Start introducing domain concepts

* Potential observers include a logger and/or an observer that writes to the DB

core/block.go

@@ -0,0 +1,7 @@
+package core
+
+import "math/big"
+
+type Block struct {
+	Number *big.Int
+}

core/blockchain.go

@@ -0,0 +1,5 @@
+package core
+
+type Blockchain interface {
+	RegisterObserver(observer BlockchainObserver)
+}

core/blockchain_logging_observer.go

@@ -0,0 +1,9 @@
+package core
+
+import "fmt"
+
+type BlockchainLoggingObserver struct{}
+
+func (blockchainObserver BlockchainLoggingObserver) NotifyBlockAdded(block Block) {
+	fmt.Println("Added block: %f", block.Number)
+}

core/blockchain_observer.go

@@ -0,0 +1,5 @@
+package core
+
+type BlockchainObserver interface {
+	NotifyBlockAdded(Block)
+}

core/fake_blockchain_test.go

@@ -0,0 +1,48 @@
+package core_test
+
+import (
+	"math/big"
+
+	"github.com/8thlight/vulcanizedb/core"
+	"github.com/8thlight/vulcanizedb/fakes"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("The fake blockchain", func() {
+
+	It("lets the only observer know when a block was added", func() {
+		blockchain := fakes.Blockchain{}
+		blockchainObserver := &fakes.BlockchainObserver{}
+		blockchain.RegisterObserver(blockchainObserver)
+
+		blockchain.AddBlock(core.Block{})
+
+		Expect(blockchainObserver.WasToldBlockAdded()).Should(Equal(true))
+	})
+
+	It("lets the second observer know when a block was added", func() {
+		blockchain := fakes.Blockchain{}
+		blockchainObserverOne := &fakes.BlockchainObserver{}
+		blockchainObserverTwo := &fakes.BlockchainObserver{}
+		blockchain.RegisterObserver(blockchainObserverOne)
+		blockchain.RegisterObserver(blockchainObserverTwo)
+
+		blockchain.AddBlock(core.Block{})
+
+		Expect(blockchainObserverTwo.WasToldBlockAdded()).Should(Equal(true))
+	})
+
+	It("passes the added block to the observer", func() {
+		blockchain := fakes.Blockchain{}
+		blockchainObserver := &fakes.BlockchainObserver{}
+		blockchain.RegisterObserver(blockchainObserver)
+
+		blockchain.AddBlock(core.Block{Number: big.NewInt(123)})
+
+		Expect(blockchainObserver.LastAddedBlock.Number).ShouldNot(BeNil())
+		Expect(blockchainObserver.LastAddedBlock.Number).Should(Equal(big.NewInt(123)))
+	})
+
+})

core/geth_blockchain.go

@@ -0,0 +1,14 @@
+package core
+
+import "fmt"
+
+type GethBlockchain struct{}
+
+func NewGethBlockchain() *GethBlockchain {
+	fmt.Println("Creating Gethblockchain")
+	return &GethBlockchain{}
+}
+
+func (blockchain *GethBlockchain) RegisterObserver(_ BlockchainObserver) {
+
+}

fakes/blockchain.go

@@ -0,0 +1,19 @@
+package fakes
+
+import (
+	"github.com/8thlight/vulcanizedb/core"
+)
+
+type Blockchain struct {
+	observers []core.BlockchainObserver
+}
+
+func (blockchain *Blockchain) RegisterObserver(observer core.BlockchainObserver) {
+	blockchain.observers = append(blockchain.observers, observer)
+}
+
+func (blockchain *Blockchain) AddBlock(block core.Block) {
+	for _, observer := range blockchain.observers {
+		observer.NotifyBlockAdded(block)
+	}
+}

fakes/blockchain_observer.go

@@ -0,0 +1,19 @@
+package fakes
+
+import (
+	"github.com/8thlight/vulcanizedb/core"
+)
+
+type BlockchainObserver struct {
+	wasToldBlockAdded bool
+	LastAddedBlock    core.Block
+}
+
+func (blockchainObserver *BlockchainObserver) WasToldBlockAdded() bool {
+	return blockchainObserver.wasToldBlockAdded
+}
+
+func (blockchainObserver *BlockchainObserver) NotifyBlockAdded(block core.Block) {
+	blockchainObserver.LastAddedBlock = block
+	blockchainObserver.wasToldBlockAdded = true
+}

main.go

@@ -1,7 +1,13 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+
+	"github.com/8thlight/vulcanizedb/core"
+)
 
 func main() {
-	fmt.Println("Hello world")
+	fmt.Println("Starting connection")
+	var blockchain core.Blockchain = core.NewGethBlockchain()
+	blockchain.RegisterObserver(core.BlockchainLoggingObserver{})
 }