package layer

import (
	"context"
	stderrors "errors"
	"fmt"
	"io"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/nspcc-dev/neofs-s3-gw/api"
	"github.com/nspcc-dev/neofs-s3-gw/api/data"
	"github.com/nspcc-dev/neofs-s3-gw/api/errors"
	"github.com/nspcc-dev/neofs-sdk-go/object"
	"github.com/nspcc-dev/neofs-sdk-go/owner"
	"go.uber.org/zap"
)

const (
	UploadIDAttributeName         = "S3-Upload-Id"
	UploadPartNumberAttributeName = "S3-Upload-Part-Number"
	UploadKeyAttributeName        = "S3-Upload-Key"
	UploadPartKeyPrefix           = ".upload-"

	MaxSizeUploadsList  = 1000
	MaxSizePartsList    = 1000
	UploadMinPartNumber = 1
	UploadMaxPartNumber = 10000
	uploadMinSize       = 5 * 1048576    // 5MB
	uploadMaxSize       = 5 * 1073741824 // 5GB
)

type (
	UploadInfoParams struct {
		UploadID string
		Bkt      *data.BucketInfo
		Key      string
	}

	UploadPartParams struct {
		Info       *UploadInfoParams
		PartNumber int
		Size       int64
		Reader     io.Reader
		Header     map[string]string
	}

	UploadCopyParams struct {
		Info       *UploadInfoParams
		SrcObjInfo *data.ObjectInfo
		PartNumber int
		Range      *RangeParams
	}

	CompleteMultipartParams struct {
		Info  *UploadInfoParams
		Parts []*CompletedPart
	}

	CompletedPart struct {
		ETag       string
		PartNumber int
	}

	Part struct {
		ETag         string
		LastModified string
		PartNumber   int
		Size         int64
	}

	ListMultipartUploadsParams struct {
		Bkt            *data.BucketInfo
		Delimiter      string
		EncodingType   string
		KeyMarker      string
		MaxUploads     int
		Prefix         string
		UploadIDMarker string
	}

	ListPartsParams struct {
		Info             *UploadInfoParams
		MaxParts         int
		PartNumberMarker int
	}

	ListPartsInfo struct {
		Parts                []*Part
		Owner                *owner.ID
		NextPartNumberMarker int
		IsTruncated          bool
	}

	ListMultipartUploadsInfo struct {
		Prefixes           []string
		Uploads            []*UploadInfo
		IsTruncated        bool
		NextKeyMarker      string
		NextUploadIDMarker string
	}
	UploadInfo struct {
		IsDir    bool
		Key      string
		UploadID string
		Owner    *owner.ID
		Created  time.Time
	}
)

func (n *layer) UploadPart(ctx context.Context, p *UploadPartParams) (*data.ObjectInfo, error) {
	if p.PartNumber != 0 {
		if _, err := n.GetUploadInitInfo(ctx, p.Info); err != nil {
			return nil, err
		}
	}

	if p.Size > uploadMaxSize {
		return nil, errors.GetAPIError(errors.ErrEntityTooLarge)
	}

	if p.Header == nil {
		p.Header = make(map[string]string)
	}

	appendUploadHeaders(p.Header, p.Info.UploadID, p.Info.Key, p.PartNumber)

	params := &PutObjectParams{
		BktInfo: p.Info.Bkt,
		Object:  createUploadPartName(p.Info.UploadID, p.Info.Key, p.PartNumber),
		Size:    p.Size,
		Reader:  p.Reader,
		Header:  p.Header,
	}

	return n.PutObject(ctx, params)
}

func (n *layer) UploadPartCopy(ctx context.Context, p *UploadCopyParams) (*data.ObjectInfo, error) {
	if _, err := n.GetUploadInitInfo(ctx, p.Info); err != nil {
		return nil, err
	}

	if p.Range != nil {
		if p.Range.End-p.Range.Start > uploadMaxSize {
			return nil, errors.GetAPIError(errors.ErrEntityTooLarge)
		}
		if p.Range.End > uint64(p.SrcObjInfo.Size) {
			return nil, errors.GetAPIError(errors.ErrInvalidCopyPartRangeSource)
		}
	} else {
		if p.SrcObjInfo.Size > uploadMaxSize {
			return nil, errors.GetAPIError(errors.ErrEntityTooLarge)
		}
	}

	metadata := make(map[string]string)
	appendUploadHeaders(metadata, p.Info.UploadID, p.Info.Key, p.PartNumber)

	c := &CopyObjectParams{
		SrcObject:  p.SrcObjInfo,
		DstBktInfo: p.Info.Bkt,
		DstObject:  createUploadPartName(p.Info.UploadID, p.Info.Key, p.PartNumber),
		SrcSize:    p.SrcObjInfo.Size,
		Header:     metadata,
		Range:      p.Range,
	}

	return n.CopyObject(ctx, c)
}

// implements io.Reader of payloads of the object list stored in the NeoFS network.
type multiObjectReader struct {
	ctx context.Context

	layer *layer

	prm getParams

	curReader io.Reader

	parts []*data.ObjectInfo
}

func (x *multiObjectReader) Read(p []byte) (n int, err error) {
	if x.curReader != nil {
		n, err = x.curReader.Read(p)
		if !stderrors.Is(err, io.EOF) {
			return n, err
		}
	}

	if len(x.parts) == 0 {
		return n, io.EOF
	}

	x.prm.oid = x.parts[0].ID

	x.curReader, err = x.layer.initObjectPayloadReader(x.ctx, x.prm)
	if err != nil {
		return n, fmt.Errorf("init payload reader for the next part: %w", err)
	}

	x.parts = x.parts[1:]

	next, err := x.Read(p[n:])

	return n + next, err
}

func (n *layer) CompleteMultipartUpload(ctx context.Context, p *CompleteMultipartParams) (*data.ObjectInfo, error) {
	var obj *data.ObjectInfo

	for i := 1; i < len(p.Parts); i++ {
		if p.Parts[i].PartNumber <= p.Parts[i-1].PartNumber {
			return nil, errors.GetAPIError(errors.ErrInvalidPartOrder)
		}
	}

	objects, err := n.getUploadParts(ctx, p.Info)
	if err != nil {
		return nil, err
	}

	if len(objects) == 1 {
		obj, err := n.headLastVersionIfNotDeleted(ctx, p.Info.Bkt, p.Info.Key)
		if err != nil {
			if errors.IsS3Error(err, errors.ErrNoSuchKey) {
				return nil, errors.GetAPIError(errors.ErrInvalidPart)
			}
			return nil, err
		}
		if obj != nil && obj.Headers[UploadIDAttributeName] != "" {
			return obj, nil
		}
		return nil, errors.GetAPIError(errors.ErrInvalidPart)
	}

	if _, ok := objects[0]; !ok {
		n.log.Error("could not get init multipart upload",
			zap.Stringer("bucket id", p.Info.Bkt.CID),
			zap.String("uploadID", p.Info.UploadID),
			zap.String("uploadKey", p.Info.Key),
		)
		// we return InternalError because if we are here it means we've checked InitPart before in handler and
		// received successful result, it's strange we didn't get the InitPart again
		return nil, errors.GetAPIError(errors.ErrInternalError)
	}

	if len(objects) < len(p.Parts) {
		return nil, errors.GetAPIError(errors.ErrInvalidPart)
	}

	parts := make([]*data.ObjectInfo, 0, len(p.Parts))

	for i, part := range p.Parts {
		info := objects[part.PartNumber]
		if info == nil || part.ETag != info.HashSum {
			return nil, errors.GetAPIError(errors.ErrInvalidPart)
		}
		// for the last part we have no minimum size limit
		if i != len(p.Parts)-1 && info.Size < uploadMinSize {
			return nil, errors.GetAPIError(errors.ErrEntityTooSmall)
		}
		parts = append(parts, info)
	}

	initMetadata := objects[0].Headers
	if len(objects[0].ContentType) != 0 {
		initMetadata[api.ContentType] = objects[0].ContentType
	}

	/* We will keep "S3-Upload-Id" attribute in completed object to determine is it "common" object or completed object.
	We will need to differ these objects if something goes wrong during completing multipart upload.
	I.e. we had completed the object but didn't put tagging/acl for some reason */
	delete(initMetadata, UploadPartNumberAttributeName)
	delete(initMetadata, UploadKeyAttributeName)
	delete(initMetadata, attrVersionsIgnore)

	r := &multiObjectReader{
		ctx:   ctx,
		layer: n,
		parts: parts,
	}

	r.prm.cid = p.Info.Bkt.CID

	obj, err = n.PutObject(ctx, &PutObjectParams{
		BktInfo: p.Info.Bkt,
		Object:  p.Info.Key,
		Reader:  r,
		Header:  initMetadata,
	})
	if err != nil {
		n.log.Error("could not put a completed object (multipart upload)",
			zap.String("uploadID", p.Info.UploadID),
			zap.String("uploadKey", p.Info.Key),
			zap.Error(err))

		return nil, errors.GetAPIError(errors.ErrInternalError)
	}

	for partNum, objInfo := range objects {
		if partNum == 0 {
			continue
		}
		if err = n.objectDelete(ctx, p.Info.Bkt.CID, objInfo.ID); err != nil {
			n.log.Warn("could not delete upload part",
				zap.Stringer("object id", objInfo.ID),
				zap.Stringer("bucket id", p.Info.Bkt.CID),
				zap.Error(err))
			return nil, errors.GetAPIError(errors.ErrInternalError)
		}
	}

	return obj, nil
}

func (n *layer) ListMultipartUploads(ctx context.Context, p *ListMultipartUploadsParams) (*ListMultipartUploadsInfo, error) {
	var result ListMultipartUploadsInfo
	if p.MaxUploads == 0 {
		return &result, nil
	}

	f := &findParams{
		attr: [2]string{UploadPartNumberAttributeName, "0"},
		cid:  p.Bkt.CID,
	}

	ids, err := n.objectSearch(ctx, f)
	if err != nil {
		return nil, err
	}

	uploads := make([]*UploadInfo, 0, len(ids))
	uniqDirs := make(map[string]struct{})

	for i := range ids {
		meta, err := n.objectHead(ctx, p.Bkt.CID, &ids[i])
		if err != nil {
			n.log.Warn("couldn't head object",
				zap.Stringer("object id", &ids[i]),
				zap.Stringer("bucket id", p.Bkt.CID),
				zap.Error(err))
			continue
		}
		info := uploadInfoFromMeta(meta, p.Prefix, p.Delimiter)
		if info != nil {
			if info.IsDir {
				if _, ok := uniqDirs[info.Key]; ok {
					continue
				}
				uniqDirs[info.Key] = struct{}{}
			}
			uploads = append(uploads, info)
		}
	}

	sort.Slice(uploads, func(i, j int) bool {
		if uploads[i].Key == uploads[j].Key {
			return uploads[i].UploadID < uploads[j].UploadID
		}
		return uploads[i].Key < uploads[j].Key
	})

	if p.KeyMarker != "" {
		if p.UploadIDMarker != "" {
			uploads = trimAfterUploadIDAndKey(p.KeyMarker, p.UploadIDMarker, uploads)
		} else {
			uploads = trimAfterUploadKey(p.KeyMarker, uploads)
		}
	}

	if len(uploads) > p.MaxUploads {
		result.IsTruncated = true
		uploads = uploads[:p.MaxUploads]
		result.NextUploadIDMarker = uploads[len(uploads)-1].UploadID
		result.NextKeyMarker = uploads[len(uploads)-1].Key
	}

	for _, ov := range uploads {
		if ov.IsDir {
			result.Prefixes = append(result.Prefixes, ov.Key)
		} else {
			result.Uploads = append(result.Uploads, ov)
		}
	}

	return &result, nil
}

func (n *layer) AbortMultipartUpload(ctx context.Context, p *UploadInfoParams) error {
	objects, err := n.getUploadParts(ctx, p)
	if err != nil {
		return err
	}

	for _, info := range objects {
		err := n.objectDelete(ctx, info.CID, info.ID)
		if err != nil {
			return err
		}
	}

	return nil
}

func (n *layer) ListParts(ctx context.Context, p *ListPartsParams) (*ListPartsInfo, error) {
	var res ListPartsInfo
	objs, err := n.getUploadParts(ctx, p.Info)
	if err != nil {
		return nil, err
	}

	res.Owner = objs[0].Owner

	parts := make([]*Part, 0, len(objs))

	for num, objInfo := range objs {
		if num == 0 {
			continue
		}
		parts = append(parts, &Part{
			ETag:         objInfo.HashSum,
			LastModified: objInfo.Created.UTC().Format(time.RFC3339),
			PartNumber:   num,
			Size:         objInfo.Size,
		})
	}

	sort.Slice(parts, func(i, j int) bool {
		return parts[i].PartNumber < parts[j].PartNumber
	})

	if p.PartNumberMarker != 0 {
		for i, part := range parts {
			if part.PartNumber > p.PartNumberMarker {
				parts = parts[i:]
				break
			}
		}
	}

	if len(parts) > p.MaxParts {
		res.IsTruncated = true
		res.NextPartNumberMarker = parts[p.MaxParts-1].PartNumber
		parts = parts[:p.MaxParts]
	}

	res.Parts = parts

	return &res, nil
}

func (n *layer) GetUploadInitInfo(ctx context.Context, p *UploadInfoParams) (*data.ObjectInfo, error) {
	ids, err := n.objectSearchByName(ctx, p.Bkt.CID, createUploadPartName(p.UploadID, p.Key, 0))
	if err != nil {
		return nil, err
	}
	if len(ids) == 0 {
		return nil, errors.GetAPIError(errors.ErrNoSuchUpload)
	}
	if len(ids) > 1 {
		return nil, errors.GetAPIError(errors.ErrInternalError)
	}

	meta, err := n.objectHead(ctx, p.Bkt.CID, &ids[0])
	if err != nil {
		return nil, err
	}

	return objInfoFromMeta(p.Bkt, meta), nil
}

func (n *layer) getUploadParts(ctx context.Context, p *UploadInfoParams) (map[int]*data.ObjectInfo, error) {
	f := &findParams{
		cid:    p.Bkt.CID,
		prefix: UploadPartKeyPrefix + p.UploadID + "-" + p.Key,
	}

	ids, err := n.objectSearch(ctx, f)
	if err != nil {
		return nil, err
	}
	if len(ids) == 0 {
		return nil, errors.GetAPIError(errors.ErrNoSuchUpload)
	}

	res := make(map[int]*data.ObjectInfo)

	for i := range ids {
		meta, err := n.objectHead(ctx, p.Bkt.CID, &ids[i])
		if err != nil {
			n.log.Warn("couldn't head a part of upload",
				zap.Stringer("object id", &ids[i]),
				zap.Stringer("bucket id", p.Bkt.CID),
				zap.Error(err))
			continue
		}
		info := objInfoFromMeta(p.Bkt, meta)
		numStr := info.Headers[UploadPartNumberAttributeName]
		num, err := strconv.Atoi(numStr)
		if err != nil {
			return nil, errors.GetAPIError(errors.ErrInternalError)
		}
		res[num] = info
	}

	return res, nil
}

func createUploadPartName(uploadID, key string, partNumber int) string {
	return UploadPartKeyPrefix + uploadID + "-" + key + "-" + strconv.Itoa(partNumber)
}

func trimAfterUploadIDAndKey(key, id string, uploads []*UploadInfo) []*UploadInfo {
	var res []*UploadInfo
	if len(uploads) != 0 && uploads[len(uploads)-1].Key < key {
		return res
	}

	for _, obj := range uploads {
		if obj.Key >= key && obj.UploadID > id {
			res = append(res, obj)
		}
	}

	return res
}

func trimAfterUploadKey(key string, objects []*UploadInfo) []*UploadInfo {
	var result []*UploadInfo
	if len(objects) != 0 && objects[len(objects)-1].Key <= key {
		return result
	}
	for i, obj := range objects {
		if obj.Key > key {
			result = objects[i:]
			break
		}
	}

	return result
}

func uploadInfoFromMeta(meta *object.Object, prefix, delimiter string) *UploadInfo {
	var (
		isDir       bool
		creation    time.Time
		userHeaders = userHeaders(meta.Attributes())
		key         = userHeaders[UploadKeyAttributeName]
	)

	if !strings.HasPrefix(key, prefix) {
		return nil
	}

	if val, ok := userHeaders[object.AttributeTimestamp]; ok {
		if dt, err := strconv.ParseInt(val, 10, 64); err == nil {
			creation = time.Unix(dt, 0)
		}
	}

	if len(delimiter) > 0 {
		tail := strings.TrimPrefix(key, prefix)
		index := strings.Index(tail, delimiter)
		if index >= 0 {
			isDir = true
			key = prefix + tail[:index+1]
		}
	}

	return &UploadInfo{
		IsDir:    isDir,
		Key:      key,
		UploadID: userHeaders[UploadIDAttributeName],
		Owner:    meta.OwnerID(),
		Created:  creation,
	}
}

func appendUploadHeaders(metadata map[string]string, uploadID, key string, partNumber int) {
	metadata[UploadIDAttributeName] = uploadID
	metadata[UploadPartNumberAttributeName] = strconv.Itoa(partNumber)
	metadata[UploadKeyAttributeName] = key
	metadata[attrVersionsIgnore] = "true"
}