package service

import (
	"bufio"
	"crypto/md5"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/hex"
	"encoding/pem"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
)

type Manager struct {
	Config           Config
	privateKey       *rsa.PrivateKey
	openVPN          *OpenVPN
	CA               *x509.Certificate
	HasCertificate   bool
	HasOpenVPNConfig bool
}

func NewManager(cfg Config) *Manager {
	return &Manager{
		Config: cfg,
	}
}

func fileExists(s string) bool {
	if _, err := os.Stat(s); err == nil {
		return true
	} else if os.IsNotExist(err) {
		return false
	} else {
		Check(err, "Failed to check %q, err: %s", s, err)
	}

	return false
}

func (it *Manager) GetOpenVPNConfigLocation() string {
	return it.Config.Zerooo.Location + "/server.conf"
}

func (it *Manager) GetCALocation() string {
	return it.Config.Zerooo.Location + "/ca.crt"
}

func (it *Manager) GetCertificateLocation() string {
	return it.Config.Zerooo.Location + "/server.crt"
}

func (it *Manager) GetKeyLocation() string {
	return it.Config.Zerooo.Location + "/server.key"
}

func (it *Manager) GetDHLocation() string {
	return it.Config.Zerooo.Location + "/dh2048.pem"
}

func (it *Manager) GetCRLLocation() string {
	return it.Config.Zerooo.Location + "/crl.pem"
}

func (it *Manager) EnsureFile(path string, generator func()) bool {
	if !fileExists(path) {
		generator()
		return true
	}

	return false
}
func (it *Manager) Init() {
	if !fileExists(it.Config.Zerooo.Location) {
		os.MkdirAll(it.Config.Zerooo.Location, 0755)
	}

	generated := it.EnsureFile(it.GetKeyLocation(), func() {
		it.GenerateKey()
	})

	if !generated {
		it.LoadKey()
	}

	it.EnsureFile(it.GetCALocation(), func() {
		it.DownloadCA()
	})

	it.LoadCA()

	it.EnsureFile(it.GetCRLLocation(), func() {
		it.DownloadCRL()
	})

	it.EnsureFile(it.GetDHLocation(), func() {
		it.DownloadDH()
	})

}

func (it *Manager) GetServerFingerprint() []byte {
	der := it.ExportPublicKeyDER()
	fp := it.GetOpenSSLLikeFingerprint(der)
	return []byte(fp)
}

func (it *Manager) GetOpenSSLLikeFingerprint(input []byte) string {
	output := md5.Sum(input)
	items := make([]string, 16)
	for i := range output {
		items[i] = strings.ToLower(hex.EncodeToString([]byte{output[i]}))
	}

	return strings.Join(items, ":")
}

func (it *Manager) Register() {
	fp := it.GetServerFingerprint()

	log.Printf("%s\n", fp)

	signed, err := rsa.SignPKCS1v15(rand.Reader, it.privateKey, 0, fp)
	Check(err, "Failed signing fingerprint, err: %s", err)

	signedHash := sha256.Sum256(signed)

	publicKey := string(it.ExportPublicKey())
	hexSignature := hex.EncodeToString(signedHash[:])

	log.Printf("Registering with\n\nsignature: %s\npublic key:\n\n%s", hexSignature, publicKey)

	resp, err := http.PostForm(it.Config.Zerooo.Endpoint+"/server/register", url.Values{
		"publicKey": []string{publicKey},
		"signature": []string{hexSignature},
	})

	Check(err, "Failed to sent register post to endpoint (%s/server/register), err: %s", it.Config.Zerooo.Endpoint, err)

	if resp.StatusCode != 200 {
		Error("Endpoint responded with %d, may not be actual zerooo endpoint", resp.StatusCode)
	}

	body, err := ioutil.ReadAll(resp.Body)
	Check(err, "Failed to read response, err: %s", err)

	strBody := string(body)
	items := strings.SplitN(strBody, "\n", 2)
	code, err := strconv.ParseInt(items[0], 10, 64)
	Check(err, "Failed reading response success code, err: %s", err)

	if code != 0 {
		Error("Register failed, server responded with:\n\n%s", items[1])
	}

	log.Printf("Register succesful, server responded with: %s", items[1])
}

func (it *Manager) ExportPublicKeyDER() []byte {
	if (it.privateKey == nil) {
		Error("No private key is loaded, can't export public key")
	}

	der, err := x509.MarshalPKIXPublicKey(&it.privateKey.PublicKey)
	Check(err, "Failed converting public key to DER, err: %s", err)
	return der
}

func (it *Manager) ExportPublicKey() []byte {
	pemKey := &pem.Block{
		Type:  "PUBLIC KEY",
		Bytes: it.ExportPublicKeyDER(),
	}

	return pem.EncodeToMemory(pemKey)
}

func (it *Manager) GenerateKey() {
	log.Printf("No key exists, generating new 4096 RSA key")
	priv, err := rsa.GenerateKey(rand.Reader, 4096)
	Check(err, "Couldn't generate key, err: %s", err)
	it.privateKey = priv

	pemKey := &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(priv),
	}

	keyFile, err := os.OpenFile(it.GetKeyLocation(), os.O_EXCL|os.O_CREATE|os.O_RDWR, 0600)
	Check(err, "Failed creating file at %q for private key, err: %s", it.GetKeyLocation(), err)
	defer keyFile.Close()

	err = pem.Encode(keyFile, pemKey)
	Check(err, "Failed encoding private key, err: %s", err)
}

func (it *Manager) LoadKey() {
	log.Printf("Loading generated key")

	keyFile, err := os.Open(it.GetKeyLocation())
	Check(err, "Failed opening private key at %q for reading, err: %s", it.GetKeyLocation(), err)
	defer keyFile.Close()

	stat, _ := keyFile.Stat()
	var size int64 = stat.Size()
	pembytes := make([]byte, size)
	buffer := bufio.NewReader(keyFile)
	_, err = buffer.Read(pembytes)
	Check(err, "Failed to read private key at %q, err: %s", it.GetKeyLocation(), err)

	data, _ := pem.Decode([]byte(pembytes))
	if data == nil {
		Error("No valid key found at %q", it.GetKeyLocation())
	}

	importedKey, err := x509.ParsePKCS1PrivateKey(data.Bytes)
	Check(err, "Failed importing private key at %q, err: %s", it.GetKeyLocation(), err)
	it.privateKey = importedKey
}

func (it *Manager) Daemon() {
	server := NewHttpServer(it)
	go server.Start()

	it.openVPN = NewOpenVPN(it)

	it.openVPN.Start()

	ch := make(chan os.Signal)

	signal.Notify(ch, syscall.SIGKILL, syscall.SIGTERM, syscall.SIGSTOP, syscall.SIGINT)

	for sig := range ch {
		log.Printf("Received signal %s, quitting.", sig)
		os.Exit(0)
	}
}

func (it *Manager) LoadCA() {
	log.Printf("Loading CA certificate")

	keyFile, err := os.Open(it.GetCALocation())
	Check(err, "Failed opening CA certificate at %q for reading, err: %s", it.GetKeyLocation(), err)
	defer keyFile.Close()

	stat, _ := keyFile.Stat()
	var size int64 = stat.Size()
	pemBytes := make([]byte, size)
	buffer := bufio.NewReader(keyFile)
	_, err = buffer.Read(pemBytes)
	Check(err, "Failed to read CA certificate at %q, err: %s", it.GetKeyLocation(), err)

	data, _ := pem.Decode([]byte(pemBytes))
	if data == nil {
		Error("No valid CA certificate found at %q", it.GetKeyLocation())
	}

	ca, err := x509.ParseCertificate(data.Bytes)
	Check(err, "Failed importing private key at %q, err: %s", it.GetKeyLocation(), err)
	it.CA = ca
}

func (it *Manager) DownloadCA() {
	caUrl := it.Config.Zerooo.Endpoint + "/ca"
	download("CA", it.GetCALocation(), caUrl)
}

func (it *Manager) CAPublicKey() (*rsa.PublicKey) {
	key, ok := it.CA.PublicKey.(*rsa.PublicKey)
	if !ok {
		Error("Can't read CA Certificate as public key")
	}

	return key
}

func (it *Manager) CreateCSR(hostname string) ([]byte, error) {
	tpl := x509.CertificateRequest{Subject: pkix.Name{CommonName: hostname}}
	csr, err := x509.CreateCertificateRequest(rand.Reader, &tpl, it.privateKey)

	if err != nil {
		return nil, err
	}

	pemCSR := &pem.Block{
		Type:  "CERTIFICATE REQUEST",
		Bytes: csr,
	}

	return pem.EncodeToMemory(pemCSR), nil
}

func (it *Manager) UpdateCertificate(s string) error {
	f, err := os.OpenFile(it.GetCertificateLocation(), os.O_RDWR|os.O_CREATE, 0644)
	if err != nil {
		return err
	}
	defer f.Close()
	_, err = f.WriteString(s)
	return err
}

func download(name string, path string, url string) {
	resp, err := http.Get(url)
	Check(err, "Failed fetching %s at %q, err: %s", name, url, err)
	cert, err := ioutil.ReadAll(resp.Body)
	Check(err, "Failed fetching %s at %q, err: %s", name, url, err)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
	Check(err, "Failed open %s for writing at %q, err: %s", name, path, err)
	defer f.Close()
	_, err = f.Write(cert)
	Check(err, "Failed writing %s at %q, err: %s", name, path, err)
}

func (it *Manager) DownloadCRL() {
	crlUrl := it.Config.Zerooo.Endpoint + "/crl"
	download("CRL", it.GetCRLLocation(), crlUrl)
}

func (it *Manager) DownloadDH() {
	dhUrl := it.Config.Zerooo.Endpoint + "/dh.pem"
	download("DH", it.GetDHLocation(), dhUrl)
}

func (it *Manager) IsOpenVPNReady() bool {
	hasConfig := fileExists(it.GetOpenVPNConfigLocation())
	hasCert := fileExists(it.GetCertificateLocation())
	return hasConfig && hasCert
}