package download

import (
	"context"
	"math/big"
	"testing"
	"time"

	"github.com/holiman/uint256"
	"github.com/ledgerwatch/erigon-lib/gointerfaces"
	proto_sentry "github.com/ledgerwatch/erigon-lib/gointerfaces/sentry"
	"github.com/ledgerwatch/erigon/common"
	"github.com/ledgerwatch/erigon/core"
	"github.com/ledgerwatch/erigon/core/forkid"
	"github.com/ledgerwatch/erigon/core/rawdb"
	"github.com/ledgerwatch/erigon/eth/protocols/eth"
	"github.com/ledgerwatch/erigon/ethdb"
	"github.com/ledgerwatch/erigon/ethdb/kv"
	"github.com/ledgerwatch/erigon/p2p"
	"github.com/ledgerwatch/erigon/params"
	"github.com/stretchr/testify/require"
)

func testSentryServer(db ethdb.KVGetter, genesis *core.Genesis, genesisHash common.Hash) *SentryServerImpl {
	s := &SentryServerImpl{
		ctx: context.Background(),
	}

	head := rawdb.ReadCurrentHeader(db)
	headTd, err := rawdb.ReadTd(db, head.Hash(), head.Number.Uint64())
	if err != nil {
		panic(err)
	}

	headTd256 := new(uint256.Int)
	headTd256.SetFromBig(headTd)
	s.statusData = &proto_sentry.StatusData{
		NetworkId:       1,
		TotalDifficulty: gointerfaces.ConvertUint256IntToH256(headTd256),
		BestHash:        gointerfaces.ConvertHashToH256(head.Hash()),
		MaxBlock:        head.Number.Uint64(),
		ForkData: &proto_sentry.Forks{
			Genesis: gointerfaces.ConvertHashToH256(genesisHash),
			Forks:   forkid.GatherForks(genesis.Config),
		},
	}
	return s

}

// Tests that peers are correctly accepted (or rejected) based on the advertised
// fork IDs in the protocol handshake.
func TestForkIDSplit66(t *testing.T) { testForkIDSplit(t, eth.ETH66) }

func testForkIDSplit(t *testing.T, protocol uint) {
	var (
		ctx           = context.Background()
		configNoFork  = &params.ChainConfig{HomesteadBlock: big.NewInt(1), ChainID: big.NewInt(1)}
		configProFork = &params.ChainConfig{
			ChainID:        big.NewInt(1),
			HomesteadBlock: big.NewInt(1),
			EIP150Block:    big.NewInt(2),
			EIP155Block:    big.NewInt(2),
			EIP158Block:    big.NewInt(2),
			ByzantiumBlock: big.NewInt(3),
		}
		dbNoFork  = kv.NewTestKV(t)
		dbProFork = kv.NewTestKV(t)

		gspecNoFork  = &core.Genesis{Config: configNoFork}
		gspecProFork = &core.Genesis{Config: configProFork}

		genesisNoFork  = gspecNoFork.MustCommit(dbNoFork)
		genesisProFork = gspecProFork.MustCommit(dbProFork)
	)

	var s1, s2 *SentryServerImpl

	err := dbNoFork.Update(context.Background(), func(tx ethdb.RwTx) error {
		s1 = testSentryServer(tx, gspecNoFork, genesisNoFork.Hash())
		return nil
	})
	require.NoError(t, err)
	err = dbProFork.Update(context.Background(), func(tx ethdb.RwTx) error {
		s2 = testSentryServer(tx, gspecProFork, genesisProFork.Hash())
		return nil
	})
	require.NoError(t, err)

	// Both nodes should allow the other to connect (same genesis, next fork is the same)
	p2pNoFork, p2pProFork := p2p.MsgPipe()
	defer p2pNoFork.Close()
	defer p2pProFork.Close()

	errc := make(chan error, 2)
	go func() { errc <- handShake(ctx, s1.GetStatus(), "1", p2pNoFork, protocol, protocol, nil) }()
	go func() { errc <- handShake(ctx, s2.GetStatus(), "2", p2pProFork, protocol, protocol, nil) }()

	for i := 0; i < 2; i++ {
		select {
		case err := <-errc:
			if err != nil {
				t.Fatalf("frontier nofork <-> profork failed: %v", err)
			}
		case <-time.After(250 * time.Millisecond):
			t.Fatalf("frontier nofork <-> profork handler timeout")
		}
	}

	// Progress into Homestead. Fork's match, so we don't care what the future holds
	s1.statusData.MaxBlock = 1
	s2.statusData.MaxBlock = 1

	go func() { errc <- handShake(ctx, s1.GetStatus(), "1", p2pNoFork, protocol, protocol, nil) }()
	go func() { errc <- handShake(ctx, s2.GetStatus(), "2", p2pProFork, protocol, protocol, nil) }()

	for i := 0; i < 2; i++ {
		select {
		case err := <-errc:
			if err != nil {
				t.Fatalf("homestead nofork <-> profork failed: %v", err)
			}
		case <-time.After(250 * time.Millisecond):
			t.Fatalf("frontier nofork <-> profork handler timeout")
		}
	}

	// Progress into Spurious. Forks mismatch, signalling differing chains, reject
	s1.statusData.MaxBlock = 2
	s2.statusData.MaxBlock = 2

	// Both nodes should allow the other to connect (same genesis, next fork is the same)
	go func() { errc <- handShake(ctx, s1.GetStatus(), "1", p2pNoFork, protocol, protocol, nil) }()
	go func() { errc <- handShake(ctx, s2.GetStatus(), "2", p2pProFork, protocol, protocol, nil) }()

	var successes int
	for i := 0; i < 2; i++ {
		select {
		case err := <-errc:
			if err == nil {
				successes++
				if successes == 2 { // Only one side disconnects
					t.Fatalf("fork ID rejection didn't happen")
				}
			}
		case <-time.After(250 * time.Millisecond):
			t.Fatalf("split peers not rejected")
		}
	}
}