/*
Copyright 2018 The Kubernetes 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 controller

import (
	"fmt"
	"net"
	"reflect"

	"github.com/golang/glog"

	corev1 "k8s.io/api/core/v1"

	"k8s.io/ingress-nginx/internal/ingress"
	"k8s.io/ingress-nginx/internal/ingress/annotations/healthcheck"
)

// getEndpoints returns a list of <endpoint ip>:<port> for a given service/target port combination.
func getEndpoints(
	s *corev1.Service,
	port *corev1.ServicePort,
	proto corev1.Protocol,
	hz *healthcheck.Config,
	getServiceEndpoints func(*corev1.Service) (*corev1.Endpoints, error),
) []ingress.Endpoint {

	upsServers := []ingress.Endpoint{}

	if s == nil || port == nil {
		return upsServers
	}

	// avoid duplicated upstream servers when the service
	// contains multiple port definitions sharing the same
	// targetport.
	adus := make(map[string]bool)

	// ExternalName services
	if s.Spec.Type == corev1.ServiceTypeExternalName {
		glog.V(3).Infof("Ingress using a service %v of type=ExternalName : %v", s.Name)

		targetPort := port.TargetPort.IntValue()
		// check for invalid port value
		if targetPort <= 0 {
			glog.Errorf("ExternalName service with an invalid port: %v", targetPort)
			return upsServers
		}

		if net.ParseIP(s.Spec.ExternalName) == nil {
			_, err := net.LookupHost(s.Spec.ExternalName)
			if err != nil {
				glog.Errorf("unexpected error resolving host %v: %v", s.Spec.ExternalName, err)
				return upsServers
			}
		}

		return append(upsServers, ingress.Endpoint{
			Address:     s.Spec.ExternalName,
			Port:        fmt.Sprintf("%v", targetPort),
			MaxFails:    hz.MaxFails,
			FailTimeout: hz.FailTimeout,
		})
	}

	glog.V(3).Infof("getting endpoints for service %v/%v and port %v", s.Namespace, s.Name, port.String())
	ep, err := getServiceEndpoints(s)
	if err != nil {
		glog.Warningf("unexpected error obtaining service endpoints: %v", err)
		return upsServers
	}

	for _, ss := range ep.Subsets {
		for _, epPort := range ss.Ports {

			if !reflect.DeepEqual(epPort.Protocol, proto) {
				continue
			}

			var targetPort int32

			if port.Name == "" {
				// port.Name is optional if there is only one port
				targetPort = epPort.Port
			} else if port.Name == epPort.Name {
				targetPort = epPort.Port
			}

			glog.Infof("TP: %v", targetPort)
			// check for invalid port value
			if targetPort <= 0 {
				continue
			}

			for _, epAddress := range ss.Addresses {
				ep := fmt.Sprintf("%v:%v", epAddress.IP, targetPort)
				if _, exists := adus[ep]; exists {
					continue
				}
				ups := ingress.Endpoint{
					Address:     epAddress.IP,
					Port:        fmt.Sprintf("%v", targetPort),
					MaxFails:    hz.MaxFails,
					FailTimeout: hz.FailTimeout,
					Target:      epAddress.TargetRef,
				}
				upsServers = append(upsServers, ups)
				adus[ep] = true
			}
		}
	}

	glog.V(3).Infof("endpoints found: %v", upsServers)
	return upsServers
}