From cb7a4f857db2ac9c930f07a6085b8b980ff5a5db Mon Sep 17 00:00:00 2001
From: arnaucube <arnaucube@gmail.com>
Date: Sun, 7 Apr 2019 00:41:41 +0200
Subject: [PATCH] blockchain data structure and initial functions

---
 core/blockchain.go      | 80 ++++++++++++++++++++++++++++++++++
 core/blockchain_test.go | 96 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 176 insertions(+)
 create mode 100644 core/blockchain.go
 create mode 100644 core/blockchain_test.go

diff --git a/core/blockchain.go b/core/blockchain.go
new file mode 100644
index 0000000..aa7891d
--- /dev/null
+++ b/core/blockchain.go
@@ -0,0 +1,80 @@
+package core
+
+import (
+	"errors"
+	"slothdb/db"
+	"time"
+)
+
+type Blockchain struct {
+	Id        []byte // Id allows to have multiple blockchains
+	Genesis   Hash
+	LastBlock *Block
+	db        *db.Db
+}
+
+func NewBlockchain(database *db.Db) *Blockchain {
+	blockchain := &Blockchain{
+		Id:        []byte{},
+		Genesis:   Hash{},
+		LastBlock: &Block{},
+		db:        database,
+	}
+	return blockchain
+}
+
+func (bc *Blockchain) NewBlock(txs []Tx) *Block {
+	block := &Block{
+		Height:    bc.GetHeight() + 1,
+		PrevHash:  bc.LastBlock.Hash,
+		Txs:       txs,
+		Miner:     Address{}, // TODO put the node address
+		Timestamp: time.Now(),
+		Nonce:     0,
+		Hash:      Hash{},
+		Signature: []byte{},
+	}
+	return block
+}
+
+func (bc *Blockchain) GetHeight() uint64 {
+	return bc.LastBlock.Height
+}
+
+func (bc *Blockchain) GetLastBlock() *Block {
+	return bc.LastBlock
+}
+
+func (bc *Blockchain) AddBlock(block *Block) error {
+	bc.LastBlock = block
+	err := bc.db.Put(block.Hash[:], block.Bytes())
+	return err
+}
+
+func (bc *Blockchain) GetBlock(hash Hash) (*Block, error) {
+	v, err := bc.db.Get(hash[:])
+	if err != nil {
+		return nil, err
+	}
+	block, err := BlockFromBytes(v)
+	if err != nil {
+		return nil, err
+	}
+	return block, nil
+}
+
+func (bc *Blockchain) GetPrevBlock(hash Hash) (*Block, error) {
+	currentBlock, err := bc.GetBlock(hash)
+	if err != nil {
+		return nil, err
+	}
+	if currentBlock.PrevHash.IsZero() {
+		return nil, errors.New("This was the oldest block")
+	}
+	prevBlock, err := bc.GetBlock(currentBlock.PrevHash)
+	if err != nil {
+		return nil, err
+	}
+
+	return prevBlock, nil
+}
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
new file mode 100644
index 0000000..8ec7396
--- /dev/null
+++ b/core/blockchain_test.go
@@ -0,0 +1,96 @@
+package core
+
+import (
+	"io/ioutil"
+	"slothdb/db"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBlockchainDataStructure(t *testing.T) {
+	dir, err := ioutil.TempDir("", "db")
+	assert.Nil(t, err)
+	db, err := db.New(dir)
+	assert.Nil(t, err)
+
+	bc := NewBlockchain(db)
+	block := bc.NewBlock([]Tx{})
+
+	block2, err := BlockFromBytes(block.Bytes())
+	assert.Nil(t, err)
+	assert.Equal(t, block2.Bytes(), block.Bytes())
+}
+
+func TestGetBlock(t *testing.T) {
+	dir, err := ioutil.TempDir("", "db")
+	assert.Nil(t, err)
+	db, err := db.New(dir)
+	assert.Nil(t, err)
+
+	bc := NewBlockchain(db)
+
+	block := bc.NewBlock([]Tx{})
+	assert.Equal(t, block.Height, uint64(1))
+
+	err = bc.AddBlock(block)
+	assert.Nil(t, err)
+
+	block2, err := bc.GetBlock(block.Hash)
+	assert.Nil(t, err)
+	assert.Equal(t, block.Bytes(), block2.Bytes())
+}
+
+func TestGetPrevBlock(t *testing.T) {
+	dir, err := ioutil.TempDir("", "db")
+	assert.Nil(t, err)
+	db, err := db.New(dir)
+	assert.Nil(t, err)
+
+	difficulty := 1
+	bc := NewBlockchain(db)
+
+	for i := 0; i < 10; i++ {
+		block := bc.NewBlock([]Tx{})
+		block.CalculatePoW(difficulty)
+		assert.Equal(t, block.Height, uint64(i+1))
+
+		err = bc.AddBlock(block)
+		assert.Nil(t, err)
+		assert.Equal(t, bc.LastBlock.Height, block.Height)
+	}
+	block9, err := bc.GetPrevBlock(bc.LastBlock.Hash)
+	assert.Nil(t, err)
+	assert.Equal(t, block9.Height, uint64(9))
+
+	block8, err := bc.GetPrevBlock(block9.Hash)
+	assert.Nil(t, err)
+	assert.Equal(t, block8.Height, uint64(8))
+
+	currentBlock := bc.LastBlock
+	for err == nil {
+		currentBlock, err = bc.GetPrevBlock(currentBlock.Hash)
+	}
+	assert.Equal(t, err.Error(), "This was the oldest block")
+}
+
+func TestAddBlockWithTx(t *testing.T) {
+	addr0 := Address(HashBytes([]byte("addr0")))
+	addr1 := Address(HashBytes([]byte("addr1")))
+
+	dir, err := ioutil.TempDir("", "db")
+	assert.Nil(t, err)
+	db, err := db.New(dir)
+	assert.Nil(t, err)
+
+	bc := NewBlockchain(db)
+
+	var txs []Tx
+	tx := NewTx(addr0, addr1, []Input{}, []Output{})
+	txs = append(txs, *tx)
+	block := bc.NewBlock(txs)
+
+	block2, err := BlockFromBytes(block.Bytes())
+	assert.Nil(t, err)
+	assert.Equal(t, block2.Bytes(), block.Bytes())
+}