/*
 * This file is part of nftables-http-api.
 * Copyright (C) 2024 Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>
 *
 *  The nftables-http-api program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
 */

package main

import (
	"encoding/json"
	"errors"
	"golang.org/x/crypto/bcrypt"
	"log"
	"net"
	"net/http"
	"strings"
)

type Response struct {
	RError  string `json:"error,omitempty"`
	RResult string `json:"result,omitempty"`
}

type ResponseSet struct {
	RError  string   `json:"error,omitempty"`
	RResult []string `json:"result,omitempty"`
}

func doReturn(w http.ResponseWriter, status int, text string) {
	var response any
	if status == http.StatusOK || status == http.StatusCreated {
		response = Response{RResult: text}
	} else {
		response = Response{RError: text}
	}
	j, err := json.Marshal(response)
	if err != nil {
		log.Fatalf("Failed to marshal JSON: %s", err)
	}
	w.WriteHeader(status)
	w.Write(j)
}

func doReturnSet(w http.ResponseWriter, status int, text string, elements []string) {
	var response any
	if status == http.StatusOK {
		response = ResponseSet{RResult: elements}
	} else {
		response = Response{RError: text}
	}
	j, err := json.Marshal(response)
	if err != nil {
		log.Fatalf("Failed to marshal JSON: %s", err)
	}
	w.WriteHeader(status)
	w.Write(j)
}

func doCheckToken(token string, hash string) bool {
	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(token))
	if err == nil {
		return true
	} else {
		log.Printf("Token check failed: %s", err)
		return false
	}
}

func parseIPAddressOrNetworkString(givenAddress string) (net.IP, *net.IPNet, string, error) {
	if strings.Contains(givenAddress, "/") {
		return parseIPNetworkString(givenAddress)
	} else {
		address, family, err := parseIPAddressString(givenAddress)
		return address, nil, family, err
	}
}

func parseIPNetworkString(givenAddress string) (net.IP, *net.IPNet, string, error) {
	ipObject, cidrObject, err := net.ParseCIDR(givenAddress)
	if err != nil {
		return nil, nil, "", err
	}
	address, family, err := parseIPAddress(ipObject)
	return address, cidrObject, family, err
}

func parseIPAddressString(givenAddress string) (net.IP, string, error) {
	return parseIPAddress(net.ParseIP(givenAddress))
}

func parseIPAddress(ipObject net.IP) (net.IP, string, error) {
	var address net.IP
	family, err := getIPAddressFamily(ipObject)
	if err == nil {
		if family == "ipv4" {
			address = ipObject.To4()
		} else if family == "ipv6" {
			address = ipObject.To16()
		} else {
			log.Println("unknown family, this should not happen")
			return nil, family, errors.New("unknown family")
		}
		return address, family, nil
	}
	log.Println("address parsing failed:", err)
	return nil, "", errors.New("invalid address")
}

func getIPAddressFamily(ipObject net.IP) (string, error) {
	ipAddress := ipObject.String()

	for i := 0; i < len(ipAddress); i++ {
		switch ipAddress[i] {
		case '.':
			return "ipv4", nil
		case ':':
			return "ipv6", nil
		}
	}

	return "", errors.New("address family detection failed")
}

func incrementIPAddress(ip net.IP) (net.IP, error) {
	for i := len(ip) - 1; i >= 0; i-- {
		ip[i]++
		if ip[i] != 0 {
			break
		}
	}
	return ip, nil
}