// Copyright 2018 The gVisor 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 cli is the main entrypoint for runsc.
package cli

import (
	"context"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"os/signal"
	"runtime"
	"syscall"
	"time"

	"github.com/google/subcommands"
	"gvisor.dev/gvisor/pkg/log"
	"gvisor.dev/gvisor/pkg/refs"
	"gvisor.dev/gvisor/pkg/sentry/platform"
	"gvisor.dev/gvisor/runsc/cmd"
	"gvisor.dev/gvisor/runsc/config"
	"gvisor.dev/gvisor/runsc/flag"
	"gvisor.dev/gvisor/runsc/specutils"
)

var (
	// Although these flags are not part of the OCI spec, they are used by
	// Docker, and thus should not be changed.
	// TODO(gvisor.dev/issue/193): support systemd cgroups
	systemdCgroup = flag.Bool("systemd-cgroup", false, "Use systemd for cgroups. NOT SUPPORTED.")
	showVersion   = flag.Bool("version", false, "show version and exit.")

	// These flags are unique to runsc, and are used to configure parts of the
	// system that are not covered by the runtime spec.

	// Debugging flags.
	logFD      = flag.Int("log-fd", -1, "file descriptor to log to.  If set, the 'log' flag is ignored.")
	debugLogFD = flag.Int("debug-log-fd", -1, "file descriptor to write debug logs to.  If set, the 'debug-log-dir' flag is ignored.")
	panicLogFD = flag.Int("panic-log-fd", -1, "file descriptor to write Go's runtime messages.")
)

// Main is the main entrypoint.
func Main(version string) {
	// Help and flags commands are generated automatically.
	help := cmd.NewHelp(subcommands.DefaultCommander)
	help.Register(new(cmd.Syscalls))
	subcommands.Register(help, "")
	subcommands.Register(subcommands.FlagsCommand(), "")

	// Installation helpers.
	const helperGroup = "helpers"
	subcommands.Register(new(cmd.Install), helperGroup)
	subcommands.Register(new(cmd.Uninstall), helperGroup)

	// Register user-facing runsc commands.
	subcommands.Register(new(cmd.Checkpoint), "")
	subcommands.Register(new(cmd.Create), "")
	subcommands.Register(new(cmd.Delete), "")
	subcommands.Register(new(cmd.Do), "")
	subcommands.Register(new(cmd.Events), "")
	subcommands.Register(new(cmd.Exec), "")
	subcommands.Register(new(cmd.Gofer), "")
	subcommands.Register(new(cmd.Kill), "")
	subcommands.Register(new(cmd.List), "")
	subcommands.Register(new(cmd.Pause), "")
	subcommands.Register(new(cmd.PS), "")
	subcommands.Register(new(cmd.Restore), "")
	subcommands.Register(new(cmd.Resume), "")
	subcommands.Register(new(cmd.Run), "")
	subcommands.Register(new(cmd.Spec), "")
	subcommands.Register(new(cmd.State), "")
	subcommands.Register(new(cmd.Start), "")
	subcommands.Register(new(cmd.Wait), "")

	// Register internal commands with the internal group name. This causes
	// them to be sorted below the user-facing commands with empty group.
	// The string below will be printed above the commands.
	const internalGroup = "internal use only"
	subcommands.Register(new(cmd.Boot), internalGroup)
	subcommands.Register(new(cmd.Debug), internalGroup)
	subcommands.Register(new(cmd.Gofer), internalGroup)
	subcommands.Register(new(cmd.Statefile), internalGroup)

	config.RegisterFlags()

	// All subcommands must be registered before flag parsing.
	flag.Parse()

	// Are we showing the version?
	if *showVersion {
		// The format here is the same as runc.
		fmt.Fprintf(os.Stdout, "runsc version %s\n", version)
		fmt.Fprintf(os.Stdout, "spec: %s\n", specutils.Version)
		os.Exit(0)
	}

	// Create a new Config from the flags.
	conf, err := config.NewFromFlags()
	if err != nil {
		cmd.Fatalf(err.Error())
	}

	// TODO(gvisor.dev/issue/193): support systemd cgroups
	if *systemdCgroup {
		fmt.Fprintln(os.Stderr, "systemd cgroup flag passed, but systemd cgroups not supported. See gvisor.dev/issue/193")
		os.Exit(1)
	}

	var errorLogger io.Writer
	if *logFD > -1 {
		errorLogger = os.NewFile(uintptr(*logFD), "error log file")

	} else if conf.LogFilename != "" {
		// We must set O_APPEND and not O_TRUNC because Docker passes
		// the same log file for all commands (and also parses these
		// log files), so we can't destroy them on each command.
		var err error
		errorLogger, err = os.OpenFile(conf.LogFilename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
		if err != nil {
			cmd.Fatalf("error opening log file %q: %v", conf.LogFilename, err)
		}
	}
	cmd.ErrorLogger = errorLogger

	if _, err := platform.Lookup(conf.Platform); err != nil {
		cmd.Fatalf("%v", err)
	}

	// Sets the reference leak check mode. Also set it in config below to
	// propagate it to child processes.
	refs.SetLeakMode(conf.ReferenceLeak)

	// Set up logging.
	if conf.Debug {
		log.SetLevel(log.Debug)
	}

	// Logging will include the local date and time via the time package.
	//
	// On first use, time.Local initializes the local time zone, which
	// involves opening tzdata files on the host. Since this requires
	// opening host files, it must be done before syscall filter
	// installation.
	//
	// Generally there will be a log message before filter installation
	// that will force initialization, but force initialization here in
	// case that does not occur.
	_ = time.Local.String()

	subcommand := flag.CommandLine.Arg(0)

	var e log.Emitter
	if *debugLogFD > -1 {
		f := os.NewFile(uintptr(*debugLogFD), "debug log file")

		e = newEmitter(conf.DebugLogFormat, f)

	} else if conf.DebugLog != "" {
		f, err := specutils.DebugLogFile(conf.DebugLog, subcommand, "" /* name */)
		if err != nil {
			cmd.Fatalf("error opening debug log file in %q: %v", conf.DebugLog, err)
		}
		e = newEmitter(conf.DebugLogFormat, f)

	} else {
		// Stderr is reserved for the application, just discard the logs if no debug
		// log is specified.
		e = newEmitter("text", ioutil.Discard)
	}

	if *panicLogFD > -1 || *debugLogFD > -1 {
		fd := *panicLogFD
		if fd < 0 {
			fd = *debugLogFD
		}
		// Quick sanity check to make sure no other commands get passed
		// a log fd (they should use log dir instead).
		if subcommand != "boot" && subcommand != "gofer" {
			cmd.Fatalf("flags --debug-log-fd and --panic-log-fd should only be passed to 'boot' and 'gofer' command, but was passed to %q", subcommand)
		}

		// If we are the boot process, then we own our stdio FDs and can do what we
		// want with them. Since Docker and Containerd both eat boot's stderr, we
		// dup our stderr to the provided log FD so that panics will appear in the
		// logs, rather than just disappear.
		if err := syscall.Dup3(fd, int(os.Stderr.Fd()), 0); err != nil {
			cmd.Fatalf("error dup'ing fd %d to stderr: %v", fd, err)
		}
	} else if conf.AlsoLogToStderr {
		e = &log.MultiEmitter{e, newEmitter(conf.DebugLogFormat, os.Stderr)}
	}

	log.SetTarget(e)

	log.Infof("***************************")
	log.Infof("Args: %s", os.Args)
	log.Infof("Version %s", version)
	log.Infof("GOOS: %s", runtime.GOOS)
	log.Infof("GOARCH: %s", runtime.GOARCH)
	log.Infof("PID: %d", os.Getpid())
	log.Infof("UID: %d, GID: %d", os.Getuid(), os.Getgid())
	log.Infof("Configuration:")
	log.Infof("\t\tRootDir: %s", conf.RootDir)
	log.Infof("\t\tPlatform: %v", conf.Platform)
	log.Infof("\t\tFileAccess: %v, overlay: %t", conf.FileAccess, conf.Overlay)
	log.Infof("\t\tNetwork: %v, logging: %t", conf.Network, conf.LogPackets)
	log.Infof("\t\tStrace: %t, max size: %d, syscalls: %s", conf.Strace, conf.StraceLogSize, conf.StraceSyscalls)
	log.Infof("\t\tVFS2 enabled: %v", conf.VFS2)
	log.Infof("***************************")

	if conf.TestOnlyAllowRunAsCurrentUserWithoutChroot {
		// SIGTERM is sent to all processes if a test exceeds its
		// timeout and this case is handled by syscall_test_runner.
		log.Warningf("Block the TERM signal. This is only safe in tests!")
		signal.Ignore(syscall.SIGTERM)
	}

	// Call the subcommand and pass in the configuration.
	var ws syscall.WaitStatus
	subcmdCode := subcommands.Execute(context.Background(), conf, &ws)
	if subcmdCode == subcommands.ExitSuccess {
		log.Infof("Exiting with status: %v", ws)
		if ws.Signaled() {
			// No good way to return it, emulate what the shell does. Maybe raise
			// signal to self?
			os.Exit(128 + int(ws.Signal()))
		}
		os.Exit(ws.ExitStatus())
	}
	// Return an error that is unlikely to be used by the application.
	log.Warningf("Failure to execute command, err: %v", subcmdCode)
	os.Exit(128)
}

func newEmitter(format string, logFile io.Writer) log.Emitter {
	switch format {
	case "text":
		return log.GoogleEmitter{&log.Writer{Next: logFile}}
	case "json":
		return log.JSONEmitter{&log.Writer{Next: logFile}}
	case "json-k8s":
		return log.K8sJSONEmitter{&log.Writer{Next: logFile}}
	}
	cmd.Fatalf("invalid log format %q, must be 'text', 'json', or 'json-k8s'", format)
	panic("unreachable")
}