/*
Copyright 2025.

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 v1

import (
	"cmp"
	"context"
	"encoding/json"
	"fmt"
	"slices"
	"strings"

	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/strategicpatch"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	logf "sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"

	nbv1 "github.com/netbirdio/kubernetes-operator/api/v1"
	nbv1alpha1 "github.com/netbirdio/kubernetes-operator/api/v1alpha1"
	"github.com/netbirdio/kubernetes-operator/internal/controller"
)

const (
	SidecarProfileAnnotation = "netbird.io/sidecar-profile"

	setupKeyAnnotation = "netbird.io/setup-key"
	sidecarAnnotation  = "netbird.io/init-sidecar"
)

// nolint:unused
// log is for logging in this package.
var podlog = logf.Log.WithName("pod-resource")

// SetupPodWebhookWithManager registers the webhook for Pod in the manager.
func SetupPodWebhookWithManager(mgr ctrl.Manager, managementURL, clientImage string) error {
	return ctrl.NewWebhookManagedBy(mgr, &corev1.Pod{}).
		WithDefaulter(&PodNetbirdInjector{
			client:        mgr.GetClient(),
			managementURL: managementURL,
			clientImage:   clientImage,
		}).
		Complete()
}

// PodNetbirdInjector struct is responsible for setting default values on the custom resource of the
// Kind Pod when those are created or updated.
type PodNetbirdInjector struct {
	client        client.Client
	managementURL string
	clientImage   string
}

var _ admission.Defaulter[*corev1.Pod] = &PodNetbirdInjector{}

func (d *PodNetbirdInjector) Default(ctx context.Context, pod *corev1.Pod) error {
	// If setup key annotations are set we do the legacy injection.
	if pod.Annotations != nil && pod.Annotations[setupKeyAnnotation] != "" {
		return d.legacyInjector(ctx, pod)
	}

	// Find sidecar profiles matching pods labels.
	sidecarProfileList := &nbv1alpha1.SidecarProfileList{}
	err := d.client.List(ctx, sidecarProfileList, client.InNamespace(pod.Namespace))
	if err != nil {
		return err
	}
	sidecarProfiles := []nbv1alpha1.SidecarProfile{}
	for _, sidecarProfile := range sidecarProfileList.Items {
		if sidecarProfile.Spec.PodSelector == nil || sidecarProfile.Spec.PodSelector.Size() == 0 {
			sidecarProfiles = append(sidecarProfiles, sidecarProfile)
			continue
		}
		selector, err := metav1.LabelSelectorAsSelector(sidecarProfile.Spec.PodSelector)
		if err != nil {
			return err
		}
		if selector.Matches(labels.Set(pod.Labels)) {
			sidecarProfiles = append(sidecarProfiles, sidecarProfile)
		}
	}
	// Do nothing if no profile matches.
	if len(sidecarProfiles) == 0 {
		return nil
	}
	// If two match we chose the first in alphabetical order.
	if len(sidecarProfiles) > 1 {
		slices.SortFunc(sidecarProfiles, func(a, b nbv1alpha1.SidecarProfile) int {
			return cmp.Compare(a.Name, b.Name)
		})
	}
	sidecarProfile := sidecarProfiles[0]

	// Get setup key referenced by sidecar profile.
	setupKey := &nbv1alpha1.SetupKey{
		ObjectMeta: metav1.ObjectMeta{
			Name:      sidecarProfile.Spec.SetupKeyRef.Name,
			Namespace: pod.Namespace,
		},
	}
	err = d.client.Get(ctx, client.ObjectKeyFromObject(setupKey), setupKey)
	if err != nil {
		return err
	}

	// Add sidecar container.
	envVars := []corev1.EnvVar{
		{
			Name: "NB_SETUP_KEY",
			ValueFrom: &corev1.EnvVarSource{
				SecretKeyRef: &corev1.SecretKeySelector{
					LocalObjectReference: corev1.LocalObjectReference{
						Name: setupKey.SecretName(),
					},
					Key: controller.SetupKeySecretKey,
				},
			},
		},
		{
			Name:  "NB_MANAGEMENT_URL",
			Value: d.managementURL,
		},
	}
	if len(sidecarProfile.Spec.ExtraDNSLabels) > 0 {
		envVars = append(envVars, corev1.EnvVar{
			Name:  "NB_EXTRA_DNS_LABELS",
			Value: strings.Join(sidecarProfile.Spec.ExtraDNSLabels, ","),
		})
	}

	container := corev1.Container{
		Name:  "netbird",
		Image: d.clientImage,
		Env:   envVars,
		SecurityContext: &corev1.SecurityContext{
			Capabilities: &corev1.Capabilities{
				Add: []corev1.Capability{"NET_ADMIN"},
			},
		},
	}
	if sidecarProfile.Spec.ContainerOverride != nil {
		baseJSON, err := json.Marshal(&container)
		if err != nil {
			return err
		}
		overrideJSON, err := json.Marshal(sidecarProfile.Spec.ContainerOverride)
		if err != nil {
			return err
		}
		mergedJSON, err := strategicpatch.StrategicMergePatch(baseJSON, overrideJSON, corev1.Container{})
		if err != nil {
			return err
		}
		err = json.Unmarshal(mergedJSON, &container)
		if err != nil {
			return err
		}
	}

	switch sidecarProfile.Spec.InjectionMode {
	case nbv1alpha1.InjectionModeSidecar:
		restartPolicy := corev1.ContainerRestartPolicyAlways
		container.RestartPolicy = &restartPolicy
		pod.Spec.InitContainers = append(pod.Spec.InitContainers, container)
	case nbv1alpha1.InjectionModeContainer:
		pod.Spec.Containers = append(pod.Spec.Containers, container)
	default:
		return fmt.Errorf("unknown injection mode %s", sidecarProfile.Spec.InjectionMode)
	}

	pod.Annotations[SidecarProfileAnnotation] = sidecarProfile.Name

	return nil
}

func (d *PodNetbirdInjector) legacyInjector(ctx context.Context, pod *corev1.Pod) error {
	podlog.Info("Defaulting for Pod", "name", pod.GetName())

	// retrieve the NBSetupKey resource
	var nbSetupKey nbv1.NBSetupKey
	err := d.client.Get(ctx, types.NamespacedName{Namespace: pod.Namespace, Name: pod.Annotations[setupKeyAnnotation]}, &nbSetupKey)
	if err != nil {
		return err
	}

	// ensure the NBSetupKey is ready.
	ready := false
	for _, c := range nbSetupKey.Status.Conditions {
		if c.Type == nbv1.NBSetupKeyReady {
			ready = c.Status == corev1.ConditionTrue
		}
	}
	if !ready {
		return fmt.Errorf("NBSetupKey is not ready")
	}

	managementURL := d.managementURL
	if nbSetupKey.Spec.ManagementURL != "" {
		managementURL = nbSetupKey.Spec.ManagementURL
	}

	// build environment variables
	envVars := []corev1.EnvVar{
		{
			Name: "NB_SETUP_KEY",
			ValueFrom: &corev1.EnvVarSource{
				SecretKeyRef: &nbSetupKey.Spec.SecretKeyRef,
			},
		},
		{
			Name:  "NB_MANAGEMENT_URL",
			Value: managementURL,
		},
	}

	// check for extra DNS labels in annotations and add as environment variable
	if pod.Annotations != nil {
		if extra, ok := pod.Annotations["netbird.io/extra-dns-labels"]; ok && extra != "" {
			podlog.Info("Found extra DNS labels", "extra", extra)
			envVars = append(envVars, corev1.EnvVar{
				Name:  "NB_EXTRA_DNS_LABELS",
				Value: extra,
			})
		}
	}

	// Build the netbird container spec.
	nbContainer := corev1.Container{
		Name:  "netbird",
		Image: d.clientImage,
		Env:   envVars,
		SecurityContext: &corev1.SecurityContext{
			Capabilities: &corev1.Capabilities{
				Add: []corev1.Capability{"NET_ADMIN"},
			},
		},
		VolumeMounts: nbSetupKey.Spec.VolumeMounts,
	}

	// If sidecar mode is requested, inject as a sidecar (init container with restartPolicy: Always).
	if pod.Annotations[sidecarAnnotation] == "true" {
		restartPolicy := corev1.ContainerRestartPolicyAlways
		nbContainer.RestartPolicy = &restartPolicy
		pod.Spec.InitContainers = append(pod.Spec.InitContainers, nbContainer)
	} else {
		pod.Spec.Containers = append(pod.Spec.Containers, nbContainer)
	}

	pod.Spec.Volumes = append(pod.Spec.Volumes, nbSetupKey.Spec.Volumes...)
	return nil
}