package controller

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

	"github.com/spf13/cobra"
	"k8s.io/cli-runtime/pkg/genericclioptions"
	"k8s.io/klog/v2"

	mkscontroller "example.com/monok8s/pkg/controller"
	osupgradectrl "example.com/monok8s/pkg/controller/osupgrade"
	"example.com/monok8s/pkg/kube"
)

type ServerConfig struct {
	Namespace         string `json:"namespace,omitempty"`
	TLSCertFile       string `json:"tlsCertFile,omitempty"`
	TLSPrivateKeyFile string `json:"tlsPrivateKeyFile,omitempty"`
}

func NewCmdController(flags *genericclioptions.ConfigFlags) *cobra.Command {
	var conf ServerConfig

	cmd := &cobra.Command{
		Use:   "controller",
		Short: "Start a controller that handles OSUpgrade resources",
		RunE: func(cmd *cobra.Command, _ []string) error {
			ns, _, err := flags.ToRawKubeConfigLoader().Namespace()
			if err != nil {
				return err
			}
			conf.Namespace = ns

			ctx := cmd.Context()

			klog.InfoS("starting controller", "namespace", conf.Namespace)

			clients, err := kube.NewClients(flags)
			if err != nil {
				return err
			}

			ctx, cancel := context.WithCancel(ctx)
			defer cancel()

			httpErrCh := make(chan error, 1)
			watchErrCh := make(chan error, 1)

			go func() {
				klog.InfoS("starting OSUpgrade watch loop", "namespace", conf.Namespace)
				watchErrCh <- osupgradectrl.Watch(ctx, clients, conf.Namespace)
			}()

			go func() {
				httpErrCh <- listenAndServe(ctx, clients, conf)
			}()

			select {
			case <-ctx.Done():
				klog.InfoS("controller context canceled")
				return ctx.Err()

			case err := <-watchErrCh:
				if err != nil && !errors.Is(err, context.Canceled) {
					cancel()
					return err
				}
				cancel()
				return nil

			case err := <-httpErrCh:
				if err != nil && !errors.Is(err, context.Canceled) {
					cancel()
					return err
				}
				cancel()
				return nil
			}
		},
	}

	cmd.Flags().StringVar(&conf.TLSCertFile, "tls-cert-file", conf.TLSCertFile,
		"File containing x509 Certificate used for serving HTTPS (with intermediate certs, if any, concatenated after server cert).")
	cmd.Flags().StringVar(&conf.TLSPrivateKeyFile, "tls-private-key-file", conf.TLSPrivateKeyFile,
		"File containing x509 private key matching --tls-cert-file.")

	return cmd
}

func listenAndServe(ctx context.Context, clients *kube.Clients, conf ServerConfig) error {
	nodeName := os.Getenv("NODE_NAME")

	controllerServer := mkscontroller.NewServer(ctx, clients, conf.Namespace, nodeName)

	healthMux := http.NewServeMux()
	healthMux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("ok\n"))
	})
	healthMux.HandleFunc("/readyz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("ok\n"))
	})

	healthAddr := net.JoinHostPort("", "8080")
	controllerAddr := net.JoinHostPort("", "8443")

	healthHTTPServer := &http.Server{
		Addr:           healthAddr,
		Handler:        healthMux,
		IdleTimeout:    90 * time.Second,
		ReadTimeout:    10 * time.Second,
		WriteTimeout:   10 * time.Second,
		MaxHeaderBytes: 1 << 20,
	}

	controllerHTTPServer := &http.Server{
		Addr:           controllerAddr,
		Handler:        controllerServer,
		IdleTimeout:    90 * time.Second,
		ReadTimeout:    4 * time.Minute,
		WriteTimeout:   4 * time.Minute,
		MaxHeaderBytes: 1 << 20,
	}

	serverErrCh := make(chan error, 2)

	go func() {
		klog.InfoS("starting health HTTP server", "addr", healthAddr)

		err := healthHTTPServer.ListenAndServe()
		if err != nil && !errors.Is(err, http.ErrServerClosed) {
			serverErrCh <- fmt.Errorf("health HTTP server: %w", err)
			return
		}

		serverErrCh <- nil
	}()

	go func() {
		if conf.TLSCertFile != "" {
			klog.InfoS("starting controller HTTPS server",
				"addr", controllerAddr,
				"certFile", conf.TLSCertFile,
				"keyFile", conf.TLSPrivateKeyFile,
			)

			err := controllerHTTPServer.ListenAndServeTLS(conf.TLSCertFile, conf.TLSPrivateKeyFile)
			if err != nil && !errors.Is(err, http.ErrServerClosed) {
				serverErrCh <- fmt.Errorf("controller HTTPS server: %w", err)
				return
			}

			serverErrCh <- nil
			return
		}

		klog.InfoS("starting controller HTTP server", "addr", controllerAddr)

		err := controllerHTTPServer.ListenAndServe()
		if err != nil && !errors.Is(err, http.ErrServerClosed) {
			serverErrCh <- fmt.Errorf("controller HTTP server: %w", err)
			return
		}

		serverErrCh <- nil
	}()

	select {
	case <-ctx.Done():
		klog.InfoS("shutting down HTTP servers",
			"healthAddr", healthAddr,
			"controllerAddr", controllerAddr,
		)

		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()

		var errs []error

		if err := healthHTTPServer.Shutdown(shutdownCtx); err != nil {
			errs = append(errs, fmt.Errorf("shutdown health HTTP server: %w", err))
		}

		if err := controllerHTTPServer.Shutdown(shutdownCtx); err != nil {
			errs = append(errs, fmt.Errorf("shutdown controller HTTP server: %w", err))
		}

		for i := 0; i < 2; i++ {
			if err := <-serverErrCh; err != nil {
				errs = append(errs, err)
			}
		}

		if len(errs) > 0 {
			return errors.Join(errs...)
		}

		return context.Canceled

	case err := <-serverErrCh:
		if err != nil {
			klog.ErrorS(err, "HTTP server failed")
			return err
		}

		// One server exited cleanly unexpectedly. Treat that as failure because
		// the process should keep both servers alive until ctx is canceled.
		return fmt.Errorf("HTTP server exited unexpectedly")
	}
}