package main

import (
	"context"
	"errors"
	"fmt"
	"net"
	"os"
	"time"

	"go.wit.com/lib/protobuf/argvpb"
	"go.wit.com/log"
)

func ipv6fails() bool {
	var s string
	var err error
	var addrs []net.IP

	addrs, err = LookupIPv6("ipv6.google.com")
	if err != nil {
		log.Printf("%v\n", err)
		log.Info(s)
		WarningForIpv4()
		s = "THIS FEATURE IS NOT SUPPORTED ON IPv4"
		argvpb.BadExit(s, err)
	}
	if len(addrs) == 0 {
		s = "THIS FEATURE IS NOT SUPPORTED ON IPv4."
		argvpb.BadExit(s, errors.New("IPv6 DNS is not returning ip addresses"))
	}

	addrs, err = LookupIPv6("cgit.grid.wit.com")
	if err != nil {
		log.Printf("%v\n", err)
		log.Info(s)
		WarningForIpv4()
		s = "Your OS is not correctly resolving IPv6 addresses."
		argvpb.BadExit(s, err)
	}
	if len(addrs) == 0 {
		s = "Your OS is not correctly resolving IPv6 addresses."
		argvpb.BadExit(s, errors.New("IPv6 DNS is not returning ip addresses"))
	}
	/*
		s, err = IPv6TestDNS()
		if err != nil {
			log.Printf("%v\n", err)
			log.Info(s)
			WarningForIpv4()
			s = "THIS FEATURE IS NOT SUPPORTED ON IPv4"
			argvpb.BadExit(s, nil)
		}
	*/

	s, err = IPv6TestPing()
	if err != nil {
		log.Printf("%v\n", err)
		log.Info(s)
		WarningForIpv4()
		s = "THIS FEATURE IS NOT SUPPORTED ON IPv4"
		argvpb.BadExit(s, nil)
	}
	return true
}

func WarningForIpv4() {
	log.Info("")
	pfile, _ := resources.ReadFile("resources/IPv4")
	log.Info("")
	log.Info(string(pfile))
}

// The host we will try to connect to.
// ipv6.google.com is a good choice as it's highly available and resolves only to AAAA records (IPv6).
const ipv6TestHost = "ipv6.google.com"
const testPort = "443" // HTTPS port, almost always open.

func LookupIPv6(hostname string) ([]net.IP, error) {
	dnsTimeout := 2 * time.Second
	ctx, cancel := context.WithTimeout(context.Background(), dnsTimeout)
	defer cancel()

	addrs, err := net.DefaultResolver.LookupIP(ctx, "ip6", ipv6TestHost)
	return addrs, err
}

// a better test that should fail right away
func IPv6TestDNS() (string, error) {
	// --- Step 1: Fast DNS Lookup ---
	// We'll use a separate, short timeout just for the DNS resolution.
	// If DNS is broken, we'll know in a second or two.
	dnsTimeout := 2 * time.Second
	ctx, cancel := context.WithTimeout(context.Background(), dnsTimeout)
	defer cancel()

	// net.DefaultResolver.LookupIPAddr forces the resolver to look up the host.
	// We specify "ip6" to ensure we only get AAAA records.
	// addrs, err := net.DefaultResolver.LookupIPAddr(ctx, "ip6", ipv6TestHost)
	addrs, err := net.DefaultResolver.LookupIP(ctx, "ip6", ipv6TestHost)
	if err != nil {
		fmt.Printf("IPv6 DNS resolution failed: %v\n", err)
		fmt.Println("This likely means your network cannot resolve IPv6 addresses.")
		return "IPv6 connectivity test failed", err
	}

	if len(addrs) == 0 {
		fmt.Printf("No IPv6 addresses found for %s\n", ipv6TestHost)
		return "this should happen", errors.New("good or bad")
	}
	testping(addrs)
	return "IPv6 DNS lookup worked.", nil
}

func testping(addrs []net.IP) {
	// If we get here, DNS is working. Let's use the first address we found.
	targetIP := addrs[0].String()
	fmt.Printf("Successfully resolved %s to IPv6 address: %s\n", ipv6TestHost, targetIP)

	// --- Step 2: Connection Attempt ---
	// Now we try to connect to the IP we found. This tests routing and firewalls.
	connectionTimeout := 3 * time.Second
	conn, err := net.DialTimeout("tcp6", net.JoinHostPort(targetIP, testPort), connectionTimeout)
	if err != nil {
		fmt.Printf("IPv6 connection to %s failed: %v\n", targetIP, err)
		fmt.Println("This likely means your network has an IPv6 routing or firewall issue.")
		os.Exit(1)
	}
	defer conn.Close()

	fmt.Println("IPv6 ping test successful.")
}

func IPv6TestPing() (string, error) {
	// We use net.DialTimeout to attempt a TCP connection.
	// By specifying "tcp6" as the network, we force the dialer to use IPv6 only.
	// If the system can't resolve the AAAA record or can't route to the IPv6 address,
	// this will fail.
	timeout := 2 * time.Second
	conn, err := net.DialTimeout("tcp6", net.JoinHostPort(ipv6TestHost, testPort), timeout)

	// Check the result.
	if err != nil {
		// The connection failed. This indicates that IPv6 is not working correctly.
		return "IPv6 ping test failed", err
	}

	// If we get here, the connection was successful.
	// It's good practice to close the connection we opened.
	conn.Close()

	return "IPv6 ping test successful.", nil
}