package handler

import (
	"io"
	"net/http"

	"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/errors"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/middleware"
	"go.uber.org/zap"
)

const sizeToDetectType = 512

func getRangeToDetectContentType(maxSize uint64) *layer.RangeParams {
	end := maxSize
	if sizeToDetectType < end {
		end = sizeToDetectType
	}

	return &layer.RangeParams{
		Start: 0,
		End:   end - 1,
	}
}

func (h *handler) HeadObjectHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	reqInfo := middleware.GetReqInfo(ctx)

	bktInfo, err := h.getBucketAndCheckOwner(r, reqInfo.BucketName)
	if err != nil {
		h.logAndSendError(ctx, w, "could not get bucket info", reqInfo, err)
		return
	}

	conditional, err := parseConditionalHeaders(r.Header)
	if err != nil {
		h.logAndSendError(ctx, w, "could not parse request params", reqInfo, err)
		return
	}

	p := &layer.HeadObjectParams{
		BktInfo:   bktInfo,
		Object:    reqInfo.ObjectName,
		VersionID: reqInfo.URL.Query().Get(api.QueryVersionID),
	}

	extendedInfo, err := h.obj.GetExtendedObjectInfo(ctx, p)
	if err != nil {
		h.logAndSendError(ctx, w, "could not find object", reqInfo, err)
		return
	}
	info := extendedInfo.ObjectInfo

	encryptionParams, err := formEncryptionParams(r)
	if err != nil {
		h.logAndSendError(ctx, w, "invalid sse headers", reqInfo, err)
		return
	}

	if err = encryptionParams.MatchObjectEncryption(layer.FormEncryptionInfo(info.Headers)); err != nil {
		h.logAndSendError(ctx, w, "encryption doesn't match object", reqInfo, errors.GetAPIError(errors.ErrBadRequest), zap.Error(err))
		return
	}

	bktSettings, err := h.obj.GetBucketSettings(ctx, bktInfo)
	if err != nil {
		h.logAndSendError(ctx, w, "could not get bucket settings", reqInfo, err)
		return
	}

	t := &data.ObjectVersion{
		BktInfo:    bktInfo,
		ObjectName: info.Name,
		VersionID:  info.VersionID(),
	}

	tagSet, lockInfo, err := h.obj.GetObjectTaggingAndLock(ctx, t, extendedInfo.NodeVersion)
	if err != nil && !errors.IsS3Error(err, errors.ErrNoSuchKey) {
		h.logAndSendError(ctx, w, "could not get object meta data", reqInfo, err)
		return
	}

	if err = checkPreconditions(info, conditional, h.cfg.MD5Enabled()); err != nil {
		if errors.IsS3Error(err, errors.ErrNotModified) {
			writeNotModifiedHeaders(w.Header(), extendedInfo, len(tagSet), bktSettings.Unversioned(), h.cfg.MD5Enabled())
		}
		h.logAndSendError(ctx, w, "precondition failed", reqInfo, err)
		return
	}

	if len(info.ContentType) == 0 {
		if info.ContentType = layer.MimeByFilePath(info.Name); len(info.ContentType) == 0 {
			getParams := &layer.GetObjectParams{
				ObjectInfo: info,
				Versioned:  p.Versioned(),
				Range:      getRangeToDetectContentType(info.Size),
				BucketInfo: bktInfo,
			}

			objPayload, err := h.obj.GetObject(ctx, getParams)
			if err != nil {
				h.logAndSendError(ctx, w, "could not get object", reqInfo, err, zap.Stringer("oid", info.ID))
				return
			}

			buffer, err := io.ReadAll(objPayload)
			if err != nil {
				h.logAndSendError(ctx, w, "could not partly read payload to detect content type", reqInfo, err, zap.Stringer("oid", info.ID))
				return
			}

			info.ContentType = http.DetectContentType(buffer)
		}
	}

	if err = h.setLockingHeaders(bktInfo, lockInfo, w.Header()); err != nil {
		h.logAndSendError(ctx, w, "could not get locking info", reqInfo, err)
		return
	}

	writeHeaders(w.Header(), r.Header, extendedInfo, len(tagSet), bktSettings.Unversioned(), h.cfg.MD5Enabled())
	w.WriteHeader(http.StatusOK)
}

func (h *handler) HeadBucketHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	reqInfo := middleware.GetReqInfo(ctx)

	bktInfo, err := h.getBucketAndCheckOwner(r, reqInfo.BucketName)
	if err != nil {
		h.logAndSendError(ctx, w, "could not get bucket info", reqInfo, err)
		return
	}

	w.Header().Set(api.OwnerID, bktInfo.Owner.EncodeToString())
	w.Header().Set(api.ContainerID, bktInfo.CID.EncodeToString())
	w.Header().Set(api.AmzBucketRegion, bktInfo.LocationConstraint)

	if isAvailableToResolve(bktInfo.Zone, h.cfg.ResolveZoneList(), h.cfg.IsResolveListAllow()) {
		w.Header().Set(api.ContainerName, bktInfo.Name)
		w.Header().Set(api.ContainerZone, bktInfo.Zone)
	}

	if err = middleware.WriteResponse(w, http.StatusOK, nil, middleware.MimeNone); err != nil {
		h.logAndSendError(ctx, w, "write response", reqInfo, err)
		return
	}
}

func (h *handler) setLockingHeaders(bktInfo *data.BucketInfo, lockInfo data.LockInfo, header http.Header) error {
	if !bktInfo.ObjectLockEnabled {
		return nil
	}

	legalHold := &data.LegalHold{Status: legalHoldOff}
	retention := &data.Retention{Mode: governanceMode}

	if lockInfo.IsLegalHoldSet() {
		legalHold.Status = legalHoldOn
	}
	if lockInfo.IsRetentionSet() {
		retention.RetainUntilDate = lockInfo.UntilDate()
		if lockInfo.IsCompliance() {
			retention.Mode = complianceMode
		}
	}

	writeLockHeaders(header, legalHold, retention)
	return nil
}

func writeLockHeaders(h http.Header, legalHold *data.LegalHold, retention *data.Retention) {
	h.Set(api.AmzObjectLockLegalHold, legalHold.Status)

	if retention.RetainUntilDate != "" {
		h.Set(api.AmzObjectLockRetainUntilDate, retention.RetainUntilDate)
		h.Set(api.AmzObjectLockMode, retention.Mode)
	}
}

func isAvailableToResolve(zone string, list []string, isAllowList bool) bool {
	// empty zone means container doesn't have proper system name,
	// so we don't have to resolve it
	if len(zone) == 0 {
		return false
	}

	var zoneInList bool
	for _, t := range list {
		if t == zone {
			zoneInList = true
			break
		}
	}
	// InList | IsAllowList | Result
	//    0         0          1
	//    0         1          0
	//    1         0          0
	//    1         1          1
	return zoneInList == isAllowList
}