package router

import "strings"

// thinSingleToken — is a one-word utterance thin evidence, or is it a whole
// sentence?
//
// The rule this replaces was `len(strings.Fields(u)) <= 1`, an English
// intuition. It does not transfer: Russian packs a subject, a tense and a
// gender into one word, so "поужинал" is a complete report and "привет" a
// complete greeting, yet both got thinned and came back as "не совсем поняла".
// Meanwhile the case the rule exists for is real — a bare noun like "вода" or
// "бэкап" genuinely does not say fact-vs-query or act-vs-report.
//
// So: still one token, but only thin it when the token is a bare nominal.
// Two escapes, both cheap and both offline:
//
//   - a closed lexicon of social and command singles, which are complete by
//     definition ("привет", "спасибо", "стоп", "yes");
//   - a suffix test for an inflected predicate — past tense, 2nd person,
//     reflexive. Verbs carry their own subject, so a verb IS a sentence.
//
// The suffix test is deliberately loose about nouns that happen to end the
// same way ("канал" reads as past tense here). That direction of error only
// costs a clarify we would not have asked for; the other direction — treating
// a real report as thin — is the bug being fixed.
func thinSingleToken(utterance string) bool {
	f := strings.Fields(utterance)
	if len(f) != 1 {
		return false
	}
	w := strings.ToLower(strings.Trim(f[0], ".,!?;:—-\"'«»()"))
	if w == "" {
		return false
	}
	if completeSingles[w] {
		return false
	}
	return !looksInflected(w)
}

// completeSingles — one-word utterances that need no second half. Greetings,
// acknowledgements and the control words a voice loop has to honour instantly.
var completeSingles = map[string]bool{
	// ru: social
	"привет": true, "здравствуй": true, "здравствуйте": true, "здорово": true,
	"пока": true, "прощай": true, "спокойной": true, "спасибо": true,
	"благодарю": true, "извини": true, "прости": true, "пожалуйста": true,
	"да": true, "нет": true, "ага": true, "угу": true, "ок": true, "окей": true,
	"хорошо": true, "ладно": true, "конечно": true, "верно": true, "точно": true,
	// ru: control
	"стоп": true, "отмена": true, "отбой": true, "хватит": true, "тихо": true,
	"повтори": true, "продолжай": true, "помоги": true, "помощь": true,
	// en
	"hi": true, "hello": true, "hey": true, "bye": true, "goodbye": true,
	"thanks": true, "thank": true, "sorry": true, "please": true,
	"yes": true, "no": true, "yep": true, "nope": true, "ok": true, "okay": true,
	"sure": true, "right": true, "stop": true, "cancel": true, "help": true,
	"repeat": true, "continue": true,
}

// inflectedSuffixes — endings that mark a finite or past-tense Russian verb.
// Ordered longest-first is unnecessary (any match wins), but each entry is
// chosen to be long enough that common nouns rarely collide.
var inflectedSuffixes = []string{
	// reflexive — strongly verbal whatever precedes it
	"ся", "сь",
	// past tense
	"ал", "ял", "ил", "ел", "ыл", "ул", "ёл", "ала", "яла", "ила", "ела",
	"ыла", "ула", "али", "яли", "или", "ели",
	// 2nd person singular
	"ешь", "ишь", "ёшь",
	// 1st/2nd person plural, 3rd person plural
	"аем", "яем", "уем", "аете", "ите", "ают", "яют", "уют", "ат", "ят",
}

// looksInflected — does the word carry a verb ending? Short words are exempt:
// a three-letter token is not enough stem to trust a two-letter suffix on
// ("газ" would otherwise never match, but "нос" and "лес" would).
func looksInflected(w string) bool {
	if len([]rune(w)) < 5 {
		return false
	}
	for _, s := range inflectedSuffixes {
		if strings.HasSuffix(w, s) {
			return true
		}
	}
	return false
}