// +build autopilotrpc

package autopilotrpc

import (
	"context"
	"os"
	"sync/atomic"

	"github.com/lightningnetwork/lnd/autopilot"
	"github.com/lightningnetwork/lnd/lnrpc"
	"google.golang.org/grpc"
	"gopkg.in/macaroon-bakery.v2/bakery"
)

const (
	// subServerName is the name of the sub rpc server. We'll use this name
	// to register ourselves, and we also require that the main
	// SubServerConfigDispatcher instance recognize tt as the name of our
	// RPC service.
	subServerName = "AutopilotRPC"
)

var (
	// macPermissions maps RPC calls to the permissions they require.
	macPermissions = map[string][]bakery.Op{
		"/autopilotrpc.Autopilot/Status": {{
			Entity: "info",
			Action: "read",
		}},
		"/autopilotrpc.Autopilot/ModifyStatus": {{
			Entity: "onchain",
			Action: "write",
		}, {
			Entity: "offchain",
			Action: "write",
		}},
	}
)

// Server is a sub-server of the main RPC server: the autopilot RPC. This sub
// RPC server allows external callers to access the status of the autopilot
// currently active within lnd, as well as configuring it at runtime.
type Server struct {
	started  int32 // To be used atomically.
	shutdown int32 // To be used atomically.

	cfg *Config

	manager *autopilot.Manager
}

// A compile time check to ensure that Server fully implements the
// AutopilotServer gRPC service.
var _ AutopilotServer = (*Server)(nil)

// fileExists reports whether the named file or directory exists.
func fileExists(name string) bool {
	if _, err := os.Stat(name); err != nil {
		if os.IsNotExist(err) {
			return false
		}
	}
	return true
}

// New returns a new instance of the autopilotrpc Autopilot sub-server. We also
// return the set of permissions for the macaroons that we may create within
// this method. If the macaroons we need aren't found in the filepath, then
// we'll create them on start up. If we're unable to locate, or create the
// macaroons we need, then we'll return with an error.
func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) {
	// We don't create any new macaroons for this subserver, instead reuse
	// existing onchain/offchain permissions.
	server := &Server{
		cfg:     cfg,
		manager: cfg.Manager,
	}

	return server, macPermissions, nil
}

// Start launches any helper goroutines required for the Server to function.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Start() error {
	if atomic.AddInt32(&s.started, 1) != 1 {
		return nil
	}

	return s.manager.Start()
}

// Stop signals any active goroutines for a graceful closure.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Stop() error {
	if atomic.AddInt32(&s.shutdown, 1) != 1 {
		return nil
	}

	return s.manager.Stop()
}

// Name returns a unique string representation of the sub-server. This can be
// used to identify the sub-server and also de-duplicate them.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Name() string {
	return subServerName
}

// RegisterWithRootServer will be called by the root gRPC server to direct a
// sub RPC server to register itself with the main gRPC root server. Until this
// is called, each sub-server won't be able to have
// requests routed towards it.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) RegisterWithRootServer(grpcServer *grpc.Server) error {
	// We make sure that we register it with the main gRPC server to ensure
	// all our methods are routed properly.
	RegisterAutopilotServer(grpcServer, s)

	log.Debugf("Autopilot RPC server successfully register with root " +
		"gRPC server")

	return nil
}

// Status returns the current status of the autopilot agent.
//
// NOTE: Part of the AutopilotServer interface.
func (s *Server) Status(ctx context.Context,
	in *StatusRequest) (*StatusResponse, error) {

	return &StatusResponse{
		Active: s.manager.IsActive(),
	}, nil
}

// ModifyStatus activates the current autopilot agent, if active.
//
// NOTE: Part of the AutopilotServer interface.
func (s *Server) ModifyStatus(ctx context.Context,
	in *ModifyStatusRequest) (*ModifyStatusResponse, error) {

	log.Debugf("Setting agent enabled=%v", in.Enable)

	var err error
	if in.Enable {
		err = s.manager.StartAgent()
	} else {
		err = s.manager.StopAgent()
	}
	return &ModifyStatusResponse{}, err
}