package updates

import (
	"context"
	"flag"
	"fmt"
	"runtime"
	"time"

	"github.com/safing/portbase/dataroot"
	"github.com/safing/portbase/log"
	"github.com/safing/portbase/modules"
	"github.com/safing/portbase/updater"
)

const (
	onWindows = runtime.GOOS == "windows"

	releaseChannelKey    = "core/releaseChannel"
	releaseChannelStable = "stable"
	releaseChannelBeta   = "beta"

	disableUpdatesKey = "core/disableUpdates"

	// ModuleName is the name of the update module
	// and can be used when declaring module dependencies.
	ModuleName = "updates"

	// VersionUpdateEvent is emitted every time a new
	// version of a monitored resource is selected.
	// During module initialization VersionUpdateEvent
	// is also emitted.
	VersionUpdateEvent = "active version update"

	// ResourceUpdateEvent is emitted every time the
	// updater successfully performed a resource update.
	// ResourceUpdateEvent is emitted even if no new
	// versions are available. Subscribers are expected
	// to check if new versions of their resources are
	// available by checking File.UpgradeAvailable().
	ResourceUpdateEvent = "resource update"

	// TriggerUpdateEvent is the event that can be emitted
	// by the updates module to trigger an update.
	TriggerUpdateEvent = "trigger update"
)

var (
	module            *modules.Module
	registry          *updater.ResourceRegistry
	userAgentFromFlag string

	updateTask          *modules.Task
	updateASAP          bool
	disableTaskSchedule bool

	// MandatoryUpdates is a list of full identifiers that
	// should always be kept up to date.
	MandatoryUpdates []string

	// UserAgent is an HTTP User-Agent that is used to add
	// more context to requests made by the registry when
	// fetching resources from the update server.
	UserAgent = "Core"
)

const (
	updateInProgress     = "update-in-progress"
	updateInProcessDescr = "Portmaster is currently checking and downloading updates."
	updateFailed         = "update-failed"
)

func init() {
	module = modules.Register(ModuleName, prep, start, stop, "base")
	module.RegisterEvent(VersionUpdateEvent)
	module.RegisterEvent(ResourceUpdateEvent)

	flag.StringVar(&userAgentFromFlag, "update-agent", "", "Sets the user agent for requests to the update server")

	// initialize mandatory updates
	if onWindows {
		MandatoryUpdates = []string{
			platform("core/portmaster-core.exe"),
			platform("start/portmaster-start.exe"),
			platform("app/portmaster-app.exe"),
			platform("notifier/portmaster-notifier.exe"),
			platform("notifier/portmaster-snoretoast.exe"),
		}
	} else {
		MandatoryUpdates = []string{
			platform("core/portmaster-core"),
			platform("start/portmaster-start"),
			platform("app/portmaster-app"),
			platform("notifier/portmaster-notifier"),
		}
	}
}

func prep() error {
	if err := registerConfig(); err != nil {
		return err
	}

	module.RegisterEvent(TriggerUpdateEvent)

	return nil
}

func start() error {
	initConfig()

	restartTask = module.NewTask("automatic restart", automaticRestart).MaxDelay(10 * time.Minute)

	if err := module.RegisterEventHook(
		"config",
		"config change",
		"update registry config",
		updateRegistryConfig); err != nil {
		return err
	}

	if err := module.RegisterEventHook(
		module.Name,
		TriggerUpdateEvent,
		"Check for and download available updates",
		func(context.Context, interface{}) error {
			_ = TriggerUpdate()
			return nil
		},
	); err != nil {
		return err
	}

	// create registry
	registry = &updater.ResourceRegistry{
		Name: ModuleName,
		UpdateURLs: []string{
			"https://updates.safing.io",
		},
		UserAgent:        UserAgent,
		MandatoryUpdates: MandatoryUpdates,
		Beta:             releaseChannel() == releaseChannelBeta,
		DevMode:          devMode(),
		Online:           true,
	}
	if userAgentFromFlag != "" {
		// override with flag value
		registry.UserAgent = userAgentFromFlag
	}
	// initialize
	err := registry.Initialize(dataroot.Root().ChildDir("updates", 0755))
	if err != nil {
		return err
	}

	registry.AddIndex(updater.Index{
		Path:   "stable.json",
		Stable: true,
		Beta:   false,
	})

	registry.AddIndex(updater.Index{
		Path:   "beta.json",
		Stable: false,
		Beta:   true,
	})

	registry.AddIndex(updater.Index{
		Path:   "all/intel/intel.json",
		Stable: true,
		Beta:   false,
	})

	err = registry.LoadIndexes(module.Ctx)
	if err != nil {
		log.Warningf("updates: failed to load indexes: %s", err)
	}

	err = registry.ScanStorage("")
	if err != nil {
		log.Warningf("updates: error during storage scan: %s", err)
	}

	registry.SelectVersions()
	module.TriggerEvent(VersionUpdateEvent, nil)

	err = initVersionExport()
	if err != nil {
		return err
	}

	// start updater task
	updateTask = module.NewTask("updater", func(ctx context.Context, task *modules.Task) error {
		return checkForUpdates(ctx)
	})

	if !disableTaskSchedule {
		updateTask.
			Repeat(1 * time.Hour).
			MaxDelay(30 * time.Minute).
			Schedule(time.Now().Add(10 * time.Second))
	}

	if updateASAP {
		updateTask.StartASAP()
	}

	// react to upgrades
	if err := initUpgrader(); err != nil {
		return err
	}

	warnOnIncorrectParentPath()

	return nil
}

// TriggerUpdate queues the update task to execute ASAP.
func TriggerUpdate() error {
	if !module.Online() {
		if !module.OnlineSoon() {
			return fmt.Errorf("module not enabled")
		}

		updateASAP = true
	} else {
		updateTask.StartASAP()
		log.Debugf("updates: triggering update to run as soon as possible")
	}

	return nil
}

// DisableUpdateSchedule disables the update schedule.
// If called, updates are only checked when TriggerUpdate()
// is called.
func DisableUpdateSchedule() error {
	if module.OnlineSoon() {
		return fmt.Errorf("module already online")
	}

	disableTaskSchedule = true

	return nil
}

func checkForUpdates(ctx context.Context) (err error) {
	if updatesCurrentlyDisabled {
		log.Debugf("updates: automatic updates are disabled")
		return nil
	}
	defer log.Debugf("updates: finished checking for updates")

	module.Hint(updateInProgress, updateInProcessDescr)

	defer func() {
		if err == nil {
			module.Resolve(updateInProgress)
		} else {
			module.Warning(updateFailed, "Failed to check for updates: "+err.Error())
		}
	}()

	if err = registry.UpdateIndexes(ctx); err != nil {
		log.Warningf("updates: failed to update indexes: %s", err)
	}

	err = registry.DownloadUpdates(ctx)
	if err != nil {
		err = fmt.Errorf("failed to update: %w", err)
		return
	}

	registry.SelectVersions()

	module.TriggerEvent(ResourceUpdateEvent, nil)
	return nil
}

func stop() error {
	if registry != nil {
		return registry.Cleanup()
	}

	return stopVersionExport()
}

func platform(identifier string) string {
	return fmt.Sprintf("%s_%s/%s", runtime.GOOS, runtime.GOARCH, identifier)
}