package server

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
)

// translations holds the loaded translation maps keyed by language code.
type translations struct {
	langs map[string]map[string]any // e.g. {"en": {...}, "de": {...}}
}

func loadTranslations(enJSON, deJSON []byte) (*translations, error) {
	t := &translations{langs: make(map[string]map[string]any)}

	var en map[string]any
	if err := json.Unmarshal(enJSON, &en); err != nil {
		return nil, fmt.Errorf("parse en.json: %w", err)
	}
	t.langs["en"] = en

	var de map[string]any
	if err := json.Unmarshal(deJSON, &de); err != nil {
		return nil, fmt.Errorf("parse de.json: %w", err)
	}
	t.langs["de"] = de

	return t, nil
}

// get resolves a dotted key (e.g. "setup.rooms.title") from the translation map.
func (t *translations) get(lang, key string) string {
	m, ok := t.langs[lang]
	if !ok {
		m = t.langs["en"]
	}
	if m == nil {
		return key
	}
	return resolve(m, key)
}

func resolve(m map[string]any, key string) string {
	parts := strings.Split(key, ".")
	var current any = m
	for _, p := range parts {
		cm, ok := current.(map[string]any)
		if !ok {
			return key
		}
		current, ok = cm[p]
		if !ok {
			return key
		}
	}
	s, ok := current.(string)
	if !ok {
		return key
	}
	return s
}

// supportedLangs are the available languages.
var supportedLangs = []string{"en", "de"}

// detectLanguage determines the active language from query param, cookie, or Accept-Language header.
func detectLanguage(r *http.Request) string {
	// 1. Query parameter
	if lang := r.URL.Query().Get("lang"); isSupported(lang) {
		return lang
	}

	// 2. Cookie
	if c, err := r.Cookie("heatguard_lang"); err == nil && isSupported(c.Value) {
		return c.Value
	}

	// 3. Accept-Language header
	accept := r.Header.Get("Accept-Language")
	for _, part := range strings.Split(accept, ",") {
		lang := strings.TrimSpace(strings.SplitN(part, ";", 2)[0])
		lang = strings.SplitN(lang, "-", 2)[0]
		if isSupported(lang) {
			return lang
		}
	}

	return "en"
}

func isSupported(lang string) bool {
	for _, l := range supportedLangs {
		if l == lang {
			return true
		}
	}
	return false
}