	totalCount++
	if newStatus {
		successCount++
	}
	newRatio := float64(successCount) / float64(totalCount)
	return successCount, totalCount, newRatio
}

func checkRatioVars(successCount, totalCount int64) (ratio float64, err error) {
	if successCount < 0 {
		return 0, errs.New("success count less than 0")
	}
	if totalCount < 0 {
		return 0, errs.New("total count less than 0")
	}
	if successCount > totalCount {
		return 0, errs.New("success count greater than total count")
	}
	if totalCount == 0 {
		return 0, nil
	}
	ratio = float64(successCount) / float64(totalCount)
	return ratio, nil
}