#5 Introduce basic REST API

cmd/node/main.go

@@ -0,0 +1,21 @@
+// cmd/myblockchain/main.go
+package main
+
+import (
+	"blockchain/internal/api"
+	"blockchain/internal/blockchain"
+	"blockchain/internal/consensus"
+	"log"
+	"net/http"
+)
+
+func main() {
+	bc := blockchain.NewBlockchain()
+
+	cons := consensus.NewPoWConsensus(&bc)
+
+	router := api.NewRouter(&bc, cons)
+
+	log.Println("Listening on :8080")
+	log.Fatal(http.ListenAndServe(":8080", router))
+}

go.mod

@@ -1,3 +1,5 @@
 module blockchain
 
 go 1.23.1
+
+require github.com/gorilla/mux v1.8.1

go.sum

@@ -0,0 +1,2 @@
+github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
+github.com/gorilla/mux v1.8.1/go.mod h1:AKf9I4AEqPTmMytcMc0KkNouC66V3BtZ4qD5fmWSiMQ=

internal/api/handlers/block.go

@@ -0,0 +1,37 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"strconv"
+
+	"blockchain/internal/blockchain"
+
+	"github.com/gorilla/mux"
+)
+
+func GetBlockHandler(bc *blockchain.Blockchain) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		vars := mux.Vars(r)
+		indexStr, ok := vars["index"]
+		if !ok {
+			http.Error(w, "Index is required", http.StatusBadRequest)
+			return
+		}
+
+		index, err := strconv.Atoi(indexStr)
+		if err != nil {
+			http.Error(w, "Invalid index format", http.StatusBadRequest)
+			return
+		}
+
+		block, err := bc.GetBlock(index)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusNotFound)
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(block)
+	}
+}

internal/api/handlers/chain.go

@@ -0,0 +1,19 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"blockchain/internal/blockchain"
+)
+
+func GetChainHandler(bc *blockchain.Blockchain) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		response := map[string]interface{}{
+			"length": len(bc.Blocks()),
+			"blocks": bc.Blocks(),
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(response)
+	}
+}

internal/api/router.go

@@ -0,0 +1,20 @@
+// internal/api/router.go
+package api
+
+import (
+	"blockchain/internal/blockchain"
+	"blockchain/internal/consensus"
+
+	"blockchain/internal/api/handlers"
+
+	"github.com/gorilla/mux"
+)
+
+func NewRouter(bc *blockchain.Blockchain, cons *consensus.PoWConsensus) *mux.Router {
+	router := mux.NewRouter()
+
+	router.HandleFunc("/chain", handlers.GetChainHandler(bc)).Methods("GET")
+	router.HandleFunc("/blocks/{index}", handlers.GetBlockHandler(bc)).Methods("GET")
+
+	return router
+}

internal/blockchain/blockchain.go

@@ -1,25 +1,58 @@
 package blockchain
 
+import (
+	"errors"
+	"sync"
+)
+
 type Blockchain struct {
-	Blocks     []Block
+	blocks     []Block
 	Difficulty int
+	mutex      sync.Mutex
 }
 
 func NewBlockchain() Blockchain {
 	return Blockchain{
-		Blocks:     []Block{GenesisBlock(2)},
+		blocks:     []Block{GenesisBlock(2)},
 		Difficulty: 2,
+		mutex:      sync.Mutex{},
 	}
 }
 
+func (bc *Blockchain) Blocks() []Block {
+	bc.mutex.Lock()
+	defer bc.mutex.Unlock()
+
+	return bc.blocks
+}
+
 func (bc *Blockchain) AddBlock(block Block) {
-	bc.Blocks = append(bc.Blocks, block)
+	bc.mutex.Lock()
+	defer bc.mutex.Unlock()
+
+	bc.blocks = append(bc.blocks, block)
 }
 
 func (bc *Blockchain) FirstBlock() Block {
-	return bc.Blocks[0]
+	bc.mutex.Lock()
+	defer bc.mutex.Unlock()
+
+	return bc.blocks[0]
 }
 
 func (bc *Blockchain) LastBlock() Block {
-	return bc.Blocks[len(bc.Blocks)-1]
+	bc.mutex.Lock()
+	defer bc.mutex.Unlock()
+
+	return bc.blocks[len(bc.blocks)-1]
+}
+
+func (bc *Blockchain) GetBlock(index int) (Block, error) {
+	bc.mutex.Lock()
+	defer bc.mutex.Unlock()
+
+	if index < 0 || index >= len(bc.blocks) {
+		return Block{}, errors.New("invalid index")
+	}
+	return bc.blocks[index], nil
 }

internal/consensus/consensus.go

@@ -41,7 +41,7 @@ func (c *PoWConsensus) CreateNewBlock(data string) blockchain.Block {
 }
 
 func (c *PoWConsensus) AdjustDifficulty() int {
-	return CalculateNewDifficulty(c.blockchain.Blocks)
+	return CalculateNewDifficulty(c.blockchain.Blocks())
 }
 
 func (c *PoWConsensus) AddNewBlock(block blockchain.Block) error {

internal/consensus/consensus_test.go

@@ -43,7 +43,7 @@ func TestAddNewBlock(t *testing.T) {
 		t.Errorf("failed to add block to blockchain: " + result.Error())
 	}
 
-	if result := ValidateBlockChain(bc); result != nil {
+	if result := ValidateBlockChain(&bc); result != nil {
 		t.Errorf("failed to validate blockchain: " + result.Error())
 	}
 }

internal/consensus/validation.go

@@ -6,11 +6,13 @@ import (
 	"strings"
 )
 
-func ValidateBlockChain(blockchain blockchain.Blockchain) error {
+func ValidateBlockChain(blockchain *blockchain.Blockchain) error {
+	var blocks = blockchain.Blocks()
+
 	// skip genesis block
-	for i := 1; i < len(blockchain.Blocks); i++ {
-		block := blockchain.Blocks[i]
-		previousBlock := blockchain.Blocks[i-1]
+	for i := 1; i < len(blocks); i++ {
+		block := blocks[i]
+		previousBlock := blocks[i-1]
 
 		if err := validateBlock(block); err != nil {
 			return err