package app

import (
	"encoding/json"
	"io"
	"net/http"
	"os"
	"strings"
	"syscall"
)

func handleRoutesUpdate(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	var body struct {
		Iface string `json:"iface"`
	}
	if r.Body != nil {
		defer r.Body.Close()
		_ = json.NewDecoder(io.LimitReader(r.Body, 1<<20)).Decode(&body)
	}
	iface := strings.TrimSpace(body.Iface)
	iface = normalizePreferredIface(iface)
	if iface == "" {
		iface, _ = resolveTrafficIface(loadTrafficModeState().PreferredIface)
	}

	lock, err := os.OpenFile(lockFile, os.O_CREATE|os.O_RDWR, 0o644)
	if err != nil {
		http.Error(w, "lock open error", http.StatusInternalServerError)
		return
	}
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		writeJSON(w, http.StatusOK, map[string]any{
			"ok":      false,
			"message": "routes update already running",
		})
		lock.Close()
		return
	}

	go func(iface string, lockFile *os.File) {
		defer syscall.Flock(int(lockFile.Fd()), syscall.LOCK_UN)
		defer lockFile.Close()

		res := routesUpdate(iface)
		evKind := "routes_update_done"
		if !res.OK {
			evKind = "routes_update_error"
		}
		events.push(evKind, map[string]any{
			"ok":      res.OK,
			"message": res.Message,
			"ip_cnt":  res.ExitCode, // reuse exitCode to pass ip_count if set
		})
	}(iface, lock)

	writeJSON(w, http.StatusOK, map[string]any{
		"ok":      true,
		"message": "routes update started",
	})
}