accounts, consensus, core, eth: make chain maker consensus agnostic (#15497)

* accounts, consensus, core, eth: make chain maker consensus agnostic

* consensus, core: move CalcDifficulty to Engine interface

* consensus: add docs for calcDifficulty function

* consensus, core: minor comment fixups

2 files changed, 13 insertions, 7 deletions

diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index 2bdb18677..5fe67c851 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -240,7 +240,8 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 		return errZeroBlockTime
 	}
 	// Verify the block's difficulty based in it's timestamp and parent's difficulty
-	expected := CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
+	expected := ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
+
 	if expected.Cmp(header.Difficulty) != 0 {
 		return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected)
 	}
@@ -287,7 +288,13 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 // 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.
-// TODO (karalabe): Move the chain maker into this package and make this private!
+func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+	return CalcDifficulty(chain.Config(), time, parent)
+}
+
+// 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 CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
 	next := new(big.Int).Add(parent.Number, big1)
 	switch {
@@ -502,8 +509,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 	if parent == nil {
 		return consensus.ErrUnknownAncestor
 	}
-	header.Difficulty = CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
-
+	header.Difficulty = ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
 	return nil
 }
 
@@ -511,7 +517,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 // setting the final state and assembling the block.
 func (ethash *Ethash) Finalize(chain consensus.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)
+	accumulateRewards(chain.Config(), state, header, uncles)
 	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
 
 	// Header seems complete, assemble into a block and return
@@ -527,8 +533,7 @@ var (
 // 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.
-// TODO (karalabe): Move the chain maker into this package and make this private!
-func AccumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
+func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
 	// Select the correct block reward based on chain progression
 	blockReward := FrontierBlockReward
 	if config.IsByzantium(header.Number) {
diff --git a/consensus/ethash/consensus_test.go b/consensus/ethash/consensus_test.go
index a58d220ef..438a99dd6 100644
--- a/consensus/ethash/consensus_test.go
+++ b/consensus/ethash/consensus_test.go
@@ -71,6 +71,7 @@ func TestCalcDifficulty(t *testing.T) {
 	}
 
 	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
+
 	for name, test := range tests {
 		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
 		diff := CalcDifficulty(config, test.CurrentTimestamp, &types.Header{