package subservers

import (
	"context"
	"fmt"
	"io/ioutil"
	"sync"
	"time"

	restProxy "github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
	"github.com/lightninglabs/lightning-terminal/perms"
	"github.com/lightninglabs/lightning-terminal/status"
	"github.com/lightninglabs/lndclient"
	"github.com/lightningnetwork/lnd/lncfg"
	"github.com/lightningnetwork/lnd/lnrpc"
	grpcProxy "github.com/mwitkow/grpc-proxy/proxy"
	"google.golang.org/grpc"
	"google.golang.org/grpc/backoff"
	"google.golang.org/grpc/credentials"
	"gopkg.in/macaroon-bakery.v2/bakery"
	"gopkg.in/macaroon.v2"
)

var (
	// maxMsgRecvSize is the largest message our REST proxy will receive. We
	// set this to 200MiB atm.
	maxMsgRecvSize = grpc.MaxCallRecvMsgSize(1 * 1024 * 1024 * 200)

	// defaultConnectTimeout is the default timeout for connecting to the
	// backend.
	defaultConnectTimeout = 15 * time.Second
)

// Manager manages a set of subServer objects.
type Manager struct {
	servers      map[string]*subServerWrapper
	permsMgr     *perms.Manager
	statusServer *status.Manager
	mu           sync.RWMutex
}

// NewManager constructs a new Manager.
func NewManager(permsMgr *perms.Manager,
	statusServer *status.Manager) *Manager {

	return &Manager{
		servers:      make(map[string]*subServerWrapper),
		permsMgr:     permsMgr,
		statusServer: statusServer,
	}
}

// AddServer adds a new subServer to the manager's set.
func (s *Manager) AddServer(ss SubServer, enable bool) error {
	// Register all sub-servers with the status server.
	err := s.statusServer.RegisterSubServer(ss.Name())
	if err != nil {
		return err
	}

	// If the sub-server has explicitly been disabled, then we don't add it
	// to the set of servers tracked by the Manager.
	if !enable {
		return nil
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	_, ok := s.servers[ss.Name()]
	if ok {
		return fmt.Errorf("a subserver with name %s has already "+
			"been registered with the subserver manager", ss.Name())
	}

	// Add the enabled server to the set of servers tracked by the Manager.
	s.servers[ss.Name()] = &subServerWrapper{
		SubServer: ss,
		quit:      make(chan struct{}),
	}

	// Register the sub-server's permissions with the permission manager.
	s.permsMgr.RegisterSubServer(
		ss.Name(), ss.Permissions(), ss.WhiteListedURLs(),
	)

	// Mark the sub-server as enabled with the status manager.
	s.statusServer.SetEnabled(ss.Name())

	return nil
}

// GetServer returns the sub-server with the given name if it exists.
func (s *Manager) GetServer(name string) (SubServer, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	ss, ok := s.servers[name]
	if !ok {
		return nil, false
	}

	return ss.SubServer, true
}

// StartIntegratedServers starts all the manager's sub-servers that should be
// started in integrated mode.
func (s *Manager) StartIntegratedServers(lndClient lnrpc.LightningClient,
	lndGrpc *lndclient.GrpcLndServices, withMacaroonService bool) {

	s.mu.Lock()
	defer s.mu.Unlock()

	for _, ss := range s.servers {
		if ss.Remote() {
			continue
		}

		err := ss.startIntegrated(
			lndClient, lndGrpc, withMacaroonService,
			func(err error) {
				s.statusServer.SetErrored(
					ss.Name(), err.Error(),
				)
			},
		)
		if err != nil {
			s.statusServer.SetErrored(ss.Name(), err.Error())
			continue
		}

		s.statusServer.SetRunning(ss.Name())
	}
}

// ConnectRemoteSubServers creates connections to all the manager's sub-servers
// that are running remotely.
func (s *Manager) ConnectRemoteSubServers() {
	s.mu.Lock()
	defer s.mu.Unlock()

	for _, ss := range s.servers {
		if !ss.Remote() {
			continue
		}

		err := ss.connectRemote()
		if err != nil {
			s.statusServer.SetErrored(ss.Name(), err.Error())
			continue
		}

		s.statusServer.SetRunning(ss.Name())
	}
}

// RegisterRPCServices registers all the manager's sub-servers with the given
// grpc registrar.
func (s *Manager) RegisterRPCServices(server grpc.ServiceRegistrar) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		// In remote mode the "director" of the RPC proxy will act as
		// a catch-all for any gRPC request that isn't known because we
		// didn't register any server for it. The director will then
		// forward the request to the remote service.
		if ss.Remote() {
			continue
		}

		ss.RegisterGrpcService(server)
	}
}

// RegisterRestServices registers all the manager's sub-servers REST handlers
// with the given endpoint.
func (s *Manager) RegisterRestServices(ctx context.Context,
	mux *restProxy.ServeMux, endpoint string,
	dialOpts []grpc.DialOption) error {

	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		// In remote mode the "director" of the RPC proxy will act as
		// a catch-all for any gRPC request that isn't known because we
		// didn't register any server for it. The director will then
		// forward the request to the remote service.
		if ss.Remote() {
			continue
		}

		err := ss.RegisterRestService(ctx, mux, endpoint, dialOpts)
		if err != nil {
			return err
		}
	}

	return nil
}

// GetRemoteConn checks if any of the manager's sub-servers owns the given uri
// and if so, the remote connection to that sub-server is returned. The bool
// return value indicates if the uri is managed by one of the sub-servers
// running in remote mode.
func (s *Manager) GetRemoteConn(uri string) (bool, *grpc.ClientConn, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if !s.permsMgr.IsSubServerURI(ss.Name(), uri) {
			continue
		}

		if !ss.Remote() {
			return false, nil, nil
		}

		if ss.remoteConn == nil {
			return true, nil, fmt.Errorf("not yet connected to "+
				"remote sub-server(%s)", ss.Name())
		}

		return true, ss.remoteConn, nil
	}

	return false, nil, nil
}

// ValidateMacaroon checks if any of the manager's sub-servers owns the given
// uri and if so, if it is running in remote mode, then true is returned since
// the macaroon will be validated by the remote subserver itself when the
// request arrives. Otherwise, the integrated sub-server's validator validates
// the macaroon.
func (s *Manager) ValidateMacaroon(ctx context.Context,
	requiredPermissions []bakery.Op, uri string) (bool, error) {

	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if !s.permsMgr.IsSubServerURI(ss.Name(), uri) {
			continue
		}

		// If the sub-server is running in remote mode, then we don't
		// need to validate the macaroon here since the remote server
		// will do it when the request arrives. But we have handled the
		// request, as we were able to identify it.
		if ss.Remote() {
			return true, nil
		}

		// If the sub-server hasn't started yet, then we can't validate
		// the macaroon. But we know that we can handle the request, as
		// we were able to identify it.
		if !ss.started() {
			return true, fmt.Errorf("%s is not yet ready for "+
				"requests, the subserver has not started or "+
				"lnd still starting/syncing",
				ss.Name())
		}

		// Validate the macaroon with the integrated sub-server's own
		// validator.
		err := ss.ValidateMacaroon(ctx, requiredPermissions, uri)
		if err != nil {
			return true, fmt.Errorf("invalid macaroon: %v", err)
		}

		// The macaroon is valid for this sub-server, we can return
		// early.
		return true, nil
	}

	// No sub-server owns the given uri, so we haven't handled this call.
	return false, nil
}

// MacaroonPath checks if any of the manager's sub-servers owns the given uri
// and if so, the appropriate macaroon path is returned for that sub-server.
func (s *Manager) MacaroonPath(uri string) (bool, string) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if !s.permsMgr.IsSubServerURI(ss.Name(), uri) {
			continue
		}

		if ss.Remote() {
			return true, ss.RemoteConfig().MacaroonPath
		}

		return true, ss.MacPath()
	}

	return false, ""
}

// ReadRemoteMacaroon checks if any of the manager's sub-servers running in
// remote mode owns the given uri and if so, the appropriate macaroon path is
// returned for that sub-server.
func (s *Manager) ReadRemoteMacaroon(uri string) (bool, []byte, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if !s.permsMgr.IsSubServerURI(ss.Name(), uri) {
			continue
		}

		if !ss.Remote() {
			return false, nil, nil
		}

		macBytes, err := readMacaroon(lncfg.CleanAndExpandPath(
			ss.RemoteConfig().MacaroonPath,
		))

		return true, macBytes, err
	}

	return false, nil, nil
}

// Handles returns true if one of its sub-servers owns the given URI along with
// the name of the service.
func (s *Manager) Handles(uri string) (bool, string) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if !s.permsMgr.IsSubServerURI(ss.Name(), uri) {
			continue
		}

		return true, ss.Name()
	}

	return false, ""
}

// Stop stops all the manager's sub-servers
func (s *Manager) Stop() error {
	var returnErr error

	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, ss := range s.servers {
		if ss.Remote() {
			continue
		}

		err := ss.stop()
		if err != nil {
			log.Errorf("Error stopping %s: %v", ss.Name(), err)
			returnErr = err
		}

		s.statusServer.SetStopped(ss.Name())
	}

	return returnErr
}

func dialBackend(name, dialAddr, tlsCertPath string) (*grpc.ClientConn, error) {
	tlsConfig, err := credentials.NewClientTLSFromFile(tlsCertPath, "")
	if err != nil {
		return nil, fmt.Errorf("could not read %s TLS cert %s: %v",
			name, tlsCertPath, err)
	}

	opts := []grpc.DialOption{
		// From the grpcProxy doc: This codec is *crucial* to the
		// functioning of the proxy.
		grpc.WithCodec(grpcProxy.Codec()), // nolint
		grpc.WithTransportCredentials(tlsConfig),
		grpc.WithDefaultCallOptions(maxMsgRecvSize),
		grpc.WithConnectParams(grpc.ConnectParams{
			Backoff:           backoff.DefaultConfig,
			MinConnectTimeout: defaultConnectTimeout,
		}),
	}

	log.Infof("Dialing %s gRPC server at %s", name, dialAddr)
	cc, err := grpc.Dial(dialAddr, opts...)
	if err != nil {
		return nil, fmt.Errorf("failed dialing %s backend: %v", name,
			err)
	}
	return cc, nil
}

// readMacaroon tries to read the macaroon file at the specified path.
func readMacaroon(macPath string) ([]byte, error) {
	// Load the specified macaroon file.
	macBytes, err := ioutil.ReadFile(macPath)
	if err != nil {
		return nil, fmt.Errorf("unable to read macaroon path: %v", err)
	}

	// Make sure it actually is a macaroon by parsing it.
	mac := &macaroon.Macaroon{}
	if err := mac.UnmarshalBinary(macBytes); err != nil {
		return nil, fmt.Errorf("unable to decode macaroon: %v", err)
	}

	// It's a macaroon alright, let's return the binary data now.
	return macBytes, nil
}