package handler

import (
	"encoding/xml"
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
	"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"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/session"
	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
)

// limitation of AWS https://docs.aws.amazon.com/AmazonS3/latest/API/API_DeleteObjects.html
const maxObjectsToDelete = 1000

// DeleteObjectsRequest -- xml carrying the object key names which should be deleted.
type DeleteObjectsRequest struct {
	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ Delete" json:"-"`
	// Element to enable quiet mode for the request
	Quiet bool `xml:"Quiet,omitempty"`
	// List of objects to be deleted
	Objects []ObjectIdentifier `xml:"Object"`
}

// ObjectIdentifier carries the key name for the object to delete.
type ObjectIdentifier struct {
	ObjectName string `xml:"Key"`
	VersionID  string `xml:"VersionId,omitempty"`
}

// DeletedObject carries the key name for the object to delete.
type DeletedObject struct {
	ObjectIdentifier
	DeleteMarker          bool   `xml:"DeleteMarker,omitempty"`
	DeleteMarkerVersionID string `xml:"DeleteMarkerVersionId,omitempty"`
}

// DeleteError structure.
type DeleteError struct {
	Code      string `xml:"Code,omitempty"`
	Message   string `xml:"Message,omitempty"`
	Key       string `xml:"Key,omitempty"`
	VersionID string `xml:"VersionId,omitempty"`
}

// DeleteObjectsResponse container for multiple object deletes.
type DeleteObjectsResponse struct {
	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ DeleteResult" json:"-"`

	// Collection of all deleted objects
	DeletedObjects []DeletedObject `xml:"Deleted,omitempty"`

	// Collection of errors deleting certain objects.
	Errors []DeleteError `xml:"Error,omitempty"`
}

func (h *handler) DeleteObjectHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	reqInfo := middleware.GetReqInfo(ctx)
	versionID := reqInfo.URL.Query().Get(api.QueryVersionID)
	versionedObject := []*layer.VersionedObject{{
		Name:      reqInfo.ObjectName,
		VersionID: versionID,
	}}

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

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

	p := &layer.DeleteObjectParams{
		BktInfo:  bktInfo,
		Objects:  versionedObject,
		Settings: bktSettings,
	}
	deletedObjects := h.obj.DeleteObjects(ctx, p)
	deletedObject := deletedObjects[0]
	if deletedObject.Error != nil {
		if isErrObjectLocked(deletedObject.Error) {
			h.logAndSendError(w, "object is locked", reqInfo, errors.GetAPIError(errors.ErrAccessDenied))
		} else {
			h.logAndSendError(w, "could not delete object", reqInfo, deletedObject.Error)
		}
		return
	}

	if deletedObject.VersionID != "" {
		w.Header().Set(api.AmzVersionID, deletedObject.VersionID)
	}
	if deletedObject.DeleteMarkVersion != "" {
		w.Header().Set(api.AmzDeleteMarker, strconv.FormatBool(true))
		if deletedObject.VersionID == "" {
			w.Header().Set(api.AmzVersionID, deletedObject.DeleteMarkVersion)
		}
	}

	w.WriteHeader(http.StatusNoContent)
}

func isErrObjectLocked(err error) bool {
	switch err.(type) {
	default:
		return strings.Contains(err.Error(), "object is locked")
	case *apistatus.ObjectLocked:
		return true
	}
}

// DeleteMultipleObjectsHandler handles multiple delete requests.
func (h *handler) DeleteMultipleObjectsHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	reqInfo := middleware.GetReqInfo(ctx)

	// Content-Md5 is required and should be set
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if _, ok := r.Header[api.ContentMD5]; !ok {
		h.logAndSendError(w, "missing Content-MD5", reqInfo, errors.GetAPIError(errors.ErrMissingContentMD5))
		return
	}

	// Content-Length is required and should be non-zero
	// http://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
	if r.ContentLength <= 0 {
		h.logAndSendError(w, "missing Content-Length", reqInfo, errors.GetAPIError(errors.ErrMissingContentLength))
		return
	}

	// Unmarshal list of keys to be deleted.
	requested := &DeleteObjectsRequest{}
	if err := h.cfg.NewXMLDecoder(r.Body).Decode(requested); err != nil {
		h.logAndSendError(w, "couldn't decode body", reqInfo, fmt.Errorf("%w: %s", errors.GetAPIError(errors.ErrMalformedXML), err.Error()))
		return
	}

	if len(requested.Objects) == 0 || len(requested.Objects) > maxObjectsToDelete {
		h.logAndSendError(w, "number of objects to delete must be greater than 0 and less or equal to 1000", reqInfo, errors.GetAPIError(errors.ErrMalformedXML))
		return
	}

	unique := make(map[string]struct{})
	toRemove := make([]*layer.VersionedObject, 0, len(requested.Objects))
	for _, obj := range requested.Objects {
		versionedObj := &layer.VersionedObject{
			Name:      obj.ObjectName,
			VersionID: obj.VersionID,
		}
		key := versionedObj.String()
		if _, ok := unique[key]; !ok {
			toRemove = append(toRemove, versionedObj)
			unique[key] = struct{}{}
		}
	}

	response := &DeleteObjectsResponse{
		Errors:         make([]DeleteError, 0, len(toRemove)),
		DeletedObjects: make([]DeletedObject, 0, len(toRemove)),
	}

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

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

	p := &layer.DeleteObjectParams{
		BktInfo:    bktInfo,
		Objects:    toRemove,
		Settings:   bktSettings,
		IsMultiple: true,
	}
	deletedObjects := h.obj.DeleteObjects(ctx, p)

	for _, obj := range deletedObjects {
		if obj.Error != nil {
			code := "BadRequest"
			if s3err, ok := obj.Error.(errors.Error); ok {
				code = s3err.Code
			}
			response.Errors = append(response.Errors, DeleteError{
				Code:      code,
				Message:   obj.Error.Error(),
				Key:       obj.Name,
				VersionID: obj.VersionID,
			})
		} else if !requested.Quiet {
			deletedObj := DeletedObject{
				ObjectIdentifier: ObjectIdentifier{
					ObjectName: obj.Name,
					VersionID:  obj.VersionID,
				},
				DeleteMarkerVersionID: obj.DeleteMarkVersion,
			}
			if deletedObj.DeleteMarkerVersionID != "" {
				deletedObj.DeleteMarker = true
			}
			response.DeletedObjects = append(response.DeletedObjects, deletedObj)
		}
	}

	if err = middleware.EncodeToResponse(w, response); err != nil {
		h.logAndSendError(w, "could not write response", reqInfo, err)
		return
	}
}

func (h *handler) DeleteBucketHandler(w http.ResponseWriter, r *http.Request) {
	reqInfo := middleware.GetReqInfo(r.Context())
	bktInfo, err := h.getBucketAndCheckOwner(r, reqInfo.BucketName)
	if err != nil {
		h.logAndSendError(w, "could not get bucket info", reqInfo, err)
		return
	}

	var sessionToken *session.Container

	boxData, err := middleware.GetBoxData(r.Context())
	if err == nil {
		sessionToken = boxData.Gate.SessionTokenForDelete()
	}

	if err = h.obj.DeleteBucket(r.Context(), &layer.DeleteBucketParams{
		BktInfo:      bktInfo,
		SessionToken: sessionToken,
	}); err != nil {
		h.logAndSendError(w, "couldn't delete bucket", reqInfo, err)
		return
	}

	chainIDs := []chain.ID{
		getBucketChainID(chain.S3, bktInfo),
		getBucketChainID(chain.Ingress, bktInfo),
		getBucketCannedChainID(chain.S3, bktInfo.CID),
		getBucketCannedChainID(chain.Ingress, bktInfo.CID),
	}
	if err = h.ape.DeleteBucketPolicy(reqInfo.Namespace, bktInfo.CID, chainIDs); err != nil {
		h.logAndSendError(w, "failed to delete policy from storage", reqInfo, err)
		return
	}

	w.WriteHeader(http.StatusNoContent)
}