/*
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements.  See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You 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 kubernetes

import (
	"context"
	"errors"
	"fmt"
	"io"

	"github.com/apache/camel-k/pkg/client"
	"github.com/apache/camel-k/pkg/util/log"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/watch"
	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
	restclient "k8s.io/client-go/rest"
	"k8s.io/client-go/tools/portforward"
	"k8s.io/client-go/transport/spdy"
	"net/http"
)

func PortForward(ctx context.Context, c client.Client, ns, labelSelector string, localPort, remotePort uint, stdOut, stdErr io.Writer) error {
	list, err := c.CoreV1().Pods(ns).List(ctx, metav1.ListOptions{
		LabelSelector: labelSelector,
	})
	if err != nil {
		return err
	}

	var forwardPod *corev1.Pod
	var forwardCtx context.Context
	var forwardCtxCancel context.CancelFunc

	setupPortForward := func(pod *corev1.Pod) error {
		if forwardPod == nil && podReady(pod) {
			forwardPod = pod
			forwardCtx, forwardCtxCancel = context.WithCancel(ctx)
			if _, err := portFowardPod(forwardCtx, c.GetConfig(), ns, forwardPod.Name, localPort, remotePort, stdOut, stdErr); err != nil {
				return err
			}
		}
		return nil
	}

	if len(list.Items) > 0 {
		if err := setupPortForward(&list.Items[0]); err != nil {
			return err
		}
	}

	watcher, err := c.CoreV1().Pods(ns).Watch(ctx, metav1.ListOptions{
		LabelSelector:   labelSelector,
		ResourceVersion: list.ResourceVersion,
	})
	if err != nil {
		return err
	}

	events := watcher.ResultChan()

	for {
		select {
		case <-ctx.Done():
			return nil
		case e, ok := <-events:
			if !ok {
				return nil
			}

			switch e.Type {
			case watch.Added:
				pod := e.Object.(*corev1.Pod)
				if err := setupPortForward(pod); err != nil {
					return err
				}
			case watch.Modified:
				pod := e.Object.(*corev1.Pod)
				if err := setupPortForward(pod); err != nil {
					return err
				}
			case watch.Deleted:
				if forwardPod != nil && e.Object != nil {
					deletedPod := e.Object.(*corev1.Pod)
					if deletedPod.Name == forwardPod.Name {
						forwardCtxCancel()
						forwardPod = nil
						forwardCtx = nil
						forwardCtxCancel = nil
					}
				}
			}
		}
	}
}

func portFowardPod(ctx context.Context, config *restclient.Config, ns, pod string, localPort, remotePort uint, stdOut, stdErr io.Writer) (host string, err error) {
	c, err := corev1client.NewForConfig(config)
	if err != nil {
		return "", err
	}

	url := c.RESTClient().Post().
		Resource("pods").
		Namespace(ns).
		Name(pod).
		SubResource("portforward").
		URL()

	transport, upgrader, err := spdy.RoundTripperFor(config)
	if err != nil {
		return "", err
	}

	dialer := spdy.NewDialer(upgrader, &http.Client{Transport: transport}, "POST", url)
	stopChan := make(chan struct{})
	readyChan := make(chan struct{})
	forwarder, err := portforward.New(dialer, []string{fmt.Sprintf("%d:%d", localPort, remotePort)}, stopChan, readyChan, stdOut, stdErr)
	if err != nil {
		return "", err
	}

	go func() {
		// Start the port forwarder
		err = forwarder.ForwardPorts()
		if err != nil {
			log.Errorf(err, "error while forwarding ports")
		}
	}()

	go func() {
		// Stop the port forwarder when the context ends
		select {
		case <-ctx.Done():
			close(stopChan)
		}
	}()

	select {
	case <-readyChan:
		ports, err := forwarder.GetPorts()
		if err != nil {
			return "", err
		}
		if len(ports) != 1 {
			return "", errors.New("wrong ports opened")
		}
		return fmt.Sprintf("localhost:%d", ports[0].Local), nil
	case <-ctx.Done():
		return "", errors.New("context closed")
	}
}

func podReady(pod *corev1.Pod) bool {
	for _, c := range pod.Status.Conditions {
		if c.Type == corev1.PodReady && c.Status == corev1.ConditionTrue {
			return true
		}
	}
	return false
}