package mirko

import (
	"sync"

	"github.com/golang/glog"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
)

var (
	// kubernetesCS is a kubernetes clientset that can connect to the cluster
	// that this program is running in, or nil if uninitialized (or not in a
	// cluster.
	kubernetesCS *kubernetes.Clientset
	// kubernetesCSValid is true when kubernetesCS is 'valid', ie. when the
	// clientset is either an actual clientset object, or nil if the program is
	// not running in production.
	kubernetesCSValid bool
	// kubernetesCSMu guards kubernetesCS and kubernetesCSValid.
	kubernetesCSMu sync.Mutex
)

// KubernetesClient attempts to connect to Kubernetes using in-cluster
// configuration and returns the resulting clientset. If connecting fails, nil
// is returned. Connection will fail if the program is not running in
// production.
// The connection result is cached for the rest of the program lifetime, so
// this function is cheap to call.
func KubernetesClient() *kubernetes.Clientset {
	kubernetesCSMu.Lock()
	defer kubernetesCSMu.Unlock()

	if kubernetesCSValid {
		return kubernetesCS
	}

	kubernetesCSValid = true
	config, err := rest.InClusterConfig()
	if err != nil {
		glog.Errorf("Kubernetes InClusterConfig: %v", err)
		glog.Infof("Mirko: no kubernetes config available...")
		return nil
	}
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		glog.Errorf("Kubernetes NewForConfig: %v", err)
		glog.Infof("Mirko: no kubernetes client available...")
		return nil
	}

	kubernetesCS = clientset
	return clientset
}