// (c) 2019-2020, Lux Partners Limited.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2020 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package gasprice

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

	"github.com/luxfi/coreth/consensus/dummy"
	"github.com/luxfi/coreth/core"
	"github.com/luxfi/coreth/core/rawdb"
	"github.com/luxfi/coreth/core/state"
	"github.com/luxfi/coreth/core/types"
	"github.com/luxfi/coreth/core/vm"
	"github.com/luxfi/coreth/params"
	"github.com/luxfi/coreth/rpc"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/event"
	"github.com/stretchr/testify/require"
)

var (
	key, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
	addr   = crypto.PubkeyToAddress(key.PublicKey)
	bal, _ = new(big.Int).SetString("100000000000000000000000", 10)
)

type testBackend struct {
	chain         *core.BlockChain
	acceptedEvent chan<- core.ChainEvent
}

func (b *testBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error) {
	if number == rpc.LatestBlockNumber {
		return b.chain.CurrentBlock(), nil
	}
	return b.chain.GetHeaderByNumber(uint64(number)), nil
}

func (b *testBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error) {
	if number == rpc.LatestBlockNumber {
		number = rpc.BlockNumber(b.chain.CurrentBlock().Number.Uint64())
	}
	return b.chain.GetBlockByNumber(uint64(number)), nil
}

func (b *testBackend) GetReceipts(ctx context.Context, hash common.Hash) (types.Receipts, error) {
	return b.chain.GetReceiptsByHash(hash), nil
}

func (b *testBackend) ChainConfig() *params.ChainConfig {
	return b.chain.Config()
}

func (b *testBackend) SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription {
	return nil
}

func (b *testBackend) SubscribeChainAcceptedEvent(ch chan<- core.ChainEvent) event.Subscription {
	b.acceptedEvent = ch
	return nil
}

func (b *testBackend) teardown() {
	b.chain.Stop()
}

func newTestBackendFakerEngine(t *testing.T, config *params.ChainConfig, numBlocks int, extDataGasUsage *big.Int, genBlocks func(i int, b *core.BlockGen)) *testBackend {
	var gspec = &core.Genesis{
		Config: config,
		Alloc:  core.GenesisAlloc{addr: core.GenesisAccount{Balance: bal}},
	}

	engine := dummy.NewETHFaker()

	// Generate testing blocks
	_, blocks, _, err := core.GenerateChainWithGenesis(gspec, engine, numBlocks, 0, genBlocks)
	if err != nil {
		t.Fatal(err)
	}
	// Construct testing chain
	diskdb := rawdb.NewMemoryDatabase()
	chain, err := core.NewBlockChain(diskdb, core.DefaultCacheConfig, gspec, engine, vm.Config{}, common.Hash{}, false)
	if err != nil {
		t.Fatalf("Failed to create local chain, %v", err)
	}
	if _, err := chain.InsertChain(blocks); err != nil {
		t.Fatalf("Failed to insert chain, %v", err)
	}
	return &testBackend{chain: chain}
}

// newTestBackend creates a test backend. OBS: don't forget to invoke tearDown
// after use, otherwise the blockchain instance will mem-leak via goroutines.
func newTestBackend(t *testing.T, config *params.ChainConfig, numBlocks int, extDataGasUsage *big.Int, genBlocks func(i int, b *core.BlockGen)) *testBackend {
	var gspec = &core.Genesis{
		Config: config,
		Alloc:  core.GenesisAlloc{addr: core.GenesisAccount{Balance: bal}},
	}

	engine := dummy.NewFakerWithCallbacks(dummy.ConsensusCallbacks{
		OnFinalizeAndAssemble: func(header *types.Header, state *state.StateDB, txs []*types.Transaction) ([]byte, *big.Int, *big.Int, error) {
			return nil, common.Big0, extDataGasUsage, nil
		},
		OnExtraStateChange: func(block *types.Block, state *state.StateDB) (*big.Int, *big.Int, error) {
			return common.Big0, extDataGasUsage, nil
		},
	})

	// Generate testing blocks
	_, blocks, _, err := core.GenerateChainWithGenesis(gspec, engine, numBlocks, 1, genBlocks)
	if err != nil {
		t.Fatal(err)
	}
	// Construct testing chain
	chain, err := core.NewBlockChain(rawdb.NewMemoryDatabase(), core.DefaultCacheConfig, gspec, engine, vm.Config{}, common.Hash{}, false)
	if err != nil {
		t.Fatalf("Failed to create local chain, %v", err)
	}
	if _, err := chain.InsertChain(blocks); err != nil {
		t.Fatalf("Failed to insert chain, %v", err)
	}
	return &testBackend{chain: chain}
}

func (b *testBackend) MinRequiredTip(ctx context.Context, header *types.Header) (*big.Int, error) {
	return dummy.MinRequiredTip(b.chain.Config(), header)
}

func (b *testBackend) CurrentHeader() *types.Header {
	return b.chain.CurrentHeader()
}

func (b *testBackend) LastAcceptedBlock() *types.Block {
	current := b.chain.CurrentBlock()
	if current == nil {
		return nil
	}
	return b.chain.GetBlockByNumber(current.Number.Uint64())
}

func (b *testBackend) GetBlockByNumber(number uint64) *types.Block {
	return b.chain.GetBlockByNumber(number)
}

type suggestTipCapTest struct {
	chainConfig     *params.ChainConfig
	numBlocks       int
	extDataGasUsage *big.Int
	genBlock        func(i int, b *core.BlockGen)
	expectedTip     *big.Int
}

func defaultOracleConfig() Config {
	return Config{
		Blocks:             20,
		Percentile:         60,
		MaxLookbackSeconds: 80,
	}
}

// timeCrunchOracleConfig returns a config with [MaxLookbackSeconds] set to 5
// to ensure that during gas price estimation, we will hit the time based look back limit
func timeCrunchOracleConfig() Config {
	return Config{
		Blocks:             20,
		Percentile:         60,
		MaxLookbackSeconds: 5,
	}
}

func applyGasPriceTest(t *testing.T, test suggestTipCapTest, config Config) {
	if test.genBlock == nil {
		test.genBlock = func(i int, b *core.BlockGen) {}
	}
	backend := newTestBackend(t, test.chainConfig, test.numBlocks, test.extDataGasUsage, test.genBlock)
	oracle, err := NewOracle(backend, config)
	require.NoError(t, err)

	// mock time to be consistent across different CI runs
	// sets currentTime to be 20 seconds
	oracle.clock.Set(time.Unix(20, 0))

	got, err := oracle.SuggestTipCap(context.Background())
	backend.teardown()
	require.NoError(t, err)

	if got.Cmp(test.expectedTip) != 0 {
		t.Fatalf("Expected tip (%d), got tip (%d)", test.expectedTip, got)
	}
}

func testGenBlock(t *testing.T, tip int64, numTx int) func(int, *core.BlockGen) {
	return func(i int, b *core.BlockGen) {
		b.SetCoinbase(common.Address{1})

		txTip := big.NewInt(tip * params.GWei)
		signer := types.LatestSigner(params.TestChainConfig)
		baseFee := b.BaseFee()
		feeCap := new(big.Int).Add(baseFee, txTip)
		for j := 0; j < numTx; j++ {
			tx := types.NewTx(&types.DynamicFeeTx{
				ChainID:   params.TestChainConfig.ChainID,
				Nonce:     b.TxNonce(addr),
				To:        &common.Address{},
				Gas:       params.TxGas,
				GasFeeCap: feeCap,
				GasTipCap: txTip,
				Data:      []byte{},
			})
			tx, err := types.SignTx(tx, signer, key)
			require.NoError(t, err, "failed to create tx")
			b.AddTx(tx)
		}
	}
}

func TestSuggestTipCapEmptyExtDataGasUsage(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       3,
		extDataGasUsage: nil,
		genBlock:        testGenBlock(t, 55, 370),
		expectedTip:     big.NewInt(5_713_963_963),
	}, defaultOracleConfig())
}

func TestSuggestTipCapSimple(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       3,
		extDataGasUsage: common.Big0,
		genBlock:        testGenBlock(t, 55, 370),
		expectedTip:     big.NewInt(5_713_963_963),
	}, defaultOracleConfig())
}

func TestSuggestTipCapSimpleFloor(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       1,
		extDataGasUsage: common.Big0,
		genBlock:        testGenBlock(t, 55, 370),
		expectedTip:     common.Big0,
	}, defaultOracleConfig())
}

func TestSuggestTipCapSmallTips(t *testing.T) {
	tip := big.NewInt(550 * params.GWei)
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       3,
		extDataGasUsage: common.Big0,
		genBlock: func(i int, b *core.BlockGen) {
			b.SetCoinbase(common.Address{1})

			signer := types.LatestSigner(params.TestChainConfig)
			baseFee := b.BaseFee()
			feeCap := new(big.Int).Add(baseFee, tip)
			for j := 0; j < 185; j++ {
				tx := types.NewTx(&types.DynamicFeeTx{
					ChainID:   params.TestChainConfig.ChainID,
					Nonce:     b.TxNonce(addr),
					To:        &common.Address{},
					Gas:       params.TxGas,
					GasFeeCap: feeCap,
					GasTipCap: tip,
					Data:      []byte{},
				})
				tx, err := types.SignTx(tx, signer, key)
				if err != nil {
					t.Fatalf("failed to create tx: %s", err)
				}
				b.AddTx(tx)
				tx = types.NewTx(&types.DynamicFeeTx{
					ChainID:   params.TestChainConfig.ChainID,
					Nonce:     b.TxNonce(addr),
					To:        &common.Address{},
					Gas:       params.TxGas,
					GasFeeCap: feeCap,
					GasTipCap: common.Big1,
					Data:      []byte{},
				})
				tx, err = types.SignTx(tx, signer, key)
				require.NoError(t, err, "failed to create tx")
				b.AddTx(tx)
			}
		},
		// NOTE: small tips do not bias estimate
		expectedTip: big.NewInt(5_713_963_963),
	}, defaultOracleConfig())
}

func TestSuggestTipCapExtDataUsage(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       3,
		extDataGasUsage: big.NewInt(10_000),
		genBlock:        testGenBlock(t, 55, 370),
		expectedTip:     big.NewInt(5_706_726_649),
	}, defaultOracleConfig())
}

func TestSuggestTipCapMinGas(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       3,
		extDataGasUsage: common.Big0,
		genBlock:        testGenBlock(t, 500, 50),
		expectedTip:     big.NewInt(0),
	}, defaultOracleConfig())
}

// Regression test to ensure that SuggestPrice does not panic prior to activation of ApricotPhase3
// Note: support for gas estimation without activated hard forks has been deprecated, but we still
// ensure that the call does not panic.
func TestSuggestGasPricePreAP3(t *testing.T) {
	config := Config{
		Blocks:     20,
		Percentile: 60,
	}

	backend := newTestBackend(t, params.TestApricotPhase2Config, 3, nil, func(i int, b *core.BlockGen) {
		b.SetCoinbase(common.Address{1})

		signer := types.LatestSigner(params.TestApricotPhase2Config)
		gasPrice := big.NewInt(params.ApricotPhase1MinGasPrice)
		for j := 0; j < 50; j++ {
			tx := types.NewTx(&types.LegacyTx{
				Nonce:    b.TxNonce(addr),
				To:       &common.Address{},
				Gas:      params.TxGas,
				GasPrice: gasPrice,
				Data:     []byte{},
			})
			tx, err := types.SignTx(tx, signer, key)
			require.NoError(t, err, "failed to create tx")
			b.AddTx(tx)
		}
	})
	defer backend.teardown()

	oracle, err := NewOracle(backend, config)
	require.NoError(t, err)

	_, err = oracle.SuggestPrice(context.Background())
	require.NoError(t, err)
}

func TestSuggestTipCapMaxBlocksLookback(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       20,
		extDataGasUsage: common.Big0,
		genBlock:        testGenBlock(t, 550, 370),
		expectedTip:     big.NewInt(51_565_264_256),
	}, defaultOracleConfig())
}

func TestSuggestTipCapMaxBlocksSecondsLookback(t *testing.T) {
	applyGasPriceTest(t, suggestTipCapTest{
		chainConfig:     params.TestChainConfig,
		numBlocks:       20,
		extDataGasUsage: big.NewInt(1),
		genBlock:        testGenBlock(t, 550, 370),
		expectedTip:     big.NewInt(92_212_529_423),
	}, timeCrunchOracleConfig())
}
