blockchain.py

import hashlib
from time import time
import json

"""
Block structure:
-index
-hash
-transactions[]
-nonce
-previousHash
-timestamp

Consider:
-bloc_0  # Root Block
-pending_transactions[]
-blockchain[]

* Nouvelle transaction 👍
* Validation de la transaction 👍
* Ajout de la transaction dans un block pendant 👍
* repeter jusqu'a ce que le block atteind la limite 👍
* démarragag du processus de minage pour ajouter le block dans la blockchain 👍
* création d'un nouveau block 👍

v2
* Possibilité d'afficher la blockhain entièrement 👍
* Le genesis block ne doit contenir aucune transaction 👍
* Fonction editer: permettant de manipuler la chaine 👍
* Fonction verifier: pour verifier la validité de la chaine 
* S'assurer que tout la chaine est valide avant d'ajouter un block 
"""

BLOCK_SIZE=3
BLOCKCHAIN=[]
MENU_STRING="1- Continuer\n2- Afficher la blockhain\n0- Quittter"
pendingBlock={}
makeDecision=1
currentIndex=0

def init():
    global currentIndex
    global pendingBlock
    block_0= {
        'index':currentIndex,
        'hash': '',
        'transactions':[],
        'nonce':0,
        'previousHash': 'NULL',
        'timestamp': time()
    }
    block_0['hash']=  hashlib.sha256(str(block_0).encode()).hexdigest()
    blockchain= [block_0]
    pendingBlock= block_0
    currentIndex+=1
    print("Genesis block initialised!")
    newPendingBlock()

init()


def newTransaction():
    """
    Adds a new transaction to the pending block
    """
    global pendingBlock
    global makeDecision
    transaction= {
        'sender': input('Expéditeur: '),
        'receiver': input('Destinataire: '),
        'amount': int(input('Montant: '))
    }
    pendingBlock['transactions'].append(transaction)
    print("Transaction ajouté!")
    if( len(pendingBlock['transactions']) == BLOCK_SIZE  ): 
        print("Block complet\n")
        mining()
        makeDecision=  int(input(MENU_STRING))
    
    return 

def newPendingBlock():
    """
    New block
    """
    global currentIndex
    global pendingBlock
    block= {
        'index':currentIndex,
        'hash': '',
        'transactions':[],
        'nonce':0,
        'previousHash': '',
        'timestamp': time()
    }
    block['previousHash']=  pendingBlock['hash']
    pendingBlock= block
    currentIndex+=1
    print("\n\nNouveau block initialisé!")
    return


def mining():
    """
    Mining Funciton 
    """
    print("Minage.... :P")
    global BLOCKCHAIN
    validHash= computeHash(pendingBlock)
    pendingBlock['hash']= validHash
    BLOCKCHAIN.append(pendingBlock)
    print("Minage Terminé\nBlock ajouté à la chaine:")
    printty(pendingBlock)
    newPendingBlock()

    return


def computeHash(block):
    """
    Hash Function
    """
    b= str(block)
    while 1:
        data= str(block)+ str(block['nonce'])
        block['nonce']+=1
        h= hashlib.sha256(data.encode()).hexdigest()
        if(h[0]=='0' and h[1]=='0'  and h[2]=='0'):
            print("Hash valide trouvé! avec un nonce de "+ str(block['nonce']))
            break
    
    return h

def displayBlockchain():
    """
    Displayin func
    """
    printty(BLOCKCHAIN)
    return

def editBlock():
    idx= int(input("Entrez l'index du bloc à modifer: "))
    block= BLOCKCHAIN[idx]
    printty(block)
    idx= int(input("Entrez l'index de la transaction à modifer: "))
    printty(block['transactions'][idx])
    block['transactions'][idx]= {
        'sender': input('Expéditeur: '),
        'receiver': input('Destinataire: '),
        'amount': int(input('Montant: '))
    }


def printty(obj):
   print (json.dumps(obj, indent=4))


while 1:
    if(makeDecision==1):
        newTransaction()
    elif (makeDecision==2):
        displayBlockchain()
        makeDecision=  int(input(MENU_STRING))
    else:
        print("Why so soon ??\nbye!")
        break