/*
 * 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 tool provides tools for operator communicating with K8S cluster
package tool

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"path/filepath"

	"github.com/pkg/errors"
	core_v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/tools/remotecommand"
)

// K8sClient is a struct which contains the kubernetes.Interface and *rest.Config.
type K8sClient struct {
	// kubernetes.Interface should be used instead of kubernets.Inteface for unit test (mocking)
	ClientSet kubernetes.Interface
	Config    *rest.Config
}

// NewK8sClient is to generate a K8s client for interacting with the K8S cluster.
func NewK8sClient() (*K8sClient, error) {
	var kubeconfig string
	if kubeConfigPath := os.Getenv("KUBECONFIG"); kubeConfigPath != "" {
		kubeconfig = kubeConfigPath // CI process
	} else {
		kubeconfig = filepath.Join(os.Getenv("HOME"), ".kube", "config") // Development environment
	}

	var config *rest.Config

	_, err := os.Stat(kubeconfig)
	if err != nil {
		// In cluster configuration
		config, err = rest.InClusterConfig()
		if err != nil {
			return nil, err
		}
	} else {
		// Out of cluster configuration
		config, err = clientcmd.BuildConfigFromFlags("", kubeconfig)
		if err != nil {
			return nil, err
		}
	}

	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		return nil, err
	}
	var client = &K8sClient{ClientSet: clientset, Config: config}
	return client, nil
}

// Exec enables operator to execute command in the pod's container in the K8S cluster.
// It returns the standard output and the standard error output.
func (client *K8sClient) Exec(namespace, podName, containerName string, command []string, stdin io.Reader) (*bytes.Buffer, *bytes.Buffer, error) {
	clientset, config := client.ClientSet, client.Config

	req := clientset.CoreV1().RESTClient().Post().
		Resource("pods").
		Name(podName).
		Namespace(namespace).
		SubResource("exec")

	scheme := runtime.NewScheme()
	if err := core_v1.AddToScheme(scheme); err != nil {
		return nil, nil, fmt.Errorf("error adding to scheme: %v", err)
	}

	parameterCodec := runtime.NewParameterCodec(scheme)
	req.VersionedParams(&core_v1.PodExecOptions{
		Command:   command,
		Container: containerName,
		Stdin:     stdin != nil,
		Stdout:    true,
		Stderr:    true,
		TTY:       false,
	}, parameterCodec)

	exec, err := remotecommand.NewSPDYExecutor(config, "POST", req.URL())
	if err != nil {
		return nil, nil, errors.Wrap(err, "Could not create SPDY executor")
	}

	var stdout, stderr bytes.Buffer
	err = exec.Stream(remotecommand.StreamOptions{
		Stdin:  stdin,
		Stdout: &stdout,
		Stderr: &stderr,
		Tty:    false,
	})

	if err != nil {
		return nil, nil, errors.Wrap(err, "Error while exec'ing stream")
	}

	return &stdout, &stderr, nil
}