package server

import (
	"fmt"
	"io"
	"os"
	"strings"
)

const (
	// According to http://man7.org/linux/man-pages/man5/resolv.conf.5.html:
	// "The search list is currently limited to six domains with a total of 256 characters."
	maxDNSSearches = 6
)

func int64Ptr(i int64) *int64 {
	return &i
}

func int32Ptr(i int32) *int32 {
	return &i
}

func sPtr(s string) *string {
	return &s
}

func copyFile(src, dest string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()

	out, err := os.Create(dest)
	if err != nil {
		return err
	}
	defer out.Close()

	_, err = io.Copy(out, in)
	return err
}

func removeFile(path string) error {
	if _, err := os.Stat(path); err == nil {
		if err := os.Remove(path); err != nil {
			return err
		}
	}
	return nil
}

func parseDNSOptions(servers, searches, options []string, path string) error {
	nServers := len(servers)
	nSearches := len(searches)
	nOptions := len(options)
	if nServers == 0 && nSearches == 0 && nOptions == 0 {
		return copyFile("/etc/resolv.conf", path)
	}

	if nSearches > maxDNSSearches {
		return fmt.Errorf("DNSOption.Searches has more than 6 domains")
	}

	f, err := os.Create(path)
	if err != nil {
		return err
	}
	defer f.Close()

	if nSearches > 0 {
		data := fmt.Sprintf("search %s\n", strings.Join(searches, " "))
		_, err = f.Write([]byte(data))
		if err != nil {
			return err
		}
	}

	if nServers > 0 {
		data := fmt.Sprintf("nameserver %s\n", strings.Join(servers, "\nnameserver "))
		_, err = f.Write([]byte(data))
		if err != nil {
			return err
		}
	}

	if nOptions > 0 {
		data := fmt.Sprintf("options %s\n", strings.Join(options, " "))
		_, err = f.Write([]byte(data))
		if err != nil {
			return err
		}
	}

	return nil
}