/*
Copyright 2017 The Kubernetes Authors.
Copyright 2020 Authors of Arktos - file modified.

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 util

import (
	"context"
	"errors"
	"fmt"
	"net"

	"k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/client-go/tools/record"
	helper "k8s.io/kubernetes/pkg/apis/core/v1/helper"
	utilnet "k8s.io/utils/net"

	"k8s.io/klog"
)

const (
	// IPv4ZeroCIDR is the CIDR block for the whole IPv4 address space
	IPv4ZeroCIDR = "0.0.0.0/0"

	// IPv6ZeroCIDR is the CIDR block for the whole IPv6 address space
	IPv6ZeroCIDR = "::/0"
)

var (
	// ErrAddressNotAllowed indicates the address is not allowed
	ErrAddressNotAllowed = errors.New("address not allowed")

	// ErrNoAddresses indicates there are no addresses for the hostname
	ErrNoAddresses = errors.New("No addresses for hostname")
)

// IsZeroCIDR checks whether the input CIDR string is either
// the IPv4 or IPv6 zero CIDR
func IsZeroCIDR(cidr string) bool {
	if cidr == IPv4ZeroCIDR || cidr == IPv6ZeroCIDR {
		return true
	}
	return false
}

// IsProxyableIP checks if a given IP address is permitted to be proxied
func IsProxyableIP(ip string) error {
	netIP := net.ParseIP(ip)
	if netIP == nil {
		return ErrAddressNotAllowed
	}
	return isProxyableIP(netIP)
}

func isProxyableIP(ip net.IP) error {
	if ip.IsLoopback() || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() || ip.IsInterfaceLocalMulticast() {
		return ErrAddressNotAllowed
	}
	return nil
}

// Resolver is an interface for net.Resolver
type Resolver interface {
	LookupIPAddr(ctx context.Context, host string) ([]net.IPAddr, error)
}

// IsProxyableHostname checks if the IP addresses for a given hostname are permitted to be proxied
func IsProxyableHostname(ctx context.Context, resolv Resolver, hostname string) error {
	resp, err := resolv.LookupIPAddr(ctx, hostname)
	if err != nil {
		return err
	}

	if len(resp) == 0 {
		return ErrNoAddresses
	}

	for _, host := range resp {
		if err := isProxyableIP(host.IP); err != nil {
			return err
		}
	}
	return nil
}

// IsLocalIP checks if a given IP address is bound to an interface
// on the local system
func IsLocalIP(ip string) (bool, error) {
	addrs, err := net.InterfaceAddrs()
	if err != nil {
		return false, err
	}
	for i := range addrs {
		intf, _, err := net.ParseCIDR(addrs[i].String())
		if err != nil {
			return false, err
		}
		if net.ParseIP(ip).Equal(intf) {
			return true, nil
		}
	}
	return false, nil
}

// ShouldSkipService checks if a given service should skip proxying
func ShouldSkipService(svcName types.NamespacednameWithTenantSource, service *v1.Service) bool {
	// if ClusterIP is "None" or empty, skip proxying
	if !helper.IsServiceIPSet(service) {
		klog.V(3).Infof("Skipping service %s due to clusterIP = %q", svcName, service.Spec.ClusterIP)
		return true
	}
	// Even if ClusterIP is set, ServiceTypeExternalName services don't get proxied
	if service.Spec.Type == v1.ServiceTypeExternalName {
		klog.V(3).Infof("Skipping service %s due to Type=ExternalName", svcName)
		return true
	}
	return false
}

// GetNodeAddresses return all matched node IP addresses based on given cidr slice.
// Some callers, e.g. IPVS proxier, need concrete IPs, not ranges, which is why this exists.
// NetworkInterfacer is injected for test purpose.
// We expect the cidrs passed in is already validated.
// Given an empty input `[]`, it will return `0.0.0.0/0` and `::/0` directly.
// If multiple cidrs is given, it will return the minimal IP sets, e.g. given input `[1.2.0.0/16, 0.0.0.0/0]`, it will
// only return `0.0.0.0/0`.
// NOTE: GetNodeAddresses only accepts CIDRs, if you want concrete IPs, e.g. 1.2.3.4, then the input should be 1.2.3.4/32.
func GetNodeAddresses(cidrs []string, nw NetworkInterfacer) (sets.String, error) {
	uniqueAddressList := sets.NewString()
	if len(cidrs) == 0 {
		uniqueAddressList.Insert(IPv4ZeroCIDR)
		uniqueAddressList.Insert(IPv6ZeroCIDR)
		return uniqueAddressList, nil
	}
	// First round of iteration to pick out `0.0.0.0/0` or `::/0` for the sake of excluding non-zero IPs.
	for _, cidr := range cidrs {
		if IsZeroCIDR(cidr) {
			uniqueAddressList.Insert(cidr)
		}
	}
	// Second round of iteration to parse IPs based on cidr.
	for _, cidr := range cidrs {
		if IsZeroCIDR(cidr) {
			continue
		}
		_, ipNet, _ := net.ParseCIDR(cidr)
		itfs, err := nw.Interfaces()
		if err != nil {
			return nil, fmt.Errorf("error listing all interfaces from host, error: %v", err)
		}
		for _, itf := range itfs {
			addrs, err := nw.Addrs(&itf)
			if err != nil {
				return nil, fmt.Errorf("error getting address from interface %s, error: %v", itf.Name, err)
			}
			for _, addr := range addrs {
				if addr == nil {
					continue
				}
				ip, _, err := net.ParseCIDR(addr.String())
				if err != nil {
					return nil, fmt.Errorf("error parsing CIDR for interface %s, error: %v", itf.Name, err)
				}
				if ipNet.Contains(ip) {
					if utilnet.IsIPv6(ip) && !uniqueAddressList.Has(IPv6ZeroCIDR) {
						uniqueAddressList.Insert(ip.String())
					}
					if !utilnet.IsIPv6(ip) && !uniqueAddressList.Has(IPv4ZeroCIDR) {
						uniqueAddressList.Insert(ip.String())
					}
				}
			}
		}
	}
	return uniqueAddressList, nil
}

// LogAndEmitIncorrectIPVersionEvent logs and emits incorrect IP version event.
func LogAndEmitIncorrectIPVersionEvent(recorder record.EventRecorder, fieldName, fieldValue, svcNamespace, svcName string, svcUID types.UID) {
	errMsg := fmt.Sprintf("%s in %s has incorrect IP version", fieldValue, fieldName)
	klog.Errorf("%s (service %s/%s).", errMsg, svcNamespace, svcName)
	if recorder != nil {
		recorder.Eventf(
			&v1.ObjectReference{
				Kind:      "Service",
				Name:      svcName,
				Namespace: svcNamespace,
				UID:       svcUID,
			}, v1.EventTypeWarning, "KubeProxyIncorrectIPVersion", errMsg)
	}
}

// FilterIncorrectIPVersion filters out the incorrect IP version case from a slice of IP strings.
func FilterIncorrectIPVersion(ipStrings []string, isIPv6Mode bool) ([]string, []string) {
	return filterWithCondition(ipStrings, isIPv6Mode, utilnet.IsIPv6String)
}

// FilterIncorrectCIDRVersion filters out the incorrect IP version case from a slice of CIDR strings.
func FilterIncorrectCIDRVersion(ipStrings []string, isIPv6Mode bool) ([]string, []string) {
	return filterWithCondition(ipStrings, isIPv6Mode, utilnet.IsIPv6CIDRString)
}

func filterWithCondition(strs []string, expectedCondition bool, conditionFunc func(string) bool) ([]string, []string) {
	var corrects, incorrects []string
	for _, str := range strs {
		if conditionFunc(str) != expectedCondition {
			incorrects = append(incorrects, str)
		} else {
			corrects = append(corrects, str)
		}
	}
	return corrects, incorrects
}

// AppendPortIfNeeded appends the given port to IP address unless it is already in
// "ipv4:port" or "[ipv6]:port" format.
func AppendPortIfNeeded(addr string, port int32) string {
	// Return if address is already in "ipv4:port" or "[ipv6]:port" format.
	if _, _, err := net.SplitHostPort(addr); err == nil {
		return addr
	}

	// Simply return for invalid case. This should be caught by validation instead.
	ip := net.ParseIP(addr)
	if ip == nil {
		return addr
	}

	// Append port to address.
	if ip.To4() != nil {
		return fmt.Sprintf("%s:%d", addr, port)
	}
	return fmt.Sprintf("[%s]:%d", addr, port)
}
