// 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 (
	"bytes"
	"context"
	"encoding/gob"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/minio/madmin-go/v2"
	xhttp "github.com/minio/minio/internal/http"
	"github.com/minio/minio/internal/logger"
	"github.com/minio/minio/internal/rest"
	xnet "github.com/minio/pkg/net"
	xbufio "github.com/philhofer/fwd"
	"github.com/tinylib/msgp/msgp"
)

func isNetworkError(err error) bool {
	if err == nil {
		return false
	}
	if nerr, ok := err.(*rest.NetworkError); ok {
		return xnet.IsNetworkOrHostDown(nerr.Err, false)
	}

	switch {
	// A peer node can be in shut down phase and proactively
	// return 503 server closed error,consider it as an offline node
	case strings.Contains(err.Error(), http.ErrServerClosed.Error()):
		return true
	// Corner case, the server closed the connection with a keep-alive timeout
	// some requests are not retried internally, such as POST request with written body
	case strings.Contains(err.Error(), "server closed idle connection"):
		return true
	}

	return false
}

// Converts network error to storageErr. This function is
// written so that the storageAPI errors are consistent
// across network disks.
func toStorageErr(err error) error {
	if err == nil {
		return nil
	}

	if isNetworkError(err) {
		return errDiskNotFound
	}

	switch err.Error() {
	case errFaultyDisk.Error():
		return errFaultyDisk
	case errFileCorrupt.Error():
		return errFileCorrupt
	case errUnexpected.Error():
		return errUnexpected
	case errDiskFull.Error():
		return errDiskFull
	case errVolumeNotFound.Error():
		return errVolumeNotFound
	case errVolumeExists.Error():
		return errVolumeExists
	case errFileNotFound.Error():
		return errFileNotFound
	case errFileVersionNotFound.Error():
		return errFileVersionNotFound
	case errFileNameTooLong.Error():
		return errFileNameTooLong
	case errFileAccessDenied.Error():
		return errFileAccessDenied
	case errPathNotFound.Error():
		return errPathNotFound
	case errIsNotRegular.Error():
		return errIsNotRegular
	case errVolumeNotEmpty.Error():
		return errVolumeNotEmpty
	case errVolumeAccessDenied.Error():
		return errVolumeAccessDenied
	case errCorruptedFormat.Error():
		return errCorruptedFormat
	case errUnformattedDisk.Error():
		return errUnformattedDisk
	case errInvalidAccessKeyID.Error():
		return errInvalidAccessKeyID
	case errAuthentication.Error():
		return errAuthentication
	case errRPCAPIVersionUnsupported.Error():
		return errRPCAPIVersionUnsupported
	case errServerTimeMismatch.Error():
		return errServerTimeMismatch
	case io.EOF.Error():
		return io.EOF
	case io.ErrUnexpectedEOF.Error():
		return io.ErrUnexpectedEOF
	case errDiskStale.Error():
		return errDiskNotFound
	case errDiskNotFound.Error():
		return errDiskNotFound
	}
	return err
}

// Abstracts a remote disk.
type storageRESTClient struct {
	endpoint   Endpoint
	restClient *rest.Client
	diskID     string

	// Indexes, will be -1 until assigned a set.
	poolIndex, setIndex, diskIndex int

	diskInfoCache timedValue
}

// Retrieve location indexes.
func (client *storageRESTClient) GetDiskLoc() (poolIdx, setIdx, diskIdx int) {
	return client.poolIndex, client.setIndex, client.diskIndex
}

// Set location indexes.
func (client *storageRESTClient) SetDiskLoc(poolIdx, setIdx, diskIdx int) {
	client.poolIndex = poolIdx
	client.setIndex = setIdx
	client.diskIndex = diskIdx
}

// Wrapper to restClient.Call to handle network errors, in case of network error the connection is makred disconnected
// permanently. The only way to restore the storage connection is at the xl-sets layer by xlsets.monitorAndConnectEndpoints()
// after verifying format.json
func (client *storageRESTClient) call(ctx context.Context, method string, values url.Values, body io.Reader, length int64) (io.ReadCloser, error) {
	if values == nil {
		values = make(url.Values)
	}
	values.Set(storageRESTDiskID, client.diskID)
	respBody, err := client.restClient.Call(ctx, method, values, body, length)
	if err == nil {
		return respBody, nil
	}

	err = toStorageErr(err)
	return nil, err
}

// Stringer provides a canonicalized representation of network device.
func (client *storageRESTClient) String() string {
	return client.endpoint.String()
}

// IsOnline - returns whether RPC client failed to connect or not.
func (client *storageRESTClient) IsOnline() bool {
	return client.restClient.IsOnline()
}

// LastConn - returns when the disk is seen to be connected the last time
func (client *storageRESTClient) LastConn() time.Time {
	return client.restClient.LastConn()
}

func (client *storageRESTClient) IsLocal() bool {
	return false
}

func (client *storageRESTClient) Hostname() string {
	return client.endpoint.Host
}

func (client *storageRESTClient) Endpoint() Endpoint {
	return client.endpoint
}

func (client *storageRESTClient) Healing() *healingTracker {
	// This call is not implemented for remote client on purpose.
	// healing tracker is always for local disks.
	return nil
}

func (client *storageRESTClient) NSScanner(ctx context.Context, cache dataUsageCache, updates chan<- dataUsageEntry, scanMode madmin.HealScanMode) (dataUsageCache, error) {
	defer close(updates)
	pr, pw := io.Pipe()
	go func() {
		pw.CloseWithError(cache.serializeTo(pw))
	}()
	vals := make(url.Values)
	vals.Set(storageRESTScanMode, strconv.Itoa(int(scanMode)))
	respBody, err := client.call(ctx, storageRESTMethodNSScanner, vals, pr, -1)
	defer xhttp.DrainBody(respBody)
	pr.CloseWithError(err)
	if err != nil {
		return cache, err
	}

	rr, rw := io.Pipe()
	go func() {
		rw.CloseWithError(waitForHTTPStream(respBody, rw))
	}()

	ms := msgp.NewReader(rr)
	for {
		// Read whether it is an update.
		upd, err := ms.ReadBool()
		if err != nil {
			rr.CloseWithError(err)
			return cache, err
		}
		if !upd {
			// No more updates... New cache follows.
			break
		}
		var update dataUsageEntry
		err = update.DecodeMsg(ms)
		if err != nil || err == io.EOF {
			rr.CloseWithError(err)
			return cache, err
		}
		select {
		case <-ctx.Done():
		case updates <- update:
		}
	}
	var newCache dataUsageCache
	err = newCache.DecodeMsg(ms)
	rr.CloseWithError(err)
	if err == io.EOF {
		err = nil
	}
	return newCache, err
}

func (client *storageRESTClient) GetDiskID() (string, error) {
	// This call should never be over the network, this is always
	// a cached value - caller should make sure to use this
	// function on a fresh disk or make sure to look at the error
	// from a different networked call to validate the GetDiskID()
	return client.diskID, nil
}

func (client *storageRESTClient) SetDiskID(id string) {
	client.diskID = id
}

// DiskInfo - fetch disk information for a remote disk.
func (client *storageRESTClient) DiskInfo(ctx context.Context) (info DiskInfo, err error) {
	if !client.IsOnline() {
		// make sure to check if the disk is offline, since the underlying
		// value is cached we should attempt to invalidate it if such calls
		// were attempted. This can lead to false success under certain conditions
		// - this change attempts to avoid stale information if the underlying
		// transport is already down.
		return info, errDiskNotFound
	}
	client.diskInfoCache.Once.Do(func() {
		client.diskInfoCache.TTL = time.Second
		client.diskInfoCache.Update = func() (interface{}, error) {
			var info DiskInfo
			ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
			defer cancel()
			respBody, err := client.call(ctx, storageRESTMethodDiskInfo, nil, nil, -1)
			if err != nil {
				return info, err
			}
			defer xhttp.DrainBody(respBody)
			if err = msgp.Decode(respBody, &info); err != nil {
				return info, err
			}
			if info.Error != "" {
				return info, toStorageErr(errors.New(info.Error))
			}
			return info, nil
		}
	})
	val, err := client.diskInfoCache.Get()
	if val != nil {
		return val.(DiskInfo), err
	}
	return info, err
}

// MakeVolBulk - create multiple volumes in a bulk operation.
func (client *storageRESTClient) MakeVolBulk(ctx context.Context, volumes ...string) (err error) {
	values := make(url.Values)
	values.Set(storageRESTVolumes, strings.Join(volumes, ","))
	respBody, err := client.call(ctx, storageRESTMethodMakeVolBulk, values, nil, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// MakeVol - create a volume on a remote disk.
func (client *storageRESTClient) MakeVol(ctx context.Context, volume string) (err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	respBody, err := client.call(ctx, storageRESTMethodMakeVol, values, nil, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// ListVols - List all volumes on a remote disk.
func (client *storageRESTClient) ListVols(ctx context.Context) (vols []VolInfo, err error) {
	respBody, err := client.call(ctx, storageRESTMethodListVols, nil, nil, -1)
	if err != nil {
		return
	}
	defer xhttp.DrainBody(respBody)
	vinfos := VolsInfo(vols)
	err = msgp.Decode(respBody, &vinfos)
	return vinfos, err
}

// StatVol - get volume info over the network.
func (client *storageRESTClient) StatVol(ctx context.Context, volume string) (vol VolInfo, err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	respBody, err := client.call(ctx, storageRESTMethodStatVol, values, nil, -1)
	if err != nil {
		return
	}
	defer xhttp.DrainBody(respBody)
	err = msgp.Decode(respBody, &vol)
	return vol, err
}

// DeleteVol - Deletes a volume over the network.
func (client *storageRESTClient) DeleteVol(ctx context.Context, volume string, forceDelete bool) (err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	if forceDelete {
		values.Set(storageRESTForceDelete, "true")
	}
	respBody, err := client.call(ctx, storageRESTMethodDeleteVol, values, nil, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// AppendFile - append to a file.
func (client *storageRESTClient) AppendFile(ctx context.Context, volume string, path string, buf []byte) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	reader := bytes.NewReader(buf)
	respBody, err := client.call(ctx, storageRESTMethodAppendFile, values, reader, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

func (client *storageRESTClient) CreateFile(ctx context.Context, volume, path string, size int64, reader io.Reader) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTLength, strconv.Itoa(int(size)))
	respBody, err := client.call(ctx, storageRESTMethodCreateFile, values, io.NopCloser(reader), size)
	defer xhttp.DrainBody(respBody)
	if err != nil {
		return err
	}
	_, err = waitForHTTPResponse(respBody)
	return err
}

func (client *storageRESTClient) WriteMetadata(ctx context.Context, volume, path string, fi FileInfo) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)

	var reader bytes.Buffer
	if err := msgp.Encode(&reader, &fi); err != nil {
		return err
	}

	respBody, err := client.call(ctx, storageRESTMethodWriteMetadata, values, &reader, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

func (client *storageRESTClient) UpdateMetadata(ctx context.Context, volume, path string, fi FileInfo) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)

	var reader bytes.Buffer
	if err := msgp.Encode(&reader, &fi); err != nil {
		return err
	}

	respBody, err := client.call(ctx, storageRESTMethodUpdateMetadata, values, &reader, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

func (client *storageRESTClient) DeleteVersion(ctx context.Context, volume, path string, fi FileInfo, forceDelMarker bool) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTForceDelMarker, strconv.FormatBool(forceDelMarker))

	var buffer bytes.Buffer
	if err := msgp.Encode(&buffer, &fi); err != nil {
		return err
	}

	respBody, err := client.call(ctx, storageRESTMethodDeleteVersion, values, &buffer, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// WriteAll - write all data to a file.
func (client *storageRESTClient) WriteAll(ctx context.Context, volume string, path string, b []byte) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	respBody, err := client.call(ctx, storageRESTMethodWriteAll, values, bytes.NewBuffer(b), int64(len(b)))
	defer xhttp.DrainBody(respBody)
	return err
}

// CheckParts - stat all file parts.
func (client *storageRESTClient) CheckParts(ctx context.Context, volume string, path string, fi FileInfo) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)

	var reader bytes.Buffer
	if err := msgp.Encode(&reader, &fi); err != nil {
		logger.LogIf(context.Background(), err)
		return err
	}

	respBody, err := client.call(ctx, storageRESTMethodCheckParts, values, &reader, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// RenameData - rename source path to destination path atomically, metadata and data file.
func (client *storageRESTClient) RenameData(ctx context.Context, srcVolume, srcPath string, fi FileInfo, dstVolume, dstPath string) (sign uint64, err error) {
	values := make(url.Values)
	values.Set(storageRESTSrcVolume, srcVolume)
	values.Set(storageRESTSrcPath, srcPath)
	values.Set(storageRESTDstVolume, dstVolume)
	values.Set(storageRESTDstPath, dstPath)

	var reader bytes.Buffer
	if err = msgp.Encode(&reader, &fi); err != nil {
		return 0, err
	}

	respBody, err := client.call(ctx, storageRESTMethodRenameData, values, &reader, -1)
	defer xhttp.DrainBody(respBody)
	if err != nil {
		return 0, err
	}

	respReader, err := waitForHTTPResponse(respBody)
	if err != nil {
		return 0, err
	}

	resp := &RenameDataResp{}
	if err = gob.NewDecoder(respReader).Decode(resp); err != nil {
		return 0, err
	}

	return resp.Signature, toStorageErr(resp.Err)
}

// where we keep old *Readers
var readMsgpReaderPool = sync.Pool{New: func() interface{} { return &msgp.Reader{} }}

// mspNewReader returns a *Reader that reads from the provided reader.
// The reader will be buffered.
func msgpNewReader(r io.Reader) *msgp.Reader {
	p := readMsgpReaderPool.Get().(*msgp.Reader)
	if p.R == nil {
		p.R = xbufio.NewReaderSize(r, 8<<10)
	} else {
		p.R.Reset(r)
	}
	return p
}

func (client *storageRESTClient) ReadVersion(ctx context.Context, volume, path, versionID string, readData bool) (fi FileInfo, err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTVersionID, versionID)
	values.Set(storageRESTReadData, strconv.FormatBool(readData))

	respBody, err := client.call(ctx, storageRESTMethodReadVersion, values, nil, -1)
	if err != nil {
		return fi, err
	}
	defer xhttp.DrainBody(respBody)

	dec := msgpNewReader(respBody)
	defer readMsgpReaderPool.Put(dec)

	err = fi.DecodeMsg(dec)
	return fi, err
}

// ReadXL - reads all contents of xl.meta of a file.
func (client *storageRESTClient) ReadXL(ctx context.Context, volume string, path string, readData bool) (rf RawFileInfo, err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTReadData, strconv.FormatBool(readData))
	respBody, err := client.call(ctx, storageRESTMethodReadXL, values, nil, -1)
	if err != nil {
		return rf, err
	}
	defer xhttp.DrainBody(respBody)

	dec := msgpNewReader(respBody)
	defer readMsgpReaderPool.Put(dec)

	err = rf.DecodeMsg(dec)
	return rf, err
}

// ReadAll - reads all contents of a file.
func (client *storageRESTClient) ReadAll(ctx context.Context, volume string, path string) ([]byte, error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	respBody, err := client.call(ctx, storageRESTMethodReadAll, values, nil, -1)
	if err != nil {
		return nil, err
	}
	defer xhttp.DrainBody(respBody)
	return io.ReadAll(respBody)
}

// ReadFileStream - returns a reader for the requested file.
func (client *storageRESTClient) ReadFileStream(ctx context.Context, volume, path string, offset, length int64) (io.ReadCloser, error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTOffset, strconv.Itoa(int(offset)))
	values.Set(storageRESTLength, strconv.Itoa(int(length)))
	respBody, err := client.call(ctx, storageRESTMethodReadFileStream, values, nil, -1)
	if err != nil {
		return nil, err
	}
	return respBody, nil
}

// ReadFile - reads section of a file.
func (client *storageRESTClient) ReadFile(ctx context.Context, volume string, path string, offset int64, buf []byte, verifier *BitrotVerifier) (int64, error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTOffset, strconv.Itoa(int(offset)))
	values.Set(storageRESTLength, strconv.Itoa(len(buf)))
	if verifier != nil {
		values.Set(storageRESTBitrotAlgo, verifier.algorithm.String())
		values.Set(storageRESTBitrotHash, hex.EncodeToString(verifier.sum))
	} else {
		values.Set(storageRESTBitrotAlgo, "")
		values.Set(storageRESTBitrotHash, "")
	}
	respBody, err := client.call(ctx, storageRESTMethodReadFile, values, nil, -1)
	if err != nil {
		return 0, err
	}
	defer xhttp.DrainBody(respBody)
	n, err := io.ReadFull(respBody, buf)
	return int64(n), err
}

// ListDir - lists a directory.
func (client *storageRESTClient) ListDir(ctx context.Context, volume, dirPath string, count int) (entries []string, err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTDirPath, dirPath)
	values.Set(storageRESTCount, strconv.Itoa(count))
	respBody, err := client.call(ctx, storageRESTMethodListDir, values, nil, -1)
	if err != nil {
		return nil, err
	}
	defer xhttp.DrainBody(respBody)
	err = gob.NewDecoder(respBody).Decode(&entries)
	return entries, err
}

// DeleteFile - deletes a file.
func (client *storageRESTClient) Delete(ctx context.Context, volume string, path string, deleteOpts DeleteOptions) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTRecursive, strconv.FormatBool(deleteOpts.Recursive))
	values.Set(storageRESTForceDelete, strconv.FormatBool(deleteOpts.Force))

	respBody, err := client.call(ctx, storageRESTMethodDeleteFile, values, nil, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

// DeleteVersions - deletes list of specified versions if present
func (client *storageRESTClient) DeleteVersions(ctx context.Context, volume string, versions []FileInfoVersions) (errs []error) {
	if len(versions) == 0 {
		return errs
	}

	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTTotalVersions, strconv.Itoa(len(versions)))

	var buffer bytes.Buffer
	encoder := msgp.NewWriter(&buffer)
	for _, version := range versions {
		version.EncodeMsg(encoder)
	}
	logger.LogIf(ctx, encoder.Flush())

	errs = make([]error, len(versions))

	respBody, err := client.call(ctx, storageRESTMethodDeleteVersions, values, &buffer, -1)
	defer xhttp.DrainBody(respBody)
	if err != nil {
		if contextCanceled(ctx) {
			err = ctx.Err()
		}
		for i := range errs {
			errs[i] = err
		}
		return errs
	}

	reader, err := waitForHTTPResponse(respBody)
	if err != nil {
		for i := range errs {
			errs[i] = err
		}
		return errs
	}

	dErrResp := &DeleteVersionsErrsResp{}
	if err = gob.NewDecoder(reader).Decode(dErrResp); err != nil {
		for i := range errs {
			errs[i] = err
		}
		return errs
	}

	for i, dErr := range dErrResp.Errs {
		errs[i] = toStorageErr(dErr)
	}

	return errs
}

// RenameFile - renames a file.
func (client *storageRESTClient) RenameFile(ctx context.Context, srcVolume, srcPath, dstVolume, dstPath string) (err error) {
	values := make(url.Values)
	values.Set(storageRESTSrcVolume, srcVolume)
	values.Set(storageRESTSrcPath, srcPath)
	values.Set(storageRESTDstVolume, dstVolume)
	values.Set(storageRESTDstPath, dstPath)
	respBody, err := client.call(ctx, storageRESTMethodRenameFile, values, nil, -1)
	defer xhttp.DrainBody(respBody)
	return err
}

func (client *storageRESTClient) VerifyFile(ctx context.Context, volume, path string, fi FileInfo) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)

	var reader bytes.Buffer
	if err := msgp.Encode(&reader, &fi); err != nil {
		return err
	}

	respBody, err := client.call(ctx, storageRESTMethodVerifyFile, values, &reader, -1)
	defer xhttp.DrainBody(respBody)
	if err != nil {
		return err
	}

	respReader, err := waitForHTTPResponse(respBody)
	if err != nil {
		return err
	}

	verifyResp := &VerifyFileResp{}
	if err = gob.NewDecoder(respReader).Decode(verifyResp); err != nil {
		return err
	}

	return toStorageErr(verifyResp.Err)
}

func (client *storageRESTClient) StatInfoFile(ctx context.Context, volume, path string, glob bool) (stat []StatInfo, err error) {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	values.Set(storageRESTGlob, fmt.Sprint(glob))
	respBody, err := client.call(ctx, storageRESTMethodStatInfoFile, values, nil, -1)
	if err != nil {
		return stat, err
	}
	defer xhttp.DrainBody(respBody)
	respReader, err := waitForHTTPResponse(respBody)
	if err != nil {
		return stat, err
	}
	rd := msgpNewReader(respReader)
	for {
		var st StatInfo
		err = st.DecodeMsg(rd)
		if err != nil {
			if errors.Is(err, io.EOF) {
				err = nil
			}
			break
		}
		stat = append(stat, st)
	}

	return stat, err
}

// ReadMultiple will read multiple files and send each back as response.
// Files are read and returned in the given order.
// The resp channel is closed before the call returns.
// Only a canceled context or network errors returns an error.
func (client *storageRESTClient) ReadMultiple(ctx context.Context, req ReadMultipleReq, resp chan<- ReadMultipleResp) error {
	defer close(resp)
	body, err := req.MarshalMsg(nil)
	if err != nil {
		return err
	}
	respBody, err := client.call(ctx, storageRESTMethodReadMultiple, nil, bytes.NewReader(body), int64(len(body)))
	if err != nil {
		return err
	}
	defer xhttp.DrainBody(respBody)
	if err != nil {
		return err
	}
	pr, pw := io.Pipe()
	go func() {
		pw.CloseWithError(waitForHTTPStream(respBody, pw))
	}()
	mr := msgp.NewReader(pr)
	for {
		var file ReadMultipleResp
		if err := file.DecodeMsg(mr); err != nil {
			if errors.Is(err, io.EOF) {
				err = nil
			}
			pr.CloseWithError(err)
			return err
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		case resp <- file:
		}
	}
}

// CleanAbandonedData will read metadata of the object on disk
// and delete any data directories and inline data that isn't referenced in metadata.
func (client *storageRESTClient) CleanAbandonedData(ctx context.Context, volume string, path string) error {
	values := make(url.Values)
	values.Set(storageRESTVolume, volume)
	values.Set(storageRESTFilePath, path)
	respBody, err := client.call(ctx, storageRESTMethodCleanAbandoned, values, nil, -1)
	if err != nil {
		return err
	}
	defer xhttp.DrainBody(respBody)
	respReader, err := waitForHTTPResponse(respBody)
	if err == nil {
		io.Copy(io.Discard, respReader)
	}
	return err
}

// Close - marks the client as closed.
func (client *storageRESTClient) Close() error {
	client.restClient.Close()
	return nil
}

// Returns a storage rest client.
func newStorageRESTClient(endpoint Endpoint, healthcheck bool) *storageRESTClient {
	serverURL := &url.URL{
		Scheme: endpoint.Scheme,
		Host:   endpoint.Host,
		Path:   path.Join(storageRESTPrefix, endpoint.Path, storageRESTVersion),
	}

	restClient := rest.NewClient(serverURL, globalInternodeTransport, newCachedAuthToken())

	if healthcheck {
		// Use a separate client to avoid recursive calls.
		healthClient := rest.NewClient(serverURL, globalInternodeTransport, newCachedAuthToken())
		healthClient.ExpectTimeouts = true
		healthClient.NoMetrics = true
		restClient.HealthCheckFn = func() bool {
			ctx, cancel := context.WithTimeout(context.Background(), restClient.HealthCheckTimeout)
			defer cancel()
			respBody, err := healthClient.Call(ctx, storageRESTMethodHealth, nil, nil, -1)
			xhttp.DrainBody(respBody)
			return toStorageErr(err) != errDiskNotFound
		}
	}

	return &storageRESTClient{endpoint: endpoint, restClient: restClient, poolIndex: -1, setIndex: -1, diskIndex: -1}
}
