Basic concept of blockchain

Blockchain/Models/Block.swift

@@ -0,0 +1,25 @@
+//
+//  Block.swift
+//  Blockchain
+//
+//  Created by Victor BODINAUD on 27/02/2020.
+//  Copyright © 2020 Victor BODINAUD. All rights reserved.
+//
+
+import Foundation
+import CryptoKit
+
+class Block {
+    var hash: String!
+    var data: String!
+    var previousHash: String!
+    var index: Int!
+    
+    func generateHash() -> String {
+        if let hashData = data.data(using: .utf8) {
+            _ = SHA256.hash(data: hashData)
+        }
+        
+        return NSUUID().uuidString.replacingOccurrences(of: "-", with: "")
+    }
+}

Blockchain/Models/Blockchain.swift

@@ -0,0 +1,34 @@
+//
+//  Blockchain.swift
+//  Blockchain
+//
+//  Created by Victor BODINAUD on 27/02/2020.
+//  Copyright © 2020 Victor BODINAUD. All rights reserved.
+//
+
+import Foundation
+
+class Blockchain {
+    var chain = [Block]()
+    
+    func createGenesisBlock(data: String) {
+        let genesisBlock = Block()
+        genesisBlock.data = data
+        genesisBlock.previousHash = "0000"
+        genesisBlock.index = 0
+        genesisBlock.hash = genesisBlock.generateHash()
+        chain.append(genesisBlock)
+        print("Genesis block created -- hash: \(genesisBlock.hash ?? "")")
+    }
+    
+    func createBlock(data: String) {
+        let newBlock = Block()
+        newBlock.data = data
+        newBlock.previousHash = chain[chain.count-1].hash
+        newBlock.index = chain.count
+        newBlock.hash = newBlock.generateHash()
+        chain.append(newBlock)
+        
+        print("Block \(newBlock.index ?? 0) created -- hash: \(newBlock.hash ?? "") previous hash: \(newBlock.previousHash ?? "") data: \(newBlock.data ?? "")")
+    }
+}

Blockchain/main.swift

@@ -8,5 +8,25 @@
 
 import Foundation
 
-print("Hello, World!")
+let blockchain = Blockchain()
+var command: String?
 
+blockchain.createGenesisBlock(data: "")
+
+repeat {
+    print("Enter command:")
+    command = readLine()
+    
+    if command == "create" {
+        print("data for the new block:")
+        let data = readLine()
+        blockchain.createBlock(data: data ?? "")
+    }
+    
+    if command == "spam" {
+        for _ in 1...1000000 {
+            blockchain.createBlock(data: "\((blockchain.chain.last?.index ?? 0)+1)")
+        }
+    }
+    
+} while command != "exit"