package handler

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"path/filepath"
	"strconv"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/data"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/response"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/tokens"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/utils"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"github.com/valyala/fasthttp"
	"go.uber.org/zap"
)

const (
	jsonHeader           = "application/json; charset=UTF-8"
	drainBufSize         = 4096
	explodeArchiveHeader = "Explode-Archive"
)

type putResponse struct {
	ObjectID    string `json:"object_id"`
	ContainerID string `json:"container_id"`
}

func newPutResponse(addr oid.Address) *putResponse {
	return &putResponse{
		ObjectID:    addr.Object().EncodeToString(),
		ContainerID: addr.Container().EncodeToString(),
	}
}

func (pr *putResponse) encode(w io.Writer) error {
	enc := json.NewEncoder(w)
	enc.SetIndent("", "\t")
	return enc.Encode(pr)
}

// Upload handles multipart upload request.
func (h *Handler) Upload(c *fasthttp.RequestCtx) {
	var file MultipartFile

	scid, _ := c.UserValue("cid").(string)
	bodyStream := c.RequestBodyStream()
	drainBuf := make([]byte, drainBufSize)

	ctx := utils.GetContextFromRequest(c)
	reqLog := utils.GetReqLogOrDefault(ctx, h.log)
	log := reqLog.With(zap.String("cid", scid))

	bktInfo, err := h.getBucketInfo(ctx, scid, log)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	defer func() {
		// If the temporary reader can be closed - let's close it.
		if file == nil {
			return
		}
		err := file.Close()
		log.Debug(
			logs.CloseTemporaryMultipartFormFile,
			zap.Stringer("container", bktInfo.CID),
			zap.String("filename", file.FileName()),
			zap.Error(err),
		)
	}()

	boundary := string(c.Request.Header.MultipartFormBoundary())
	if file, err = fetchMultipartFile(log, bodyStream, boundary); err != nil {
		log.Error(logs.CouldNotReceiveMultipartForm, zap.Error(err))
		response.Error(c, "could not receive multipart/form: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}

	if header := c.Request.Header.Peek(utils.UserAttributeHeaderPrefix + explodeArchiveHeader); header != nil {
		h.explodeGzip(c, log, bktInfo, file)
	} else {
		h.uploadSingleObject(c, log, bktInfo, file)
	}

	// Multipart is multipart and thus can contain more than one part which
	// we ignore at the moment. Also, when dealing with chunked encoding
	// the last zero-length chunk might be left unread (because multipart
	// reader only cares about its boundary and doesn't look further) and
	// it will be (erroneously) interpreted as the start of the next
	// pipelined header. Thus we need to drain the body buffer.
	for {
		_, err = bodyStream.Read(drainBuf)
		if err == io.EOF || errors.Is(err, io.ErrUnexpectedEOF) {
			break
		}
	}
}

func (h *Handler) uploadSingleObject(c *fasthttp.RequestCtx, log *zap.Logger, bktInfo *data.BucketInfo, file MultipartFile) {
	idObj, err := h.uploadObject(c, log, bktInfo, file.FileName(), file)
	if err != nil {
		log.Error(logs.FailedToUploadObject, zap.Error(err))
		return
	}
	addr := newAddress(bktInfo.CID, idObj)

	// Try to return the response, otherwise, if something went wrong, throw an error.
	if err = newPutResponse(addr).encode(c); err != nil {
		log.Error(logs.CouldNotEncodeResponse, zap.Error(err))
		response.Error(c, "could not encode response", fasthttp.StatusBadRequest)
		return
	}

	c.Response.Header.SetContentType(jsonHeader)
}

func (h *Handler) uploadObject(c *fasthttp.RequestCtx, log *zap.Logger, bktInfo *data.BucketInfo, fileName string, file io.Reader) (oid.ID, error) {
	ctx := utils.GetContextFromRequest(c)
	filtered, err := filterHeaders(log, &c.Request.Header)
	if err != nil {
		log.Error(logs.FailedToFilterHeaders, zap.Error(err))
		response.Error(c, "could not filter headers", fasthttp.StatusBadRequest)
		return oid.ID{}, err
	}

	now := time.Now()
	if rawHeader := c.Request.Header.Peek(fasthttp.HeaderDate); rawHeader != nil {
		if parsed, err := time.Parse(http.TimeFormat, string(rawHeader)); err != nil {
			log.Warn(logs.CouldNotParseClientTime, zap.String("Date header", string(rawHeader)), zap.Error(err))
		} else {
			now = parsed
		}
	}

	if err = utils.PrepareExpirationHeader(c, h.frostfs, filtered, now); err != nil {
		log.Error(logs.CouldNotPrepareExpirationHeader, zap.Error(err))
		response.Error(c, "could not prepare expiration header: "+err.Error(), fasthttp.StatusBadRequest)
		return oid.ID{}, err
	}

	attributes := make([]object.Attribute, 0, len(filtered))
	// prepares attributes from filtered headers
	for key, val := range filtered {
		attribute := object.NewAttribute()
		attribute.SetKey(key)
		attribute.SetValue(val)
		attributes = append(attributes, *attribute)
	}
	// sets FileName attribute if it wasn't set from header
	if _, ok := filtered[object.AttributeFileName]; !ok {
		fileNameAttr := object.NewAttribute()
		fileNameAttr.SetKey(object.AttributeFileName)
		fileNameAttr.SetValue(fileName)
		attributes = append(attributes, *fileNameAttr)
	}
	// sets Timestamp attribute if it wasn't set from header and enabled by settings
	if _, ok := filtered[object.AttributeTimestamp]; !ok && h.config.DefaultTimestamp() {
		timestamp := object.NewAttribute()
		timestamp.SetKey(object.AttributeTimestamp)
		timestamp.SetValue(strconv.FormatInt(time.Now().Unix(), 10))
		attributes = append(attributes, *timestamp)
	}

	obj := object.New()
	obj.SetContainerID(bktInfo.CID)
	obj.SetOwnerID(*h.ownerID)
	obj.SetAttributes(attributes...)

	prm := PrmObjectCreate{
		PrmAuth: PrmAuth{
			BearerToken: h.fetchBearerToken(ctx),
		},
		Object:                 obj,
		Payload:                file,
		ClientCut:              h.config.ClientCut(),
		WithoutHomomorphicHash: bktInfo.HomomorphicHashDisabled,
		BufferMaxSize:          h.config.BufferMaxSizeForPut(),
	}

	var idObj oid.ID
	if idObj, err = h.frostfs.CreateObject(ctx, prm); err != nil {
		h.handlePutFrostFSErr(c, err, log)
		return oid.ID{}, err
	}
	return idObj, nil
}

// explodeGzip read files from tar.gz archive and creates objects for each of them.
// Sets FilePath attribute with name from tar.Header
func (h *Handler) explodeGzip(c *fasthttp.RequestCtx, log *zap.Logger, bktInfo *data.BucketInfo, file io.Reader) {
	gzipReader, err := gzip.NewReader(file)
	if err != nil {
		log.Error(logs.FailedToCreateReader, zap.Error(err))
		response.Error(c, "could not create gzip reader: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}
	defer func() {
		if err := gzipReader.Close(); err != nil {
			log.Error(logs.FailedToCloseReader, zap.Error(err))
		}
	}()

	tarReader := tar.NewReader(gzipReader)
	var obj *tar.Header

	for {
		obj, err = tarReader.Next()
		if errors.Is(err, io.EOF) {
			break
		} else if err != nil {
			log.Error(logs.FailedToReadFileFromTar, zap.Error(err))
			continue
		}
		if isDir(obj.Name) {
			continue
		}
		c.Request.Header.Set(utils.UserAttributeHeaderPrefix+object.AttributeFilePath, obj.Name)
		idObj, err := h.uploadObject(c, log, bktInfo, filepath.Base(obj.Name), tarReader)
		if err != nil {
			log.Error(logs.FailedToUploadObject, zap.Error(err))
			response.Error(c, "could not upload object: "+err.Error(), fasthttp.StatusBadRequest)
		}
		log.Debug(logs.ObjectUploaded, zap.String("object ID", idObj.EncodeToString()))
	}
}

func (h *Handler) handlePutFrostFSErr(r *fasthttp.RequestCtx, err error, log *zap.Logger) {
	statusCode, msg, additionalFields := response.FormErrorResponse("could not store file in frostfs", err)
	logFields := append([]zap.Field{zap.Error(err)}, additionalFields...)

	log.Error(logs.CouldNotStoreFileInFrostfs, logFields...)
	response.Error(r, msg, statusCode)
}

func (h *Handler) fetchBearerToken(ctx context.Context) *bearer.Token {
	if tkn, err := tokens.LoadBearerToken(ctx); err == nil && tkn != nil {
		return tkn
	}
	return nil
}