Add Update Chain Method

core/Block.go

@@ -32,3 +32,7 @@ func (block *Block) Hash() string {
 func (block *Block) AsJSON() JSONBlock {
 	return JSONBlock{Timestamp: block.Timestamp, Hash: block.Hash(), PreviousHash: block.PreviousHash, Data: block.Data, Proof: block.Proof}
 }
+
+func (block *JSONBlock) FromJSON() Block {
+	return Block{Timestamp: block.Timestamp, PreviousHash: block.PreviousHash, Data: block.Data, Proof: block.Proof}
+}

core/Blockchain.go

@@ -1,6 +1,7 @@
 package core
 
 import (
+	"encoding/json"
 	"log"
 	"net/http"
 	"strings"
@@ -100,6 +101,34 @@ func (bc *Blockchain) IsValid() bool {
 	return true
 }
 
+func (bc *Blockchain) Update() bool {
+
+	var hasBeenReplaced = false
+
+	for _, peer := range bc.Peers {
+		resp, err := http.Get("http://" + peer)
+
+		decoder := json.NewDecoder(resp.Body)
+		var receivedBlockchain JSONBlockchain
+		err = decoder.Decode(&receivedBlockchain)
+		if err == nil {
+			if receivedBlockchain.Blockcount > bc.AsJSON().Blockcount {
+
+				newBlocks := make([]Block, 0)
+				for _, block := range receivedBlockchain.Blocks {
+					newBlocks = append(newBlocks, block.FromJSON())
+				}
+
+				bc.Blocks = newBlocks
+
+				log.Println("Blockchain has been updated by " + peer)
+				hasBeenReplaced = true
+			}
+		}
+	}
+	return hasBeenReplaced
+}
+
 // JSONBlockchain is needed, because the hash of each block is calculated dynamically, and therefore is not stored in the `Block` struct
 type JSONBlockchain struct {
 	Blocks              []JSONBlock

server/webserver.go

@@ -33,6 +33,7 @@ func registerRouteHandlers() {
 	http.HandleFunc("/pending_transactions", handleListPendingTransactions)
 	http.HandleFunc("/add_transaction", handleAddTransaction)
 	http.HandleFunc("/is_valid", handleIsValid)
+	http.HandleFunc("/update", handleUpdate)
 
 	http.HandleFunc("/add_peers", handleAddPeers)
 }
@@ -91,5 +92,8 @@ func handleAddPeers(w http.ResponseWriter, r *http.Request) {
 	}
 
 	json.NewEncoder(w).Encode(blockchain.Peers)
+}
 
+func handleUpdate(w http.ResponseWriter, r *http.Request) {
+	json.NewEncoder(w).Encode(blockchain.Update())
 }