/*
Copyright 2021 The Karmada Authors.

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 propagationpolicy

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

	"github.com/google/uuid"
	admissionv1 "k8s.io/api/admission/v1"
	"k8s.io/klog/v2"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
	"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"
	"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{}

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

// Handle yields a response to an AdmissionRequest.
func (a *MutatingAdmission) Handle(_ 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))

	if helper.ContainsServiceImport(policy.Spec.ResourceSelectors) {
		policy.Spec.PropagateDeps = true
	}

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

	if policy.Spec.Failover != nil {
		if policy.Spec.Failover.Application != nil {
			helper.SetDefaultGracePeriodSeconds(policy.Spec.Failover.Application)
		}
	}

	if req.Operation == admissionv1.Create {
		util.MergeLabel(policy, policyv1alpha1.PropagationPolicyPermanentIDLabel, uuid.New().String())
		controllerutil.AddFinalizer(policy, util.PropagationPolicyControllerFinalizer)
	}

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

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