blockchain.py

import hashlib
import networking
import time
from time import sleep
import ecdsa



#Mining difficulty
difficulty = 5
print("Difficulty: " + str(difficulty) + "\n")

#Maximum amount of time (in minutes) that the oldest block will have to wait before being added to a block
max_transaction_time = 1
print("Max transaction wait time: " + str(max_transaction_time) + "\n\n\n")



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DO NOT CHANGE THESE VARIABLES!!!
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#Time oldest transaction has been waiting to be added to block
#(starts at 0, and a Unix-time replaces it once a transaction is added)
transaction_countdown = 0

#List of transactions that have been verified and are waiting to be added to block
pending_transactions = []

#Blockchain object/list
blockchain = []

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genesis = {
            'block_data':   {
                                'index': 0,
                                'previous_hash': "0"*64
                            }, 
           'transactions': 
                            [
                                "This is the genesis block of PearCoin! This currency has a fixed value of 1 (one) Australian Dollar; no more, and no less."
                            ],
           'block_hash': 
                            {
                                'nonce': "",
                                'hash': "0fcc64eda3ca6a55fd06fb0676540e68af26da8f553afeb9e6acc7392ac85de5"
                            }
            }



blockchain.append(genesis)





#Function for easy hashing of any object or string
def hash(*args):
    hash = ""
    for arg in args:
        hash += str(arg)

    return str(hashlib.sha256(hash.encode('utf-8')).hexdigest())




'''Check that the fields are filled, sender has sufficient funds, 
sender's signature is correct, a suitable fee is attached'''
def verify_transaction(transaction):


    new_balances = {}

    for x in range(len(blockchain),0 ,-1):
        for y in range(len(blockchain['transactions'])):
            #if statement to check if the sender's address is in the block as sender
            #if statement to check if the sender's address is in the block as receiver
            #if the address is not found: break
            #if the address is found, use it to check the signature of the transaction
            #if the sender does not have adequate funds: break

            #if everything is fine:

                # new_balances['sender'] = "sender_new_balance"

                #find the balance of the sender and calculate their new balance
                # for x in range(len(blockchain),0 ,-1):
                #     for y in range(len(blockchain['transactions'])):

                #         find the balance of the receiver and calculate their new balance
                #         if the address was not found, assume the balance is 0, and then add the transaction amount
                #         new_balances['receiver'] = "receiver_new_balance"

                # transaction['new_balances'] = new_balances



    pending_transactions.append(transaction)


    global transaction_countdown
    if transaction_countdown == 0:
        transaction_countdown = time.time()








class Block():

    def __init__(self):
        pass


    def create_and_mine(self, data=pending_transactions):

        self.block = {}
        self.block_data = {}
        self.transactions = []
        self.block_hash = {}


        self.block_data['index'] = int(blockchain[-1]['block_data']['index']) + 1
        self.block_data['previous_hash'] = blockchain[-1]['block_hash']['hash']



        self.transactions = data


        self.block['block_data'] = self.block_data
        self.block['transactions'] = self.transactions

        self.block_hash['nonce'] = 0
        self.block_hash['hash'] = hash(str(self.block['block_data']) + str(self.block['transactions']))
        while self.block_hash['hash'][:difficulty] != difficulty * "0":
                
                self.block_hash['hash'] = hash(str(self.block['block_data']) 
                                            + str(self.block['transactions']) 
                                            + str(self.block_hash['nonce']))

                # print("nonce: " + str(self.block_hash['nonce']) + (20 * " ") + "hash: " + self.block_hash['hash'], end='\r')

                self.block_hash['nonce'] +=1



        self.block['block_hash'] = self.block_hash 

        # return(json.dumps(self.block, indent=4))

        global pending_transactions 
        pending_transactions = []

        return(self.block)






'''All the code needed to run (just runs other functions in a loop;
taking in, validating and adding transactions from half_nodes or blocks from full_nodes)'''
def main():


    print(str(blockchain[-1]) + "\n\n\n")


    while 2+2 == 4:

        verify_transaction(networking.listen_half_node())


        if (transaction_countdown) + int(max_transaction_time * 60) <= time.time() or len(pending_transactions) >= 5:
            #create block object
            block = Block()

            #Fill block object with data and calculate hash
            #add block to blockchain and delete block
            blockchain.append(block.create_and_mine())

            del block

            print(str(blockchain[-1]) + "\n\n\n")
            # print(str(blockchain[-1]["transactions"][0]['new_balances']['sender']) + "\n\n\n")







#Apparently this is a good thing to do???
if __name__ == '__main__':
    main()