package configkit

// Metadata provides detached effective presence/origin and chronological history
// queries for a load. Its zero value contains no paths.
type Metadata struct {
	fields  map[string]FieldInfo
	history map[string][]Change
}

// Lookup returns information for an effective path. Unknown and invalid paths
// return false.
func (m Metadata) Lookup(path Path) (FieldInfo, bool) {
	if !path.valid() {
		return FieldInfo{}, false
	}
	info, ok := m.fields[path.String()]
	if !ok {
		return FieldInfo{}, false
	}
	return cloneFieldInfo(info), true
}

// IsExplicit reports whether a surviving input contribution explicitly defined
// path.
func (m Metadata) IsExplicit(path Path) bool {
	info, ok := m.Lookup(path)
	return ok && info.Explicit
}

// History returns detached definition and resolution records for path. A record's
// Path can be an ancestor when that container operation replaced or removed path.
// Removed historical paths can have history even though Lookup returns false.
// Unknown and invalid paths return nil.
func (m Metadata) History(path Path) []Change {
	if !path.valid() {
		return nil
	}
	history, ok := m.history[path.String()]
	if !ok {
		return nil
	}
	cloned := make([]Change, len(history))
	for i, change := range history {
		cloned[i] = cloneChange(change)
	}
	return cloned
}