package i18n

import (
	"strings"
	"unicode"
)

var (
	esStopwords = map[string]bool{
		"el": true, "la": true, "los": true, "las": true, "de": true,
		"que": true, "y": true, "en": true, "un": true, "una": true,
		"es": true, "se": true, "no": true, "con": true, "para": true,
		"por": true, "su": true, "del": true, "al": true, "lo": true,
		"qué": true, "cómo": true, "dónde": true, "cuándo": true,
		"cuál": true, "cuáles": true, "quién": true, "habla": true,
		"tienes": true, "dime": true, "háblame": true, "sobre": true,
		"más": true, "pero": true, "como": true, "este": true, "esta": true,
		"estos": true, "estas": true, "ese": true, "esa": true, "aquel": true,
		"muy": true, "sin": true, "hay": true, "sí": true, "yo": true,
		"tú": true, "él": true, "ella": true, "nosotros": true,
	}
	enStopwords = map[string]bool{
		"the": true, "is": true, "are": true, "of": true, "and": true,
		"in": true, "to": true, "a": true, "an": true, "for": true,
		"with": true, "on": true, "by": true, "from": true, "what": true,
		"which": true, "who": true, "how": true, "when": true, "where": true,
		"tell": true, "about": true, "do": true, "does": true, "can": true,
		"you": true, "your": true, "have": true, "has": true, "i": true,
		"we": true, "they": true, "this": true, "that": true, "these": true,
		"those": true, "be": true, "been": true, "will": true, "would": true,
		"should": true, "could": true, "my": true, "our": true, "their": true,
	}
)

// Detect returns "es" or "en" based on lightweight heuristics. Good enough
// to choose the response language for a portfolio chatbot; the LLM (once
// wired in) is the final authority.
//
// Heuristic:
//   - Spanish diacritics or ¿/¡ → +N Spanish markers
//   - Tokenize and count stopwords in each language
//   - Whichever side wins; tie → English
func Detect(text string) string {
	if text == "" {
		return "en"
	}

	markers := 0
	for _, c := range text {
		switch c {
		case '¿', '¡':
			markers += 2
		case 'ñ':
			markers += 2
		case 'á', 'é', 'í', 'ó', 'ú', 'ü':
			markers++
		}
	}

	es, en := 0, 0
	for _, tok := range tokenize(text) {
		if esStopwords[tok] {
			es++
		}
		if enStopwords[tok] {
			en++
		}
	}

	switch {
	case markers >= 2:
		return "es"
	case es > en:
		return "es"
	case en > es:
		return "en"
	default:
		return "en"
	}
}

func tokenize(s string) []string {
	s = strings.ToLower(s)
	f := func(c rune) bool {
		if unicode.IsLetter(c) || unicode.IsDigit(c) {
			return false
		}
		return true
	}
	return strings.FieldsFunc(s, f)
}