from classes.Blockchain import CBlock
from helpers.SignatureHelper import *
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.backends import default_backend

import random

REWARD_VALUE = 50.0
leading_zeros = 1
leading_extra = 2
next_char_limit = 25

class TxBlock (CBlock):

    def __init__(self, previousBlock):
        self.nonce = "A random nonce"
        self.metadata = {}
        self.time = None
        self.date = None
        super(TxBlock, self).__init__([], previousBlock)

    def addTx(self, Tx_in):
        self.data.append(Tx_in)

    def is_valid(self):
        if not super(TxBlock, self).is_valid():
            return False
        for tx in self.data:
            if not tx.is_valid():
                return False
            
        if self.nonce != "A random nonce":
            if not self.good_nonce():
                return False
        
        return True

    def good_nonce(self):
        digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
        digest.update(bytes(str(self.data), 'utf8'))
        digest.update(bytes(str(self.previousHash), 'utf8'))
        digest.update(bytes(str(self.nonce), 'utf8'))
        this_hash = digest.finalize()

        bytes_array = [b'\x00', b'\x01', b'\x02', b'\x03', b'\x04', b'\x05', b'\x06', b'\x07', b'\x08', b'\x09']
        if this_hash[:leading_zeros] == b'\x00'*leading_zeros:

            for i in range(leading_extra):
                if this_hash[:leading_extra + i + 1][leading_extra+i:] in bytes_array:
                    continue

                else:
                    return False

            return True

    def find_nonce(self):
        for i in range(350000):
            self.nonce = "".join([random.choice("1234567890ABCDEF") for n in range(next_char_limit)])
            if self.good_nonce():
                return self.nonce
        return None