package discovery

import (
	"context"
	"slices"
	"sync"

	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/watch"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/tools/cache"
	toolsWatch "k8s.io/client-go/tools/watch"
)

type K8sDiscovery struct {
	ctx         context.Context
	client      *kubernetes.Clientset
	listOptions metav1.ListOptions
}

func (k *K8sDiscovery) Discover() ([]string, error) {
	return k.DiscoverInNamespace("")
}
func (k *K8sDiscovery) DiscoverInNamespace(namespace string) ([]string, error) {
	pods, err := k.client.CoreV1().Pods(namespace).List(k.ctx, k.listOptions)
	if err != nil {
		return nil, err
	}
	hosts := make([]string, 0, len(pods.Items))
	for _, pod := range pods.Items {
		if hasReadyCondition(&pod) {
			hosts = append(hosts, pod.Status.PodIP)
		}
	}
	return hosts, nil
}

func hasReadyCondition(pod *v1.Pod) bool {
	return slices.ContainsFunc(pod.Status.Conditions, func(condition v1.PodCondition) bool {
		return condition.Type == v1.PodReady && condition.Status == v1.ConditionTrue
	})
}

func (k *K8sDiscovery) Watch() (<-chan HostChange, error) {
	ipsThatAreReady := make(map[string]bool)
	m := sync.Mutex{}
	watcherFn := func(options metav1.ListOptions) (watch.Interface, error) {
		return k.client.CoreV1().Pods("").Watch(k.ctx, k.listOptions)
	}
	watcher, err := toolsWatch.NewRetryWatcherWithContext(k.ctx, "1", &cache.ListWatch{WatchFunc: watcherFn})
	if err != nil {
		return nil, err
	}
	ch := make(chan HostChange)
	go func() {
		for event := range watcher.ResultChan() {

			pod := event.Object.(*v1.Pod)
			isReady := hasReadyCondition(pod)
			m.Lock()
			oldState := ipsThatAreReady[pod.Status.PodIP]
			ipsThatAreReady[pod.Status.PodIP] = isReady
			m.Unlock()
			if oldState != isReady {
				ch <- HostChange{
					Host:    pod.Status.PodIP,
					IsReady: isReady,
				}
			}
			ch <- HostChange{
				Host:    pod.Status.PodIP,
				IsReady: isReady,
			}
		}
	}()
	return ch, nil
}

func NewK8sDiscovery(client *kubernetes.Clientset, listOptions metav1.ListOptions) *K8sDiscovery {
	return &K8sDiscovery{
		ctx:         context.Background(),
		client:      client,
		listOptions: listOptions,
	}
}