fsnode

type Cacheable interface {
	// CacheableFor is the maximum allowed cache time.
	// Zero means don't cache. Negative means cache forever.
	// TODO: Make this a non-Duration type to avoid confusion with negatives?
	CacheableFor() time.Duration
}

type ChildrenGenerator interface {
	GenerateChildren(context.Context) ([]T, error)
}

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

type Iterator interface {
	// Next gets the next node. Must return (nil, io.EOF) at the end, not (non-nil, io.EOF).
	Next(context.Context) (T, error)
	// Close frees resources.
	Close(context.Context) error
}

type Leaf interface {
	// T is implementation of common node operations. The FileInfo returned
	// by T.Info must be consistent with a regular file (mode and !IsDir).
	T
	// OpenFile opens the file. File.Stat()'s result must be consistent
	// with T.Info. flag holds the flag bits, specified the same as those
	// passed to os.OpenFile.See os.O_*.
	OpenFile(ctx context.Context, flag int) (fsctx.File, error)
}

type Parent interface {
	// T.Info must be consistent with directory (mode and IsDir).
	T
	// Child returns the named child. Returns nil, os.ErrNotExist if no such child exists.
	// name is not a path and must not contain '/'. It must satisfy fs.ValidPath, too.
	//
	// In some implementations, Child lookup may be relatively expensive and implementations
	// may want to reduce the cost of accessing a deeply-nested node. They may make all Child()
	// requests succeed immediately and then return path errors from listing or Leaf.Open
	// operations for the earlier path segment.
	Child(_ context.Context, name string) (T, error)
	// Children returns an iterator that can list all children.
	// Children takes no Context; it's expected to simply construct a view and return errors to
	// callers when they choose an Iterator operation.
	Children() Iterator
	// AddChildLeaf adds a child leaf to this parent, returning the new
	// leaf and an open file for the leaf's contents. The behavior of name
	// collisions may vary by implementation. It may be convenient to embed
	// ParentReadOnly if your Parent implementation is read-only.
	// TODO: Include mode?
	AddChildLeaf(_ context.Context, name string, flags uint32) (Leaf, fsctx.File, error)
	// AddChildParent adds a child parent to this parent, returning the new
	// parent. The behavior of name collisions may vary by implementation.
	// It may be convenient to embed ParentReadOnly if your Parent
	// implementation is read-only.
	AddChildParent(_ context.Context, name string) (Parent, error)
	// RemoveChild removes a child. It may be convenient to embed
	// ParentReadOnly if your Parent implementation is read-only.
	RemoveChild(_ context.Context, name string) error
}

type ParentReadOnly struct{}

type T interface {
	// Info provides immediately-available information. A subset of fields must be accurate:
	//   Name
	//   Mode&os.ModeType
	//   IsDir
	// The rest can be zero values if they're not immediately available.
	// Implementations may find FileInfo (in this package) convenient for embedding or use
	// in public API.
	//
	// Leaf.Open().Stat() gets complete information. That returned FileInfo must have the same
	// values for the fields listed above. The others can change if better information is
	// available.
	// TODO: Specify something about Info()'s return changing after a Stat call?
	Info() os.FileInfo
	// FSNodeT distinguishes T from os.FileInfo. It does nothing.
	FSNodeT()
}