package nsnetworkpolicy

import (
	"context"
	corev1 "k8s.io/api/core/v1"
	k8snet "k8s.io/api/networking/v1"
	"k8s.io/apimachinery/pkg/util/intstr"
	"k8s.io/apimachinery/pkg/util/validation"
	"k8s.io/apimachinery/pkg/util/validation/field"
	networkv1alpha1 "kubesphere.io/kubesphere/pkg/apis/network/v1alpha1"
	"net"
	"net/http"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
)

type NSNPValidator struct {
	Client  client.Client
	decoder *admission.Decoder
}

func (v *NSNPValidator) Handle(ctx context.Context, req admission.Request) admission.Response {
	nsnp := &networkv1alpha1.NamespaceNetworkPolicy{}

	err := v.decoder.Decode(req, nsnp)
	if err != nil {
		return admission.Errored(http.StatusBadRequest, err)
	}

	allErrs := field.ErrorList{}
	allErrs = append(allErrs, v.ValidateNSNPSpec(&nsnp.Spec, field.NewPath("spec"))...)

	if len(allErrs) != 0 {
		return admission.Denied(allErrs.ToAggregate().Error())
	}

	return admission.Allowed("")
}

func (v *NSNPValidator) InjectDecoder(d *admission.Decoder) error {
	v.decoder = d
	return nil
}

// ValidateNetworkPolicyPort validates a NetworkPolicyPort
func (v *NSNPValidator) ValidateNetworkPolicyPort(port *k8snet.NetworkPolicyPort, portPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if port.Protocol != nil && *port.Protocol != corev1.ProtocolTCP && *port.Protocol != corev1.ProtocolUDP && *port.Protocol != corev1.ProtocolSCTP {
		allErrs = append(allErrs, field.NotSupported(portPath.Child("protocol"), *port.Protocol, []string{string(corev1.ProtocolTCP), string(corev1.ProtocolUDP), string(corev1.ProtocolSCTP)}))
	}
	if port.Port != nil {
		if port.Port.Type == intstr.Int {
			for _, msg := range validation.IsValidPortNum(int(port.Port.IntVal)) {
				allErrs = append(allErrs, field.Invalid(portPath.Child("port"), port.Port.IntVal, msg))
			}
		} else {
			for _, msg := range validation.IsValidPortName(port.Port.StrVal) {
				allErrs = append(allErrs, field.Invalid(portPath.Child("port"), port.Port.StrVal, msg))
			}
		}
	}

	return allErrs
}

func (v *NSNPValidator) ValidateServiceSelector(serviceSelector *networkv1alpha1.ServiceSelector, fldPath *field.Path) field.ErrorList {
	service := &corev1.Service{}
	allErrs := field.ErrorList{}

	err := v.Client.Get(context.TODO(), client.ObjectKey{Namespace: serviceSelector.Namespace, Name: serviceSelector.Name}, service)
	if err != nil {
		allErrs = append(allErrs, field.Invalid(fldPath, serviceSelector, "cannot get service"))
		return allErrs
	}

	if len(service.Spec.Selector) <= 0 {
		allErrs = append(allErrs, field.Invalid(fldPath, serviceSelector, "service should have selector"))
	}

	return allErrs
}

// ValidateCIDR validates whether a CIDR matches the conventions expected by net.ParseCIDR
func ValidateCIDR(cidr string) (*net.IPNet, error) {
	_, net, err := net.ParseCIDR(cidr)
	if err != nil {
		return nil, err
	}
	return net, nil
}

// ValidateIPBlock validates a cidr and the except fields of an IpBlock NetworkPolicyPeer
func (v *NSNPValidator) ValidateIPBlock(ipb *k8snet.IPBlock, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if len(ipb.CIDR) == 0 || ipb.CIDR == "" {
		allErrs = append(allErrs, field.Required(fldPath.Child("cidr"), ""))
		return allErrs
	}
	cidrIPNet, err := ValidateCIDR(ipb.CIDR)
	if err != nil {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("cidr"), ipb.CIDR, "not a valid CIDR"))
		return allErrs
	}
	exceptCIDR := ipb.Except
	for i, exceptIP := range exceptCIDR {
		exceptPath := fldPath.Child("except").Index(i)
		exceptCIDR, err := ValidateCIDR(exceptIP)
		if err != nil {
			allErrs = append(allErrs, field.Invalid(exceptPath, exceptIP, "not a valid CIDR"))
			return allErrs
		}
		if !cidrIPNet.Contains(exceptCIDR.IP) {
			allErrs = append(allErrs, field.Invalid(exceptPath, exceptCIDR.IP, "not within CIDR range"))
		}
	}
	return allErrs
}

// ValidateNSNPPeer validates a NetworkPolicyPeer
func (v *NSNPValidator) ValidateNSNPPeer(peer *networkv1alpha1.NetworkPolicyPeer, peerPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	numPeers := 0

	if peer.ServiceSelector != nil {
		numPeers++
		allErrs = append(allErrs, v.ValidateServiceSelector(peer.ServiceSelector, peerPath.Child("service"))...)
	}
	if peer.NamespaceSelector != nil {
		numPeers++
	}
	if peer.IPBlock != nil {
		numPeers++
		allErrs = append(allErrs, v.ValidateIPBlock(peer.IPBlock, peerPath.Child("ipBlock"))...)
	}

	if numPeers == 0 {
		allErrs = append(allErrs, field.Required(peerPath, "must specify a peer"))
	} else if numPeers > 1 && peer.IPBlock != nil {
		allErrs = append(allErrs, field.Forbidden(peerPath, "may not specify both ipBlock and another peer"))
	}

	return allErrs
}

func (v *NSNPValidator) ValidateNSNPSpec(spec *networkv1alpha1.NamespaceNetworkPolicySpec, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	// Validate ingress rules.
	for i, ingress := range spec.Ingress {
		ingressPath := fldPath.Child("ingress").Index(i)
		for i, port := range ingress.Ports {
			portPath := ingressPath.Child("ports").Index(i)
			allErrs = append(allErrs, v.ValidateNetworkPolicyPort(&port, portPath)...)
		}
		for i, from := range ingress.From {
			fromPath := ingressPath.Child("from").Index(i)
			allErrs = append(allErrs, v.ValidateNSNPPeer(&from, fromPath)...)
		}
	}
	// Validate egress rules
	for i, egress := range spec.Egress {
		egressPath := fldPath.Child("egress").Index(i)
		for i, port := range egress.Ports {
			portPath := egressPath.Child("ports").Index(i)
			allErrs = append(allErrs, v.ValidateNetworkPolicyPort(&port, portPath)...)
		}
		for i, to := range egress.To {
			toPath := egressPath.Child("to").Index(i)
			allErrs = append(allErrs, v.ValidateNSNPPeer(&to, toPath)...)
		}
	}

	return allErrs
}