package k8s

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"net"
	"strings"
	"sync"
	"syscall"
	"time"

	corev1 "k8s.io/api/core/v1"
	k8serrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/resource"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/util/rand"
	"k8s.io/client-go/kubernetes"
	restclient "k8s.io/client-go/rest"
	k8sclientcmd "k8s.io/client-go/tools/clientcmd"
)

func GetPersistentVolumeClaim(ctx context.Context, name, namespaceOverride string) (*corev1.PersistentVolumeClaim, error) {
	client, namespace, err := NewClientAndResolvedNamespace(namespaceOverride)
	if err != nil {
		return nil, err
	}

	return client.CoreV1().PersistentVolumeClaims(namespace).Get(ctx, name, metav1.GetOptions{})
}

func CreatePersistentVolumeClaim(ctx context.Context, name, namespaceOverride string, labels map[string]string, annotations map[string]string, accessMode corev1.PersistentVolumeAccessMode, resourceRequest resource.Quantity, storageClassName string) (err error) {
	client, namespace, err := NewClientAndResolvedNamespace(namespaceOverride)
	if err != nil {
		return
	}

	pvc := &corev1.PersistentVolumeClaim{
		ObjectMeta: metav1.ObjectMeta{
			Name:        name,
			Namespace:   namespace,
			Labels:      labels,
			Annotations: annotations,
		},
		Spec: corev1.PersistentVolumeClaimSpec{
			AccessModes: []corev1.PersistentVolumeAccessMode{accessMode},
			Resources: corev1.VolumeResourceRequirements{
				Requests: corev1.ResourceList{},
			},
		},
	}

	pvc.Spec.Resources.Requests[corev1.ResourceStorage] = resourceRequest

	if storageClassName != "" {
		pvc.Spec.StorageClassName = &storageClassName
	}

	_, err = client.CoreV1().PersistentVolumeClaims(namespace).Create(ctx, pvc, metav1.CreateOptions{})
	return
}

func DeletePersistentVolumeClaims(ctx context.Context, namespaceOverride string, listOptions metav1.ListOptions) (err error) {
	client, namespace, err := NewClientAndResolvedNamespace(namespaceOverride)
	if err != nil {
		return
	}

	return client.CoreV1().PersistentVolumeClaims(namespace).DeleteCollection(ctx, metav1.DeleteOptions{}, listOptions)
}

var TarImage = "ghcr.io/knative/func-utils:v2"

// UploadToVolume uploads files (passed in form of tar stream) into volume.
func UploadToVolume(ctx context.Context, content io.Reader, claimName, namespace string) error {
	return runWithVolumeMounted(ctx, TarImage, []string{"sh", "-c", "umask 0000 && exec tar -xmf -"}, content, claimName, namespace)
}

// Runs a pod with given image, command and stdin
// while having the volume mounted and working directory set to it.
func runWithVolumeMounted(ctx context.Context, podImage string, podCommand []string, podInput io.Reader, claimName, namespace string) error {
	var err error

	cliConf := GetClientConfig()
	restConf, err := cliConf.ClientConfig()
	if err != nil {
		return fmt.Errorf("cannot get client config: %w", err)
	}
	restConf.WarningHandler = restclient.NoWarnings{}

	err = setConfigDefaults(restConf)
	if err != nil {
		return fmt.Errorf("cannot set config defaults: %w", err)
	}

	client, err := kubernetes.NewForConfig(restConf)
	if err != nil {
		return fmt.Errorf("cannot create k8s client: %w", err)
	}

	if namespace == "" {
		namespace, err = GetDefaultNamespace()
		if err != nil {
			return fmt.Errorf("cannot get namespace: %w", err)
		}
	}

	podName := "volume-uploader-" + rand.String(5)

	pods := client.CoreV1().Pods(namespace)

	defer func() {
		_ = pods.Delete(ctx, podName, metav1.DeleteOptions{})
	}()

	const volumeMntPoint = "/tmp/volume_mnt"
	const pVol = "p-vol"
	pod := &corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{
			Name:        podName,
			Labels:      nil,
			Annotations: nil,
		},
		Spec: corev1.PodSpec{
			SecurityContext: defaultPodSecurityContext(),
			Containers: []corev1.Container{
				{
					Name:       podName,
					Image:      podImage,
					Stdin:      true,
					StdinOnce:  true,
					WorkingDir: volumeMntPoint,
					Command:    podCommand,
					VolumeMounts: []corev1.VolumeMount{
						{
							Name:      pVol,
							MountPath: volumeMntPoint,
						},
					},
					SecurityContext: defaultSecurityContext(client),
				},
			},
			Volumes: []corev1.Volume{{
				Name: pVol,
				VolumeSource: corev1.VolumeSource{
					PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
						ClaimName: claimName,
					},
				},
			}},
			DNSPolicy:     corev1.DNSClusterFirst,
			RestartPolicy: corev1.RestartPolicyNever,
		},
	}

	localCtx, cancel := context.WithCancel(ctx)
	defer cancel()
	ready := podReady(localCtx, client.CoreV1(), podName, namespace)

	_, err = pods.Create(ctx, pod, metav1.CreateOptions{})
	if err != nil {
		return fmt.Errorf("cannot create pod: %w", err)
	}

	select {
	case err = <-ready:
	case <-ctx.Done():
		err = ctx.Err()
	case <-time.After(time.Minute * 5):
		err = errors.New("timeout waiting for pod to start")
	}

	if err != nil {
		return fmt.Errorf("cannot start the pod: %w", err)
	}

	nameSelector := fields.OneTermEqualSelector("metadata.name", podName).String()
	listOpts := metav1.ListOptions{
		FieldSelector: nameSelector,
		Watch:         true,
	}
	watcher, err := pods.Watch(localCtx, listOpts)
	if err != nil {
		return fmt.Errorf("cannot set up the watcher: %w", err)
	}
	defer watcher.Stop()
	termCh := make(chan corev1.ContainerStateTerminated, 1)
	go func() {
		for event := range watcher.ResultChan() {
			p, ok := event.Object.(*corev1.Pod)
			if !ok {
				continue
			}
			if len(p.Status.ContainerStatuses) > 0 {
				termState := event.Object.(*corev1.Pod).Status.ContainerStatuses[0].State.Terminated
				if termState != nil {
					termCh <- *termState
					break
				}
			}
		}
	}()

	var outBuff tsBuff
	err = attach(ctx, client.CoreV1().RESTClient(), restConf, podName, namespace, podInput, &outBuff, &outBuff)
	if err != nil {
		return fmt.Errorf("cannot attach stdio to the pod: %w", err)
	}

	termState := <-termCh
	if termState.ExitCode != 0 {
		cmdOut := strings.Trim(outBuff.String(), "\n")
		err = fmt.Errorf("the command failed: exitcode=%d, out=%q", termState.ExitCode, cmdOut)
	}

	return err
}

// thread safe buffer for logging
type tsBuff struct {
	buff bytes.Buffer
	mu   sync.Mutex
}

func (t *tsBuff) String() string {
	t.mu.Lock()
	defer t.mu.Unlock()
	return t.buff.String()
}

func (t *tsBuff) Write(p []byte) (n int, err error) {
	t.mu.Lock()
	defer t.mu.Unlock()
	return t.buff.Write(p)
}

// ListPersistentVolumeClaimsNamesIfConnected lists names of PersistentVolumeClaims present and the current k8s context
// returns empty list, if not connected to any cluster
func ListPersistentVolumeClaimsNamesIfConnected(ctx context.Context, namespaceOverride string) (names []string, err error) {
	names, err = listPersistentVolumeClaimsNames(ctx, namespaceOverride)
	if err != nil {
		// not logged our authorized to access resources
		if k8serrors.IsForbidden(err) || k8serrors.IsUnauthorized(err) || k8serrors.IsInvalid(err) || k8serrors.IsTimeout(err) {
			return []string{}, nil
		}

		// non existent k8s cluster
		var dnsErr *net.DNSError
		if errors.As(err, &dnsErr) {
			if dnsErr.IsNotFound || dnsErr.IsTemporary || dnsErr.IsTimeout {
				return []string{}, nil
			}
		}

		// connection refused
		if errors.Is(err, syscall.ECONNREFUSED) {
			return []string{}, nil
		}

		// invalid configuration: no configuration has been provided
		if k8sclientcmd.IsEmptyConfig(err) {
			return []string{}, nil
		}
	}

	return
}

func listPersistentVolumeClaimsNames(ctx context.Context, namespaceOverride string) (names []string, err error) {
	client, namespace, err := NewClientAndResolvedNamespace(namespaceOverride)
	if err != nil {
		return
	}

	pvcs, err := client.CoreV1().PersistentVolumeClaims(namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return
	}

	for _, pv := range pvcs.Items {
		names = append(names, pv.Name)
	}

	return
}