package auth

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

	"quickip/internal/config"
	"quickip/internal/model"
)

func Middleware(cfg config.Config, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !allowedSource(r.RemoteAddr) {
			writeJSON(w, http.StatusForbidden, model.APIResponse{Code: 1003, Message: "来源 IP 不允许", Data: nil})
			return
		}

		password := r.Header.Get("X-Admin-Password")
		if password == "" {
			writeJSON(w, http.StatusUnauthorized, model.APIResponse{Code: 1001, Message: "缺少密码", Data: nil})
			return
		}
		if password != cfg.AdminPassword {
			writeJSON(w, http.StatusUnauthorized, model.APIResponse{Code: 1002, Message: "密码错误", Data: nil})
			return
		}
		next.ServeHTTP(w, r)
	})
}

func allowedSource(remoteAddr string) bool {
	host, _, err := net.SplitHostPort(remoteAddr)
	if err != nil {
		host = remoteAddr
	}
	ip := net.ParseIP(strings.TrimSpace(host))
	if ip == nil {
		return false
	}
	_, subnet, _ := net.ParseCIDR("169.254.0.0/16")
	return subnet.Contains(ip)
}

func writeJSON(w http.ResponseWriter, status int, payload model.APIResponse) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(payload)
}