defhandler.go

// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-juchain 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-juchain 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-juchain library. If not, see <http://www.gnu.org/licenses/>.

package consensus

import (
	"errors"
	"fmt"
	"math/big"
	"runtime"
	"time"

	"github.com/juchain/go-juchain/common"
	"github.com/juchain/go-juchain/common/math"
	"github.com/juchain/go-juchain/core/store"
	"github.com/juchain/go-juchain/core/state"
	"github.com/juchain/go-juchain/core/types"
	"github.com/juchain/go-juchain/config"
	"github.com/juchain/go-juchain/rpc"

	"gopkg.in/fatih/set.v0"
	"bytes"
)

// this is exactly the same file copied from dpos.handle.go
// just want to solve the cycle dependency issue for test case.
// Please sync this file if you made any change!

var (
	ByzantiumBlockReward   *big.Int = big.NewInt(3e+18) // Block reward in wei for successfully mining a block upward from Byzantium
	maxUncles                       = 2                 // Maximum number of uncles allowed in a single block
	allowedFutureBlockTime          = 15 * time.Second  // Max time from current time allowed for blocks, before they're considered future blocks
)

// Various error messages to mark blocks invalid. These should be private to
// prevent engine specific errors from being referenced in the remainder of the
// codebase, inherently breaking if the engine is swapped out. Please put common
// error types into the consensus package.
var (
	errLargeBlockTime    = errors.New("timestamp too big")
	errZeroBlockTime     = errors.New("timestamp small than parent's")
	errTooManyUncles     = errors.New("too many uncles")
	errDuplicateUncle    = errors.New("duplicate uncle")
	errUncleIsAncestor   = errors.New("uncle is ancestor")
	errDanglingUncle     = errors.New("uncle's parent is not ancestor")
	errInvalidDifficulty = errors.New("non-positive difficulty")
	errInvalidMixDigest  = errors.New("invalid mix digest")
	errInvalidPoW        = errors.New("invalid proof-of-work")

)

// this is only used for test case.

func CreateFakeEngine() Engine {
	return New(&config.DPoSConfig{
		PoSMode: config.ModeFake,
	}, nil)
}
// NewFakeFailer creates a ethash consensus engine with a fake PoW scheme that
// accepts all blocks as valid apart from the single one specified, though they
// still have to conform to the Ethereum consensus rules.
func NewFakeFailer(fail uint64) Engine {
	return New(&config.DPoSConfig{
		PoSMode: config.ModeFake,
		FakeFail: fail,
	}, nil)
}
// NewFakeDelayer creates a ethash consensus engine with a fake PoW scheme that
// accepts all blocks as valid, but delays verifications by some time, though
// they still have to conform to the Ethereum consensus rules.
func NewFakeDelayer(delay time.Duration) Engine {
	return New(&config.DPoSConfig{
		PoSMode: config.ModeFake,
		FakeDelay: delay,
	}, nil)
}
// NewFullFaker creates an ethash consensus engine with a full fake scheme that
// accepts all blocks as valid, without checking any consensus rules whatsoever.
func NewFullFaker() Engine {
	return New(&config.DPoSConfig{
		PoSMode: config.ModeFullFake,
	}, nil)
}

type DElection struct {
	config    *config.DPoSConfig   // Consensus engine configuration parameters
	db        store.Database       // Database to store and retrieve snapshot checkpoints
	fakeFail  uint64        // Block number which fails PoW check even in fake mode
	fakeDelay time.Duration // Time delay to sleep for before returning from verify
}

// New creates a Clique proof-of-authority consensus engine with the initial
// signers set to the ones provided by the user.
func New(config *config.DPoSConfig, db store.Database) *DElection {
	// Set any missing consensus parameters to their defaults
	conf := *config

	return &DElection{
		config:     &conf,
		db:         db,
	}
}

// Author implements Engine, returning the header's coinbase as the
// proof-of-work verified author of the block.
func (dpos *DElection) Author(header *types.Header) (common.Address, error) {
	return header.Coinbase, nil
}

// VerifyHeader checks whether a header conforms to the consensus rules of the
// stock Ethereum dpos engine.
func (dpos *DElection) VerifyHeader(chain ChainReader, header *types.Header, seal bool) error {
	// Short circuit if the header is known, or it's parent not
	number := header.Number.Uint64()
	if chain.GetHeader(header.Hash(), number) != nil {
		return nil
	}
	parent := chain.GetHeader(header.ParentHash, number-1)
	if parent == nil {
		return ErrUnknownAncestor
	}
	// Sanity checks passed, do a proper verification
	return dpos.verifyHeader(chain, header, parent, false, seal)
}

// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers
// concurrently. The method returns a quit channel to abort the operations and
// a results channel to retrieve the async verifications.
func (dpos *DElection) VerifyHeaders(chain ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
	// If we're running a full engine faking, accept any input as valid
	if dpos.config.PoSMode == config.ModeFullFake || len(headers) == 0 {
		abort, results := make(chan struct{}), make(chan error, len(headers))
		for i := 0; i < len(headers); i++ {
			results <- nil
		}
		return abort, results
	}

	// Spawn as many workers as allowed threads
	workers := runtime.GOMAXPROCS(0)
	if len(headers) < workers {
		workers = len(headers)
	}

	// Create a task channel and spawn the verifiers
	var (
		inputs = make(chan int)
		done   = make(chan int, workers)
		errors = make([]error, len(headers))
		abort  = make(chan struct{})
	)
	for i := 0; i < workers; i++ {
		go func() {
			for index := range inputs {
				errors[index] = dpos.verifyHeaderWorker(chain, headers, seals, index)
				done <- index
			}
		}()
	}

	errorsOut := make(chan error, len(headers))
	go func() {
		defer close(inputs)
		var (
			in, out = 0, 0
			checked = make([]bool, len(headers))
			inputs  = inputs
		)
		for {
			select {
			case inputs <- in:
				if in++; in == len(headers) {
					// Reached end of headers. Stop sending to workers.
					inputs = nil
				}
			case index := <-done:
				for checked[index] = true; checked[out]; out++ {
					errorsOut <- errors[out]
					if out == len(headers)-1 {
						return
					}
				}
			case <-abort:
				return
			}
		}
	}()
	return abort, errorsOut
}

func (dpos *DElection) verifyHeaderWorker(chain ChainReader, headers []*types.Header, seals []bool, index int) error {
	var parent *types.Header
	if index == 0 {
		parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1)
	} else if headers[index-1].Hash() == headers[index].ParentHash {
		parent = headers[index-1]
	}
	if parent == nil {
		return ErrUnknownAncestor
	}
	if chain.GetHeader(headers[index].Hash(), headers[index].Number.Uint64()) != nil {
		return nil // known block
	}
	return dpos.verifyHeader(chain, headers[index], parent, false, seals[index])
}

// VerifyUncles verifies that the given block's uncles conform to the consensus
// rules of the stock Ethereum dpos engine.
func (dpos *DElection) VerifyUncles(chain ChainReader, block *types.Block) error {
	// Verify that there are at most 2 uncles included in this block
	if len(block.Uncles()) > maxUncles {
		return errTooManyUncles
	}
	// Gather the set of past uncles and ancestors
	uncles, ancestors := set.New(), make(map[common.Hash]*types.Header)

	number, parent := block.NumberU64()-1, block.ParentHash()
	for i := 0; i < 7; i++ {
		ancestor := chain.GetBlock(parent, number)
		if ancestor == nil {
			break
		}
		ancestors[ancestor.Hash()] = ancestor.Header()
		for _, uncle := range ancestor.Uncles() {
			uncles.Add(uncle.Hash())
		}
		parent, number = ancestor.ParentHash(), number-1
	}
	ancestors[block.Hash()] = block.Header()
	uncles.Add(block.Hash())

	// Verify each of the uncles that it's recent, but not an ancestor
	for _, uncle := range block.Uncles() {
		// Make sure every uncle is rewarded only once
		hash := uncle.Hash()
		if uncles.Has(hash) {
			return errDuplicateUncle
		}
		uncles.Add(hash)

		// Make sure the uncle has a valid ancestry
		if ancestors[hash] != nil {
			return errUncleIsAncestor
		}
		if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == block.ParentHash() {
			return errDanglingUncle
		}
		if err := dpos.verifyHeader(chain, uncle, ancestors[uncle.ParentHash], true, true); err != nil {
			return err
		}
	}
	return nil
}

// verifyHeader checks whether a header conforms to the consensus rules of the
// stock Ethereum dpos engine.
// See YP section 4.3.4. "Block Header Validity"
func (dpos *DElection) verifyHeader(chain ChainReader, header, parent *types.Header, uncle bool, seal bool) error {
	// Ensure that the header's extra-data section is of a reasonable size
	if uint64(len(header.Extra)) > config.MaximumExtraDataSize {
		return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), config.MaximumExtraDataSize)
	}
	if !bytes.Equal(header.DAppID.Bytes(),types.EmptyDAppIdHash.Bytes()) {
		//todo dapp block verification
		if bytes.Equal(header.DAppMainHash.Bytes(), types.EmptyHash.Bytes()) {

		}
	}
	// Verify the header's timestamp
	if uncle {
		if header.Time.Cmp(math.MaxBig256) > 0 {
			return errLargeBlockTime
		}
	} else {
		if header.Time.Cmp(big.NewInt(time.Now().Add(allowedFutureBlockTime).Unix())) > 0 {
			return ErrFutureBlock
		}
	}
	if header.Time.Cmp(parent.Time) < 0 {
		return errZeroBlockTime
	}
	// Verify the block's difficulty based in it's timestamp and parent's difficulty
	expected := dpos.CalcDifficulty(chain, header.Time.Uint64(), parent)
	if bytes.Equal(header.DAppID.Bytes(), types.EmptyDAppIdHash.Bytes()) && expected.Cmp(header.Difficulty) != 0 {
		return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected)
	}
	// Verify that the gas limit is <= 2^63-1
	cap := uint64(0x7fffffffffffffff)
	if header.GasLimit > cap {
		return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, cap)
	}
	// Verify that the gasUsed is <= gasLimit
	if header.GasUsed > header.GasLimit {
		return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit)
	}

	// Verify that the gas limit remains within allowed bounds
	diff := int64(parent.GasLimit) - int64(header.GasLimit)
	if diff < 0 {
		diff *= -1
	}
	limit := parent.GasLimit / config.GasLimitBoundDivisor

	if uint64(diff) >= limit || header.GasLimit < config.MinGasLimit {
		return fmt.Errorf("invalid gas limit: have %d, want %d += %d", header.GasLimit, parent.GasLimit, limit)
	}
	// Verify that the block number is parent's +1
	if diff := new(big.Int).Sub(header.Number, parent.Number); diff.Cmp(big.NewInt(1)) != 0 {
		return ErrInvalidNumber
	}
	// Verify the engine specific seal securing the block
	if seal {
		if err := dpos.VerifySeal(chain, header); err != nil {
			return err
		}
	}
	return nil
}

// CalcDifficulty is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time
// given the parent block's time and difficulty.
func (dpos *DElection) CalcDifficulty(chain ChainReader, time uint64, parent *types.Header) *big.Int {
	return dpos.calcDifficultyByzantium(time, parent)
}

// Some weird constants to avoid constant memory allocs for them.
var (
	expDiffPeriod = big.NewInt(100000)
	big1          = big.NewInt(1)
	big2          = big.NewInt(2)
	big9          = big.NewInt(9)
	big10         = big.NewInt(10)
	bigMinus99    = big.NewInt(-99)
	big2999999    = big.NewInt(2999999)
)

// calcDifficultyByzantium is the difficulty adjustment algorithm. It returns
// the difficulty that a new block should have when created at time given the
// parent block's time and difficulty. The calculation uses the Byzantium rules.
func (dpos *DElection) calcDifficultyByzantium(time uint64, parent *types.Header) *big.Int {
	// https://github.com/ethereum/EIPs/issues/100.
	// algorithm:
	// diff = (parent_diff +
	//         (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99))
	//        ) + 2^(periodCount - 2)

	bigTime := new(big.Int).SetUint64(time)
	bigParentTime := new(big.Int).Set(parent.Time)

	// holds intermediate values to make the algo easier to read & audit
	x := new(big.Int)
	y := new(big.Int)

	// (2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9
	x.Sub(bigTime, bigParentTime)
	x.Div(x, big9)
	if parent.UncleHash == types.EmptyUncleHash {
		x.Sub(big1, x)
	} else {
		x.Sub(big2, x)
	}
	// max((2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9, -99)
	if x.Cmp(bigMinus99) < 0 {
		x.Set(bigMinus99)
	}
	// parent_diff + (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99))
	y.Div(parent.Difficulty, config.DifficultyBoundDivisor)
	x.Mul(y, x)
	x.Add(parent.Difficulty, x)

	// minimum difficulty can ever be (before exponential factor)
	if x.Cmp(config.MinimumDifficulty) < 0 {
		x.Set(config.MinimumDifficulty)
	}
	// calculate a fake block number for the ice-age delay:
	//   https://github.com/ethereum/EIPs/pull/669
	//   fake_block_number = min(0, block.number - 3_000_000
	fakeBlockNumber := new(big.Int)
	if parent.Number.Cmp(big2999999) >= 0 {
		fakeBlockNumber = fakeBlockNumber.Sub(parent.Number, big2999999) // Note, parent is 1 less than the actual block number
	}
	// for the exponential factor
	periodCount := fakeBlockNumber
	periodCount.Div(periodCount, expDiffPeriod)

	// the exponential factor, commonly referred to as "the bomb"
	// diff = diff + 2^(periodCount - 2)
	if periodCount.Cmp(big1) > 0 {
		y.Sub(periodCount, big2)
		y.Exp(big2, y, nil)
		x.Add(x, y)
	}
	return x
}

// VerifySeal implements Engine, checking whether the given block satisfies
// the DPoS difficulty requirements.
func (dpos *DElection) VerifySeal(chain ChainReader, header *types.Header) error {
	if dpos.config.PoSMode == config.ModeFake || dpos.config.PoSMode == config.ModeFullFake {
		//time.Sleep(dpos.config.FakeDelay)
		if dpos.config.FakeFail == header.Number.Uint64() {
			return errInvalidPoW
		}
	}
	// Ensure that we have a valid difficulty for the block
	if header.Difficulty.Sign() <= 0 {
		return errInvalidDifficulty
	}
	return nil
}

// Prepare implements Engine, initializing the difficulty field of a
// header to conform to the dpos protocol. The changes are done inline.
func (dpos *DElection) Prepare(chain ChainReader, header *types.Header) error {
	parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)
	if parent == nil {
		return ErrUnknownAncestor
	}
	header.Difficulty = dpos.CalcDifficulty(chain, header.Time.Uint64(), parent)
	return nil
}

// Finalize implements Engine, accumulating the block and uncle rewards,
// setting the final state and assembling the block.
func (dpos *DElection) Finalize(chain ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
	// Accumulate any block and uncle rewards and commit the final state root
	accumulateRewards(chain.Config(), state, header, uncles)
	header.Root = state.IntermediateRoot(true)
	//log.Info("Generated block with root: " + header.Root.String() + ", Parent: " + header.ParentHash.String())
	// Header seems complete, assemble into a block and return
	b := types.NewBlock(header, txs, uncles, receipts)
	b.ToString()
	return b, nil;
}

// Seal generates a new block for the given input block with the local miner's
// seal place on top.
func (dpos *DElection) Seal(chain ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
	header := block.Header()
	//TODO
	header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
	return block.WithSeal(header), nil
}

// APIs returns the RPC APIs this consensus engine provides.
func (dpos *DElection) APIs(chain ChainReader) []rpc.API {
	return []rpc.API{{
		Namespace: "dpos",
		Version:   "1.0",
		Service:   &DPoSAPI{chain, dpos},
		Public:    false,
	}}
}

// PublicDebugAPI is the collection of Ethereum APIs exposed over the public
// debugging endpoint.
type DPoSAPI struct {
	chain  ChainReader
	dpos *DElection
}

func (dpos *DPoSAPI) Test() string {
	return "test";
}


// Some weird constants to avoid constant memory allocs for them.
var (
	big8  = big.NewInt(8)
	big32 = big.NewInt(32)
)

// AccumulateRewards credits the coinbase of the given block with the mining
// reward. The total reward consists of the static block reward and rewards for
// included uncles. The coinbase of each uncle block is also rewarded.
func accumulateRewards(config *config.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
	// Select the correct block reward based on chain progression
	blockReward := ByzantiumBlockReward

	// Accumulate the rewards for the miner and any included uncles
	reward := new(big.Int).Set(blockReward)
	r := new(big.Int)
	for _, uncle := range uncles {
		r.Add(uncle.Number, big8)
		r.Sub(r, header.Number)
		r.Mul(r, blockReward)
		r.Div(r, big8)
		state.AddBalance(uncle.Coinbase, r)

		r.Div(blockReward, big32)
		reward.Add(reward, r)
	}
	state.AddBalance(header.Coinbase, reward)
}