Implement GethBlockchain

core/blockchain.go

@@ -2,4 +2,5 @@ package core
 
 type Blockchain interface {
 	RegisterObserver(observer BlockchainObserver)
+	SubscribeToEvents()
 }

core/blockchain_logging_observer.go

@@ -5,5 +5,5 @@ import "fmt"
 type BlockchainLoggingObserver struct{}
 
 func (blockchainObserver BlockchainLoggingObserver) NotifyBlockAdded(block Block) {
-	fmt.Println("Added block: %f", block.Number)
+	fmt.Printf("New block was added: %d\n", block.Number)
 }

core/fake_blockchain_test.go

@@ -12,6 +12,11 @@ import (
 
 var _ = Describe("The fake blockchain", func() {
 
+	It("conforms to the Blockchain interface", func() {
+		var blockchain core.Blockchain = &fakes.Blockchain{}
+		Expect(blockchain).ShouldNot(BeNil())
+	})
+
 	It("lets the only observer know when a block was added", func() {
 		blockchain := fakes.Blockchain{}
 		blockchainObserver := &fakes.BlockchainObserver{}

core/geth_blockchain.go

@@ -1,14 +1,43 @@
 package core
 
-import "fmt"
+import (
+	"fmt"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/ethclient"
+	"golang.org/x/net/context"
+	"reflect"
+)
 
-type GethBlockchain struct{}
+type GethBlockchain struct {
+	client    *ethclient.Client
+	observers []BlockchainObserver
+}
 
 func NewGethBlockchain() *GethBlockchain {
-	fmt.Println("Creating Gethblockchain")
-	return &GethBlockchain{}
+	fmt.Println("Creating Geth Blockchain")
+	blockchain := GethBlockchain{}
+	client, _ := ethclient.Dial("/var/folders/b3/z7fhy7cs06q8d7y3_pwwt4x40000gn/T/ethereum_dev_mode/geth.ipc")
+	// TODO: handle error gracefully
+	blockchain.client = client
+	return &blockchain
+}
+func (blockchain GethBlockchain) notifyObservers(header *types.Header) {
+	block := Block{Number: header.Number}
+	for _, observer := range blockchain.observers {
+		observer.NotifyBlockAdded(block)
+	}
 }
 
-func (blockchain *GethBlockchain) RegisterObserver(_ BlockchainObserver) {
-
+func (blockchain *GethBlockchain) RegisterObserver(observer BlockchainObserver) {
+	fmt.Printf("Registering observer: %v\n", reflect.TypeOf(observer))
+	blockchain.observers = append(blockchain.observers, observer)
+}
+
+func (blockchain *GethBlockchain) SubscribeToEvents() {
+	blocks := make(chan *types.Header, 10)
+	myContext := context.Background()
+	blockchain.client.SubscribeNewHead(myContext, blocks)
+	for block := range blocks {
+		blockchain.notifyObservers(block)
+	}
 }

fakes/blockchain.go

@@ -17,3 +17,6 @@ func (blockchain *Blockchain) AddBlock(block core.Block) {
 		observer.NotifyBlockAdded(block)
 	}
 }
+
+func (_ *Blockchain) SubscribeToEvents() {
+}

main.go

@@ -1,13 +1,11 @@
 package main
 
 import (
-	"fmt"
-
 	"github.com/8thlight/vulcanizedb/core"
 )
 
 func main() {
-	fmt.Println("Starting connection")
 	var blockchain core.Blockchain = core.NewGethBlockchain()
 	blockchain.RegisterObserver(core.BlockchainLoggingObserver{})
+	blockchain.SubscribeToEvents()
 }