// Copyright 2020-2025 Project Capsule Authors
// SPDX-License-Identifier: Apache-2.0

package resourcepool

import (
	"context"
	"fmt"

	"github.com/go-logr/logr"
	"k8s.io/apimachinery/pkg/api/equality"
	"k8s.io/apimachinery/pkg/api/resource"
	"k8s.io/client-go/tools/record"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"

	capsulev1beta2 "github.com/projectcapsule/capsule/api/v1beta2"
	capsulewebhook "github.com/projectcapsule/capsule/pkg/webhook"
	"github.com/projectcapsule/capsule/pkg/webhook/utils"
)

type poolValidationHandler struct {
	log logr.Logger
}

func PoolValidationHandler(log logr.Logger) capsulewebhook.Handler {
	return &poolValidationHandler{log: log}
}

func (h *poolValidationHandler) OnCreate(client.Client, admission.Decoder, record.EventRecorder) capsulewebhook.Func {
	return func(context.Context, admission.Request) *admission.Response {
		return nil
	}
}

func (h *poolValidationHandler) OnDelete(client.Client, admission.Decoder, record.EventRecorder) capsulewebhook.Func {
	return func(context.Context, admission.Request) *admission.Response {
		return nil
	}
}

func (h *poolValidationHandler) OnUpdate(_ client.Client, decoder admission.Decoder, _ record.EventRecorder) capsulewebhook.Func {
	return func(_ context.Context, req admission.Request) *admission.Response {
		oldPool := &capsulev1beta2.ResourcePool{}
		if err := decoder.DecodeRaw(req.OldObject, oldPool); err != nil {
			return utils.ErroredResponse(err)
		}

		pool := &capsulev1beta2.ResourcePool{}
		if err := decoder.Decode(req, pool); err != nil {
			return utils.ErroredResponse(err)
		}

		// Verify if resource decrease is allowed or no
		if !equality.Semantic.DeepEqual(pool.Spec.Quota.Hard, oldPool.Spec.Quota.Hard) {
			zeroValue := resource.MustParse("0")

			for resourceName, qt := range oldPool.Status.Allocation.Claimed {
				allocation, exists := pool.Spec.Quota.Hard[resourceName]

				if !exists {
					// May remove resources when unused
					if zeroValue.Cmp(qt) == 0 {
						continue
					}

					response := admission.Denied(fmt.Sprintf(
						"can not remove resource %s as it is still being allocated. Remove corresponding claims or keep the resources in the pool",
						resourceName,
					))

					return &response
				}

				if allocation.Cmp(qt) < 0 {
					response := admission.Denied(
						fmt.Sprintf(
							"can not reduce %s usage to %s because quantity %s is claimed . Remove corresponding claims or keep the resources in the pool",
							resourceName,
							allocation.String(),
							qt.String(),
						))

					return &response
				}
			}
		}

		return nil
	}
}