/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import (
	"bytes"
	"crypto/tls"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"net"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"text/template"
	"time"

	proxyproto "github.com/armon/go-proxyproto"
	"github.com/eapache/channels"
	apiv1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/util/intstr"
	"k8s.io/client-go/kubernetes/scheme"
	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/flowcontrol"
	"k8s.io/ingress-nginx/pkg/tcpproxy"

	adm_controller "k8s.io/ingress-nginx/internal/admission/controller"
	ngx_config "k8s.io/ingress-nginx/internal/ingress/controller/config"
	"k8s.io/ingress-nginx/internal/ingress/controller/process"
	"k8s.io/ingress-nginx/internal/ingress/controller/store"
	ngx_template "k8s.io/ingress-nginx/internal/ingress/controller/template"
	"k8s.io/ingress-nginx/internal/ingress/metric"
	"k8s.io/ingress-nginx/internal/ingress/status"
	ing_net "k8s.io/ingress-nginx/internal/net"
	"k8s.io/ingress-nginx/internal/net/dns"
	"k8s.io/ingress-nginx/internal/net/ssl"
	"k8s.io/ingress-nginx/internal/nginx"
	"k8s.io/ingress-nginx/internal/task"
	"k8s.io/ingress-nginx/pkg/apis/ingress"

	"k8s.io/ingress-nginx/pkg/util/file"
	utilingress "k8s.io/ingress-nginx/pkg/util/ingress"

	klog "k8s.io/klog/v2"
)

const (
	tempNginxPattern = "nginx-cfg"
	emptyUID         = "-1"
)

// NewNGINXController creates a new NGINX Ingress controller.
func NewNGINXController(config *Configuration, mc metric.Collector) *NGINXController {
	eventBroadcaster := record.NewBroadcaster()
	eventBroadcaster.StartLogging(klog.Infof)
	eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{
		Interface: config.Client.CoreV1().Events(config.Namespace),
	})

	h, err := dns.GetSystemNameServers()
	if err != nil {
		klog.Warningf("Error reading system nameservers: %v", err)
	}

	n := &NGINXController{
		isIPV6Enabled: ing_net.IsIPv6Enabled(),

		resolver:        h,
		cfg:             config,
		syncRateLimiter: flowcontrol.NewTokenBucketRateLimiter(config.SyncRateLimit, 1),

		recorder: eventBroadcaster.NewRecorder(scheme.Scheme, apiv1.EventSource{
			Component: "nginx-ingress-controller",
		}),

		stopCh:   make(chan struct{}),
		updateCh: channels.NewRingChannel(1024),

		ngxErrCh: make(chan error),

		stopLock: &sync.Mutex{},

		runningConfig: new(ingress.Configuration),

		Proxy: &tcpproxy.TCPProxy{},

		metricCollector: mc,

		command: NewNginxCommand(),
	}

	if n.cfg.ValidationWebhook != "" {
		n.validationWebhookServer = &http.Server{
			Addr: config.ValidationWebhook,
			// G112 (CWE-400): Potential Slowloris Attack
			ReadHeaderTimeout: 10 * time.Second,
			Handler:           adm_controller.NewAdmissionControllerServer(&adm_controller.IngressAdmission{Checker: n}),
			TLSConfig:         ssl.NewTLSListener(n.cfg.ValidationWebhookCertPath, n.cfg.ValidationWebhookKeyPath).TLSConfig(),
			// disable http/2
			// https://github.com/kubernetes/kubernetes/issues/80313
			// https://github.com/kubernetes/ingress-nginx/issues/6323#issuecomment-737239159
			TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
		}
	}

	n.store = store.New(
		config.Namespace,
		config.WatchNamespaceSelector,
		config.ConfigMapName,
		config.TCPConfigMapName,
		config.UDPConfigMapName,
		config.DefaultSSLCertificate,
		config.ResyncPeriod,
		config.Client,
		n.updateCh,
		config.DisableCatchAll,
		config.DeepInspector,
		config.IngressClassConfiguration,
		config.DisableSyncEvents)

	n.syncQueue = task.NewTaskQueue(n.syncIngress)

	if config.UpdateStatus {
		n.syncStatus = status.NewStatusSyncer(status.Config{
			Client:                 config.Client,
			PublishService:         config.PublishService,
			PublishStatusAddress:   config.PublishStatusAddress,
			IngressLister:          n.store,
			UpdateStatusOnShutdown: config.UpdateStatusOnShutdown,
			UseNodeInternalIP:      config.UseNodeInternalIP,
		})
	} else {
		klog.Warning("Update of Ingress status is disabled (flag --update-status)")
	}

	onTemplateChange := func() {
		template, err := ngx_template.NewTemplate(nginx.TemplatePath)
		if err != nil {
			// this error is different from the rest because it must be clear why nginx is not working
			klog.ErrorS(err, "Error loading new template")
			return
		}

		n.t = template
		klog.InfoS("New NGINX configuration template loaded")
		n.syncQueue.EnqueueTask(task.GetDummyObject("template-change"))
	}

	ngxTpl, err := ngx_template.NewTemplate(nginx.TemplatePath)
	if err != nil {
		klog.Fatalf("Invalid NGINX configuration template: %v", err)
	}

	n.t = ngxTpl

	_, err = file.NewFileWatcher(nginx.TemplatePath, onTemplateChange)
	if err != nil {
		klog.Fatalf("Error creating file watcher for %v: %v", nginx.TemplatePath, err)
	}

	filesToWatch := []string{}

	if err := os.Mkdir("/etc/ingress-controller/geoip/", 0o755); err != nil && !os.IsExist(err) {
		klog.Fatalf("Error creating geoip dir: %v", err)
	}
	err = filepath.WalkDir("/etc/ingress-controller/geoip/", func(path string, info fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			return nil
		}

		filesToWatch = append(filesToWatch, path)
		return nil
	})
	if err != nil {
		klog.Fatalf("Error creating file watchers: %v", err)
	}

	for _, f := range filesToWatch {
		_, err = file.NewFileWatcher(f, func() {
			klog.InfoS("File changed detected. Reloading NGINX", "path", f)
			n.syncQueue.EnqueueTask(task.GetDummyObject("file-change"))
		})
		if err != nil {
			klog.Fatalf("Error creating file watcher for %v: %v", f, err)
		}
	}

	return n
}

// NGINXController describes a NGINX Ingress controller.
type NGINXController struct {
	cfg *Configuration

	recorder record.EventRecorder

	syncQueue *task.Queue

	syncStatus status.Syncer

	syncRateLimiter flowcontrol.RateLimiter

	// stopLock is used to enforce that only a single call to Stop send at
	// a given time. We allow stopping through an HTTP endpoint and
	// allowing concurrent stoppers leads to stack traces.
	stopLock *sync.Mutex

	stopCh   chan struct{}
	updateCh *channels.RingChannel

	// ngxErrCh is used to detect errors with the NGINX processes
	ngxErrCh chan error

	// runningConfig contains the running configuration in the Backend
	runningConfig *ingress.Configuration

	t ngx_template.Writer

	resolver []net.IP

	isIPV6Enabled bool

	isShuttingDown bool

	Proxy *tcpproxy.TCPProxy

	store store.Storer

	metricCollector metric.Collector

	validationWebhookServer *http.Server

	command NginxExecTester
}

// Start starts a new NGINX master process running in the foreground.
func (n *NGINXController) Start() {
	klog.InfoS("Starting NGINX Ingress controller")

	n.store.Run(n.stopCh)

	// we need to use the defined ingress class to allow multiple leaders
	// in order to update information about ingress status
	// TODO: For now, as the the IngressClass logics has changed, is up to the
	// cluster admin to create different Leader Election IDs.
	// Should revisit this in a future

	if !n.cfg.DisableLeaderElection {
		electionID := n.cfg.ElectionID
		setupLeaderElection(&leaderElectionConfig{
			Client:     n.cfg.Client,
			ElectionID: electionID,
			OnStartedLeading: func(stopCh chan struct{}) {
				if n.syncStatus != nil {
					go n.syncStatus.Run(stopCh)
				}

				n.metricCollector.OnStartedLeading(electionID)
				// manually update SSL expiration metrics
				// (to not wait for a reload)
				n.metricCollector.SetSSLExpireTime(n.runningConfig.Servers)
				n.metricCollector.SetSSLInfo(n.runningConfig.Servers)
			},
			OnStoppedLeading: func() {
				n.metricCollector.OnStoppedLeading(electionID)
			},
		})
	}

	cmd := n.command.ExecCommand()

	// put NGINX in another process group to prevent it
	// to receive signals meant for the controller
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Setpgid: true,
		Pgid:    0,
	}

	if n.cfg.EnableSSLPassthrough {
		n.setupSSLProxy()
	}

	klog.InfoS("Starting NGINX process")
	n.start(cmd)

	go n.syncQueue.Run(time.Second, n.stopCh)
	// force initial sync
	n.syncQueue.EnqueueTask(task.GetDummyObject("initial-sync"))

	// In case of error the temporal configuration file will
	// be available up to five minutes after the error
	go func() {
		for {
			time.Sleep(5 * time.Minute)
			err := cleanTempNginxCfg()
			if err != nil {
				klog.ErrorS(err, "Unexpected error removing temporal configuration files")
			}
		}
	}()

	if n.validationWebhookServer != nil {
		klog.InfoS("Starting validation webhook", "address", n.validationWebhookServer.Addr,
			"certPath", n.cfg.ValidationWebhookCertPath, "keyPath", n.cfg.ValidationWebhookKeyPath)
		go func() {
			klog.ErrorS(n.validationWebhookServer.ListenAndServeTLS("", ""), "Error listening for TLS connections")
		}()
	}

	for {
		select {
		case err := <-n.ngxErrCh:
			if n.isShuttingDown {
				return
			}

			// if the nginx master process dies, the workers continue to process requests
			// until the failure of the configured livenessProbe and restart of the pod.
			if process.IsRespawnIfRequired(err) {
				return
			}

		case event := <-n.updateCh.Out():
			if n.isShuttingDown {
				break
			}

			if evt, ok := event.(store.Event); ok {
				klog.V(3).InfoS("Event received", "type", evt.Type, "object", evt.Obj)
				if evt.Type == store.ConfigurationEvent {
					// TODO: is this necessary? Consider removing this special case
					n.syncQueue.EnqueueTask(task.GetDummyObject("configmap-change"))
					continue
				}

				n.syncQueue.EnqueueSkippableTask(evt.Obj)
			} else {
				klog.Warningf("Unexpected event type received %T", event)
			}
		case <-n.stopCh:
			return
		}
	}
}

// Stop gracefully stops the NGINX master process.
func (n *NGINXController) Stop() error {
	n.isShuttingDown = true

	n.stopLock.Lock()
	defer n.stopLock.Unlock()

	if n.syncQueue.IsShuttingDown() {
		return fmt.Errorf("shutdown already in progress")
	}

	time.Sleep(time.Duration(n.cfg.ShutdownGracePeriod) * time.Second)

	klog.InfoS("Shutting down controller queues")
	close(n.stopCh)
	go n.syncQueue.Shutdown()
	if n.syncStatus != nil {
		n.syncStatus.Shutdown()
	}

	if n.validationWebhookServer != nil {
		klog.InfoS("Stopping admission controller")
		err := n.validationWebhookServer.Close()
		if err != nil {
			return err
		}
	}

	// send stop signal to NGINX
	klog.InfoS("Stopping NGINX process")
	cmd := n.command.ExecCommand("-s", "quit")
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	if err != nil {
		return err
	}

	// wait for the NGINX process to terminate
	timer := time.NewTicker(time.Second * 1)
	for range timer.C {
		if !nginx.IsRunning() {
			klog.InfoS("NGINX process has stopped")
			timer.Stop()
			break
		}
	}

	return nil
}

func (n *NGINXController) start(cmd *exec.Cmd) {
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Start(); err != nil {
		klog.Fatalf("NGINX error: %v", err)
		n.ngxErrCh <- err
		return
	}

	go func() {
		n.ngxErrCh <- cmd.Wait()
	}()
}

// DefaultEndpoint returns the default endpoint to be use as default server that returns 404.
func (n *NGINXController) DefaultEndpoint() ingress.Endpoint {
	return ingress.Endpoint{
		Address: "127.0.0.1",
		Port:    fmt.Sprintf("%v", n.cfg.ListenPorts.Default),
		Target:  &apiv1.ObjectReference{},
	}
}

// generateTemplate returns the nginx configuration file content
//
//nolint:gocritic // the cfg shouldn't be changed, and shouldn't be mutated by other processes while being rendered.
func (n *NGINXController) generateTemplate(cfg ngx_config.Configuration, ingressCfg ingress.Configuration) ([]byte, error) {
	if n.cfg.EnableSSLPassthrough {
		servers := []*tcpproxy.TCPServer{}
		for _, pb := range ingressCfg.PassthroughBackends {
			svc := pb.Service
			if svc == nil {
				klog.Warningf("Missing Service for SSL Passthrough backend %q", pb.Backend)
				continue
			}
			port, err := strconv.Atoi(pb.Port.String()) // #nosec
			if err != nil {
				for _, sp := range svc.Spec.Ports {
					if sp.Name == pb.Port.String() {
						port = int(sp.Port)
						break
					}
				}
			} else {
				for _, sp := range svc.Spec.Ports {
					//nolint:gosec // Ignore G109 error
					if sp.Port == int32(port) {
						port = int(sp.Port)
						break
					}
				}
			}

			// TODO: Allow PassthroughBackends to specify they support proxy-protocol
			servers = append(servers, &tcpproxy.TCPServer{
				Hostname:      pb.Hostname,
				IP:            svc.Spec.ClusterIP,
				Port:          port,
				ProxyProtocol: false,
			})
		}

		n.Proxy.ServerList = servers
	}

	// NGINX cannot resize the hash tables used to store server names. For
	// this reason we check if the current size is correct for the host
	// names defined in the Ingress rules and adjust the value if
	// necessary.
	// https://trac.nginx.org/nginx/ticket/352
	// https://trac.nginx.org/nginx/ticket/631
	var longestName int
	var serverNameBytes int

	for _, srv := range ingressCfg.Servers {
		hostnameLength := len(srv.Hostname)
		if srv.RedirectFromToWWW {
			hostnameLength += 4
		}
		if longestName < hostnameLength {
			longestName = hostnameLength
		}

		for _, alias := range srv.Aliases {
			if longestName < len(alias) {
				longestName = len(alias)
			}
		}

		serverNameBytes += hostnameLength
	}

	nameHashBucketSize := nginxHashBucketSize(longestName)
	if cfg.ServerNameHashBucketSize < nameHashBucketSize {
		klog.V(3).InfoS("Adjusting ServerNameHashBucketSize variable", "value", nameHashBucketSize)
		cfg.ServerNameHashBucketSize = nameHashBucketSize
	}

	serverNameHashMaxSize := nextPowerOf2(serverNameBytes)
	if cfg.ServerNameHashMaxSize < serverNameHashMaxSize {
		klog.V(3).InfoS("Adjusting ServerNameHashMaxSize variable", "value", serverNameHashMaxSize)
		cfg.ServerNameHashMaxSize = serverNameHashMaxSize
	}

	if cfg.MaxWorkerOpenFiles == 0 {
		// the limit of open files is per worker process
		// and we leave some room to avoid consuming all the FDs available
		maxOpenFiles := rlimitMaxNumFiles() - 1024
		klog.V(3).InfoS("Maximum number of open file descriptors", "value", maxOpenFiles)
		if maxOpenFiles < 1024 {
			// this means the value of RLIMIT_NOFILE is too low.
			maxOpenFiles = 1024
		}
		klog.V(3).InfoS("Adjusting MaxWorkerOpenFiles variable", "value", maxOpenFiles)
		cfg.MaxWorkerOpenFiles = maxOpenFiles
	}

	if cfg.MaxWorkerConnections == 0 {
		maxWorkerConnections := int(float64(cfg.MaxWorkerOpenFiles * 3.0 / 4))
		klog.V(3).InfoS("Adjusting MaxWorkerConnections variable", "value", maxWorkerConnections)
		cfg.MaxWorkerConnections = maxWorkerConnections
	}

	setHeaders := map[string]string{}
	if cfg.ProxySetHeaders != "" {
		cmap, err := n.store.GetConfigMap(cfg.ProxySetHeaders)
		if err != nil {
			klog.Warningf("Error reading ConfigMap %q from local store: %v", cfg.ProxySetHeaders, err)
		} else {
			setHeaders = cmap.Data
		}
	}

	addHeaders := map[string]string{}
	if cfg.AddHeaders != "" {
		cmap, err := n.store.GetConfigMap(cfg.AddHeaders)
		if err != nil {
			klog.Warningf("Error reading ConfigMap %q from local store: %v", cfg.AddHeaders, err)
		} else {
			addHeaders = cmap.Data
		}
	}

	sslDHParam := ""
	if cfg.SSLDHParam != "" {
		secretName := cfg.SSLDHParam

		secret, err := n.store.GetSecret(secretName)
		if err != nil {
			klog.Warningf("Error reading Secret %q from local store: %v", secretName, err)
		} else {
			nsSecName := strings.ReplaceAll(secretName, "/", "-")
			dh, ok := secret.Data["dhparam.pem"]
			if ok {
				pemFileName, err := ssl.AddOrUpdateDHParam(nsSecName, dh)
				if err != nil {
					klog.Warningf("Error adding or updating dhparam file %v: %v", nsSecName, err)
				} else {
					sslDHParam = pemFileName
				}
			}
		}
	}

	cfg.SSLDHParam = sslDHParam

	cfg.DefaultSSLCertificate = n.getDefaultSSLCertificate()

	if n.cfg.IsChroot {
		if cfg.AccessLogPath == "/var/log/nginx/access.log" {
			cfg.AccessLogPath = fmt.Sprintf("syslog:server=%s", n.cfg.InternalLoggerAddress)
		}
		if cfg.ErrorLogPath == "/var/log/nginx/error.log" {
			cfg.ErrorLogPath = fmt.Sprintf("syslog:server=%s", n.cfg.InternalLoggerAddress)
		}
	}

	tc := &ngx_config.TemplateConfig{
		ProxySetHeaders:          setHeaders,
		AddHeaders:               addHeaders,
		BacklogSize:              sysctlSomaxconn(),
		Backends:                 ingressCfg.Backends,
		PassthroughBackends:      ingressCfg.PassthroughBackends,
		Servers:                  ingressCfg.Servers,
		TCPBackends:              ingressCfg.TCPEndpoints,
		UDPBackends:              ingressCfg.UDPEndpoints,
		Cfg:                      cfg,
		IsIPV6Enabled:            n.isIPV6Enabled && !cfg.DisableIpv6,
		NginxStatusIpv4Whitelist: cfg.NginxStatusIpv4Whitelist,
		NginxStatusIpv6Whitelist: cfg.NginxStatusIpv6Whitelist,
		RedirectServers:          utilingress.BuildRedirects(ingressCfg.Servers),
		IsSSLPassthroughEnabled:  n.cfg.EnableSSLPassthrough,
		ListenPorts:              n.cfg.ListenPorts,
		EnableMetrics:            n.cfg.EnableMetrics,
		MaxmindEditionFiles:      n.cfg.MaxmindEditionFiles,
		HealthzURI:               nginx.HealthPath,
		MonitorMaxBatchSize:      n.cfg.MonitorMaxBatchSize,
		PID:                      nginx.PID,
		StatusPath:               nginx.StatusPath,
		StatusPort:               nginx.StatusPort,
		StreamPort:               nginx.StreamPort,
		StreamSnippets:           append(ingressCfg.StreamSnippets, cfg.StreamSnippet),
	}

	tc.Cfg.Checksum = ingressCfg.ConfigurationChecksum

	return n.t.Write(tc)
}

// testTemplate checks if the NGINX configuration inside the byte array is valid
// running the command "nginx -t" using a temporal file.
func (n *NGINXController) testTemplate(cfg []byte) error {
	if len(cfg) == 0 {
		return fmt.Errorf("invalid NGINX configuration (empty)")
	}
	tmpDir := os.TempDir() + "/nginx"
	tmpfile, err := os.CreateTemp(tmpDir, tempNginxPattern)
	if err != nil {
		return err
	}
	defer tmpfile.Close()
	err = os.WriteFile(tmpfile.Name(), cfg, file.ReadWriteByUser)
	if err != nil {
		return err
	}
	out, err := n.command.Test(tmpfile.Name())
	if err != nil {
		// this error is different from the rest because it must be clear why nginx is not working
		oe := fmt.Sprintf(`
-------------------------------------------------------------------------------
Error: %v
%v
-------------------------------------------------------------------------------
`, err, string(out))

		return errors.New(oe)
	}

	os.Remove(tmpfile.Name())
	return nil
}

// OnUpdate is called by the synchronization loop whenever configuration
// changes were detected. The received backend Configuration is merged with the
// configuration ConfigMap before generating the final configuration file.
// Returns nil in case the backend was successfully reloaded.
//
//nolint:gocritic // the cfg shouldn't be changed, and shouldn't be mutated by other processes while being rendered.
func (n *NGINXController) OnUpdate(ingressCfg ingress.Configuration) error {
	cfg := n.store.GetBackendConfiguration()
	cfg.Resolver = n.resolver

	content, err := n.generateTemplate(cfg, ingressCfg)
	if err != nil {
		return err
	}

	err = createOpentelemetryCfg(&cfg)
	if err != nil {
		return err
	}

	err = n.testTemplate(content)
	if err != nil {
		return err
	}

	if klog.V(2).Enabled() {
		src, err := os.ReadFile(cfgPath)
		if err != nil {
			return err
		}
		if !bytes.Equal(src, content) {
			tmpfile, err := os.CreateTemp("", "new-nginx-cfg")
			if err != nil {
				return err
			}
			defer tmpfile.Close()
			err = os.WriteFile(tmpfile.Name(), content, file.ReadWriteByUser)
			if err != nil {
				return err
			}
			//nolint:gosec //Ignore G204 error
			diffOutput, err := exec.Command("diff", "-I", "'# Configuration.*'", "-u", cfgPath, tmpfile.Name()).CombinedOutput()
			if err != nil {
				if exitError, ok := err.(*exec.ExitError); ok {
					ws, ok := exitError.Sys().(syscall.WaitStatus)
					if !ok {
						klog.Errorf("unexpected type: %T", exitError.Sys())
					}
					if ws.ExitStatus() == 2 {
						klog.Warningf("Failed to executing diff command: %v", err)
					}
				}
			}

			klog.InfoS("NGINX configuration change", "diff", string(diffOutput))

			// we do not defer the deletion of temp files in order
			// to keep them around for inspection in case of error
			os.Remove(tmpfile.Name())
		}
	}

	err = os.WriteFile(cfgPath, content, file.ReadWriteByUser)
	if err != nil {
		return err
	}

	o, err := n.command.ExecCommand("-s", "reload").CombinedOutput()
	if err != nil {
		return fmt.Errorf("%v\n%v", err, string(o))
	}

	return nil
}

// nginxHashBucketSize computes the correct NGINX hash_bucket_size for a hash
// with the given longest key.
func nginxHashBucketSize(longestString int) int {
	// see https://github.com/kubernetes/ingress-nginxs/issues/623 for an explanation
	wordSize := 8 // Assume 64 bit CPU
	n := longestString + 2
	aligned := (n + wordSize - 1) & ^(wordSize - 1)
	rawSize := wordSize + wordSize + aligned
	return nextPowerOf2(rawSize)
}

// http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
// https://play.golang.org/p/TVSyCcdxUh
func nextPowerOf2(v int) int {
	v--
	v |= v >> 1
	v |= v >> 2
	v |= v >> 4
	v |= v >> 8
	v |= v >> 16
	v++

	return v
}

func (n *NGINXController) setupSSLProxy() {
	cfg := n.store.GetBackendConfiguration()
	sslPort := n.cfg.ListenPorts.HTTPS
	proxyPort := n.cfg.ListenPorts.SSLProxy

	klog.InfoS("Starting TLS proxy for SSL Passthrough")
	n.Proxy = &tcpproxy.TCPProxy{
		Default: &tcpproxy.TCPServer{
			Hostname:      "localhost",
			IP:            "127.0.0.1",
			Port:          proxyPort,
			ProxyProtocol: true,
		},
	}

	listener, err := net.Listen("tcp", fmt.Sprintf(":%v", sslPort))
	if err != nil {
		klog.Fatalf("%v", err)
	}

	proxyList := &proxyproto.Listener{Listener: listener, ProxyHeaderTimeout: cfg.ProxyProtocolHeaderTimeout}

	// accept TCP connections on the configured HTTPS port
	go func() {
		for {
			var conn net.Conn
			var err error

			if n.store.GetBackendConfiguration().UseProxyProtocol {
				// wrap the listener in order to decode Proxy
				// Protocol before handling the connection
				conn, err = proxyList.Accept()
			} else {
				conn, err = listener.Accept()
			}

			if err != nil {
				klog.Warningf("Error accepting TCP connection: %v", err)
				continue
			}

			klog.V(3).InfoS("Handling TCP connection", "remote", conn.RemoteAddr(), "local", conn.LocalAddr())
			go n.Proxy.Handle(conn)
		}
	}()
}

// configureDynamically encodes new Backends in JSON format and POSTs the
// payload to an internal HTTP endpoint handled by Lua.
func (n *NGINXController) configureDynamically(pcfg *ingress.Configuration) error {
	backendsChanged := !reflect.DeepEqual(n.runningConfig.Backends, pcfg.Backends)
	if backendsChanged {
		err := configureBackends(pcfg.Backends)
		if err != nil {
			return err
		}
	}

	streamConfigurationChanged := !reflect.DeepEqual(n.runningConfig.TCPEndpoints, pcfg.TCPEndpoints) || !reflect.DeepEqual(n.runningConfig.UDPEndpoints, pcfg.UDPEndpoints)
	if streamConfigurationChanged {
		err := updateStreamConfiguration(pcfg.TCPEndpoints, pcfg.UDPEndpoints)
		if err != nil {
			return err
		}
	}

	serversChanged := !reflect.DeepEqual(n.runningConfig.Servers, pcfg.Servers)
	if serversChanged {
		err := configureCertificates(pcfg.Servers)
		if err != nil {
			return err
		}
	}

	return nil
}

func updateStreamConfiguration(tcpEndpoints, udpEndpoints []ingress.L4Service) error {
	streams := make([]ingress.Backend, 0)
	for i := range tcpEndpoints {
		ep := &tcpEndpoints[i]
		var service *apiv1.Service
		if ep.Service != nil {
			service = &apiv1.Service{Spec: ep.Service.Spec}
		}

		key := fmt.Sprintf("tcp-%v-%v-%v", ep.Backend.Namespace, ep.Backend.Name, ep.Backend.Port.String())
		streams = append(streams, ingress.Backend{
			Name:      key,
			Endpoints: ep.Endpoints,
			Port:      intstr.FromInt(ep.Port),
			Service:   service,
		})
	}
	for i := range udpEndpoints {
		ep := &udpEndpoints[i]
		var service *apiv1.Service
		if ep.Service != nil {
			service = &apiv1.Service{Spec: ep.Service.Spec}
		}

		key := fmt.Sprintf("udp-%v-%v-%v", ep.Backend.Namespace, ep.Backend.Name, ep.Backend.Port.String())
		streams = append(streams, ingress.Backend{
			Name:      key,
			Endpoints: ep.Endpoints,
			Port:      intstr.FromInt(ep.Port),
			Service:   service,
		})
	}

	buf, err := json.Marshal(streams)
	if err != nil {
		return err
	}

	hostPort := net.JoinHostPort("127.0.0.1", fmt.Sprintf("%v", nginx.StreamPort))
	conn, err := net.Dial("tcp", hostPort)
	if err != nil {
		return err
	}
	defer conn.Close()

	_, err = conn.Write(buf)
	if err != nil {
		return err
	}
	_, err = fmt.Fprintf(conn, "\r\n")
	if err != nil {
		return err
	}

	return nil
}

func configureBackends(rawBackends []*ingress.Backend) error {
	backends := make([]*ingress.Backend, len(rawBackends))

	for i, backend := range rawBackends {
		var service *apiv1.Service
		if backend.Service != nil {
			service = &apiv1.Service{Spec: backend.Service.Spec}
		}
		luaBackend := &ingress.Backend{
			Name:                 backend.Name,
			Port:                 backend.Port,
			SSLPassthrough:       backend.SSLPassthrough,
			SessionAffinity:      backend.SessionAffinity,
			UpstreamHashBy:       backend.UpstreamHashBy,
			LoadBalancing:        backend.LoadBalancing,
			Service:              service,
			NoServer:             backend.NoServer,
			TrafficShapingPolicy: backend.TrafficShapingPolicy,
			AlternativeBackends:  backend.AlternativeBackends,
		}

		var endpoints []ingress.Endpoint
		for _, endpoint := range backend.Endpoints {
			endpoints = append(endpoints, ingress.Endpoint{
				Address: endpoint.Address,
				Port:    endpoint.Port,
			})
		}

		luaBackend.Endpoints = endpoints
		backends[i] = luaBackend
	}

	statusCode, _, err := nginx.NewPostStatusRequest("/configuration/backends", "application/json", backends)
	if err != nil {
		return err
	}

	if statusCode != http.StatusCreated {
		return fmt.Errorf("unexpected error code: %d", statusCode)
	}

	return nil
}

type sslConfiguration struct {
	Certificates map[string]string `json:"certificates"`
	Servers      map[string]string `json:"servers"`
}

// configureCertificates JSON encodes certificates and POSTs it to an internal HTTP endpoint
// that is handled by Lua
func configureCertificates(rawServers []*ingress.Server) error {
	configuration := &sslConfiguration{
		Certificates: map[string]string{},
		Servers:      map[string]string{},
	}

	configure := func(hostname string, sslCert *ingress.SSLCert) {
		uid := emptyUID

		if sslCert != nil {
			uid = sslCert.UID

			if _, ok := configuration.Certificates[uid]; !ok {
				configuration.Certificates[uid] = sslCert.PemCertKey
			}
		}

		configuration.Servers[hostname] = uid
	}

	for _, rawServer := range rawServers {
		configure(rawServer.Hostname, rawServer.SSLCert)

		for _, alias := range rawServer.Aliases {
			if rawServer.SSLCert != nil && ssl.IsValidHostname(alias, rawServer.SSLCert.CN) {
				configuration.Servers[alias] = rawServer.SSLCert.UID
			} else {
				configuration.Servers[alias] = emptyUID
			}
		}
	}

	redirects := utilingress.BuildRedirects(rawServers)
	for _, redirect := range redirects {
		configure(redirect.From, redirect.SSLCert)
	}

	statusCode, _, err := nginx.NewPostStatusRequest("/configuration/servers", "application/json", configuration)
	if err != nil {
		return err
	}

	if statusCode != http.StatusCreated {
		return fmt.Errorf("unexpected error code: %d", statusCode)
	}

	return nil
}

const otelTmpl = `
exporter = "otlp"
processor = "batch"

[exporters.otlp]
# Alternatively the OTEL_EXPORTER_OTLP_ENDPOINT environment variable can also be used.
host = "{{ .OtlpCollectorHost }}"
port = {{ .OtlpCollectorPort }}

[processors.batch]
max_queue_size = {{ .OtelMaxQueueSize }}
schedule_delay_millis = {{ .OtelScheduleDelayMillis }}
max_export_batch_size = {{ .OtelMaxExportBatchSize }}

[service]
name = "{{ .OtelServiceName }}" # Opentelemetry resource name

[sampler]
name = "{{ .OtelSampler }}" # Also: AlwaysOff, TraceIdRatioBased
ratio = {{ .OtelSamplerRatio }}
parent_based = {{ .OtelSamplerParentBased }}
`

func createOpentelemetryCfg(cfg *ngx_config.Configuration) error {
	tmpl, err := template.New("otel").Parse(otelTmpl)
	if err != nil {
		return err
	}
	tmplBuf := bytes.NewBuffer(make([]byte, 0))
	err = tmpl.Execute(tmplBuf, cfg)
	if err != nil {
		return err
	}

	return os.WriteFile(cfg.OpentelemetryConfig, tmplBuf.Bytes(), file.ReadWriteByUser)
}

func cleanTempNginxCfg() error {
	var files []string

	err := filepath.Walk(os.TempDir(), func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() && os.TempDir() != path {
			return filepath.SkipDir
		}

		dur, err := time.ParseDuration("-5m")
		if err != nil {
			return err
		}
		fiveMinutesAgo := time.Now().Add(dur)
		if strings.HasPrefix(info.Name(), tempNginxPattern) && info.ModTime().Before(fiveMinutesAgo) {
			files = append(files, path)
		}
		return nil
	})
	if err != nil {
		return err
	}

	for _, file := range files {
		err := os.Remove(file)
		if err != nil {
			return err
		}
	}

	return nil
}