// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

package compositefs

import (
	"context"
	"io/fs"
	"os"

	"github.com/tailscale/xnet/webdav"
	"tailscale.com/tailfs/shared"
)

// OpenFile implements interface webdav.Filesystem.
func (cfs *CompositeFileSystem) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
	if !shared.IsRoot(name) {
		pathInfo, err := cfs.pathInfoFor(name)
		if err != nil {
			return nil, err
		}

		if pathInfo.refersToChild {
			// this is the child itself, ask it to open its root
			return pathInfo.child.FS.OpenFile(ctx, "/", flag, perm)
		}

		return pathInfo.child.FS.OpenFile(ctx, pathInfo.pathOnChild, flag, perm)
	}

	// the root directory contains one directory for each child
	di, err := cfs.Stat(ctx, name)
	if err != nil {
		return nil, err
	}

	return &shared.DirFile{
		Info: di,
		LoadChildren: func() ([]fs.FileInfo, error) {
			cfs.childrenMu.Lock()
			children := cfs.children
			cfs.childrenMu.Unlock()

			childInfos := make([]fs.FileInfo, 0, len(cfs.children))
			for _, c := range children {
				if c.isAvailable() {
					var childInfo fs.FileInfo
					if cfs.statChildren {
						fi, err := c.FS.Stat(ctx, "/")
						if err != nil {
							return nil, err
						}
						// we use the full name
						childInfo = shared.RenamedFileInfo(ctx, c.Name, fi)
					} else {
						// always use now() as the modified time to bust caches
						childInfo = shared.ReadOnlyDirInfo(c.Name, cfs.now())
					}
					childInfos = append(childInfos, childInfo)
				}
			}
			return childInfos, nil
		},
	}, nil
}