package layer

import (
	"bytes"
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"strconv"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer/frostfs"
)

type PatchObjectParams struct {
	Object            *data.ExtendedObjectInfo
	BktInfo           *data.BucketInfo
	NewBytes          io.Reader
	Range             *RangeParams
	VersioningEnabled bool
	CopiesNumbers     []uint32
}

func (n *Layer) PatchObject(ctx context.Context, p *PatchObjectParams) (*data.ExtendedObjectInfo, error) {
	if p.Object.ObjectInfo.Headers[AttributeDecryptedSize] != "" {
		return nil, fmt.Errorf("patch encrypted object")
	}

	if p.Object.ObjectInfo.Headers[MultipartObjectSize] != "" {
		return n.patchMultipartObject(ctx, p)
	}

	prmPatch := frostfs.PrmObjectPatch{
		Container:  p.BktInfo.CID,
		Object:     p.Object.ObjectInfo.ID,
		Payload:    p.NewBytes,
		Offset:     p.Range.Start,
		Length:     p.Range.End - p.Range.Start + 1,
		ObjectSize: p.Object.ObjectInfo.Size,
	}
	n.prepareAuthParameters(ctx, &prmPatch.PrmAuth, p.BktInfo.Owner)

	createdObj, err := n.patchObject(ctx, prmPatch)
	if err != nil {
		return nil, fmt.Errorf("patch object: %w", err)
	}

	newVersion := &data.NodeVersion{
		BaseNodeVersion: data.BaseNodeVersion{
			OID:           createdObj.ID,
			ETag:          hex.EncodeToString(createdObj.HashSum),
			FilePath:      p.Object.ObjectInfo.Name,
			Size:          createdObj.Size,
			Created:       &p.Object.ObjectInfo.Created,
			Owner:         &n.gateOwner,
			CreationEpoch: p.Object.NodeVersion.CreationEpoch,
		},
		IsUnversioned: !p.VersioningEnabled,
		IsCombined:    p.Object.ObjectInfo.Headers[MultipartObjectSize] != "",
	}

	if newVersion.ID, err = n.treeService.AddVersion(ctx, p.BktInfo, newVersion); err != nil {
		return nil, fmt.Errorf("couldn't add new version to tree service: %w", err)
	}

	p.Object.ObjectInfo.ID = createdObj.ID
	p.Object.ObjectInfo.Size = createdObj.Size
	p.Object.ObjectInfo.MD5Sum = ""
	p.Object.ObjectInfo.HashSum = hex.EncodeToString(createdObj.HashSum)
	p.Object.NodeVersion = newVersion

	return p.Object, nil
}

func (n *Layer) patchObject(ctx context.Context, p frostfs.PrmObjectPatch) (*data.CreatedObjectInfo, error) {
	objID, err := n.frostFS.PatchObject(ctx, p)
	if err != nil {
		return nil, fmt.Errorf("patch object: %w", err)
	}

	prmHead := frostfs.PrmObjectHead{
		PrmAuth:   p.PrmAuth,
		Container: p.Container,
		Object:    objID,
	}
	obj, err := n.frostFS.HeadObject(ctx, prmHead)
	if err != nil {
		return nil, fmt.Errorf("head object: %w", err)
	}

	payloadChecksum, _ := obj.PayloadChecksum()

	return &data.CreatedObjectInfo{
		ID:      objID,
		Size:    obj.PayloadSize(),
		HashSum: payloadChecksum.Value(),
	}, nil
}

func (n *Layer) patchMultipartObject(ctx context.Context, p *PatchObjectParams) (*data.ExtendedObjectInfo, error) {
	combinedObj, err := n.objectGet(ctx, p.BktInfo, p.Object.ObjectInfo.ID)
	if err != nil {
		return nil, fmt.Errorf("get combined object '%s': %w", p.Object.ObjectInfo.ID.EncodeToString(), err)
	}

	var parts []*data.PartInfo
	if err = json.NewDecoder(combinedObj.Payload).Decode(&parts); err != nil {
		return nil, fmt.Errorf("unmarshal combined object parts: %w", err)
	}

	prmPatch := frostfs.PrmObjectPatch{
		Container: p.BktInfo.CID,
	}
	n.prepareAuthParameters(ctx, &prmPatch.PrmAuth, p.BktInfo.Owner)

	off, ln := p.Range.Start, p.Range.End-p.Range.Start+1
	var multipartObjectSize uint64
	for i, part := range parts {
		if off > part.Size || (off == part.Size && i != len(parts)-1) || ln == 0 {
			multipartObjectSize += part.Size
			if ln != 0 {
				off -= part.Size
			}
			continue
		}

		var createdObj *data.CreatedObjectInfo
		createdObj, off, ln, err = n.patchPart(ctx, part, p, &prmPatch, off, ln, i == len(parts)-1)
		if err != nil {
			return nil, fmt.Errorf("patch part: %w", err)
		}

		parts[i].OID = createdObj.ID
		parts[i].Size = createdObj.Size
		parts[i].MD5 = ""
		parts[i].ETag = hex.EncodeToString(createdObj.HashSum)

		multipartObjectSize += createdObj.Size
	}

	return n.updateCombinedObject(ctx, parts, multipartObjectSize, p)
}

// Returns patched part info, updated offset and length.
func (n *Layer) patchPart(ctx context.Context, part *data.PartInfo, p *PatchObjectParams, prmPatch *frostfs.PrmObjectPatch, off, ln uint64, lastPart bool) (*data.CreatedObjectInfo, uint64, uint64, error) {
	if off == 0 && ln >= part.Size {
		curLen := part.Size
		if lastPart {
			curLen = ln
		}
		prm := frostfs.PrmObjectCreate{
			Container:    p.BktInfo.CID,
			Payload:      io.LimitReader(p.NewBytes, int64(curLen)),
			CreationTime: part.Created,
			CopiesNumber: p.CopiesNumbers,
		}

		createdObj, err := n.objectPutAndHash(ctx, prm, p.BktInfo)
		if err != nil {
			return nil, 0, 0, fmt.Errorf("put new part object '%s': %w", part.OID.EncodeToString(), err)
		}

		ln -= curLen

		return createdObj, off, ln, err
	}

	curLen := ln
	if off+curLen > part.Size && !lastPart {
		curLen = part.Size - off
	}
	prmPatch.Object = part.OID
	prmPatch.ObjectSize = part.Size
	prmPatch.Offset = off
	prmPatch.Length = curLen

	prmPatch.Payload = io.LimitReader(p.NewBytes, int64(prmPatch.Length))

	createdObj, err := n.patchObject(ctx, *prmPatch)
	if err != nil {
		return nil, 0, 0, fmt.Errorf("patch part object '%s': %w", part.OID.EncodeToString(), err)
	}

	ln -= curLen
	off = 0

	return createdObj, off, ln, nil
}

func (n *Layer) updateCombinedObject(ctx context.Context, parts []*data.PartInfo, fullObjSize uint64, p *PatchObjectParams) (*data.ExtendedObjectInfo, error) {
	newParts, err := json.Marshal(parts)
	if err != nil {
		return nil, fmt.Errorf("marshal parts for combined object: %w", err)
	}

	var headerParts strings.Builder
	for i, part := range parts {
		headerPart := part.ToHeaderString()
		if i != len(parts)-1 {
			headerPart += ","
		}
		headerParts.WriteString(headerPart)
	}

	prm := frostfs.PrmObjectCreate{
		Container:    p.BktInfo.CID,
		PayloadSize:  fullObjSize,
		Filepath:     p.Object.ObjectInfo.Name,
		Payload:      bytes.NewReader(newParts),
		CreationTime: p.Object.ObjectInfo.Created,
		CopiesNumber: p.CopiesNumbers,
	}

	prm.Attributes = make([][2]string, 0, len(p.Object.ObjectInfo.Headers)+1)

	for k, v := range p.Object.ObjectInfo.Headers {
		switch k {
		case MultipartObjectSize:
			prm.Attributes = append(prm.Attributes, [2]string{MultipartObjectSize, strconv.FormatUint(fullObjSize, 10)})
		case UploadCompletedParts:
			prm.Attributes = append(prm.Attributes, [2]string{UploadCompletedParts, headerParts.String()})
		case api.ContentType:
		default:
			prm.Attributes = append(prm.Attributes, [2]string{k, v})
		}
	}
	prm.Attributes = append(prm.Attributes, [2]string{api.ContentType, p.Object.ObjectInfo.ContentType})

	createdObj, err := n.objectPutAndHash(ctx, prm, p.BktInfo)
	if err != nil {
		return nil, fmt.Errorf("put new combined object: %w", err)
	}

	newVersion := &data.NodeVersion{
		BaseNodeVersion: data.BaseNodeVersion{
			OID:           createdObj.ID,
			ETag:          hex.EncodeToString(createdObj.HashSum),
			MD5:           hex.EncodeToString(createdObj.MD5Sum) + "-" + strconv.Itoa(len(parts)),
			FilePath:      p.Object.ObjectInfo.Name,
			Size:          fullObjSize,
			Created:       &p.Object.ObjectInfo.Created,
			Owner:         &n.gateOwner,
			CreationEpoch: p.Object.NodeVersion.CreationEpoch,
		},
		IsUnversioned: !p.VersioningEnabled,
		IsCombined:    p.Object.ObjectInfo.Headers[MultipartObjectSize] != "",
	}

	if newVersion.ID, err = n.treeService.AddVersion(ctx, p.BktInfo, newVersion); err != nil {
		return nil, fmt.Errorf("couldn't add new version to tree service: %w", err)
	}

	p.Object.ObjectInfo.ID = createdObj.ID
	p.Object.ObjectInfo.Size = createdObj.Size
	p.Object.ObjectInfo.MD5Sum = hex.EncodeToString(createdObj.MD5Sum) + "-" + strconv.Itoa(len(parts))
	p.Object.ObjectInfo.HashSum = hex.EncodeToString(createdObj.HashSum)
	p.Object.ObjectInfo.Headers[MultipartObjectSize] = strconv.FormatUint(fullObjSize, 10)
	p.Object.ObjectInfo.Headers[UploadCompletedParts] = headerParts.String()
	p.Object.NodeVersion = newVersion

	return p.Object, nil
}