import hashlib
import datetime


class Block:
    def __init__(self, index, timestamp, data, previous_hash):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.hashblock()

    def hashblock(self):
        sha = hashlib.sha256()
        sha.update((str(self.index) + str(self.timestamp) + str(
            self.data) + str(self.previous_hash)).encode())
        return sha.hexdigest()


def create_genesis_block():
    return Block(0, datetime.datetime.now(), "Genesis Block", "0")


def next_block(last_block):
    this_index = last_block.index + 1
    this_timestamp = datetime.datetime.now()
    this_data = "I am block " + str(this_index)
    # hash accumulates
    this_hash = last_block.hash
    return Block(this_index, this_timestamp, this_data, this_hash)


blockchain = [create_genesis_block()]


num_of_blocks_to_add = 20
previous_block = blockchain[0]

for i in range(0, num_of_blocks_to_add):
    block_to_add = next_block(previous_block)
    blockchain.append(block_to_add)
    previous_block = block_to_add
    print(block_to_add.data)
    print(block_to_add.hash)


