package main

// SPDX-License-Identifier: GPL-3.0-or-later

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"net/url"
	"os"
	"os/signal"
	"runtime"
	"sync"
	"syscall"
	"time"

	"github.com/benbjohnson/clock"
	"github.com/mattn/go-colorable"
	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"

	"projects.blender.org/studio/flamenco/internal/appinfo"
	"projects.blender.org/studio/flamenco/internal/worker"
	"projects.blender.org/studio/flamenco/internal/worker/cli_runner"
)

var (
	w                *worker.Worker
	listener         *worker.Listener
	buffer           *worker.UpstreamBufferDB
	shutdownComplete chan struct{}
)

const flamencoWorkerDatabase = "flamenco-worker.sqlite"

var cliArgs struct {
	// Do-and-quit flags.
	version bool
	flush   bool

	// Logging level flags.
	quiet, debug, trace bool

	managerURL  *url.URL
	findManager bool

	manager  string
	register bool

	restartExitCode int
}

func main() {
	parseCliArgs()
	if cliArgs.version {
		fmt.Println(appinfo.ExtendedVersion())
		return
	}

	output := zerolog.ConsoleWriter{Out: colorable.NewColorableStdout(), TimeFormat: time.RFC3339}
	log.Logger = log.Output(output)

	log.Info().
		Str("version", appinfo.ApplicationVersion).
		Str("git", appinfo.ApplicationGitHash).
		Str("releaseCycle", appinfo.ReleaseCycle).
		Str("OS", runtime.GOOS).
		Str("ARCH", runtime.GOARCH).
		Int("pid", os.Getpid()).
		Msgf("starting %v Worker", appinfo.ApplicationName)
	configLogLevel()

	if cliArgs.findManager {
		// TODO: move this to a more suitable place.
		discoverTimeout := 1 * time.Minute
		discoverCtx, discoverCancel := context.WithTimeout(context.Background(), discoverTimeout)
		defer discoverCancel()
		managerURL, err := worker.AutodiscoverManager(discoverCtx)
		if err != nil {
			logFatalManagerDiscoveryError(err, discoverTimeout)
		}
		log.Info().Str("manager", managerURL).Msg("found Manager")
		return
	}

	// Load configuration, and override things from the CLI arguments if necessary.
	configWrangler := worker.NewConfigWrangler()

	// Before the config can be overridden, it has to be loaded.
	if _, err := configWrangler.WorkerConfig(); err != nil {
		log.Fatal().Err(err).Msg("error loading worker configuration")
	}

	if cliArgs.managerURL != nil {
		url := cliArgs.managerURL.String()
		log.Info().Str("manager", url).Msg("using Manager URL from commandline")
		configWrangler.SetManagerURL(url)
	}
	if cliArgs.restartExitCode != 0 {
		log.Info().Int("exitCode", cliArgs.restartExitCode).
			Msg("will tell Manager this Worker can restart")
		configWrangler.SetRestartExitCode(cliArgs.restartExitCode)
	}

	findBlender()
	findFFmpeg()

	// Give the auto-discovery some time to find a Manager.
	discoverTimeout := 10 * time.Minute
	discoverCtx, discoverCancel := context.WithTimeout(context.Background(), discoverTimeout)
	defer discoverCancel()
	if err := worker.MaybeAutodiscoverManager(discoverCtx, &configWrangler); err != nil {
		logFatalManagerDiscoveryError(err, discoverTimeout)
	}

	// Startup can take arbitrarily long, as it only ends when the Manager can be
	// reached and accepts our sign-on request. An offline Manager would cause the
	// Worker to wait for it indefinitely.
	startupCtx := context.Background()
	client, startupState := worker.RegisterOrSignOn(startupCtx, &configWrangler)

	shutdownComplete = make(chan struct{})
	workerCtx, workerCtxCancel := context.WithCancel(context.Background())

	timeService := clock.New()
	buffer = upstreamBufferOrDie(client, timeService)
	if queueSize, err := buffer.QueueSize(); err != nil {
		log.Fatal().Err(err).Msg("error checking upstream buffer")
	} else if queueSize > 0 {
		// Flush any updates before actually starting the Worker.
		log.Info().Int("queueSize", queueSize).Msg("flushing upstream buffer")
		buffer.Flush(workerCtx)
	}

	if cliArgs.flush {
		log.Info().Msg("upstream buffer flushed, shutting down")
		worker.SignOff(workerCtx, log.Logger, client)
		workerCtxCancel()
		shutdown()
		return
	}

	cliRunner := cli_runner.NewCLIRunner()
	listener = worker.NewListener(client, buffer)
	cmdRunner := worker.NewCommandExecutor(cliRunner, listener, timeService)
	taskRunner := worker.NewTaskExecutor(cmdRunner, listener)
	w = worker.NewWorker(client, taskRunner)

	// Handle Ctrl+C
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	signal.Notify(c, syscall.SIGTERM)
	go func() {
		for signum := range c {
			log.Info().Str("signal", signum.String()).Msg("signal received, shutting down.")

			// Run the shutdown sequence in a goroutine, so that multiple Ctrl+C presses can be handled in parallel.
			workerCtxCancel()
			go shutdown()
		}
	}()

	wg := sync.WaitGroup{}
	wg.Add(1)
	go func() {
		defer wg.Done()
		listener.Run(workerCtx)
	}()

	go w.Start(workerCtx, startupState)

	shutdownReason := w.WaitForShutdown(workerCtx)
	if shutdownReason != worker.ReasonContextClosed {
		go shutdown()
	}
	<-shutdownComplete

	workerCtxCancel()
	wg.Wait()

	log.Debug().Msg("process shutting down")
	config, _ := configWrangler.WorkerConfig()
	stopProcess(config, shutdownReason)
}

func shutdown() {
	done := make(chan struct{})
	go func() {
		if w != nil {
			w.Close()
			if err := buffer.Close(); err != nil {
				log.Error().Err(err).Msg("closing upstream task buffer")
			}

			// Sign off as the last step. Any flushes should happen while we're still signed on.
			signoffCtx, cancelFunc := context.WithTimeout(context.Background(), 3*time.Second)
			defer cancelFunc()
			w.SignOff(signoffCtx)
		}
		close(done)
	}()

	select {
	case <-done:
		log.Debug().Msg("shutdown OK")
	case <-time.After(20 * time.Second):
		log.Error().Msg("shutdown forced, stopping process.")
		os.Exit(-2)
	}

	log.Warn().Msg("shutdown complete, stopping process.")
	close(shutdownComplete)
}

func stopProcess(config worker.WorkerConfig, shutdownReason worker.ShutdownReason) {
	switch shutdownReason {
	case worker.ReasonContextClosed:
		os.Exit(1)
	case worker.ReasonShutdownReq:
		os.Exit(0)
	case worker.ReasonRestartReq:
		os.Exit(config.RestartExitCode)
	}
}

func parseCliArgs() {
	flag.BoolVar(&cliArgs.version, "version", false, "Shows the application version, then exits.")
	flag.BoolVar(&cliArgs.flush, "flush", false, "Flush any buffered task updates to the Manager, then exits.")

	flag.BoolVar(&cliArgs.quiet, "quiet", false, "Only log warning-level and worse.")
	flag.BoolVar(&cliArgs.debug, "debug", false, "Enable debug-level logging.")
	flag.BoolVar(&cliArgs.trace, "trace", false, "Enable trace-level logging.")

	// TODO: make this override whatever was stored in the configuration file.
	flag.StringVar(&cliArgs.manager, "manager", "", "URL of the Flamenco Manager.")
	flag.BoolVar(&cliArgs.register, "register", false, "(Re-)register at the Manager.")
	flag.BoolVar(&cliArgs.findManager, "find-manager", false, "Autodiscover a Manager, then quit.")

	flag.IntVar(&cliArgs.restartExitCode, "restart-exit-code", 0,
		"Mark this Worker as restartable. It will exit with this code to signify it needs to be restarted.")

	flag.Parse()

	if cliArgs.manager != "" {
		var err error
		cliArgs.managerURL, err = worker.ParseURL(cliArgs.manager)
		if err != nil {
			log.Fatal().Err(err).Msg("invalid manager URL")
		}
	}
}

func configLogLevel() {
	var logLevel zerolog.Level
	switch {
	case cliArgs.trace:
		logLevel = zerolog.TraceLevel
	case cliArgs.debug:
		logLevel = zerolog.DebugLevel
	case cliArgs.quiet:
		logLevel = zerolog.WarnLevel
	default:
		logLevel = zerolog.InfoLevel
	}
	zerolog.SetGlobalLevel(logLevel)
}

func upstreamBufferOrDie(client worker.FlamencoClient, timeService clock.Clock) *worker.UpstreamBufferDB {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	buffer, err := worker.NewUpstreamBuffer(client, timeService)
	if err != nil {
		log.Fatal().Err(err).Msg("unable to create task update queue database")
	}

	dbPath, err := appinfo.InFlamencoHome(flamencoWorkerDatabase)
	if err != nil {
		log.Fatal().Err(err).Msg("unable to figure out where to save my database")
	}

	if err := buffer.OpenDB(ctx, dbPath); err != nil {
		log.Fatal().Err(err).Msg("unable to open task update queue database")
	}

	return buffer
}

func logFatalManagerDiscoveryError(err error, discoverTimeout time.Duration) {
	if errors.Is(err, context.DeadlineExceeded) {
		log.Fatal().Str("timeout", discoverTimeout.String()).Msg("could not discover Manager in time")
	} else {
		log.Fatal().Err(err).Msg("auto-discovery error")
	}
}