/*
   Copyright 2021 Erigon contributors

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package txpool

import (
	"context"
	"fmt"
	"net"
	"sync"
	"time"

	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
	grpc_recovery "github.com/grpc-ecosystem/go-grpc-middleware/recovery"
	"github.com/holiman/uint256"
	"github.com/ledgerwatch/erigon-lib/chain"
	"github.com/ledgerwatch/erigon-lib/gointerfaces"
	txpool_proto "github.com/ledgerwatch/erigon-lib/gointerfaces/txpool"
	types2 "github.com/ledgerwatch/erigon-lib/gointerfaces/types"
	"github.com/ledgerwatch/erigon-lib/kv"
	"github.com/ledgerwatch/log/v3"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/keepalive"
	"google.golang.org/grpc/reflection"
	"google.golang.org/protobuf/types/known/emptypb"
)

// TxPoolAPIVersion
var TxPoolAPIVersion = &types2.VersionReply{Major: 1, Minor: 0, Patch: 0}

type txPool interface {
	GetRlp(tx kv.Tx, hash []byte) ([]byte, error)
	AddLocalTxs(ctx context.Context, newTxs TxSlots) ([]DiscardReason, error)
	deprecatedForEach(_ context.Context, f func(rlp, sender []byte, t SubPoolType), tx kv.Tx) error
	CountContent() (int, int, int)
	IdHashKnown(tx kv.Tx, hash []byte) (bool, error)
}

type GrpcServer struct {
	txpool_proto.UnimplementedTxpoolServer
	ctx             context.Context
	txPool          txPool
	db              kv.RoDB
	NewSlotsStreams *NewSlotsStreams

	rules   chain.Rules
	chainID uint256.Int
}

func NewGrpcServer(ctx context.Context, txPool txPool, db kv.RoDB, rules chain.Rules, chainID uint256.Int) *GrpcServer {
	return &GrpcServer{ctx: ctx, txPool: txPool, db: db, NewSlotsStreams: &NewSlotsStreams{}, rules: rules, chainID: chainID}
}

func (s *GrpcServer) Version(context.Context, *emptypb.Empty) (*types2.VersionReply, error) {
	return TxPoolAPIVersion, nil
}
func convertSubPoolType(t SubPoolType) txpool_proto.AllReply_Type {
	switch t {
	case PendingSubPool:
		return txpool_proto.AllReply_PENDING
	case BaseFeeSubPool:
		return txpool_proto.AllReply_PENDING
	case QueuedSubPool:
		return txpool_proto.AllReply_QUEUED
	default:
		panic("unknown")
	}
}
func (s *GrpcServer) All(ctx context.Context, _ *txpool_proto.AllRequest) (*txpool_proto.AllReply, error) {
	tx, err := s.db.BeginRo(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()
	reply := &txpool_proto.AllReply{}
	reply.Txs = make([]*txpool_proto.AllReply_Tx, 0, 32)
	if err := s.txPool.deprecatedForEach(ctx, func(rlp, sender []byte, t SubPoolType) {
		reply.Txs = append(reply.Txs, &txpool_proto.AllReply_Tx{
			Sender: sender,
			Type:   convertSubPoolType(t),
			RlpTx:  rlp,
		})
	}, tx); err != nil {
		return nil, err
	}
	return reply, nil
}

func (s *GrpcServer) FindUnknown(ctx context.Context, in *txpool_proto.TxHashes) (*txpool_proto.TxHashes, error) {
	return nil, fmt.Errorf("unimplemented")
	/*
		var underpriced int
		for i := range in.Hashes {
			h := gointerfaces.ConvertH256ToHash(in.Hashes[i])
			if s.txPool.Has(h) {
				continue
			}
			if s.underpriced.Contains(h) {
				underpriced++
				continue
			}
			reply.Hashes = append(reply.Hashes, in.Hashes[i])
		}
		txAnnounceInMeter.Mark(int64(len(in.Hashes)))
		txAnnounceKnownMeter.Mark(int64(len(in.Hashes) - len(reply.Hashes)))
		txAnnounceUnderpricedMeter.Mark(int64(underpriced))
	*/
}

func (s *GrpcServer) Add(ctx context.Context, in *txpool_proto.AddRequest) (*txpool_proto.AddReply, error) {
	tx, err := s.db.BeginRo(context.Background())
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	var slots TxSlots
	slots.Resize(uint(len(in.RlpTxs)))
	parseCtx := NewTxParseContext(s.rules, s.chainID)
	parseCtx.Reject(func(hash []byte) error {
		if known, _ := s.txPool.IdHashKnown(tx, hash); known {
			return ErrAlreadyKnown
		}
		return nil
	})
	reply := &txpool_proto.AddReply{Imported: make([]txpool_proto.ImportResult, len(in.RlpTxs)), Errors: make([]string, len(in.RlpTxs))}

	for i, j := 0, 0; i < len(in.RlpTxs); i, j = i+1, j+1 { // some incoming txs may be rejected, so - need secnod index
		slots.txs[j] = &TxSlot{}
		slots.isLocal[j] = true
		if _, err := parseCtx.ParseTransaction(in.RlpTxs[j], 0, slots.txs[j], slots.senders.At(j)); err != nil {
			j--
			switch err {
			case ErrAlreadyKnown: // Noop, but need to handle to not count these
				reply.Imported[i] = txpool_proto.ImportResult_ALREADY_EXISTS
			default:
				reply.Imported[i] = txpool_proto.ImportResult_INTERNAL_ERROR
			}
		}
	}

	discardReasons, err := s.txPool.AddLocalTxs(ctx, slots)
	if err != nil {
		return nil, err
	}
	//TODO: concept of discardReasonsLRU not really implemented yet. Indices are not match here!
	_ = discardReasons
	/*
		for i, err := range discardReasonsLRU {
			if err == nil {
				continue
			}

			reply.Errors[i] = err.Error()

			// Track a few interesting failure types
			switch err {
			case Success: // Noop, but need to handle to not count these

			//case core.ErrAlreadyKnown:
			//	reply.Imported[i] = txpool_proto.ImportResult_ALREADY_EXISTS
			//case core.ErrUnderpriced, core.ErrReplaceUnderpriced:
			//	reply.Imported[i] = txpool_proto.ImportResult_FEE_TOO_LOW
			//case core.ErrInvalidSender, core.ErrGasLimit, core.ErrNegativeValue, core.ErrOversizedData:
			//	reply.Imported[i] = txpool_proto.ImportResult_INVALID
			default:
				reply.Imported[i] = txpool_proto.ImportResult_INTERNAL_ERROR
			}
		}
	*/
	return reply, nil
}

func (s *GrpcServer) OnAdd(req *txpool_proto.OnAddRequest, stream txpool_proto.Txpool_OnAddServer) error {
	log.Info("New txs subscriber joined")
	//txpool.Loop does send messages to this streams
	remove := s.NewSlotsStreams.Add(stream)
	defer remove()
	select {
	case <-stream.Context().Done():
		return stream.Context().Err()
	case <-s.ctx.Done():
		return s.ctx.Err()
	}
}

func (s *GrpcServer) Transactions(ctx context.Context, in *txpool_proto.TransactionsRequest) (*txpool_proto.TransactionsReply, error) {
	tx, err := s.db.BeginRo(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	reply := &txpool_proto.TransactionsReply{RlpTxs: make([][]byte, len(in.Hashes))}
	for i := range in.Hashes {
		h := gointerfaces.ConvertH256ToHash(in.Hashes[i])
		txnRlp, err := s.txPool.GetRlp(tx, h[:])
		if err != nil {
			return nil, err
		}
		reply.RlpTxs[i] = txnRlp
	}

	return reply, nil
}

func (s *GrpcServer) Status(_ context.Context, _ *txpool_proto.StatusRequest) (*txpool_proto.StatusReply, error) {
	pending, baseFee, queued := s.txPool.CountContent()
	return &txpool_proto.StatusReply{
		PendingCount: uint32(pending),
		QueuedCount:  uint32(queued),
		BaseFeeCount: uint32(baseFee),
	}, nil
}

// NewSlotsStreams - it's safe to use this class as non-pointer
type NewSlotsStreams struct {
	chans map[uint]txpool_proto.Txpool_OnAddServer
	mu    sync.Mutex
	id    uint
}

func (s *NewSlotsStreams) Add(stream txpool_proto.Txpool_OnAddServer) (remove func()) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.chans == nil {
		s.chans = make(map[uint]txpool_proto.Txpool_OnAddServer)
	}
	s.id++
	id := s.id
	s.chans[id] = stream
	return func() { s.remove(id) }
}

func (s *NewSlotsStreams) Broadcast(reply *txpool_proto.OnAddReply) {
	s.mu.Lock()
	defer s.mu.Unlock()
	for id, stream := range s.chans {
		err := stream.Send(reply)
		if err != nil {
			log.Debug("failed send to mined block stream", "err", err)
			select {
			case <-stream.Context().Done():
				delete(s.chans, id)
			default:
			}
		}
	}
}

func (s *NewSlotsStreams) remove(id uint) {
	s.mu.Lock()
	defer s.mu.Unlock()
	_, ok := s.chans[id]
	if !ok { // double-unsubscribe support
		return
	}
	delete(s.chans, id)
}

func StartGrpc(txPoolServer txpool_proto.TxpoolServer, miningServer txpool_proto.MiningServer, addr string, creds *credentials.TransportCredentials) (*grpc.Server, error) {
	lis, err := net.Listen("tcp", addr)
	if err != nil {
		return nil, fmt.Errorf("could not create listener: %w, addr=%s", err, addr)
	}

	var (
		streamInterceptors []grpc.StreamServerInterceptor
		unaryInterceptors  []grpc.UnaryServerInterceptor
	)
	streamInterceptors = append(streamInterceptors, grpc_recovery.StreamServerInterceptor())
	unaryInterceptors = append(unaryInterceptors, grpc_recovery.UnaryServerInterceptor())

	//if metrics.Enabled {
	//	streamInterceptors = append(streamInterceptors, grpc_prometheus.StreamServerInterceptor)
	//	unaryInterceptors = append(unaryInterceptors, grpc_prometheus.UnaryServerInterceptor)
	//}

	//cpus := uint32(runtime.GOMAXPROCS(-1))
	opts := []grpc.ServerOption{
		//grpc.NumStreamWorkers(cpus), // reduce amount of goroutines

		// Don't drop the connection, settings accordign to this comment on GitHub
		// https://github.com/grpc/grpc-go/issues/3171#issuecomment-552796779
		grpc.KeepaliveEnforcementPolicy(keepalive.EnforcementPolicy{
			MinTime:             10 * time.Second,
			PermitWithoutStream: true,
		}),
		grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(streamInterceptors...)),
		grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(unaryInterceptors...)),
	}
	if creds == nil {
		// no specific opts
	} else {
		opts = append(opts, grpc.Creds(*creds))
	}
	grpcServer := grpc.NewServer(opts...)
	reflection.Register(grpcServer) // Register reflection service on gRPC server.
	if txPoolServer != nil {
		txpool_proto.RegisterTxpoolServer(grpcServer, txPoolServer)
	}
	if miningServer != nil {
		txpool_proto.RegisterMiningServer(grpcServer, miningServer)
	}

	//if metrics.Enabled {
	//	grpc_prometheus.Register(grpcServer)
	//}

	go func() {
		if err := grpcServer.Serve(lis); err != nil {
			log.Error("private RPC server fail", "err", err)
		}
	}()
	log.Info("Started gRPC server", "on", addr)
	return grpcServer, nil
}