package propagationpolicy

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"

	"k8s.io/klog/v2"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"

	policyv1alpha1 "github.com/karmada-io/karmada/pkg/apis/policy/v1alpha1"
	"github.com/karmada-io/karmada/pkg/util/helper"
	"github.com/karmada-io/karmada/pkg/util/validation"
)

// MutatingAdmission mutates API request if necessary.
type MutatingAdmission struct {
	decoder *admission.Decoder

	DefaultNotReadyTolerationSeconds    int64
	DefaultUnreachableTolerationSeconds int64
}

// Check if our MutatingAdmission implements necessary interface
var _ admission.Handler = &MutatingAdmission{}
var _ admission.DecoderInjector = &MutatingAdmission{}

// NewMutatingHandler builds a new admission.Handler.
func NewMutatingHandler(notReadyTolerationSeconds, unreachableTolerationSeconds int64) admission.Handler {
	return &MutatingAdmission{
		DefaultNotReadyTolerationSeconds:    notReadyTolerationSeconds,
		DefaultUnreachableTolerationSeconds: unreachableTolerationSeconds,
	}
}

// Handle yields a response to an AdmissionRequest.
func (a *MutatingAdmission) Handle(ctx context.Context, req admission.Request) admission.Response {
	policy := &policyv1alpha1.PropagationPolicy{}

	err := a.decoder.Decode(req, policy)
	if err != nil {
		return admission.Errored(http.StatusBadRequest, err)
	}
	klog.V(2).Infof("Mutating PropagationPolicy(%s/%s) for request: %s", req.Namespace, policy.Name, req.Operation)

	// Set default namespace for all resource selector if not set.
	// We need to get the default namespace from the request because for kube-apiserver < v1.24,
	// the namespace of the object with namespace unset in the mutating webook chain of a create request
	// is not populated yet. See https://github.com/kubernetes/kubernetes/pull/94637 for more details.
	for i := range policy.Spec.ResourceSelectors {
		if len(policy.Spec.ResourceSelectors[i].Namespace) == 0 {
			klog.Infof("Setting resource selector default namespace for policy: %s/%s", req.Namespace, policy.Name)
			policy.Spec.ResourceSelectors[i].Namespace = req.Namespace
		}
	}

	if len(policy.Name) > validation.LabelValueMaxLength {
		return admission.Errored(http.StatusBadRequest, fmt.Errorf("PropagationPolicy's name should be no more than %d characters", validation.LabelValueMaxLength))
	}
	// Set default spread constraints if both 'SpreadByField' and 'SpreadByLabel' not set.
	helper.SetDefaultSpreadConstraints(policy.Spec.Placement.SpreadConstraints)
	helper.AddTolerations(&policy.Spec.Placement, helper.NewNotReadyToleration(a.DefaultNotReadyTolerationSeconds),
		helper.NewUnreachableToleration(a.DefaultUnreachableTolerationSeconds))

	addedResourceSelectors := helper.GetFollowedResourceSelectorsWhenMatchServiceImport(policy.Spec.ResourceSelectors)
	if addedResourceSelectors != nil {
		policy.Spec.ResourceSelectors = append(policy.Spec.ResourceSelectors, addedResourceSelectors...)
	}

	// When ReplicaSchedulingType is Divided, set the default value of ReplicaDivisionPreference to Weighted.
	helper.SetReplicaDivisionPreferenceWeighted(&policy.Spec.Placement)

	marshaledBytes, err := json.Marshal(policy)
	if err != nil {
		return admission.Errored(http.StatusInternalServerError, err)
	}

	return admission.PatchResponseFromRaw(req.Object.Raw, marshaledBytes)
}

// InjectDecoder implements admission.DecoderInjector interface.
// A decoder will be automatically injected.
func (a *MutatingAdmission) InjectDecoder(d *admission.Decoder) error {
	a.decoder = d
	return nil
}
