# -*- coding: utf-8 -*-
"""Blockchain.ipynb

Automatically generated by Colaboratory.

Original file is located at
    https://colab.research.google.com/drive/1wfXS6MTMX2J77EP5X1qFiKQzdo_eh511
"""

import datetime
import hashlib
import json
 
class Blockchain:

    def __init__(self):
        self.chain = []
        self.create_block(proof=1, previous_hash='0')
    
    def create_block(self, proof, previous_hash):
        block = {'index': len(self.chain) + 1,
                 'timestamp': str(datetime.datetime.now()),
                 'proof': proof,
                 'previous_hash': previous_hash}
        self.chain.append(block)
        return block
    
    def print_previous_block(self):
        return self.chain[-1]
       
    def proof_of_work(self, previous_proof):
        new_proof = 1
        check_proof = False
         
        while check_proof is False:
            hash_operation = hashlib.sha256(
                str(new_proof**2 - previous_proof**2).encode()).hexdigest()
            if hash_operation[:5] == '00000':
                check_proof = True
            else:
                new_proof += 1
                 
        return new_proof
 
    def hash(self, block):
        encoded_block = json.dumps(block, sort_keys=True).encode()
        return hashlib.sha256(encoded_block).hexdigest()
 
    def chain_valid(self, chain):
        previous_block = chain[0]
        block_index = 1
         
        while block_index < len(chain):
            block = chain[block_index]
            if block['previous_hash'] != self.hash(previous_block):
                return False
               
            previous_proof = previous_block['proof']
            proof = block['proof']
            hash_operation = hashlib.sha256(
                str(proof**2 - previous_proof**2).encode()).hexdigest()
             
            if hash_operation[:5] != '00000':
                return False
            previous_block = block
            block_index += 1
         
        return True

def create_chain():
  global blockchain
  blockchain = Blockchain()
  return "Chain Instantiated"

def del_chain():
  global blockchain
  del blockchain
  return "Chain Deleted"

def mine_block():
    previous_block = blockchain.print_previous_block()
    previous_proof = previous_block['proof']
    proof = blockchain.proof_of_work(previous_proof)
    previous_hash = blockchain.hash(previous_block)
    block = blockchain.create_block(proof, previous_hash)
     
    response = {'message': 'A block is MINED',
                'index': block['index'],
                'timestamp': block['timestamp'],
                'proof': block['proof'],
                'previous_hash': block['previous_hash']}
     
    return response

def hack_block(index,value):
  index=int(index.split(" ")[1])-1
  blockchain.chain[index]['proof']=value
  return f"block modified at index:{index+1}"

def display_chain():
    try:
      response = {'chain': blockchain.chain,'length': len(blockchain.chain)}
      
    except:
      response = "No chain found"
    return response

def valid():
    valid = blockchain.chain_valid(blockchain.chain)
     
    if valid:
        response = {'message': 'The Blockchain is valid.'}
    else:
        response = {'message': 'The Blockchain is not valid.'}
    return response

import gradio as gr

with gr.Blocks(title='Blockchain Simulator') as demo:
    gr.Image(value="./Blockchain.jpg",show_label=False,shape=(1500,300))
    with gr.Row():
        with gr.Column(scale=3):
            display = gr.Textbox(label="Blockchain Output",lines=5)
            dblock = gr.Button("Display/Refresh Blockchain")
        with gr.Column(scale=2):
            cblock = gr.Button("Instantiate Blockchain")
            mblock = gr.Button("Mine a Block")
            vblock = gr.Button("Validate Blockchain")
            delblock = gr.Button("Delete Blockchain") 
        with gr.Column(scale=2):
            index = gr.Radio(choices=["index 1", "index 2", "index 3"],label="Choose an Index to hack")
            value = gr.Textbox(label="New Value", placeholder = "Enter a Value")
            hblock = gr.Button("Hack a Block")
    dblock.click(fn=display_chain, inputs=[], outputs=[display],show_progress=True)
    cblock.click(fn=create_chain, inputs=[], outputs=[display],show_progress=True)
    mblock.click(fn=mine_block, inputs=[], outputs=[display],show_progress=True)
    vblock.click(fn=valid, inputs=[], outputs=[display],show_progress=True)
    delblock.click(fn=del_chain, inputs=[], outputs=[display],show_progress=True)
    hblock.click(fn=hack_block, inputs=[index,value], outputs=[display],show_progress=True)

demo.launch()