package app

import (
	"net/http"
	"os"
	"syscall"
)

func handleTrafficInterfaces(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	st := loadTrafficModeState()
	active, reason := resolveTrafficIface(st.PreferredIface)
	resp := TrafficInterfacesResponse{
		Interfaces:     listSelectableIfaces(st.PreferredIface),
		PreferredIface: normalizePreferredIface(st.PreferredIface),
		ActiveIface:    active,
		IfaceReason:    reason,
	}
	writeJSON(w, http.StatusOK, resp)
}

func handleTrafficModeTest(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	st := loadTrafficModeState()
	writeJSON(w, http.StatusOK, evaluateTrafficMode(st))
}

func acquireTrafficApplyLock() (*os.File, *TrafficModeStatusResponse) {
	lock, err := os.OpenFile(lockFile, os.O_CREATE|os.O_RDWR, 0o644)
	if err != nil {
		msg := evaluateTrafficMode(loadTrafficModeState())
		msg.Message = "traffic lock open failed: " + err.Error()
		return nil, &msg
	}
	if err := syscall.Flock(int(lock.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		_ = lock.Close()
		msg := evaluateTrafficMode(loadTrafficModeState())
		msg.Message = "traffic apply skipped: routes operation already running"
		return nil, &msg
	}
	return lock, nil
}

func handleTrafficMode(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		st := loadTrafficModeState()
		writeJSON(w, http.StatusOK, evaluateTrafficMode(st))
	case http.MethodPost:
		handleTrafficModePost(w, r)
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}