var AppendDirsMerger overlayfs.DirsMerger = func(lofi, bofi []fs.DirEntry) []fs.DirEntry {
	for _, fi1 := range bofi {
		var found bool

		if fi1.IsDir() {
			for _, fi2 := range lofi {
				if fi2.IsDir() && fi2.Name() == fi1.Name() {
					found = true
					break
				}
			}
		}
		if !found {
			lofi = append(lofi, fi1)
		}
	}

	return lofi
}

var LanguageDirsMerger overlayfs.DirsMerger = func(lofi, bofi []fs.DirEntry) []fs.DirEntry {
	for _, fi1 := range bofi {
		fim1 := fi1.(FileMetaInfo)
		var found bool
		for _, fi2 := range lofi {
			fim2 := fi2.(FileMetaInfo)
			if fi1.Name() == fi2.Name() && fim1.Meta().Lang == fim2.Meta().Lang {
				found = true
				break
			}
		}
		if !found {
			lofi = append(lofi, fi1)
		}
	}

	return lofi
}

var (

	// NoOpFs provides a no-op filesystem that implements the afero.Fs
	// interface.
	NoOpFs = &noOpFs{}
)

var Os = &afero.OsFs{}

type ComponentFsOptions struct {
	// The filesystem where one or more components are mounted.
	Fs afero.Fs

	// The component name, e.g. "content", "layouts" etc.
	Component string

	DefaultContentLanguage string

	// The parser used to parse paths provided by this filesystem.
	PathParser *paths.PathParser
}

type ComponentPath struct {
	Component string
	Path      string
	Lang      string
	Watch     bool
}

type DirOnlyOps interface {
	io.Closer
	Name() string
	Readdir(count int) ([]os.FileInfo, error)
	Readdirnames(n int) ([]string, error)
	Stat() (os.FileInfo, error)
}

type DuplicatesReporter interface {
	ReportDuplicates() string
}

type FileHashReceiver interface {
	OnFileClose(name string, checksum uint64)
}

type FileInfoOptionals interface {
	Size() int64
	Mode() fs.FileMode
	ModTime() time.Time
	Sys() any
}

type FileInfoProvider interface {
	FileInfo() FileMetaInfo
}

type FileMeta struct {
	PathInfo *paths.Path
	Name     string
	Filename string

	BaseDir       string
	SourceRoot    string
	Module        string
	ModuleOrdinal int
	Component     string

	Weight    int
	IsProject bool
	Watch     bool

	// The lang associated with this file. This may be
	// either the language set in the filename or
	// the language defined in the source mount configuration.
	Lang string
	// The language index for the above lang. This is the index
	// in the sorted list of languages/sites.
	LangIndex int

	OpenFunc     func() (afero.File, error)
	JoinStatFunc func(name string) (FileMetaInfo, error)

	// Include only files or directories that match.
	InclusionFilter *glob.FilenameFilter

	// Rename the name part of the file (not the directory).
	// Returns the new name and a boolean indicating if the file
	// should be included.
	Rename func(name string, toFrom bool) (string, bool)
}

type FileMetaInfo interface {
	fs.DirEntry
	MetaProvider

	// This is a real hybrid as it also implements the fs.FileInfo interface.
	FileInfoOptionals
}

type FileNameIsDir interface {
	Name() string
	IsDir() bool
}

type FilesystemUnwrapper interface {
	UnwrapFilesystem() afero.Fs
}

type FilesystemsUnwrapper interface {
	UnwrapFilesystems() []afero.Fs
}

type Fs struct {
	// Source is Hugo's source file system.
	// Note that this will always be a "plain" Afero filesystem:
	// * afero.OsFs when running in production
	// * afero.MemMapFs for many of the tests.
	Source afero.Fs

	// PublishDir is where Hugo publishes its rendered content.
	// It's mounted inside publishDir (default /public).
	PublishDir afero.Fs

	// PublishDirStatic is the file system used for static files.
	PublishDirStatic afero.Fs

	// PublishDirServer is the file system used for serving the public directory with Hugo's development server.
	// This will typically be the same as PublishDir, but not if --renderStaticToDisk is set.
	PublishDirServer afero.Fs

	// Os is an OS file system.
	// NOTE: Field is currently unused.
	Os afero.Fs

	// WorkingDirReadOnly is a read-only file system
	// restricted to the project working dir.
	WorkingDirReadOnly afero.Fs

	// WorkingDirWritable is a writable file system
	// restricted to the project working dir.
	WorkingDirWritable afero.Fs
}

type MetaProvider interface {
	Meta() *FileMeta
}

type OpenFilesFs struct {
	afero.Fs
	// contains filtered or unexported fields
}

type Reseter interface {
	Reset()
}

type ReverseLookupProvder interface {
	ReverseLookup(filename string) ([]ComponentPath, error)
	ReverseLookupComponent(component, filename string) ([]ComponentPath, error)
}

type RootMapping struct {
	From          string    // The virtual mount.
	FromBase      string    // The base directory of the virtual mount.
	To            string    // The source directory or file.
	ToBase        string    // The base of To. May be empty if an absolute path was provided.
	Module        string    // The module path/ID.
	ModuleOrdinal int       // The module ordinal starting with 0 which is the project.
	IsProject     bool      // Whether this is a mount in the main project.
	Meta          *FileMeta // File metadata (lang etc.)
	// contains filtered or unexported fields
}

type RootMappingFs struct {
	afero.Fs
	// contains filtered or unexported fields
}

type WalkFn func(fs afero.Fs) bool

type WalkFunc func(path string, info FileMetaInfo) error

type WalkHook func(dir FileMetaInfo, path string, readdir []FileMetaInfo) ([]FileMetaInfo, error)

type Walkway struct {
	// contains filtered or unexported fields
}

type WalkwayConfig struct {
	// The filesystem to walk.
	Fs afero.Fs

	// The root to start from in Fs.
	Root string

	// The logger to use.
	Logger     loggers.Logger
	PathParser *paths.PathParser

	// One or both of these may be pre-set.
	Info       FileMetaInfo               // The start info.
	DirEntries []FileMetaInfo             // The start info's dir entries.
	IgnoreFile func(filename string) bool // Optional

	// Will be called in order.
	HookPre  WalkHook // Optional.
	WalkFn   WalkFunc
	HookPost WalkHook // Optional.

	// Some optional flags.
	FailOnNotExist bool // If set, return an error if a directory is not found.
	SortDirEntries bool // If set, sort the dir entries by Name before calling the WalkFn, default is ReaDir order.
}