package info

import (
	"context"
	"reflect"

	"github.com/go-logr/logr"

	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/fields"
	kwatch "k8s.io/apimachinery/pkg/watch"

	"sigs.k8s.io/controller-runtime/pkg/client"
)

// OnConfigMapUpdate watches for configmap updates, execute function param if valid configmap and based on optional filters
// returns a watch ref that can be called to stop the watch `defer watch.Stop()`
func OnConfigMapUpdate(ctx context.Context, cl client.WithWatch, logger logr.Logger, fn func(cfg *EdgeInfo), filters ...string) (kwatch.Interface, error) {
	list := &v1.ConfigMapList{}
	watch, err := cl.Watch(ctx, list, &client.ListOptions{
		FieldSelector: fields.OneTermEqualSelector("metadata.name", EdgeConfigMapName),
		Namespace:     EdgeConfigMapNS,
	})
	if err != nil {
		return nil, err
	}
	go func() {
		var old *v1.ConfigMap
		for event := range watch.ResultChan() {
			switch event.Type {
			case kwatch.Added, kwatch.Modified:
				updatedConfigmap := event.Object.(*v1.ConfigMap)
				edgeInfoUpdated, err := New(updatedConfigmap)
				if err != nil { // skip for invalid config
					logger.Error(err, "fail to parse edge info ConfigMap, will watch for update")
					continue
				}
				if old == nil {
					old = updatedConfigmap
					fn(edgeInfoUpdated)
					continue
				}
				configMapChanged := !reflect.DeepEqual(FromConfigMap(old), edgeInfoUpdated)
				matchedOnFilters := cfgValuesMatches(old, updatedConfigmap, filters)
				if configMapChanged && matchedOnFilters {
					old = updatedConfigmap
					fn(edgeInfoUpdated)
				}
			}
		}
	}()
	return watch, err
}

func cfgValuesMatches(old, updated *v1.ConfigMap, filters []string) bool {
	for _, f := range filters {
		if old.Data[f] != updated.Data[f] {
			return true
		}
	}
	return len(filters) == 0
}