/*
Copyright 2022 Gravitational, Inc.

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 proxy

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"testing"

	"github.com/stretchr/testify/require"
	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/remotecommand"
	"k8s.io/kubectl/pkg/scheme"

	testingkubemock "github.com/gravitational/teleport/lib/kube/proxy/testing/kube_server"
)

var (
	kubeCluster              = "test_cluster"
	username                 = "test_user"
	roleName                 = "kube_role"
	usernameMultiUsers       = "test_user_multi_users"
	roleNameMultiUsers       = "kube_role_multi_users"
	roleKubeGroups           = []string{"kube"}
	roleKubeUsers            = []string{"kube"}
	podName                  = "teleport"
	podNamespace             = "default"
	podContainerName         = "teleportContainer"
	containerCommmandExecute = []string{"sh"}
	stdinContent             = []byte("stdin_data")
)

func TestExecKubeService(t *testing.T) {
	kubeMock, err := testingkubemock.NewKubeAPIMock()
	require.NoError(t, err)
	t.Cleanup(func() { kubeMock.Close() })

	// creates a Kubernetes service with a configured cluster pointing to mock api server
	testCtx := SetupTestContext(
		context.Background(),
		t,
		TestConfig{
			Clusters: []KubeClusterConfig{{Name: kubeCluster, APIEndpoint: kubeMock.URL}},
		},
	)

	t.Cleanup(func() { require.NoError(t, testCtx.Close()) })

	// create a user with access to kubernetes (kubernetes_user and kubernetes_groups specified)
	userWithSingleKubeUser, _ := testCtx.CreateUserAndRole(
		testCtx.Context,
		t,
		username,
		RoleSpec{
			Name:       roleName,
			KubeUsers:  roleKubeUsers,
			KubeGroups: roleKubeGroups,
		})

	// generate a kube client with user certs for auth
	_, configWithSingleKubeUser := testCtx.GenTestKubeClientTLSCert(
		t,
		userWithSingleKubeUser.GetName(),
		kubeCluster,
	)
	require.NoError(t, err)

	// create a user with access to kubernetes (kubernetes_user and kubernetes_groups specified)
	userMultiKubeUsers, _ := testCtx.CreateUserAndRole(
		testCtx.Context,
		t,
		usernameMultiUsers,
		RoleSpec{
			Name:       roleNameMultiUsers,
			KubeUsers:  append(roleKubeUsers, "admin"),
			KubeGroups: roleKubeGroups,
		})

	// generate a kube client with user certs for auth
	_, configMultiKubeUsers := testCtx.GenTestKubeClientTLSCert(
		t,
		userMultiKubeUsers.GetName(),
		kubeCluster,
	)
	require.NoError(t, err)

	type args struct {
		executorBuilder func(*rest.Config, string, *url.URL) (remotecommand.Executor, error)
		impersonateUser string
		config          *rest.Config
	}
	tests := []struct {
		name    string
		args    args
		wantErr bool
	}{
		{
			name: "SPDY protocol",
			args: args{
				executorBuilder: remotecommand.NewSPDYExecutor,
				config:          configWithSingleKubeUser,
			},
		},
		{
			name: "Websocket protocol",
			args: args{
				// We can delete the dummy client once https://github.com/kubernetes/kubernetes/pull/110142
				// is merged into k8s go-client.
				// For now go-client does not support connections over websockets.
				executorBuilder: func(c *rest.Config, s string, u *url.URL) (remotecommand.Executor, error) {
					return newWebSocketClient(c, s, u)
				},
				config: configWithSingleKubeUser,
			},
		},
		{
			name: "SPDY protocol for user with multiple kubernetes users",
			args: args{
				executorBuilder: remotecommand.NewSPDYExecutor,
				config:          configMultiKubeUsers,
				impersonateUser: "admin",
			},
		},
		{
			name: "Websocket protocol for user with multiple kubernetes users",
			args: args{
				// We can delete the dummy client once https://github.com/kubernetes/kubernetes/pull/110142
				// is merged into k8s go-client.
				// For now go-client does not support connections over websockets.
				executorBuilder: func(c *rest.Config, s string, u *url.URL) (remotecommand.Executor, error) {
					return newWebSocketClient(c, s, u)
				},
				config:          configMultiKubeUsers,
				impersonateUser: "admin",
			},
		},
		{
			name: "SPDY protocol for user with multiple kubernetes users without specifying impersonate user",
			args: args{
				executorBuilder: remotecommand.NewSPDYExecutor,
				config:          configMultiKubeUsers,
			},
			wantErr: true,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			var (
				stdinWrite = &bytes.Buffer{}
				stdout     = &bytes.Buffer{}
				stderr     = &bytes.Buffer{}
			)

			_, err = stdinWrite.Write(stdinContent)
			require.NoError(t, err)

			streamOpts := remotecommand.StreamOptions{
				Stdin:  io.NopCloser(stdinWrite),
				Stdout: stdout,
				Stderr: stderr,
				Tty:    false,
			}

			req, err := generateExecRequest(
				testCtx.KubeServiceAddress(),
				podName,
				podNamespace,
				podContainerName,
				containerCommmandExecute, // placeholder for commands to execute in the dummy pod
				streamOpts,
			)
			require.NoError(t, err)
			// configure the client to impersonate the user.
			// If empty, the client ignores it.
			tt.args.config.Impersonate.UserName = tt.args.impersonateUser
			exec, err := tt.args.executorBuilder(tt.args.config, http.MethodPost, req.URL())
			require.NoError(t, err)

			err = exec.StreamWithContext(testCtx.Context, streamOpts)
			if tt.wantErr {
				require.Error(t, err)
				return
			}
			require.NoError(t, err)
			require.Equal(t, fmt.Sprintf("%s\n%s", podContainerName, string(stdinContent)), stdout.String())
			require.Equal(t, fmt.Sprintf("%s\n%s", podContainerName, string(stdinContent)), stderr.String())
		})
	}
}

// generateExecRequest generates a Kube API url for executing commands in pods.
// The url format is the following:
// "/api/v1/namespaces/{podNamespace}/pods/{podName}/exec?stderr={stdout}&stdout={stdout}&tty={tty}.
func generateExecRequest(addr, podName, podNamespace, containerName string, cmd []string, options remotecommand.StreamOptions) (*rest.Request, error) {
	restClient, err := rest.RESTClientFor(&rest.Config{
		Host:    addr,
		APIPath: "/api",
		ContentConfig: rest.ContentConfig{
			GroupVersion:         &corev1.SchemeGroupVersion,
			NegotiatedSerializer: runtime.NewSimpleNegotiatedSerializer(runtime.SerializerInfo{}),
		},
		TLSClientConfig: rest.TLSClientConfig{Insecure: true},
	})
	if err != nil {
		return nil, err
	}

	req := restClient.Post().
		Resource("pods").
		Name(podName).
		Namespace(podNamespace).
		SubResource("exec").
		VersionedParams(&corev1.PodExecOptions{
			Container: containerName,
			Command:   cmd,
			Stdin:     options.Stdin != nil,
			Stdout:    options.Stdout != nil,
			Stderr:    options.Stderr != nil,
			TTY:       options.Tty,
		}, scheme.ParameterCodec)

	return req, nil
}