package podbackend

import (
	"context"
	"encoding/json"
	"fmt"
	"reflect"

	corev1 "k8s.io/api/core/v1"
	apierrors "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/runtime/schema"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
)

var identityEntryResource = schema.GroupVersionResource{
	Group: "spire.spiffe.io", Version: "v1alpha1", Resource: "clusterstaticentries",
}

// Client uses client-go's typed client for Pods and its dynamic client for the
// SPIRE Operator CRD.
type Client struct {
	Kubernetes kubernetes.Interface
	Dynamic    dynamic.Interface
}

func NewClient(config *rest.Config) (*Client, error) {
	kubernetesClient, err := kubernetes.NewForConfig(config)
	if err != nil {
		return nil, fmt.Errorf("create Kubernetes client: %w", err)
	}
	dynamicClient, err := dynamic.NewForConfig(config)
	if err != nil {
		return nil, fmt.Errorf("create Kubernetes dynamic client: %w", err)
	}
	return &Client{Kubernetes: kubernetesClient, Dynamic: dynamicClient}, nil
}

func NewInClusterClient() (*Client, error) {
	config, err := rest.InClusterConfig()
	if err != nil {
		return nil, fmt.Errorf("load in-cluster Kubernetes config: %w", err)
	}
	return NewClient(config)
}

func (c *Client) ListPods(ctx context.Context, namespace, selector string) ([]Pod, error) {
	list, err := c.Kubernetes.CoreV1().Pods(namespace).List(ctx, metav1.ListOptions{LabelSelector: selector})
	if err != nil {
		return nil, err
	}
	pods := make([]Pod, 0, len(list.Items))
	for _, item := range list.Items {
		pods = append(pods, podFromKubernetes(item))
	}
	return pods, nil
}

func (c *Client) CreatePod(ctx context.Context, manifest PodManifest) (Pod, error) {
	environment := make([]corev1.EnvVar, 0, len(manifest.Environment))
	for name, value := range manifest.Environment {
		environment = append(environment, corev1.EnvVar{Name: name, Value: value})
	}
	document := &corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{
			Name: manifest.Name, Namespace: manifest.Namespace,
			Labels: manifest.Labels, Annotations: manifest.Annotations,
		},
		Spec: corev1.PodSpec{
			ServiceAccountName: manifest.ServiceAccount,
			RestartPolicy:      corev1.RestartPolicyNever,
			Containers: []corev1.Container{{
				Name: "executor", Image: manifest.Image, Args: manifest.Args, Env: environment,
				SecurityContext: &corev1.SecurityContext{Privileged: boolPointer(true)},
				VolumeMounts: []corev1.VolumeMount{{
					Name: "spire-agent-socket", MountPath: "/run/spire/agent-sockets", ReadOnly: true,
				}},
			}},
			Volumes: []corev1.Volume{{
				Name: "spire-agent-socket",
				VolumeSource: corev1.VolumeSource{CSI: &corev1.CSIVolumeSource{
					Driver: "csi.spiffe.io", ReadOnly: boolPointer(true),
				}},
			}},
		},
	}
	created, err := c.Kubernetes.CoreV1().Pods(manifest.Namespace).Create(ctx, document, metav1.CreateOptions{})
	if err != nil {
		return Pod{}, err
	}
	return podFromKubernetes(*created), nil
}

func (c *Client) DeletePod(ctx context.Context, namespace, name string) error {
	policy := metav1.DeletePropagationBackground
	err := c.Kubernetes.CoreV1().Pods(namespace).Delete(ctx, name, metav1.DeleteOptions{PropagationPolicy: &policy})
	if apierrors.IsNotFound(err) {
		return nil
	}
	return err
}

func (c *Client) LabelPod(ctx context.Context, namespace, name string, labels map[string]string) error {
	patch, err := json.Marshal(map[string]any{"metadata": map[string]any{"labels": labels}})
	if err != nil {
		return err
	}
	_, err = c.Kubernetes.CoreV1().Pods(namespace).Patch(ctx, name, types.MergePatchType, patch, metav1.PatchOptions{})
	return err
}

func (c *Client) EnsureIdentityEntry(ctx context.Context, entry IdentityEntry) error {
	resource := c.Dynamic.Resource(identityEntryResource)
	existing, err := resource.Get(ctx, entry.Name, metav1.GetOptions{})
	if err == nil {
		existingSpec, _, nestedErr := unstructured.NestedMap(existing.Object, "spec")
		if nestedErr != nil {
			return nestedErr
		}
		if !reflect.DeepEqual(existingSpec, identityEntryObject(entry).Object["spec"]) {
			return fmt.Errorf("identity entry %s exists with different selectors or SPIFFE ID", entry.Name)
		}
		return nil
	}
	if !apierrors.IsNotFound(err) {
		return err
	}
	_, err = resource.Create(ctx, identityEntryObject(entry), metav1.CreateOptions{})
	return err
}

func (c *Client) DeleteIdentityEntry(ctx context.Context, name string) error {
	policy := metav1.DeletePropagationBackground
	err := c.Dynamic.Resource(identityEntryResource).Delete(ctx, name, metav1.DeleteOptions{PropagationPolicy: &policy})
	if apierrors.IsNotFound(err) {
		return nil
	}
	return err
}

func identityEntryObject(entry IdentityEntry) *unstructured.Unstructured {
	selectors := make([]any, len(entry.Selectors))
	for index, selector := range entry.Selectors {
		selectors[index] = selector
	}
	return &unstructured.Unstructured{Object: map[string]any{
		"apiVersion": "spire.spiffe.io/v1alpha1",
		"kind":       "ClusterStaticEntry",
		"metadata": map[string]any{
			"name": entry.Name, "labels": stringMap(entry.Labels),
		},
		"spec": map[string]any{
			"className": entry.ClassName, "parentID": entry.ParentID,
			"spiffeID": entry.SPIFFEID, "selectors": selectors,
		},
	}}
}

func podFromKubernetes(pod corev1.Pod) Pod {
	return Pod{
		Name: pod.Name, Namespace: pod.Namespace, UID: string(pod.UID),
		Phase: string(pod.Status.Phase), Labels: pod.Labels, Annotations: pod.Annotations,
	}
}

func boolPointer(value bool) *bool { return &value }

func stringMap(values map[string]string) map[string]any {
	result := make(map[string]any, len(values))
	for key, value := range values {
		result[key] = value
	}
	return result
}