package kubernetes

import (
	"bytes"
	"compress/gzip"
	"crypto/md5"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"strings"

	"github.com/hashicorp/terraform/state"
	"github.com/hashicorp/terraform/state/remote"
	k8serrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/util/validation"
	"k8s.io/client-go/dynamic"
	"k8s.io/utils/pointer"

	coordinationv1 "k8s.io/api/coordination/v1"
	coordinationclientv1 "k8s.io/client-go/kubernetes/typed/coordination/v1"
)

const (
	tfstateKey                = "tfstate"
	tfstateSecretSuffixKey    = "tfstateSecretSuffix"
	tfstateWorkspaceKey       = "tfstateWorkspace"
	tfstateLockInfoAnnotation = "app.terraform.io/lock-info"
	managedByKey              = "app.kubernetes.io/managed-by"
)

type RemoteClient struct {
	kubernetesSecretClient dynamic.ResourceInterface
	kubernetesLeaseClient  coordinationclientv1.LeaseInterface
	namespace              string
	labels                 map[string]string
	nameSuffix             string
	workspace              string
}

func (c *RemoteClient) Get() (payload *remote.Payload, err error) {
	secretName, err := c.createSecretName()
	if err != nil {
		return nil, err
	}
	secret, err := c.kubernetesSecretClient.Get(secretName, metav1.GetOptions{})
	if err != nil {
		if k8serrors.IsNotFound(err) {
			return nil, nil
		}
		return nil, err
	}

	secretData := getSecretData(secret)
	stateRaw, ok := secretData[tfstateKey]
	if !ok {
		// The secret exists but there is no state in it
		return nil, nil
	}

	stateRawString := stateRaw.(string)

	state, err := uncompressState(stateRawString)
	if err != nil {
		return nil, err
	}

	md5 := md5.Sum(state)

	p := &remote.Payload{
		Data: state,
		MD5:  md5[:],
	}
	return p, nil
}

func (c *RemoteClient) Put(data []byte) error {
	secretName, err := c.createSecretName()
	if err != nil {
		return err
	}

	payload, err := compressState(data)
	if err != nil {
		return err
	}

	secret, err := c.getSecret(secretName)
	if err != nil {
		if !k8serrors.IsNotFound(err) {
			return err
		}

		secret = &unstructured.Unstructured{
			Object: map[string]interface{}{
				"metadata": metav1.ObjectMeta{
					Name:        secretName,
					Namespace:   c.namespace,
					Labels:      c.getLabels(),
					Annotations: map[string]string{"encoding": "gzip"},
				},
			},
		}

		secret, err = c.kubernetesSecretClient.Create(secret, metav1.CreateOptions{})
		if err != nil {
			return err
		}
	}

	setState(secret, payload)
	_, err = c.kubernetesSecretClient.Update(secret, metav1.UpdateOptions{})
	return err
}

// Delete the state secret
func (c *RemoteClient) Delete() error {
	secretName, err := c.createSecretName()
	if err != nil {
		return err
	}

	err = c.deleteSecret(secretName)
	if err != nil {
		if !k8serrors.IsNotFound(err) {
			return err
		}
	}

	leaseName, err := c.createLeaseName()
	if err != nil {
		return err
	}

	err = c.deleteLease(leaseName)
	if err != nil {
		if !k8serrors.IsNotFound(err) {
			return err
		}
	}
	return nil
}

func (c *RemoteClient) Lock(info *state.LockInfo) (string, error) {
	leaseName, err := c.createLeaseName()
	if err != nil {
		return "", err
	}

	lease, err := c.getLease(leaseName)
	if err != nil {
		if !k8serrors.IsNotFound(err) {
			return "", err
		}

		labels := c.getLabels()
		lease = &coordinationv1.Lease{
			ObjectMeta: metav1.ObjectMeta{
				Name:   leaseName,
				Labels: labels,
				Annotations: map[string]string{
					tfstateLockInfoAnnotation: string(info.Marshal()),
				},
			},
			Spec: coordinationv1.LeaseSpec{
				HolderIdentity: pointer.StringPtr(info.ID),
			},
		}

		_, err = c.kubernetesLeaseClient.Create(lease)
		if err != nil {
			return "", err
		} else {
			return info.ID, nil
		}
	}

	if lease.Spec.HolderIdentity != nil {
		if *lease.Spec.HolderIdentity == info.ID {
			return info.ID, nil
		}

		currentLockInfo, err := c.getLockInfo(lease)
		if err != nil {
			return "", err
		}

		lockErr := &state.LockError{
			Info: currentLockInfo,
			Err:  errors.New("the state is already locked by another terraform client"),
		}
		return "", lockErr
	}

	lease.Spec.HolderIdentity = pointer.StringPtr(info.ID)
	setLockInfo(lease, info.Marshal())
	_, err = c.kubernetesLeaseClient.Update(lease)
	if err != nil {
		return "", err
	}

	return info.ID, err
}

func (c *RemoteClient) Unlock(id string) error {
	leaseName, err := c.createLeaseName()
	if err != nil {
		return err
	}

	lease, err := c.getLease(leaseName)
	if err != nil {
		return err
	}

	if lease.Spec.HolderIdentity == nil {
		return fmt.Errorf("state is already unlocked")
	}

	lockInfo, err := c.getLockInfo(lease)
	if err != nil {
		return err
	}

	lockErr := &state.LockError{Info: lockInfo}
	if *lease.Spec.HolderIdentity != id {
		lockErr.Err = fmt.Errorf("lock id %q does not match existing lock", id)
		return lockErr
	}

	lease.Spec.HolderIdentity = nil
	removeLockInfo(lease)

	_, err = c.kubernetesLeaseClient.Update(lease)
	if err != nil {
		lockErr.Err = err
		return lockErr
	}

	return nil
}

func (c *RemoteClient) getLockInfo(lease *coordinationv1.Lease) (*state.LockInfo, error) {
	lockData, ok := getLockInfo(lease)
	if len(lockData) == 0 || !ok {
		return nil, nil
	}

	lockInfo := &state.LockInfo{}
	err := json.Unmarshal(lockData, lockInfo)
	if err != nil {
		return nil, err
	}

	return lockInfo, nil
}

func (c *RemoteClient) getLabels() map[string]string {
	l := map[string]string{
		tfstateKey:             "true",
		tfstateSecretSuffixKey: c.nameSuffix,
		tfstateWorkspaceKey:    c.workspace,
		managedByKey:           "terraform",
	}

	if len(c.labels) != 0 {
		for k, v := range c.labels {
			l[k] = v
		}
	}

	return l
}

func (c *RemoteClient) getSecret(name string) (*unstructured.Unstructured, error) {
	return c.kubernetesSecretClient.Get(name, metav1.GetOptions{})
}

func (c *RemoteClient) getLease(name string) (*coordinationv1.Lease, error) {
	return c.kubernetesLeaseClient.Get(name, metav1.GetOptions{})
}

func (c *RemoteClient) deleteSecret(name string) error {
	secret, err := c.getSecret(name)
	if err != nil {
		return err
	}

	labels := secret.GetLabels()
	v, ok := labels[tfstateKey]
	if !ok || v != "true" {
		return fmt.Errorf("Secret does does not have %q label", tfstateKey)
	}

	delProp := metav1.DeletePropagationBackground
	delOps := &metav1.DeleteOptions{PropagationPolicy: &delProp}
	return c.kubernetesSecretClient.Delete(name, delOps)
}

func (c *RemoteClient) deleteLease(name string) error {
	secret, err := c.getLease(name)
	if err != nil {
		return err
	}

	labels := secret.GetLabels()
	v, ok := labels[tfstateKey]
	if !ok || v != "true" {
		return fmt.Errorf("Lease does does not have %q label", tfstateKey)
	}

	delProp := metav1.DeletePropagationBackground
	delOps := &metav1.DeleteOptions{PropagationPolicy: &delProp}
	return c.kubernetesLeaseClient.Delete(name, delOps)
}

func (c *RemoteClient) createSecretName() (string, error) {
	secretName := strings.Join([]string{tfstateKey, c.workspace, c.nameSuffix}, "-")

	errs := validation.IsDNS1123Subdomain(secretName)
	if len(errs) > 0 {
		k8sInfo := `
This is a requirement for Kubernetes secret names. 
The workspace name and key must adhere to Kubernetes naming conventions.`
		msg := fmt.Sprintf("the secret name %v is invalid, ", secretName)
		return "", errors.New(msg + strings.Join(errs, ",") + k8sInfo)
	}

	return secretName, nil
}

func (c *RemoteClient) createLeaseName() (string, error) {
	n, err := c.createSecretName()
	if err != nil {
		return "", err
	}
	return "lock-" + n, nil
}

func compressState(data []byte) ([]byte, error) {
	b := new(bytes.Buffer)
	gz := gzip.NewWriter(b)
	if _, err := gz.Write(data); err != nil {
		return nil, err
	}
	if err := gz.Close(); err != nil {
		return nil, err
	}
	return b.Bytes(), nil
}

func uncompressState(data string) ([]byte, error) {
	decode, err := base64.StdEncoding.DecodeString(data)
	if err != nil {
		return nil, err
	}

	b := new(bytes.Buffer)
	gz, err := gzip.NewReader(bytes.NewReader(decode))
	if err != nil {
		return nil, err
	}
	b.ReadFrom(gz)
	if err := gz.Close(); err != nil {
		return nil, err
	}
	return b.Bytes(), nil
}

func getSecretData(secret *unstructured.Unstructured) map[string]interface{} {
	if m, ok := secret.Object["data"].(map[string]interface{}); ok {
		return m
	}
	return map[string]interface{}{}
}

func getLockInfo(lease *coordinationv1.Lease) ([]byte, bool) {
	info, ok := lease.ObjectMeta.GetAnnotations()[tfstateLockInfoAnnotation]
	if !ok {
		return nil, false
	}
	return []byte(info), true
}

func setLockInfo(lease *coordinationv1.Lease, l []byte) {
	annotations := lease.ObjectMeta.GetAnnotations()
	if annotations != nil {
		annotations[tfstateLockInfoAnnotation] = string(l)
	} else {
		annotations = map[string]string{
			tfstateLockInfoAnnotation: string(l),
		}
	}
	lease.ObjectMeta.SetAnnotations(annotations)
}

func removeLockInfo(lease *coordinationv1.Lease) {
	annotations := lease.ObjectMeta.GetAnnotations()
	delete(annotations, tfstateLockInfoAnnotation)
	lease.ObjectMeta.SetAnnotations(annotations)
}

func setState(secret *unstructured.Unstructured, t []byte) {
	secretData := getSecretData(secret)
	secretData[tfstateKey] = t
	secret.Object["data"] = secretData
}