package s3api

import (
	"bytes"
	"context"
	"crypto/sha256"
	"errors"
	"sort"
	"strconv"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/s3_lifecycle_pb"
	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
)

// LifecycleDelete executes one (rule, action) verdict: re-fetch, identity
// CAS, object-lock check, dispatch by kind. Errors surface as outcomes;
// reader cursors and pending state are the worker's concern.
func (s3a *S3ApiServer) LifecycleDelete(ctx context.Context, req *s3_lifecycle_pb.LifecycleDeleteRequest) (*s3_lifecycle_pb.LifecycleDeleteResponse, error) {
	if req == nil || req.Bucket == "" || req.ObjectPath == "" {
		return blocked("FATAL_EVENT_ERROR: empty bucket or object_path"), nil
	}

	// MPU init lives at .uploads/<id>/; not handled by getObjectEntry.
	if req.ActionKind == s3_lifecycle_pb.ActionKind_ABORT_MPU {
		return s3a.lifecycleAbortMPU(ctx, req)
	}

	entry, err := s3a.getObjectEntry(req.Bucket, req.ObjectPath, req.VersionId)
	if err != nil {
		if errors.Is(err, filer_pb.ErrNotFound) || errors.Is(err, ErrObjectNotFound) || errors.Is(err, ErrVersionNotFound) || errors.Is(err, ErrLatestVersionNotFound) {
			return noopResolved("NOT_FOUND"), nil
		}
		glog.V(1).Infof("lifecycle: live fetch %s/%s@%s: %v", req.Bucket, req.ObjectPath, req.VersionId, err)
		return retryLater("TRANSPORT_ERROR: " + err.Error()), nil
	}

	live := computeEntryIdentity(entry)
	if !identityMatches(live, req.ExpectedIdentity) {
		return noopResolved("STALE_IDENTITY"), nil
	}

	// Lifecycle never bypasses governance/compliance; the http.Request is
	// only read when bypass is allowed, so nil is safe here.
	if err := s3a.enforceObjectLockProtections(nil, req.Bucket, req.ObjectPath, req.VersionId, false); err != nil {
		glog.V(2).Infof("lifecycle: SKIPPED_OBJECT_LOCK %s/%s@%s: %v", req.Bucket, req.ObjectPath, req.VersionId, err)
		return &s3_lifecycle_pb.LifecycleDeleteResponse{
			Outcome: s3_lifecycle_pb.LifecycleDeleteOutcome_SKIPPED_OBJECT_LOCK,
			Reason:  err.Error(),
		}, nil
	}

	return s3a.lifecycleDispatch(ctx, req, entry)
}

func (s3a *S3ApiServer) lifecycleDispatch(ctx context.Context, req *s3_lifecycle_pb.LifecycleDeleteRequest, entry *filer_pb.Entry) (*s3_lifecycle_pb.LifecycleDeleteResponse, error) {
	switch req.ActionKind {
	case s3_lifecycle_pb.ActionKind_EXPIRATION_DAYS, s3_lifecycle_pb.ActionKind_EXPIRATION_DATE:
		// Current-version expiration: Enabled -> delete marker; Suspended
		// -> delete null + new marker; Off -> remove. Filer errors classify
		// as RETRY_LATER; the worker's budget promotes to BLOCKED.
		state, vErr := s3a.getVersioningState(req.Bucket)
		if vErr != nil {
			if errors.Is(vErr, filer_pb.ErrNotFound) {
				return noopResolved("BUCKET_NOT_FOUND"), nil
			}
			return retryLater("TRANSPORT_ERROR: versioning lookup: " + vErr.Error()), nil
		}
		switch state {
		case s3_constants.VersioningEnabled:
			if _, err := s3a.createDeleteMarker(req.Bucket, req.ObjectPath); err != nil {
				return retryLater("TRANSPORT_ERROR: createDeleteMarker: " + err.Error()), nil
			}
			return done(), nil
		case s3_constants.VersioningSuspended:
			// Best-effort null delete; NotFound is benign.
			if err := s3a.deleteSpecificObjectVersion(req.Bucket, req.ObjectPath, "null"); err != nil {
				if !errors.Is(err, filer_pb.ErrNotFound) && !errors.Is(err, ErrVersionNotFound) {
					return retryLater("TRANSPORT_ERROR: deleteNullVersion: " + err.Error()), nil
				}
			}
			if _, err := s3a.createDeleteMarker(req.Bucket, req.ObjectPath); err != nil {
				return retryLater("TRANSPORT_ERROR: createDeleteMarker: " + err.Error()), nil
			}
			return done(), nil
		default:
			err := s3a.WithFilerClient(false, func(c filer_pb.SeaweedFilerClient) error {
				return s3a.deleteUnversionedObjectWithClient(c, req.Bucket, req.ObjectPath)
			})
			if err != nil {
				if errors.Is(err, filer_pb.ErrNotFound) || errors.Is(err, ErrObjectNotFound) {
					return noopResolved("NOT_FOUND_AT_DELETE"), nil
				}
				return retryLater("TRANSPORT_ERROR: deleteUnversioned: " + err.Error()), nil
			}
			return done(), nil
		}

	case s3_lifecycle_pb.ActionKind_NONCURRENT_DAYS,
		s3_lifecycle_pb.ActionKind_NEWER_NONCURRENT,
		s3_lifecycle_pb.ActionKind_EXPIRED_DELETE_MARKER:
		// EXPIRED_DELETE_MARKER targets the marker version itself.
		if req.VersionId == "" {
			return blocked("FATAL_EVENT_ERROR: version_id required for noncurrent / delete-marker delete"), nil
		}
		if err := s3a.deleteSpecificObjectVersion(req.Bucket, req.ObjectPath, req.VersionId); err != nil {
			if errors.Is(err, filer_pb.ErrNotFound) || errors.Is(err, ErrVersionNotFound) || errors.Is(err, ErrObjectNotFound) {
				return noopResolved("NOT_FOUND_AT_DELETE"), nil
			}
			return retryLater("TRANSPORT_ERROR: deleteSpecificVersion: " + err.Error()), nil
		}
		return done(), nil

	case s3_lifecycle_pb.ActionKind_ABORT_MPU:
		return blocked("FATAL_EVENT_ERROR: ABORT_MPU dispatched after fetch"), nil

	default:
		return blocked("FATAL_EVENT_ERROR: unknown action_kind " + req.ActionKind.String()), nil
	}
}

func (s3a *S3ApiServer) lifecycleAbortMPU(ctx context.Context, req *s3_lifecycle_pb.LifecycleDeleteRequest) (*s3_lifecycle_pb.LifecycleDeleteResponse, error) {
	// TODO(phase-5): plumb to abortMultipartUpload (currently expects an
	// *s3.AbortMultipartUploadInput; lifecycle has no HTTP request).
	return retryLater("ABORT_MPU not yet wired"), nil
}

// computeEntryIdentity captures (mtime, size, head fid, sorted-Extended hash):
// an overwrite changes mtime/size/fid; a metadata edit changes Extended; a
// snapshot-restore that preserves mtime+size still differs in head_fid.
func computeEntryIdentity(entry *filer_pb.Entry) *s3_lifecycle_pb.EntryIdentity {
	if entry == nil {
		return nil
	}
	id := &s3_lifecycle_pb.EntryIdentity{}
	if entry.Attributes != nil {
		// FuseAttributes splits the timestamp across Mtime (seconds) and
		// MtimeNs (nanosecond component); EntryIdentity.MtimeNs is the
		// combined nanoseconds-since-epoch value.
		id.MtimeNs = entry.Attributes.Mtime*int64(1e9) + int64(entry.Attributes.MtimeNs)
		id.Size = int64(entry.Attributes.FileSize)
	}
	if len(entry.GetChunks()) > 0 {
		id.HeadFid = entry.GetChunks()[0].FileId
	}
	id.ExtendedHash = hashExtended(entry.Extended)
	return id
}

// hashExtended is length-prefixed; a forged tag value can't collide with a
// legitimate multi-tag map.
func hashExtended(ext map[string][]byte) []byte {
	if len(ext) == 0 {
		return nil
	}
	keys := make([]string, 0, len(ext))
	for k := range ext {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	h := sha256.New()
	for _, k := range keys {
		h.Write([]byte(strconv.Itoa(len(k))))
		h.Write([]byte{':'})
		h.Write([]byte(k))
		v := ext[k]
		h.Write([]byte(strconv.Itoa(len(v))))
		h.Write([]byte{':'})
		h.Write(v)
	}
	return h.Sum(nil)
}

func identityMatches(live, want *s3_lifecycle_pb.EntryIdentity) bool {
	if want == nil {
		// No CAS witness (early bootstrap); skip.
		return true
	}
	if live == nil {
		return false
	}
	if live.MtimeNs != want.MtimeNs || live.Size != want.Size {
		return false
	}
	if live.HeadFid != want.HeadFid {
		return false
	}
	return bytes.Equal(live.ExtendedHash, want.ExtendedHash)
}

func done() *s3_lifecycle_pb.LifecycleDeleteResponse {
	return &s3_lifecycle_pb.LifecycleDeleteResponse{Outcome: s3_lifecycle_pb.LifecycleDeleteOutcome_DONE}
}
func noopResolved(reason string) *s3_lifecycle_pb.LifecycleDeleteResponse {
	return &s3_lifecycle_pb.LifecycleDeleteResponse{Outcome: s3_lifecycle_pb.LifecycleDeleteOutcome_NOOP_RESOLVED, Reason: reason}
}
func blocked(reason string) *s3_lifecycle_pb.LifecycleDeleteResponse {
	return &s3_lifecycle_pb.LifecycleDeleteResponse{Outcome: s3_lifecycle_pb.LifecycleDeleteOutcome_BLOCKED, Reason: reason}
}
func retryLater(reason string) *s3_lifecycle_pb.LifecycleDeleteResponse {
	return &s3_lifecycle_pb.LifecycleDeleteResponse{Outcome: s3_lifecycle_pb.LifecycleDeleteOutcome_RETRY_LATER, Reason: reason}
}