package webhook

import (
	"context"
	"crypto/rand"
	"crypto/rsa"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"fmt"
	"math/big"
	"net"
	"os"
	"testing"
	"time"
)

func TestWebhookCertReload(t *testing.T) {
	// Initialize test space
	tmpDir := os.TempDir() + "/webhook-cert-tests"
	certFile = tmpDir + "/tls.crt"
	keyFile = tmpDir + "/tls.key"
	port = 30443
	err := os.Mkdir(tmpDir, 0o777)
	if err != nil && err != os.ErrExist {
		t.Errorf("unexpected error occurred while creating tmp dir: %v", err)
	}
	defer func() {
		err := os.RemoveAll(tmpDir)
		if err != nil {
			t.Errorf("unexpected error occurred while deleting certs: %v", err)
		}
	}()
	err = generateTestCertKeyPair(t, certFile, keyFile)
	if err != nil {
		t.Errorf("unexpected error occurred while generating test certs: %v", err)
	}

	// Start test server
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	cw, err := NewCertWatcher(certFile, keyFile)
	if err != nil {
		t.Errorf("failed to initialize new cert watcher: %v", err)
	}
	tlsConfig := &tls.Config{
		GetCertificate: cw.GetCertificate,
	}
	go func() {
		err := startServer(ctx,
			tlsConfig,
			cw,
			&fakeSnapshotLister{},
			&fakeGroupSnapshotLister{})
		if err != nil {
			panic(err)
		}
	}()
	time.Sleep(250 * time.Millisecond) // Give some time for watcher to start

	// TC: Original cert should not change with no file changes
	originalCert, err := tlsConfig.GetCertificate(nil)
	if err != nil {
		t.Errorf("unexpected error occurred while getting cert: %v", err)
	}
	originalCertStr := string(originalCert.Certificate[0])
	originalKey := originalCert.PrivateKey.(*rsa.PrivateKey)

	newCert, err := tlsConfig.GetCertificate(nil) // get certificate again
	if err != nil {
		t.Errorf("unexpected error occurred while getting  newcert: %v", err)
	}
	if string(newCert.Certificate[0]) != originalCertStr {
		t.Error("new cert was updated when it should not have been")
	}
	newKey := newCert.PrivateKey.(*rsa.PrivateKey)
	if !newKey.Equal(originalKey) {
		t.Error("new key was updated when it should not have been")
	}

	// TC: Certificate should consistently change with a file change
	for i := 0; i < 5; i++ {
		// Generate new key/cert
		err = generateTestCertKeyPair(t, certFile, keyFile)
		if err != nil {
			t.Errorf("unexpected error occurred while generating test certs: %v", err)
		}

		// Wait for certwatcher to update
		time.Sleep(250 * time.Millisecond)
		newCert, err = tlsConfig.GetCertificate(nil)
		if err != nil {
			t.Errorf("unexpected error occurred while getting  newcert: %v", err)
		}
		if string(newCert.Certificate[0]) == originalCertStr {
			t.Errorf("new cert was not updated")
		}

		newKey = newCert.PrivateKey.(*rsa.PrivateKey)
		if newKey.Equal(originalKey) {
			t.Error("new key was not updated")
		}

		originalCertStr = string(newCert.Certificate[0])
		originalKey = newKey
	}
}

// generateTestCertKeyPair generates a new random test key/crt and writes it to tmpDir
// based on https://golang.org/src/crypto/tls/generate_cert.go
func generateTestCertKeyPair(t *testing.T, certPath, keyPath string) error {
	notBefore := time.Now()
	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
	if err != nil {
		return fmt.Errorf("Failed to generate serial number: %v", err)
	}

	var priv interface{}
	priv, err = rsa.GenerateKey(rand.Reader, 4096)
	if err != nil {
		return fmt.Errorf("Failed to generate key: %v", err)
	}
	keyUsage := x509.KeyUsageDigitalSignature
	if _, isRSA := priv.(*rsa.PrivateKey); isRSA {
		keyUsage |= x509.KeyUsageKeyEncipherment
	}
	randomOrganizationStr := time.Now().String()
	template := x509.Certificate{
		SerialNumber: serialNumber,
		Subject: pkix.Name{
			Organization: []string{randomOrganizationStr},
		},
		NotBefore: notBefore,
		NotAfter:  time.Now().Add(1 * time.Hour),

		KeyUsage:              keyUsage,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		IPAddresses:           []net.IP{net.ParseIP("127.0.0.1")},
		DNSNames:              []string{"127.0.0.1"},
	}

	rk := priv.(*rsa.PrivateKey)
	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &rk.PublicKey, priv)
	if err != nil {
		return fmt.Errorf("Failed to create certificate: %v", err)
	}

	certOut, err := os.Create(certPath)
	if err != nil {
		return fmt.Errorf("Failed to open tls.crt for writing: %v", err)
	}
	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
		return fmt.Errorf("Failed to write data to tls.crt: %v", err)
	}
	if err := certOut.Close(); err != nil {
		return fmt.Errorf("Error closing tls.crt: %v", err)
	}
	fmt.Printf("wrote new cert: %s\n", certPath)

	keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
	if err != nil {
		return fmt.Errorf("Failed to open tls.key for writing: %v", err)
	}
	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
	if err != nil {
		return fmt.Errorf("Unable to marshal private key: %v", err)
	}
	if err := pem.Encode(keyOut, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
		return fmt.Errorf("Failed to write data to tls.key: %v", err)
	}
	if err := keyOut.Close(); err != nil {
		return fmt.Errorf("Error closing tls.key: %v", err)
	}
	fmt.Printf("wrote new key: %s\n", keyPath)

	return nil
}
