//
//  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]()
    
    /**
        Initialize the first block of the blockchain.
        
        - Parameters:
            - data: The datas of the block
     */
    func createGenesisBlock(data: String) {
        let genesisBlock = Block()
        genesisBlock.data = data
        genesisBlock.previousHash = "0000"
        genesisBlock.index = 0
        genesisBlock.nonce = 0
        genesisBlock.timestamp = genesisBlock.generateTimestamp()
        genesisBlock.hash = genesisBlock.generateHash()
        chain.append(genesisBlock)
        print("Genesis block created -- hash: \(genesisBlock.hash)")
    }
    
    /**
        Initialize a new block of the blockchain.
     
        - Parameters:
            - data: The datas of the block
     */
    func createBlock(data: String) {
        let newBlock = Block()
        newBlock.data = data
        newBlock.previousHash = chain.last!.hash
        newBlock.index = chain.count
        newBlock.nonce = 0
        newBlock.timestamp = newBlock.generateTimestamp()
        newBlock.hash = newBlock.generateHash()
        chain.append(newBlock)
        
        print("-- Block \(newBlock.index) created --\n hash: \(newBlock.hash)\n previous hash: \(newBlock.previousHash)\n data: \(newBlock.data)")
    }
    
    /**
        Insert a corrupted block in the blockhain.
        (for testing purpose)
     */
    func insertCorruptedBlock() {
        let newCorruptedBlock = Block()
        newCorruptedBlock.data = "Corrupted block"
        newCorruptedBlock.previousHash = "1234567890"
        newCorruptedBlock.index = chain.count
        newCorruptedBlock.nonce = 0
        newCorruptedBlock.timestamp = newCorruptedBlock.generateTimestamp()
        newCorruptedBlock.hash = newCorruptedBlock.generateHash()
        chain.append(newCorruptedBlock)
        
        print("-- Corrupted block \(newCorruptedBlock.index) created --\n hash: \(newCorruptedBlock.hash)\n previous hash: \(newCorruptedBlock.previousHash)\n data: \(newCorruptedBlock.data)")
    }
    
    /**
        Check validity of the blockchain.
     */
    func chainValidity() {
        var isChainValid = true
        var corruptedBlock = Block()
        
        for i in 1...chain.count-1 {
            if chain[i].previousHash != chain[i-1].hash {
                isChainValid = false
                corruptedBlock = chain[i]
            }
        }
        
        print("Chain is valid : \(isChainValid)")
        
        if !isChainValid {
            print("Corrupted block is : \(corruptedBlock.index)")
        }
    }
}