/*
Copyright 2017 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 apiclient

import (
	"fmt"
	"io"
	"net/http"
	"time"

	"k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/util/wait"
	clientset "k8s.io/client-go/kubernetes"
	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
)

// Waiter is an interface for waiting for criterias in Kubernetes to happen
type Waiter interface {
	// WaitForAPI waits for the API Server's /healthz endpoint to become "ok"
	WaitForAPI() error
	// WaitForPodsWithLabel waits for Pods in the kube-system namespace to become Ready
	WaitForPodsWithLabel(kvLabel string) error
	// WaitForPodToDisappear waits for the given Pod in the kube-system namespace to be deleted
	WaitForPodToDisappear(staticPodName string) error
	// SetTimeout adjusts the timeout to the specified duration
	SetTimeout(timeout time.Duration)
}

// KubeWaiter is an implementation of Waiter that is backed by a Kubernetes client
type KubeWaiter struct {
	client  clientset.Interface
	timeout time.Duration
	writer  io.Writer
}

// NewKubeWaiter returns a new Waiter object that talks to the given Kubernetes cluster
func NewKubeWaiter(client clientset.Interface, timeout time.Duration, writer io.Writer) Waiter {
	return &KubeWaiter{
		client:  client,
		timeout: timeout,
		writer:  writer,
	}
}

// WaitForAPI waits for the API Server's /healthz endpoint to report "ok"
func (w *KubeWaiter) WaitForAPI() error {
	start := time.Now()
	return wait.PollImmediate(constants.APICallRetryInterval, w.timeout, func() (bool, error) {
		healthStatus := 0
		w.client.Discovery().RESTClient().Get().AbsPath("/healthz").Do().StatusCode(&healthStatus)
		if healthStatus != http.StatusOK {
			return false, nil
		}

		fmt.Printf("[apiclient] All control plane components are healthy after %f seconds\n", time.Since(start).Seconds())
		return true, nil
	})
}

// WaitForPodsWithLabel will lookup pods with the given label and wait until they are all
// reporting status as running.
func (w *KubeWaiter) WaitForPodsWithLabel(kvLabel string) error {

	lastKnownPodNumber := -1
	return wait.PollImmediate(constants.APICallRetryInterval, w.timeout, func() (bool, error) {
		listOpts := metav1.ListOptions{LabelSelector: kvLabel}
		pods, err := w.client.CoreV1().Pods(metav1.NamespaceSystem).List(listOpts)
		if err != nil {
			fmt.Fprintf(w.writer, "[apiclient] Error getting Pods with label selector %q [%v]\n", kvLabel, err)
			return false, nil
		}

		if lastKnownPodNumber != len(pods.Items) {
			fmt.Fprintf(w.writer, "[apiclient] Found %d Pods for label selector %s\n", len(pods.Items), kvLabel)
			lastKnownPodNumber = len(pods.Items)
		}

		if len(pods.Items) == 0 {
			return false, nil
		}

		for _, pod := range pods.Items {
			if pod.Status.Phase != v1.PodRunning {
				return false, nil
			}
		}

		return true, nil
	})
}

// WaitForPodToDisappear blocks until it timeouts or gets a "NotFound" response from the API Server when getting the Static Pod in question
func (w *KubeWaiter) WaitForPodToDisappear(podName string) error {
	return wait.PollImmediate(constants.APICallRetryInterval, w.timeout, func() (bool, error) {
		_, err := w.client.CoreV1().Pods(metav1.NamespaceSystem).Get(podName, metav1.GetOptions{})
		if apierrors.IsNotFound(err) {
			fmt.Printf("[apiclient] The Static Pod %q is now removed\n", podName)
			return true, nil
		}
		return false, nil
	})
}

// SetTimeout adjusts the timeout to the specified duration
func (w *KubeWaiter) SetTimeout(timeout time.Duration) {
	w.timeout = timeout
}

// TryRunCommand runs a function a maximum of failureThreshold times, and retries on error. If failureThreshold is hit; the last error is returned
func TryRunCommand(f func() error, failureThreshold uint8) error {
	var numFailures uint8
	return wait.PollImmediate(5*time.Second, 20*time.Minute, func() (bool, error) {
		err := f()
		if err != nil {
			numFailures++
			// If we've reached the maximum amount of failures, error out
			if numFailures == failureThreshold {
				return false, err
			}
			// Retry
			return false, nil
		}
		// The last f() call was a success!
		return true, nil
	})
}