package captain

import (
	"errors"
	"fmt"
	"time"

	"github.com/tevino/abool"

	"github.com/safing/portmaster/base/log"
	"github.com/safing/portmaster/base/notifications"
	"github.com/safing/portmaster/service/mgr"
	"github.com/safing/portmaster/service/netenv"
	"github.com/safing/portmaster/service/network/netutils"
	"github.com/safing/portmaster/spn/access"
	"github.com/safing/portmaster/spn/conf"
	"github.com/safing/portmaster/spn/crew"
	"github.com/safing/portmaster/spn/docks"
	"github.com/safing/portmaster/spn/navigator"
	"github.com/safing/portmaster/spn/terminal"
)

var (
	ready = abool.New()

	spnLoginButton = notifications.Action{
		Text:    "Login",
		Type:    notifications.ActionTypeOpenPage,
		Payload: "spn",
	}
	spnOpenAccountPage = notifications.Action{
		Text:    "Open Account Page",
		Type:    notifications.ActionTypeOpenURL,
		Payload: "https://account.safing.io",
	}
)

// ClientReady signifies if the SPN client is fully ready to handle connections.
func ClientReady() bool {
	return ready.IsSet()
}

type (
	clientComponentFunc   func(ctx *mgr.WorkerCtx) clientComponentResult
	clientComponentResult uint8
)

const (
	clientResultOk        clientComponentResult = iota // Continue and clean module status.
	clientResultRetry                                  // Go back to start of current step, don't clear module status.
	clientResultReconnect                              // Stop current connection and start from zero.
	clientResultShutdown                               // SPN Module is shutting down.
)

var (
	clientNetworkChangedFlag               = netenv.GetNetworkChangedFlag()
	clientIneligibleAccountUpdateDelay     = 1 * time.Minute
	clientRetryConnectBackoffDuration      = 5 * time.Second
	clientInitialHealthCheckDelay          = 10 * time.Second
	clientHealthCheckTickDuration          = 1 * time.Minute
	clientHealthCheckTickDurationSleepMode = 5 * time.Minute
	clientHealthCheckTimeout               = 15 * time.Second

	clientHealthCheckTrigger = make(chan struct{}, 1)
	lastHealthCheck          time.Time
)

func triggerClientHealthCheck() {
	select {
	case clientHealthCheckTrigger <- struct{}{}:
	default:
	}
}

func clientManager(ctx *mgr.WorkerCtx) error {
	defer func() {
		ready.UnSet()
		netenv.ConnectedToSPN.UnSet()
		resetSPNStatus(StatusDisabled, true)
		module.states.Clear()
		clientStopHomeHub(ctx)
	}()

	module.states.Add(mgr.State{
		ID:      "spn:establishing-home-hub",
		Name:    "Connecting to SPN...",
		Message: "Connecting to the SPN network is in progress.",
		Type:    mgr.StateTypeHint,
	})

	// TODO: When we are starting and the SPN module is faster online than the
	// nameserver, then updating the account will fail as the DNS query is
	// redirected to a closed port.
	// We also can't add the nameserver as a module dependency, as the nameserver
	// is not part of the server.
	select {
	case <-time.After(1 * time.Second):
	case <-ctx.Done():
		return nil
	}

	module.healthCheckTicker = mgr.NewSleepyTicker(clientHealthCheckTickDuration, clientHealthCheckTickDurationSleepMode)
	defer module.healthCheckTicker.Stop()

reconnect:
	for {
		// Check if we are shutting down.
		if ctx.IsDone() {
			return nil
		}

		// Reset SPN status.
		if ready.SetToIf(true, false) {
			netenv.ConnectedToSPN.UnSet()
			log.Info("spn/captain: client not ready")
		}
		resetSPNStatus(StatusConnecting, true)

		// Check everything and connect to the SPN.
		for _, clientFunc := range []clientComponentFunc{
			clientStopHomeHub,
			clientCheckNetworkReady,
			clientCheckAccountAndTokens,
			clientConnectToHomeHub,
			clientSetActiveConnectionStatus,
		} {
			switch clientFunc(ctx) {
			case clientResultOk:
				// Continue
			case clientResultRetry, clientResultReconnect:
				// Wait for a short time to not loop too quickly.
				select {
				case <-time.After(clientRetryConnectBackoffDuration):
					continue reconnect
				case <-ctx.Done():
					return nil
				}
			case clientResultShutdown:
				return nil
			}
		}

		log.Info("spn/captain: client is ready")
		ready.Set()
		netenv.ConnectedToSPN.Set()

		module.EventSPNConnected.Submit(struct{}{})
		if conf.Integrated() {
			module.mgr.Go("update quick setting countries", navigator.Main.UpdateConfigQuickSettings)
		}

		// Reset last health check value, as we have just connected.
		lastHealthCheck = time.Now()

		// Back off before starting initial health checks.
		select {
		case <-time.After(clientInitialHealthCheckDelay):
		case <-ctx.Done():
			return nil
		}

		for {
			// Check health of the current SPN connection and monitor the user status.
		maintainers:
			for _, clientFunc := range []clientComponentFunc{
				clientCheckHomeHubConnection,
				clientCheckAccountAndTokens,
				clientSetActiveConnectionStatus,
			} {
				switch clientFunc(ctx) {
				case clientResultOk:
					// Continue
				case clientResultRetry:
					// Abort and wait for the next run.
					break maintainers
				case clientResultReconnect:
					continue reconnect
				case clientResultShutdown:
					return nil
				}
			}

			// Wait for signal to run maintenance again.
			select {
			case <-module.healthCheckTicker.Wait():
			case <-clientHealthCheckTrigger:
			case <-crew.ConnectErrors():
			case <-clientNetworkChangedFlag.Signal():
				clientNetworkChangedFlag.Refresh()
			case <-ctx.Done():
				return nil
			}
		}
	}
}

func clientCheckNetworkReady(ctx *mgr.WorkerCtx) clientComponentResult {
	// Check if we are online enough for connecting.
	switch netenv.GetOnlineStatus() { //nolint:exhaustive
	case netenv.StatusOffline,
		netenv.StatusLimited:
		select {
		case <-ctx.Done():
			return clientResultShutdown
		case <-time.After(1 * time.Second):
			return clientResultRetry
		}
	}

	return clientResultOk
}

// DisableAccount disables using any account related SPN functionality.
// Attempts to use the same will result in errors.
var DisableAccount bool

func clientCheckAccountAndTokens(ctx *mgr.WorkerCtx) clientComponentResult {
	if DisableAccount {
		return clientResultOk
	}

	// Get SPN user.
	user, err := access.GetUser()
	if err != nil && !errors.Is(err, access.ErrNotLoggedIn) {
		notifications.NotifyError(
			"spn:failed-to-get-user",
			"SPN Internal Error",
			`Please restart Portmaster.`,
			// TODO: Add restart button.
			// TODO: Use special UI restart action in order to reload UI on restart.
		).SyncWithState(module.states)
		resetSPNStatus(StatusFailed, true)
		log.Errorf("spn/captain: client internal error: %s", err)
		return clientResultReconnect
	}

	// Check if user is logged in.
	if user == nil || !user.IsLoggedIn() {
		notifications.NotifyWarn(
			"spn:not-logged-in",
			"SPN Login Required",
			`Please log in to access the SPN.`,
			spnLoginButton,
		).SyncWithState(module.states)
		resetSPNStatus(StatusFailed, true)
		log.Warningf("spn/captain: enabled but not logged in")
		return clientResultReconnect
	}

	// Check if user is eligible.
	if !user.MayUseTheSPN() {
		// Update user in case there was a change.
		// Only update here if we need to - there is an update task in the access
		// module for periodic updates.
		if time.Now().Add(-clientIneligibleAccountUpdateDelay).After(time.Unix(user.Meta().Modified, 0)) {
			_, _, err := access.UpdateUser()
			if err != nil {
				notifications.NotifyError(
					"spn:failed-to-update-user",
					"SPN Account Server Error",
					fmt.Sprintf(`The status of your SPN account could not be updated: %s`, err),
				).SyncWithState(module.states)
				resetSPNStatus(StatusFailed, true)
				log.Errorf("spn/captain: failed to update ineligible account: %s", err)
				return clientResultReconnect
			}
		}

		// Check if user is eligible after a possible update.
		if !user.MayUseTheSPN() {

			// If package is generally valid, then the current package does not have access to the SPN.
			if user.MayUse("") {
				notifications.NotifyError(
					"spn:package-not-eligible",
					"SPN Not Included In Package",
					"Your current Portmaster Package does not include access to the SPN. Please upgrade your package on the Account Page.",
					spnOpenAccountPage,
				).SyncWithState(module.states)
				resetSPNStatus(StatusFailed, true)
				return clientResultReconnect
			}

			// Otherwise, include the message from the user view.
			message := "There is an issue with your Portmaster Package. Please check the Account Page."
			if user.View != nil && user.View.Message != "" {
				message = user.View.Message
			}
			notifications.NotifyError(
				"spn:subscription-inactive",
				"Portmaster Package Issue",
				"Cannot enable SPN: "+message,
				spnOpenAccountPage,
			).SyncWithState(module.states)
			resetSPNStatus(StatusFailed, true)
			return clientResultReconnect
		}
	}

	// Check if we have enough tokens.
	if access.ShouldRequest(access.ExpandAndConnectZones) {
		err := access.UpdateTokens()
		if err != nil {
			log.Errorf("spn/captain: failed to get tokens: %s", err)

			// There was an error updating the account.
			// Check if we have enough tokens to continue anyway.
			regular, _ := access.GetTokenAmount(access.ExpandAndConnectZones)
			if regular == 0 /* && fallback == 0 */ { // TODO: Add fallback token check when fallback was tested on servers.
				notifications.NotifyError(
					"spn:tokens-exhausted",
					"SPN Access Tokens Exhausted",
					`The Portmaster failed to get new access tokens to access the SPN. The Portmaster will automatically retry to get new access tokens.`,
				).SyncWithState(module.states)
				resetSPNStatus(StatusFailed, false)
			}
			return clientResultRetry
		}
	}

	return clientResultOk
}

func clientStopHomeHub(ctx *mgr.WorkerCtx) clientComponentResult {
	// Don't use the context in this function, as it will likely be canceled
	// already and would disrupt any context usage in here.

	// Get crane connecting to home.
	home, _ := navigator.Main.GetHome()
	if home == nil {
		return clientResultOk
	}
	crane := docks.GetAssignedCrane(home.Hub.ID)
	if crane == nil {
		return clientResultOk
	}

	// Stop crane and all connected terminals.
	crane.Stop(nil)
	return clientResultOk
}

func clientConnectToHomeHub(ctx *mgr.WorkerCtx) clientComponentResult {
	err := establishHomeHub(ctx)
	if err != nil {
		if ctx.IsDone() {
			return clientResultShutdown
		}

		log.Errorf("spn/captain: failed to establish connection to home hub: %s", err)
		resetSPNStatus(StatusFailed, true)

		switch {
		case errors.Is(err, ErrAllHomeHubsExcluded):
			notifications.NotifyError(
				"spn:all-home-hubs-excluded",
				"All Home Nodes Excluded",
				"Your current Home Node Rules exclude all available and eligible SPN Nodes. Please change your rules to allow for at least one available and eligible Home Node.",
				notifications.Action{
					Text: "Configure",
					Type: notifications.ActionTypeOpenSetting,
					Payload: &notifications.ActionTypeOpenSettingPayload{
						Key: CfgOptionHomeHubPolicyKey,
					},
				},
			).SyncWithState(module.states)

		case errors.Is(err, ErrReInitSPNSuggested):
			notifications.NotifyError(
				"spn:cannot-bootstrap",
				"SPN Cannot Bootstrap",
				"The local state of the SPN network is likely outdated. Portmaster was not able to identify a server to connect to. Please re-initialize the SPN using the tools menu or the button on the notification.",
				notifications.Action{
					ID:   "re-init",
					Text: "Re-Init SPN",
					Type: notifications.ActionTypeWebhook,
					Payload: &notifications.ActionTypeWebhookPayload{
						URL:          apiPathForSPNReInit,
						ResultAction: "display",
					},
				},
			).SyncWithState(module.states)

		default:
			notifications.NotifyWarn(
				"spn:home-hub-failure",
				"SPN Failed to Connect",
				fmt.Sprintf("Failed to connect to a home hub: %s. The Portmaster will retry to connect automatically.", err),
			).SyncWithState(module.states)
		}

		return clientResultReconnect
	}

	// Log new connection.
	home, _ := navigator.Main.GetHome()
	if home != nil {
		log.Infof("spn/captain: established new home %s", home.Hub)
	}

	return clientResultOk
}

func clientSetActiveConnectionStatus(ctx *mgr.WorkerCtx) clientComponentResult {
	// Get current home.
	home, homeTerminal := navigator.Main.GetHome()
	if home == nil || homeTerminal == nil {
		return clientResultReconnect
	}

	// Resolve any connection error.
	module.states.Clear()

	// Update SPN Status with connection information, if not already correctly set.
	spnStatus.Lock()
	defer spnStatus.Unlock()

	if spnStatus.Status != StatusConnected || spnStatus.HomeHubID != home.Hub.ID {
		// Fill connection status data.
		spnStatus.Status = StatusConnected
		spnStatus.HomeHubID = home.Hub.ID
		spnStatus.HomeHubName = home.Hub.Info.Name

		connectedIP, _, err := netutils.IPPortFromAddr(homeTerminal.RemoteAddr())
		if err != nil {
			spnStatus.ConnectedIP = homeTerminal.RemoteAddr().String()
		} else {
			spnStatus.ConnectedIP = connectedIP.String()
		}
		spnStatus.ConnectedTransport = homeTerminal.Transport().String()

		geoLoc := home.GetLocation(connectedIP)
		if geoLoc != nil {
			spnStatus.ConnectedCountry = &geoLoc.Country
		}

		now := time.Now()
		spnStatus.ConnectedSince = &now

		// Push new status.
		pushSPNStatusUpdate()
	}

	return clientResultOk
}

func clientCheckHomeHubConnection(ctx *mgr.WorkerCtx) clientComponentResult {
	// Check the status of the Home Hub.
	home, homeTerminal := navigator.Main.GetHome()
	if home == nil || homeTerminal == nil || homeTerminal.IsBeingAbandoned() {
		return clientResultReconnect
	}

	// Get crane controller for health check.
	crane := docks.GetAssignedCrane(home.Hub.ID)
	if crane == nil {
		log.Errorf("spn/captain: could not find home hub crane for health check")
		return clientResultOk
	}

	// Ping home hub.
	latency, tErr := pingHome(ctx, crane.Controller, clientHealthCheckTimeout)
	if tErr != nil {
		log.Warningf("spn/captain: failed to ping home hub: %s", tErr)

		// Prepare to reconnect to the network.

		// Reset all failing states, as these might have been caused by the failing home hub.
		navigator.Main.ResetFailingStates()

		// If the last health check is clearly too long ago, assume that the device was sleeping and do not set the home node to failing yet.
		if time.Since(lastHealthCheck) > clientHealthCheckTickDuration+
			clientHealthCheckTickDurationSleepMode+
			(clientHealthCheckTimeout*2) {
			return clientResultReconnect
		}

		// Mark the home hub itself as failing, as we want to try to connect to somewhere else.
		home.MarkAsFailingFor(5 * time.Minute)

		return clientResultReconnect
	}
	lastHealthCheck = time.Now()

	log.Debugf("spn/captain: pinged home hub in %s", latency)
	return clientResultOk
}

func pingHome(ctx *mgr.WorkerCtx, t terminal.Terminal, timeout time.Duration) (latency time.Duration, err *terminal.Error) {
	started := time.Now()

	// Start ping operation.
	pingOp, tErr := crew.NewPingOp(t)
	if tErr != nil {
		return 0, tErr
	}

	// Wait for response.
	select {
	case <-ctx.Done():
		return 0, terminal.ErrCanceled
	case <-time.After(timeout):
		return 0, terminal.ErrTimeout
	case result := <-pingOp.Result:
		if result.Is(terminal.ErrExplicitAck) {
			return time.Since(started), nil
		}
		if result.IsOK() {
			return 0, result.Wrap("unexpected response")
		}
		return 0, result
	}
}