package mount

import (
	"context"
	"fmt"
	"syscall"
	"time"

	"github.com/seaweedfs/go-fuse/v2/fuse"
	"google.golang.org/protobuf/proto"

	"github.com/seaweedfs/seaweedfs/weed/cluster/lock_manager"
	"github.com/seaweedfs/seaweedfs/weed/filer"
	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
	"github.com/seaweedfs/seaweedfs/weed/util"
)

/**
 * Create and open a file
 *
 * If the file does not exist, first create it with the specified
 * mode, and then open it.
 *
 * If this method is not implemented or under Linux kernel
 * versions earlier than 2.6.15, the mknod() and open() methods
 * will be called instead.
 */
func (wfs *WFS) Create(cancel <-chan struct{}, in *fuse.CreateIn, name string, out *fuse.CreateOut) (code fuse.Status) {
	var s fuse.Status
	if name, s = checkName(name); s != fuse.OK {
		return s
	}

	dirFullPath, code := wfs.inodeToPath.GetPath(in.NodeId)
	if code != fuse.OK {
		return code
	}

	entryFullPath := dirFullPath.Child(name)
	var inode uint64

	newEntry, _, code := wfs.maybeLoadEntry(entryFullPath)
	if code == fuse.OK {
		if newEntry == nil || newEntry.Attributes == nil {
			return fuse.EIO
		}
		if in.Flags&syscall.O_EXCL != 0 {
			glog.V(0).Infof("Create O_EXCL %s: already exists (uid=%d gid=%d mode=%o)",
				entryFullPath, newEntry.Attributes.Uid, newEntry.Attributes.Gid, newEntry.Attributes.FileMode)
			return fuse.Status(syscall.EEXIST)
		}
		inode = wfs.inodeToPath.Lookup(entryFullPath, newEntry.Attributes.Crtime, false, len(newEntry.HardLinkId) > 0, newEntry.Attributes.Inode, true)
		fileHandle, status := wfs.AcquireHandle(inode, in.Flags, in.Uid, in.Gid)
		if status != fuse.OK {
			return status
		}
		if in.Flags&syscall.O_TRUNC != 0 && in.Flags&fuse.O_ANYWRITE != 0 {
			if code = wfs.truncateEntry(entryFullPath, newEntry); code != fuse.OK {
				wfs.ReleaseHandle(fileHandle.fh)
				return code
			}
			newEntry = fileHandle.GetEntry().GetEntry()
		}

		wfs.outputPbEntry(&out.EntryOut, inode, newEntry)
		out.Fh = uint64(fileHandle.fh)
		out.OpenFlags = 0
		return fuse.OK
	}
	if code != fuse.ENOENT {
		return code
	}

	inode, newEntry, code = wfs.createRegularFile(dirFullPath, name, in.Mode, in.Uid, in.Gid, 0, !wfs.option.EagerFilerCreate, true)
	if code == fuse.Status(syscall.EEXIST) && in.Flags&syscall.O_EXCL == 0 {
		// Race: another process created the file between our check and create.
		// Reopen the winner's entry.
		newEntry, _, code = wfs.maybeLoadEntry(entryFullPath)
		if code != fuse.OK {
			return code
		}
		if newEntry == nil || newEntry.Attributes == nil {
			return fuse.EIO
		}
		inode = wfs.inodeToPath.Lookup(entryFullPath, newEntry.Attributes.Crtime, false, len(newEntry.HardLinkId) > 0, newEntry.Attributes.Inode, true)
		fileHandle, status := wfs.AcquireHandle(inode, in.Flags, in.Uid, in.Gid)
		if status != fuse.OK {
			return status
		}
		if in.Flags&syscall.O_TRUNC != 0 && in.Flags&fuse.O_ANYWRITE != 0 {
			if code = wfs.truncateEntry(entryFullPath, newEntry); code != fuse.OK {
				wfs.ReleaseHandle(fileHandle.fh)
				return code
			}
			newEntry = fileHandle.GetEntry().GetEntry()
		}
		wfs.outputPbEntry(&out.EntryOut, inode, newEntry)
		out.Fh = uint64(fileHandle.fh)
		out.OpenFlags = 0
		return fuse.OK
	} else if code != fuse.OK {
		return code
	} else {
		inode = wfs.inodeToPath.Lookup(entryFullPath, newEntry.Attributes.Crtime, false, false, inode, true)
	}

	wfs.outputPbEntry(&out.EntryOut, inode, newEntry)

	// For deferred creates, bypass AcquireHandle (which calls maybeReadEntry
	// and would fail since the entry is not yet on the filer or in the meta cache).
	// We already have the entry from createRegularFile, so create the handle directly.
	fileHandle, existed := wfs.fhMap.AcquireFileHandle(wfs, inode, newEntry, 0, 0)
	if existed {
		// A create is authoritative for the entry it just made, so it takes
		// effect even on a handle that outlived a previous incarnation.
		fileHandle.SetEntry(newEntry)
	}
	fileHandle.RememberPath(entryFullPath)
	// Mark dirty so the deferred filer create happens on Flush, even if the
	// file is closed without any writes. An eager create has already
	// persisted the entry, so its handle starts clean.
	fileHandle.dirtyMetadata = !wfs.option.EagerFilerCreate

	// Acquire DLM lock for new file creation (Create bypasses AcquireHandle
	// so we must acquire the lock here). Always lock on Create since file
	// creation is inherently a write operation.
	if wfs.lockClient != nil && fileHandle.dlmLock == nil {
		owner := fmt.Sprintf("mount-%d", wfs.signature)
		fileHandle.dlmLock = wfs.lockClient.NewBlockingLongLivedLock(
			string(entryFullPath), owner, lock_manager.LiveLockTTL,
		)
		glog.V(1).Infof("DLM lock acquired for new file %s", entryFullPath)
	}

	out.Fh = uint64(fileHandle.fh)
	out.OpenFlags = 0

	return fuse.OK
}

/** Create a file node
 *
 * This is called for creation of all non-directory, non-symlink
 * nodes.  If the filesystem defines a create() method, then for
 * regular files that will be called instead.
 */
func (wfs *WFS) Mknod(cancel <-chan struct{}, in *fuse.MknodIn, name string, out *fuse.EntryOut) (code fuse.Status) {

	var s fuse.Status
	if name, s = checkName(name); s != fuse.OK {
		return s
	}

	dirFullPath, code := wfs.inodeToPath.GetPath(in.NodeId)
	if code != fuse.OK {
		return
	}

	inode, newEntry, code := wfs.createRegularFile(dirFullPath, name, in.Mode, in.Uid, in.Gid, in.Rdev, false, false)
	if code != fuse.OK {
		return code
	}

	// this is to increase nlookup counter
	entryFullPath := dirFullPath.Child(name)
	inode = wfs.inodeToPath.Lookup(entryFullPath, newEntry.Attributes.Crtime, false, false, inode, true)

	wfs.outputPbEntry(out, inode, newEntry)

	return fuse.OK

}

/** Remove a file */
func (wfs *WFS) Unlink(cancel <-chan struct{}, header *fuse.InHeader, name string) (code fuse.Status) {

	// Sanitize before it reaches DeleteEntryRequest.Name; see sanitizeFuseName.
	name = sanitizeFuseName(name)

	dirFullPath, code := wfs.inodeToPath.GetPath(header.NodeId)
	if code != fuse.OK {
		if code == fuse.ENOENT {
			return fuse.OK
		}
		return code
	}
	entryFullPath := dirFullPath.Child(name)

	entry, _, code := wfs.maybeLoadEntry(entryFullPath)
	if code != fuse.OK {
		if code == fuse.ENOENT {
			return fuse.OK
		}
		return code
	}

	if wormEnforced, _ := wfs.wormEnforcedForEntry(entryFullPath, entry); wormEnforced {
		return fuse.EPERM
	}

	// For hard-linked files, serialize all concurrent mutations on the
	// same HardLinkId so the filer-side blob decrement and the mount-side
	// sibling cache sync are observed atomically by other unlinkers.
	// Without this, two concurrent unlinks on different links of the same
	// file both read the same pre-decrement counter and both stamp their
	// siblings to counter-1, leaving the cache one higher than the blob.
	// Re-load the entry under the lock so we see any sibling update a
	// prior holder just applied.
	if entry != nil && len(entry.HardLinkId) > 0 {
		hlKey := string(entry.HardLinkId)
		lock := wfs.hardLinkLockTable.AcquireLock("unlink", hlKey, util.ExclusiveLock)
		defer wfs.hardLinkLockTable.ReleaseLock(hlKey, lock)
		// If another thread unlinked the entry while we waited for the
		// lock, the file is already gone — return OK like the initial
		// maybeLoadEntry path above. Do not fall back to the stale
		// pre-lock snapshot: proceeding with its HardLinkCounter would
		// reintroduce the stale-base update the lock is meant to prevent.
		fresh, _, freshCode := wfs.maybeLoadEntry(entryFullPath)
		if freshCode == fuse.ENOENT {
			return fuse.OK
		}
		if freshCode != fuse.OK {
			return freshCode
		}
		entry = fresh
	}

	// POSIX: enforce sticky bit on the parent directory.
	if dirEntry, _, dirCode := wfs.maybeLoadEntry(dirFullPath); dirCode == fuse.OK && dirEntry != nil && dirEntry.Attributes != nil {
		targetUid := uint32(0)
		if entry != nil && entry.Attributes != nil {
			targetUid = entry.Attributes.Uid
		}
		if code := checkStickyBit(dirEntry.Attributes.FileMode, dirEntry.Attributes.Uid, targetUid, header.Uid); code != fuse.OK {
			return code
		}
	}

	// Before deleting from the filer, mark any draining async-flush handle
	// as deleted and wait for it to complete.  Without this, the async flush
	// can race with the filer delete and recreate the just-unlinked entry
	// (the worker checks isDeleted, but it may have already passed that check
	// before Unlink sets the flag).  By waiting here, any in-flight flush
	// finishes first; even if it recreated the entry, the filer delete below
	// will remove it again.
	if inode, found := wfs.inodeToPath.GetInode(entryFullPath); found {
		wfs.markHandleDeleted(inode)
		wfs.waitForPendingAsyncFlush(inode)
	} else if entry != nil && entry.Attributes != nil && entry.Attributes.Inode != 0 {
		inodeFromEntry := entry.Attributes.Inode
		wfs.markHandleDeleted(inodeFromEntry)
		wfs.waitForPendingAsyncFlush(inodeFromEntry)
	}

	// first, ensure the filer store can correctly delete
	glog.V(3).Infof("remove file: %v", entryFullPath)
	// Always let the filer decide whether to delete chunks based on its authoritative data.
	// The filer has the correct hard link count and will only delete chunks when appropriate.
	deleteReq := &filer_pb.DeleteEntryRequest{
		// See weedfs_dir_mkrm.go Mkdir for why Directory is sanitized.
		Directory:    dirFullPath.Sanitized(),
		Name:         name,
		IsDeleteData: true,
		Signatures:   []int32{wfs.signature},
	}
	resp, err := wfs.streamDeleteEntry(context.Background(), deleteReq)
	if err != nil {
		glog.V(0).Infof("remove %s: %v", entryFullPath, err)
		return fuse.OK
	}

	var event *filer_pb.SubscribeMetadataResponse
	if resp != nil && resp.MetadataEvent != nil {
		event = resp.MetadataEvent
	} else {
		event = metadataDeleteEvent(string(dirFullPath), name, false)
	}
	if applyErr := wfs.applyLocalMetadataEvent(context.Background(), event); applyErr != nil {
		glog.Warningf("unlink %s: best-effort metadata apply failed: %v", entryFullPath, applyErr)
		wfs.inodeToPath.InvalidateChildrenCache(dirFullPath)
	}
	wfs.inodeToPath.TouchDirectory(dirFullPath)
	wfs.touchDirMtimeCtimeBest(dirFullPath)

	// For hard-linked files, the filer's DeleteHardLink decremented the
	// shared blob, but the sibling link entries in the local metacache
	// still carry the pre-unlink HardLinkCounter, and the kernel has
	// cached attrs on the shared inode. Resolve the shared inode before
	// removing the path from inodeToPath, then propagate the decrement
	// to every sibling cache entry and invalidate the kernel attr cache
	// so subsequent lstats on other links see the new nlink — pjdfstest
	// link/00.t asserts this after `unlink n0` leaves n1/n2 behind.
	isHardLink := entry != nil && entry.Attributes != nil && len(entry.HardLinkId) > 0 && entry.HardLinkCounter > 1
	var sharedInode uint64
	if isHardLink {
		sharedInode = entry.Attributes.Inode
		if sharedInode == 0 {
			if resolved, found := wfs.inodeToPath.GetInode(entryFullPath); found {
				sharedInode = resolved
			}
		}
	}

	wfs.inodeToPath.RemovePath(entryFullPath)

	if isHardLink && sharedInode != 0 {
		decremented := proto.Clone(entry).(*filer_pb.Entry)
		decremented.HardLinkCounter = entry.HardLinkCounter - 1
		now := time.Now()
		decremented.Attributes.Ctime = now.Unix()
		decremented.Attributes.CtimeNs = int32(now.Nanosecond())
		wfs.syncHardLinkSiblings(sharedInode, decremented, entryFullPath)
	}

	return fuse.OK

}

func (wfs *WFS) createRegularFile(dirFullPath util.FullPath, name string, mode uint32, uid, gid, rdev uint32, deferFilerCreate bool, skipExistenceCheck bool) (inode uint64, newEntry *filer_pb.Entry, code fuse.Status) {
	if wfs.IsOverQuotaWithUncommitted() {
		return 0, nil, fuse.Status(syscall.ENOSPC)
	}

	// Load the parent directory to validate it exists (the create RPC sets
	// SkipCheckParentDirectory, so this is the only parent check). With
	// default_permissions the kernel already verified write+search on it before
	// Create/Mknod, so skip only the mode-bit check and its group lookup.
	parentEntry, _, parentStatus := wfs.maybeLoadEntry(dirFullPath)
	if parentStatus != fuse.OK {
		return 0, nil, parentStatus
	}
	if parentEntry == nil || parentEntry.Attributes == nil {
		return 0, nil, fuse.EIO
	}
	if !wfs.option.DefaultPermissions {
		// Map parent dir uid/gid from filer-space to local-space so the
		// permission check compares like with like (caller uid/gid are local).
		parentUid, parentGid := parentEntry.Attributes.Uid, parentEntry.Attributes.Gid
		if wfs.option.UidGidMapper != nil {
			parentUid, parentGid = wfs.option.UidGidMapper.FilerToLocal(parentUid, parentGid)
		}
		if !hasAccess(uid, gid, parentUid, parentGid, parentEntry.Attributes.FileMode, fuse.W_OK|fuse.X_OK) {
			return 0, nil, fuse.Status(syscall.EACCES)
		}
	}

	entryFullPath := dirFullPath.Child(name)
	if !skipExistenceCheck {
		if _, _, status := wfs.maybeLoadEntry(entryFullPath); status == fuse.OK {
			return 0, nil, fuse.Status(syscall.EEXIST)
		} else if status != fuse.ENOENT {
			return 0, nil, status
		}
	}
	fileMode := toOsFileMode(mode)
	now := time.Now().Unix()
	inode = wfs.inodeToPath.AllocateInode(entryFullPath, now)

	newEntry = &filer_pb.Entry{
		Name:        name,
		IsDirectory: false,
		Attributes: &filer_pb.FuseAttributes{
			Mtime:    now,
			Crtime:   now,
			Ctime:    now,
			FileMode: uint32(fileMode),
			Uid:      uid,
			Gid:      gid,
			TtlSec:   wfs.option.TtlSec,
			Rdev:     rdev,
			Inode:    inode,
		},
	}

	if deferFilerCreate || wfs.option.WritebackCache {
		// Insert a local placeholder into the metadata cache so that
		// maybeLoadEntry() can find the file immediately (e.g., duplicate-
		// create checks, stat, readdir).
		// We use InsertEntry directly instead of applyLocalMetadataEvent to avoid
		// triggering directory hot-threshold eviction that would wipe the entry.
		if insertErr := wfs.metaCache.InsertEntry(context.Background(), filer.FromPbEntry(string(dirFullPath), newEntry), 0); insertErr != nil {
			glog.Warningf("createFile %s: insert local entry: %v", entryFullPath, insertErr)
		}
		wfs.inodeToPath.TouchDirectory(dirFullPath)
		wfs.touchDirMtimeCtimeBest(dirFullPath)

		if deferFilerCreate {
			// Fully deferred: the caller (Create) will build a file handle
			// directly from newEntry. The actual filer entry is created by
			// flushMetadataToFiler on close.
			glog.V(3).Infof("createFile %s: deferred to flush", entryFullPath)
		} else {
			// Async create: Mknod with writeback caching. The node is
			// visible locally; fire the filer RPC in the background.
			wfs.asyncCreateEntry(dirFullPath, newEntry)
			glog.V(3).Infof("createFile %s: async create", entryFullPath)
		}
		return inode, newEntry, fuse.OK
	}

	wfs.mapPbIdFromLocalToFiler(newEntry)
	defer wfs.mapPbIdFromFilerToLocal(newEntry)

	request := &filer_pb.CreateEntryRequest{
		Directory:                string(dirFullPath),
		Entry:                    newEntry,
		Signatures:               []int32{wfs.signature},
		SkipCheckParentDirectory: true,
	}

	glog.V(1).Infof("createFile: %v", request)
	resp, err := wfs.streamCreateEntry(context.Background(), request)
	if err != nil {
		glog.V(0).Infof("createFile %s: %v", entryFullPath, err)
	} else {
		event := resp.GetMetadataEvent()
		if event == nil {
			event = metadataCreateEvent(string(dirFullPath), newEntry)
		}
		if applyErr := wfs.applyLocalMetadataEvent(context.Background(), event); applyErr != nil {
			glog.Warningf("createFile %s: best-effort metadata apply failed: %v", entryFullPath, applyErr)
			wfs.inodeToPath.InvalidateChildrenCache(dirFullPath)
		}
		wfs.inodeToPath.TouchDirectory(dirFullPath)
		wfs.touchDirMtimeCtimeBest(dirFullPath)
	}

	glog.V(3).Infof("createFile %s: %v", entryFullPath, err)

	if err != nil {
		return 0, nil, grpcErrorToFuseStatus(err)
	}

	return inode, newEntry, fuse.OK
}

// markHandleDeleted flags the inode's open handle so its flushes stop writing
// the entry back, and reports which mark this was. Taken and released under
// the handle's flush lock: a flush already holding it finishes before the
// caller's delete runs, and any later flush sees the flag; setting the flag
// bare raced the flush's own check and resurrected the entry right after the
// delete.
func (wfs *WFS) markHandleDeleted(inode uint64) uint64 {
	fh, found := wfs.fhMap.FindFileHandle(inode)
	if !found {
		return 0
	}
	fhActiveLock := wfs.fhLockTable.AcquireLock("markHandleDeleted", fh.fh, util.ExclusiveLock)
	fh.isDeleted = true
	fh.deleteEpoch++
	epoch := fh.deleteEpoch
	wfs.fhLockTable.ReleaseLock(fh.fh, fhActiveLock)
	return epoch
}

// clearHandleDeleted lifts a mark whose delete did not go through. Only the
// mark epoch names: an unlink that raised the flag after it owns the entry's
// fate and keeps it.
func (wfs *WFS) clearHandleDeleted(inode uint64, epoch uint64) {
	if epoch == 0 {
		return
	}
	fh, found := wfs.fhMap.FindFileHandle(inode)
	if !found {
		return
	}
	fhActiveLock := wfs.fhLockTable.AcquireLock("clearHandleDeleted", fh.fh, util.ExclusiveLock)
	if fh.deleteEpoch == epoch {
		fh.isDeleted = false
	}
	wfs.fhLockTable.ReleaseLock(fh.fh, fhActiveLock)
}

// asyncCreateEntry sends a CreateEntry RPC to the filer in the background.
// The entry is already in the local meta cache; this persists it to the filer.
// Used by Mknod with writeback caching — the node is visible locally right away.
//
// If the filer RPC fails after retries, the local cache entry is removed so the
// phantom file does not persist across cache invalidation or mount restart.
func (wfs *WFS) asyncCreateEntry(dirFullPath util.FullPath, entry *filer_pb.Entry) {
	// Clone so the goroutine has its own copy for uid/gid mapping.
	requestEntry := proto.Clone(entry).(*filer_pb.Entry)
	dir := string(dirFullPath)
	entryPath := dirFullPath.Child(entry.Name)
	go func() {
		wfs.mapPbIdFromLocalToFiler(requestEntry)
		request := &filer_pb.CreateEntryRequest{
			Directory:                dir,
			Entry:                    requestEntry,
			Signatures:               []int32{wfs.signature},
			SkipCheckParentDirectory: true,
		}
		err := retryMetadataFlush(context.Background(), func() error {
			resp, createErr := wfs.streamCreateEntry(context.Background(), request)
			if createErr != nil {
				return createErr
			}
			event := resp.GetMetadataEvent()
			if event == nil {
				event = metadataCreateEvent(dir, requestEntry)
			}
			if applyErr := wfs.applyLocalMetadataEvent(context.Background(), event); applyErr != nil {
				glog.Warningf("async createFile %s: metadata apply: %v", entryPath, applyErr)
				wfs.inodeToPath.InvalidateChildrenCache(dirFullPath)
			}
			return nil
		}, func(nextAttempt, totalAttempts int, backoff time.Duration, err error) {
			glog.Warningf("async createFile %s: retrying (attempt %d/%d) after %v: %v",
				entryPath, nextAttempt, totalAttempts, backoff, err)
		})
		if err != nil {
			glog.Errorf("async createFile %s: failed after retries: %v — removing local entry", entryPath, err)
			wfs.metaCache.DeleteEntry(context.Background(), entryPath)
			wfs.inodeToPath.InvalidateChildrenCache(dirFullPath)
		}
	}()
}

func (wfs *WFS) truncateEntry(entryFullPath util.FullPath, entry *filer_pb.Entry) fuse.Status {
	if entry == nil {
		return fuse.EIO
	}
	if entry.Attributes == nil {
		entry.Attributes = &filer_pb.FuseAttributes{}
	}

	entry.Content = nil
	entry.Chunks = nil
	entry.Attributes.FileSize = 0
	truncNow := time.Now()
	entry.Attributes.Mtime = truncNow.Unix()
	entry.Attributes.MtimeNs = int32(truncNow.Nanosecond())
	entry.Attributes.Ctime = truncNow.Unix()
	entry.Attributes.CtimeNs = int32(truncNow.Nanosecond())

	if code := wfs.saveEntry(entryFullPath, entry); code != fuse.OK {
		return code
	}

	if inode, found := wfs.inodeToPath.GetInode(entryFullPath); found {
		wfs.invalidateOpenMtimeCache(inode)
		if fh, fhFound := wfs.fhMap.FindFileHandle(inode); fhFound {
			fhActiveLock := fh.wfs.fhLockTable.AcquireLock("truncateEntry", fh.fh, util.ExclusiveLock)
			fh.ResetDirtyPages()
			fh.SetEntry(entry)
			fh.setAuthoritativeBase(proto.Clone(entry).(*filer_pb.Entry))
			fh.wfs.fhLockTable.ReleaseLock(fh.fh, fhActiveLock)
		}
	}

	return fuse.OK
}