// Copyright 2020-2026 Project Capsule Authors
// SPDX-License-Identifier: Apache-2.0

package mutation

import (
	"context"
	"encoding/json"

	corev1 "k8s.io/api/core/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"

	webhookutils "github.com/projectcapsule/capsule/internal/webhook/utils"
	ad "github.com/projectcapsule/capsule/pkg/runtime/admission"
	"github.com/projectcapsule/capsule/pkg/runtime/configuration"
	"github.com/projectcapsule/capsule/pkg/runtime/events"
	"github.com/projectcapsule/capsule/pkg/runtime/handlers"
	"github.com/projectcapsule/capsule/pkg/tenant"
)

func NamespaceHandler(configuration configuration.Configuration, handlers ...handlers.TypedHandlerWithUser[*corev1.Namespace]) handlers.Handler {
	return &handler{
		cfg:      configuration,
		handlers: handlers,
	}
}

type handler struct {
	cfg      configuration.Configuration
	handlers []handlers.TypedHandlerWithUser[*corev1.Namespace]
}

func (h *handler) OnCreate(
	c client.Client,
	reader client.Reader,
	decoder admission.Decoder,
	recorder events.EventRecorder,
) handlers.Func {
	return func(ctx context.Context, req admission.Request) *admission.Response {
		reader = webhookutils.NewTenantCachingReader(reader)

		user := handlers.ResolveAdmissionUser(ctx, c, req, h.cfg)

		if !user.IsAdmin() && !user.IsCapsule() {
			return nil
		}

		ns := &corev1.Namespace{}
		if err := decoder.Decode(req, ns); err != nil {
			return ad.ErroredResponse(err)
		}

		tnt, err := tenant.GetTenantByLabels(ctx, reader, ns)
		if err != nil {
			return ad.ErroredResponse(err)
		}

		if tnt == nil && user.IsAdmin() {
			return nil
		}

		for _, hndl := range h.handlers {
			response := hndl.OnCreate(c, reader, user, ns, decoder, recorder)(ctx, req)

			if response == nil {
				continue
			}

			if !response.Allowed {
				return response
			}
		}

		marshaled, err := json.Marshal(ns)
		if err != nil {
			return ad.ErroredResponse(err)
		}

		response := admission.PatchResponseFromRaw(req.Object.Raw, marshaled)
		if len(response.Patches) == 0 {
			allowed := admission.Allowed("")

			return &allowed
		}

		return &response
	}
}

func (h *handler) OnUpdate(
	c client.Client,
	reader client.Reader,
	decoder admission.Decoder,
	recorder events.EventRecorder,
) handlers.Func {
	return func(ctx context.Context, req admission.Request) *admission.Response {
		ns := &corev1.Namespace{}
		if err := decoder.Decode(req, ns); err != nil {
			return ad.ErroredResponse(err)
		}

		oldNs := &corev1.Namespace{}
		if err := decoder.DecodeRaw(req.OldObject, oldNs); err != nil {
			return ad.ErroredResponse(err)
		}

		// Namespace finalization and terminating updates must never depend on
		// Tenant resolution. The standard mutating rule excludes subresources,
		// but retain this guard for custom webhook configurations.
		if req.SubResource != "" ||
			ns.DeletionTimestamp != nil ||
			oldNs.DeletionTimestamp != nil ||
			ns.Status.Phase == corev1.NamespaceTerminating ||
			oldNs.Status.Phase == corev1.NamespaceTerminating {
			return nil
		}

		reader = webhookutils.NewTenantCachingReader(reader)

		user := handlers.ResolveAdmissionUser(ctx, c, req, h.cfg)

		if !user.IsAdmin() && !user.IsCapsule() {
			return nil
		}

		for _, hndl := range h.handlers {
			response := hndl.OnUpdate(c, reader, user, ns, oldNs, decoder, recorder)(ctx, req)
			if response == nil {
				continue
			}

			if !response.Allowed {
				return response
			}
		}

		marshaled, err := json.Marshal(ns)
		if err != nil {
			return ad.ErroredResponse(err)
		}

		response := admission.PatchResponseFromRaw(req.Object.Raw, marshaled)
		if len(response.Patches) == 0 {
			allowed := admission.Allowed("")

			return &allowed
		}

		return &response
	}
}

func (h *handler) OnDelete(
	client.Client,
	client.Reader,
	admission.Decoder,
	events.EventRecorder,
) handlers.Func {
	return func(context.Context, admission.Request) *admission.Response {
		return nil
	}
}