groupfile

type Entry[K GroupName, T any] struct {
	// FileData is the full contents of the file that contain this entry
	FileData []byte
	Beg, End uint32

	// MStmt is statement about membership
	MStmt *MStmt[K, T]
	// Comment is a line that starts with #
	Comment *string
	// Include is a line that starts with !include
	// The rest of the line is interpretted as a paths to include
	Include *string
}

type ErrParsing struct {
	FileData []byte
	Beg, End uint32
	Err      error
}

type GroupFile[K GroupName, T any] = []Entry[K, T]

type GroupName interface {
	comparable
	String() string
}

type MStmt[K GroupName, T any] struct {
	Group   K
	Members []Member[K, T]
}

type Member[K GroupName, T any] struct {
	// Unit references a single element
	Unit *T
	// GroupRef references another group by name.
	GroupRef *K
	// Empty is used to create empty groups.
	Empty *struct{}
}

type Membership[K GroupName, T any] struct {
	Group  K
	Member Member[K, T]
}