package server

import (
	"context"
	"crypto/tls"
	"errors"
	"fmt"
	"net"

	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/credentials"
	grpcstatus "google.golang.org/grpc/status"

	metacryptv1 "git.wntrmute.dev/kyle/metacrypt/gen/metacrypt/v1"
	"git.wntrmute.dev/kyle/metacrypt/internal/crypto"
	"git.wntrmute.dev/kyle/metacrypt/internal/seal"
)

// systemServiceServer implements metacryptv1.SystemServiceServer.
type systemServiceServer struct {
	metacryptv1.UnimplementedSystemServiceServer
	s *Server
}

func (g *systemServiceServer) Status(_ context.Context, _ *metacryptv1.StatusRequest) (*metacryptv1.StatusResponse, error) {
	return &metacryptv1.StatusResponse{State: g.s.seal.State().String()}, nil
}

func (g *systemServiceServer) Init(ctx context.Context, req *metacryptv1.InitRequest) (*metacryptv1.InitResponse, error) {
	params := crypto.Argon2Params{
		Time:    g.s.cfg.Seal.Argon2Time,
		Memory:  g.s.cfg.Seal.Argon2Memory,
		Threads: g.s.cfg.Seal.Argon2Threads,
	}
	if err := g.s.seal.Initialize(ctx, []byte(req.Password), params); err != nil {
		if errors.Is(err, seal.ErrAlreadyInitialized) {
			return nil, grpcstatus.Error(codes.AlreadyExists, "already initialized")
		}
		g.s.logger.Error("grpc init failed", "error", err)
		return nil, grpcstatus.Error(codes.Internal, "initialization failed")
	}
	return &metacryptv1.InitResponse{State: g.s.seal.State().String()}, nil
}

func (g *systemServiceServer) Unseal(ctx context.Context, req *metacryptv1.UnsealRequest) (*metacryptv1.UnsealResponse, error) {
	if err := g.s.seal.Unseal([]byte(req.Password)); err != nil {
		switch {
		case errors.Is(err, seal.ErrNotInitialized):
			return nil, grpcstatus.Error(codes.FailedPrecondition, "not initialized")
		case errors.Is(err, seal.ErrInvalidPassword):
			return nil, grpcstatus.Error(codes.Unauthenticated, "invalid password")
		case errors.Is(err, seal.ErrRateLimited):
			return nil, grpcstatus.Error(codes.ResourceExhausted, "too many attempts, try again later")
		case errors.Is(err, seal.ErrNotSealed):
			return nil, grpcstatus.Error(codes.AlreadyExists, "already unsealed")
		default:
			g.s.logger.Error("grpc unseal failed", "error", err)
			return nil, grpcstatus.Error(codes.Internal, "unseal failed")
		}
	}

	if err := g.s.engines.UnsealAll(ctx); err != nil {
		g.s.logger.Error("grpc engine unseal failed", "error", err)
		return nil, grpcstatus.Error(codes.Internal, "engine unseal failed")
	}

	return &metacryptv1.UnsealResponse{State: g.s.seal.State().String()}, nil
}

func (g *systemServiceServer) Seal(_ context.Context, _ *metacryptv1.SealRequest) (*metacryptv1.SealResponse, error) {
	if err := g.s.engines.SealAll(); err != nil {
		g.s.logger.Error("grpc seal engines failed", "error", err)
	}
	if err := g.s.seal.Seal(); err != nil {
		g.s.logger.Error("grpc seal failed", "error", err)
		return nil, grpcstatus.Error(codes.Internal, "seal failed")
	}
	g.s.auth.ClearCache()
	return &metacryptv1.SealResponse{State: g.s.seal.State().String()}, nil
}

// StartGRPC starts the gRPC server on cfg.Server.GRPCAddr using the same TLS
// certificate as the HTTP server. It blocks until the listener closes.
func (s *Server) StartGRPC() error {
	if s.cfg.Server.GRPCAddr == "" {
		return nil
	}

	cert, err := tls.LoadX509KeyPair(s.cfg.Server.TLSCert, s.cfg.Server.TLSKey)
	if err != nil {
		return fmt.Errorf("grpc: load TLS key pair: %w", err)
	}
	tlsCfg := &tls.Config{
		Certificates: []tls.Certificate{cert},
		MinVersion:   tls.VersionTLS12,
		CipherSuites: []uint16{
			tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
		},
	}

	grpcSrv := grpc.NewServer(grpc.Creds(credentials.NewTLS(tlsCfg)))
	metacryptv1.RegisterSystemServiceServer(grpcSrv, &systemServiceServer{s: s})

	lis, err := net.Listen("tcp", s.cfg.Server.GRPCAddr)
	if err != nil {
		return fmt.Errorf("grpc: listen: %w", err)
	}

	s.grpcSrv = grpcSrv
	s.logger.Info("starting gRPC server", "addr", s.cfg.Server.GRPCAddr)
	if err := grpcSrv.Serve(lis); err != nil {
		return fmt.Errorf("grpc: serve: %w", err)
	}
	return nil
}

// ShutdownGRPC gracefully stops the gRPC server.
func (s *Server) ShutdownGRPC() {
	if s.grpcSrv != nil {
		s.grpcSrv.GracefulStop()
	}
}