core, miner: move Backend to miner

This ensures that package core doesn't depend on package accounts and
resolves an age-old TODO.

core/types.go

@@ -19,12 +19,9 @@ package core
 import (
 	"math/big"
 
-	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
-	"github.com/ethereum/go-ethereum/ethdb"
-	"github.com/ethereum/go-ethereum/event"
 )
 
 // Validator is an interface which defines the standard for block validation.
@@ -63,15 +60,3 @@ type HeaderValidator interface {
 type Processor interface {
 	Process(block *types.Block, statedb *state.StateDB, cfg vm.Config) (types.Receipts, vm.Logs, *big.Int, error)
 }
-
-// Backend is an interface defining the basic functionality for an operable node
-// with all the functionality to be a functional, valid Ethereum operator.
-//
-// TODO Remove this
-type Backend interface {
-	AccountManager() *accounts.Manager
-	BlockChain() *BlockChain
-	TxPool() *TxPool
-	ChainDb() ethdb.Database
-	EventMux() *event.TypeMux
-}

miner/miner.go

@@ -22,11 +22,13 @@ import (
 	"math/big"
 	"sync/atomic"
 
+	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/downloader"
+	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
@@ -34,6 +36,15 @@ import (
 	"github.com/ethereum/go-ethereum/pow"
 )
 
+// Backend wraps all methods required for mining.
+type Backend interface {
+	AccountManager() *accounts.Manager
+	BlockChain() *core.BlockChain
+	TxPool() *core.TxPool
+	ChainDb() ethdb.Database
+}
+
+// Miner creates blocks and searches for proof-of-work values.
 type Miner struct {
 	mux *event.TypeMux
 
@@ -44,15 +55,21 @@ type Miner struct {
 	threads  int
 	coinbase common.Address
 	mining   int32
-	eth      core.Backend
+	eth      Backend
 	pow      pow.PoW
 
 	canStart    int32 // can start indicates whether we can start the mining operation
 	shouldStart int32 // should start indicates whether we should start after sync
 }
 
-func New(eth core.Backend, config *core.ChainConfig, mux *event.TypeMux, pow pow.PoW) *Miner {
-	miner := &Miner{eth: eth, mux: mux, pow: pow, worker: newWorker(config, common.Address{}, eth), canStart: 1}
+func New(eth Backend, config *core.ChainConfig, mux *event.TypeMux, pow pow.PoW) *Miner {
+	miner := &Miner{
+		eth:      eth,
+		mux:      mux,
+		pow:      pow,
+		worker:   newWorker(config, common.Address{}, eth, mux),
+		canStart: 1,
+	}
 	go miner.update()
 
 	return miner

miner/worker.go

@@ -60,7 +60,7 @@ type uint64RingBuffer struct {
 	next int      //where is the next insertion? assert 0 <= next < len(ints)
 }
 
-// environment is the workers current environment and holds
+// Work is the workers current environment and holds
 // all of the current state information
 type Work struct {
 	config             *core.ChainConfig
@@ -105,7 +105,7 @@ type worker struct {
 	recv   chan *Result
 	pow    pow.PoW
 
-	eth     core.Backend
+	eth     Backend
 	chain   *core.BlockChain
 	proc    core.Validator
 	chainDb ethdb.Database
@@ -130,11 +130,11 @@ type worker struct {
 	fullValidation bool
 }
 
-func newWorker(config *core.ChainConfig, coinbase common.Address, eth core.Backend) *worker {
+func newWorker(config *core.ChainConfig, coinbase common.Address, eth Backend, mux *event.TypeMux) *worker {
 	worker := &worker{
 		config:         config,
 		eth:            eth,
-		mux:            eth.EventMux(),
+		mux:            mux,
 		chainDb:        eth.ChainDb(),
 		recv:           make(chan *Result, resultQueueSize),
 		gasPrice:       new(big.Int),