// OpenFile opens a File, ie. indicates operations are to be done on this file.
//
// Required for fuse.FileSystem.
func (k *KodingNetworkFS) OpenFile(ctx context.Context, op *fuseops.OpenFileOp) error {
	file, err := k.getFile(ctx, op.Inode)
	if err != nil {
		return err
	}

	file.Open()

	handleID := k.setEntryByHandle(file)
	op.Handle = handleID

	// KeepPageCache tells Kernel to cache this file contents or not. Say an user
	// opens a file on their local and then changes that same file on the VM, by
	// setting this to be false, the user can close and open the file to see the
	// changes. See https://goo.gl/vjhjFY.
	op.KeepPageCache = false

	return nil
}

func (fs *cachingFS) OpenFile(
	ctx context.Context,
	op *fuseops.OpenFileOp) (err error) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	op.KeepPageCache = fs.keepPageCache

	return
}

func (fs *Goofys) OpenFile(
	ctx context.Context,
	op *fuseops.OpenFileOp) (err error) {
	fs.mu.Lock()
	in := fs.getInodeOrDie(op.Inode)
	fs.mu.Unlock()

	fh := in.OpenFile(fs)

	fs.mu.Lock()
	defer fs.mu.Unlock()

	handleID := fs.nextHandleID
	fs.nextHandleID++

	fs.fileHandles[handleID] = fh

	op.Handle = handleID
	op.KeepPageCache = true

	return
}

// LOCKS_EXCLUDED(fs.mu)
func (fs *fileSystem) OpenFile(
	ctx context.Context,
	op *fuseops.OpenFileOp) (err error) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	// Find the inode.
	in := fs.inodes[op.Inode].(*inode.FileInode)

	// Allocate a handle.
	handleID := fs.nextHandleID
	fs.nextHandleID++

	fs.handles[handleID] = handle.NewFileHandle(in, fs.bucket)
	op.Handle = handleID

	// When we observe object generations that we didn't create, we assign them
	// new inode IDs. So for a given inode, all modifications go through the
	// kernel. Therefore it's safe to tell the kernel to keep the page cache from
	// open to open for a given inode.
	op.KeepPageCache = true

	return
}