package catalogue

// TakesSettingsField is the key a mergeable file carries to name the top-level setting keys it takes.
const TakesSettingsField = "takes-settings"

// Fields of a renamed takes-config entry.
const (
	takenKeyField = "key"
	takenAsField  = "as"
)

// takenEntry is one value a mergeable file takes: its key and the name the file has for it.
type takenEntry struct {
	key, as string
	renamed bool
}

// takenEntries is the entries of a takes-settings list in their order, a usable entry only: a string is a key
// under its own name, an object with exactly key and as a key under another (TakenSettingsProblems says the rest).
func takenEntries(raw any) []takenEntry {
	list, _ := raw.([]any)
	var out []takenEntry
	for _, item := range list {
		if e, ok := asTakenEntry(item); ok {
			out = append(out, e)
		}
	}
	return out
}

// asTakenEntry reads one item of a takes-settings list, and whether it is shaped as an entry at all.
func asTakenEntry(item any) (takenEntry, bool) {
	switch v := item.(type) {
	case string:
		return takenEntry{key: v, as: v}, true
	case map[string]any:
		key, keyOK := v[takenKeyField].(string)
		as, asOK := v[takenAsField].(string)
		if !keyOK || !asOK || len(v) != 2 {
			return takenEntry{}, false
		}
		return takenEntry{key: key, as: as, renamed: true}, true
	}
	return takenEntry{}, false
}

// takenKeys is the keys a resource names in takes-settings, each with the name the file has for it, and whether
// it names any list at all. An empty list is a list: that file takes no setting.
func takenKeys(resource map[string]any) (map[string]string, bool) {
	raw, said := resource[TakesSettingsField]
	if !said {
		return nil, false
	}
	keys := map[string]string{}
	for _, e := range takenEntries(raw) {
		keys[e.key] = e.as
	}
	return keys, true
}

// takenNames is every key a layer may say for the values a resource takes: each config key and, for a renamed
// one, the file's own spelling a layer said before its module moved (onlyTaken).
func takenNames(resource map[string]any) []string {
	var names []string
	for _, e := range takenEntries(resource[TakesSettingsField]) {
		names = append(names, e.key)
		if e.renamed {
			names = append(names, e.as)
		}
	}
	return names
}