feat: add initial implementation of persistent state

blockchain/blockchain.go

@@ -14,7 +14,16 @@ type Blockchain struct {
 }
 
 func NewBlockchain(genesisBlock *Block) *Blockchain {
-	bc := new(Blockchain)
+	state, err := ReadFromDb()
+	bc := &Blockchain{}
+
+	if err != nil {
+		bc = new(Blockchain)
+	} else {
+		log.Println("Found existing blockchain state, persisting state from datastore")
+		bc = &state
+	}
+
 	bc.TransactionPool = []*Transaction{}
 	bc.Blocks = append(bc.Blocks, genesisBlock)
 

blockchain/store.go

@@ -33,3 +33,39 @@ func PutIntoDb(bc *Blockchain) error {
 
 	return nil
 }
+
+func ReadFromDb() (Blockchain, error) {
+	var bc Blockchain
+
+	db, err := badger.Open(badger.DefaultOptions(constants.DB_PATH))
+
+	if err != nil {
+		return bc, err
+	}
+
+	defer db.Close()
+
+	err = db.View(func(txn *badger.Txn) error {
+		item, err := txn.Get([]byte(constants.DB_KEY))
+		if err != nil {
+			return err
+		}
+		val, err := item.ValueCopy(nil)
+		if err != nil {
+			return err
+		}
+
+		err = json.Unmarshal(val, &bc)
+
+		if err != nil {
+			return err
+		}
+		return nil
+	})
+
+	if err != nil {
+		return bc, err
+	}
+
+	return bc, nil
+}