/*
Copyright 2015 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 ssh

import (
	"context"
	"fmt"
	"io"
	"net"
	"os"
	"reflect"
	"strings"
	"testing"
	"time"

	"golang.org/x/crypto/ssh"

	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/klog/v2"
)

type testSSHServer struct {
	Host       string
	Port       string
	Type       string
	Data       []byte
	PrivateKey []byte
	PublicKey  []byte
}

func runTestSSHServer(user, password string) (*testSSHServer, error) {
	result := &testSSHServer{}
	// Largely derived from https://godoc.org/golang.org/x/crypto/ssh#example-NewServerConn
	config := &ssh.ServerConfig{
		PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
			if c.User() == user && string(pass) == password {
				return nil, nil
			}
			return nil, fmt.Errorf("password rejected for %s", c.User())
		},
		PublicKeyCallback: func(c ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
			result.Type = key.Type()
			result.Data = ssh.MarshalAuthorizedKey(key)
			return nil, nil
		},
	}

	privateKey, publicKey, err := GenerateKey(2048)
	if err != nil {
		return nil, err
	}
	privateBytes := EncodePrivateKey(privateKey)
	signer, err := ssh.ParsePrivateKey(privateBytes)
	if err != nil {
		return nil, err
	}
	config.AddHostKey(signer)
	result.PrivateKey = privateBytes

	publicBytes, err := EncodePublicKey(publicKey)
	if err != nil {
		return nil, err
	}
	result.PublicKey = publicBytes

	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return nil, err
	}

	host, port, err := net.SplitHostPort(listener.Addr().String())
	if err != nil {
		return nil, err
	}
	result.Host = host
	result.Port = port
	go func() {
		// TODO: return this port.
		defer listener.Close()

		conn, err := listener.Accept()
		if err != nil {
			klog.Errorf("Failed to accept: %v", err)
		}
		_, chans, reqs, err := ssh.NewServerConn(conn, config)
		if err != nil {
			klog.Errorf("Failed handshake: %v", err)
		}
		go ssh.DiscardRequests(reqs)
		for newChannel := range chans {
			if newChannel.ChannelType() != "direct-tcpip" {
				newChannel.Reject(ssh.UnknownChannelType, fmt.Sprintf("unknown channel type: %s", newChannel.ChannelType()))
				continue
			}
			channel, requests, err := newChannel.Accept()
			if err != nil {
				klog.Errorf("Failed to accept channel: %v", err)
			}

			for req := range requests {
				klog.Infof("Got request: %v", req)
			}

			channel.Close()
		}
	}()
	return result, nil
}

func TestSSHTunnel(t *testing.T) {
	private, public, err := GenerateKey(2048)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
		t.FailNow()
	}
	server, err := runTestSSHServer("foo", "bar")
	if err != nil {
		t.Errorf("unexpected error: %v", err)
		t.FailNow()
	}

	privateData := EncodePrivateKey(private)
	tunnel, err := newSSHTunnelFromBytes("foo", privateData, server.Host)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
		t.FailNow()
	}
	tunnel.SSHPort = server.Port

	if err := tunnel.Open(); err != nil {
		t.Errorf("unexpected error: %v", err)
		t.FailNow()
	}

	_, err = tunnel.Dial(context.Background(), "tcp", "127.0.0.1:8080")
	if err != nil {
		t.Errorf("unexpected error: %v", err)
	}
	if server.Type != "ssh-rsa" {
		t.Errorf("expected %s, got %s", "ssh-rsa", server.Type)
	}

	publicData, err := EncodeSSHKey(public)
	if err != nil {
		t.Errorf("unexpected error: %v", err)
	}
	if !reflect.DeepEqual(server.Data, publicData) {
		t.Errorf("expected %s, got %s", string(server.Data), string(privateData))
	}

	if err := tunnel.Close(); err != nil {
		t.Errorf("unexpected error: %v", err)
	}
}

type fakeTunnel struct{}

func (*fakeTunnel) Open() error {
	return nil
}

func (*fakeTunnel) Close() error {
	return nil
}

func (*fakeTunnel) Dial(ctx context.Context, network, address string) (net.Conn, error) {
	return nil, nil
}

type fakeTunnelCreator struct{}

func (*fakeTunnelCreator) newSSHTunnel(string, string, string) (tunnel, error) {
	return &fakeTunnel{}, nil
}

func TestSSHTunnelListUpdate(t *testing.T) {
	// Start with an empty tunnel list.
	l := &SSHTunnelList{
		adding:        make(map[string]bool),
		tunnelCreator: &fakeTunnelCreator{},
	}

	// Start with 2 tunnels.
	addressStrings := []string{"1.2.3.4", "5.6.7.8"}
	l.Update(addressStrings)
	checkTunnelsCorrect(t, l, addressStrings)

	// Add another tunnel.
	addressStrings = append(addressStrings, "9.10.11.12")
	l.Update(addressStrings)
	checkTunnelsCorrect(t, l, addressStrings)

	// Go down to a single tunnel.
	addressStrings = []string{"1.2.3.4"}
	l.Update(addressStrings)
	checkTunnelsCorrect(t, l, addressStrings)

	// Replace w/ all new tunnels.
	addressStrings = []string{"21.22.23.24", "25.26.27.28"}
	l.Update(addressStrings)
	checkTunnelsCorrect(t, l, addressStrings)

	// Call update with the same tunnels.
	l.Update(addressStrings)
	checkTunnelsCorrect(t, l, addressStrings)
}

func checkTunnelsCorrect(t *testing.T, tunnelList *SSHTunnelList, addresses []string) {
	if err := wait.Poll(100*time.Millisecond, 2*time.Second, func() (bool, error) {
		return hasCorrectTunnels(tunnelList, addresses), nil
	}); err != nil {
		t.Errorf("Error waiting for tunnels to reach expected state: %v. Expected %v, had %v", err, addresses, tunnelList)
	}
}

func hasCorrectTunnels(tunnelList *SSHTunnelList, addresses []string) bool {
	tunnelList.tunnelsLock.Lock()
	defer tunnelList.tunnelsLock.Unlock()
	wantMap := make(map[string]bool)
	for _, addr := range addresses {
		wantMap[addr] = true
	}
	haveMap := make(map[string]bool)
	for _, entry := range tunnelList.entries {
		if wantMap[entry.Address] == false {
			return false
		}
		haveMap[entry.Address] = true
	}
	for _, addr := range addresses {
		if haveMap[addr] == false {
			return false
		}
	}
	return true
}

type mockSSHDialer struct {
	network string
	addr    string
	config  *ssh.ClientConfig
}

func (d *mockSSHDialer) Dial(network, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
	d.network = network
	d.addr = addr
	d.config = config
	return nil, fmt.Errorf("mock error from Dial")
}

type mockSigner struct {
}

func (s *mockSigner) PublicKey() ssh.PublicKey {
	panic("mockSigner.PublicKey not implemented")
}

func (s *mockSigner) Sign(rand io.Reader, data []byte) (*ssh.Signature, error) {
	panic("mockSigner.Sign not implemented")
}

func TestSSHUser(t *testing.T) {
	signer := &mockSigner{}

	table := []struct {
		title      string
		user       string
		host       string
		signer     ssh.Signer
		command    string
		expectUser string
	}{
		{
			title:      "all values provided",
			user:       "testuser",
			host:       "testhost",
			signer:     signer,
			command:    "uptime",
			expectUser: "testuser",
		},
		{
			title:      "empty user defaults to GetEnv(USER)",
			user:       "",
			host:       "testhost",
			signer:     signer,
			command:    "uptime",
			expectUser: os.Getenv("USER"),
		},
	}

	for _, item := range table {
		dialer := &mockSSHDialer{}

		_, _, _, err := runSSHCommand(dialer, item.command, item.user, item.host, item.signer, false)
		if err == nil {
			t.Errorf("expected error (as mock returns error); did not get one")
		}
		errString := err.Error()
		if !strings.HasPrefix(errString, fmt.Sprintf("error getting SSH client to %s@%s:", item.expectUser, item.host)) {
			t.Errorf("unexpected error: %v", errString)
		}

		if dialer.network != "tcp" {
			t.Errorf("unexpected network: %v", dialer.network)
		}

		if dialer.config.User != item.expectUser {
			t.Errorf("unexpected user: %v", dialer.config.User)
		}
		if len(dialer.config.Auth) != 1 {
			t.Errorf("unexpected auth: %v", dialer.config.Auth)
		}
		// (No way to test Auth - nothing exported?)

	}

}

func TestTimeoutDialer(t *testing.T) {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Errorf("unexpected error: %v", err)
		t.FailNow()
	}

	testCases := []struct {
		timeout           time.Duration
		expectedErrString string
	}{
		// delay > timeout should cause ssh.Dial to timeout.
		{1, "i/o timeout"},
	}
	for _, tc := range testCases {
		dialer := &timeoutDialer{&realSSHDialer{}, tc.timeout}
		_, err := dialer.Dial("tcp", listener.Addr().String(), &ssh.ClientConfig{})
		if len(tc.expectedErrString) == 0 && err != nil ||
			!strings.Contains(fmt.Sprint(err), tc.expectedErrString) {
			t.Errorf("Expected error to contain %q; got %v", tc.expectedErrString, err)
		}
	}

	listener.Close()
}

func newSSHTunnelFromBytes(user string, privateKey []byte, host string) (*sshTunnel, error) {
	signer, err := MakePrivateKeySignerFromBytes(privateKey)
	if err != nil {
		return nil, err
	}
	return makeSSHTunnel(user, signer, host)
}
