From d60df6531ac22963dcc0f7b966e76f0fa0400f6d Mon Sep 17 00:00:00 2001
From: stinkymonkeyph <monkeydev.team@gmail.com>
Date: Mon, 29 Jul 2024 20:32:43 +0800
Subject: [PATCH] feat: add initial implementation of persistent state

---
 blockchain/blockchain.go | 11 ++++++++++-
 blockchain/store.go      | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/blockchain/blockchain.go b/blockchain/blockchain.go
index 56d738e..bda00fa 100644
--- a/blockchain/blockchain.go
+++ b/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)
 
diff --git a/blockchain/store.go b/blockchain/store.go
index bc2782f..622f3d1 100644
--- a/blockchain/store.go
+++ b/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
+}