package handlers

import (
	"encoding/json"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

const nominatimURL = "https://nominatim.openstreetmap.org/reverse"

var geocodeClient = &http.Client{Timeout: 5 * time.Second}

type nominatimResponse struct {
	DisplayName string `json:"display_name"`
}

func GeocodeReverse(w http.ResponseWriter, r *http.Request) {
	lat := r.URL.Query().Get("lat")
	lon := r.URL.Query().Get("lon")
	if lat == "" || lon == "" {
		writeError(w, http.StatusBadRequest, "lat and lon are required", nil)
		return
	}

	u, _ := url.Parse(nominatimURL)
	q := u.Query()
	q.Set("lat", lat)
	q.Set("lon", lon)
	q.Set("format", "json")
	q.Set("accept-language", "ru")
	u.RawQuery = q.Encode()

	req, _ := http.NewRequestWithContext(r.Context(), http.MethodGet, u.String(), nil)
	req.Header.Set("User-Agent", "Photoplaces/1.0")

	resp, err := geocodeClient.Do(req)
	if err != nil {
		writeError(w, http.StatusBadGateway, "geocoding service unavailable", err)
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		// Тело ответа вышестоящего сервиса наружу не отдаём, только логируем.
		io.Copy(io.Discard, resp.Body)
		writeJSON(w, http.StatusOK, map[string]interface{}{
			"display_name": nil,
		})
		return
	}

	var data nominatimResponse
	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to parse geocoding response", err)
		return
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"display_name": reverseAddress(data.DisplayName),
	})
}

func reverseAddress(addr string) string {
	if addr == "" {
		return ""
	}
	parts := strings.Split(addr, ", ")
	for i, j := 0, len(parts)-1; i < j; i, j = i+1, j-1 {
		parts[i], parts[j] = parts[j], parts[i]
	}
	return strings.Join(parts, ", ")
}