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import streamlit as st
import hashlib
import time
import json
from datetime import datetime
import pytz
# Blockchain Classes
class Block:
def __init__(self, index, timestamp, transactions, previous_hash):
self.index = index
self.timestamp = self.get_pakistan_time(timestamp)
self.transactions = transactions
self.previous_hash = previous_hash
self.hash = self.calculate_hash()
def get_pakistan_time(self, utc_time):
"""Convert UTC time to Pakistan Standard Time."""
pst_timezone = pytz.timezone("Asia/Karachi")
local_time = datetime.fromtimestamp(utc_time, pytz.utc).astimezone(pst_timezone)
return local_time.strftime("%a %b %d %H:%M:%S %Y") # Human-readable format
def calculate_hash(self):
block_content = json.dumps({
"index": self.index,
"timestamp": self.timestamp,
"transactions": self.transactions,
"previous_hash": self.previous_hash
}, sort_keys=True).encode()
return hashlib.sha256(block_content).hexdigest()
class Blockchain:
def __init__(self):
self.chain = [self.create_genesis_block()]
self.pending_transactions = []
def create_genesis_block(self):
return Block(0, time.time(), [], "0")
def get_latest_block(self):
return self.chain[-1]
def add_transaction(self, transaction):
self.pending_transactions.append(transaction)
def mine_block(self):
if not self.pending_transactions:
return None
new_block = Block(
index=len(self.chain),
timestamp=time.time(),
transactions=self.pending_transactions,
previous_hash=self.get_latest_block().hash
)
self.chain.append(new_block)
self.pending_transactions = [] # Clear pending transactions
return new_block
def is_chain_valid(self):
for i in range(1, len(self.chain)):
current_block = self.chain[i]
previous_block = self.chain[i - 1]
if current_block.hash != current_block.calculate_hash():
return False
if current_block.previous_hash != previous_block.hash:
return False
return True
# Streamlit App
st.title("Simple Blockchain Demo")
st.sidebar.header("Add a Transaction")
# Initialize Blockchain
if "blockchain" not in st.session_state:
st.session_state.blockchain = Blockchain()
blockchain = st.session_state.blockchain
# Add a Transaction
sender = st.sidebar.text_input("Sender")
recipient = st.sidebar.text_input("Recipient")
amount = st.sidebar.number_input("Amount", min_value=0.01, step=0.01)
if st.sidebar.button("Add Transaction"):
if sender and recipient and amount:
blockchain.add_transaction({"from": sender, "to": recipient, "amount": amount})
st.sidebar.success("Transaction added to the pool!")
else:
st.sidebar.error("Please provide valid transaction details.")
# Mine a Block
if st.button("Mine a Block"):
new_block = blockchain.mine_block()
if new_block:
st.success(f"Block {new_block.index} mined successfully!")
else:
st.error("No transactions to mine.")
# Display Blockchain
st.subheader("Blockchain Ledger")
for block in blockchain.chain:
st.write({
"Index": block.index,
"Timestamp": block.timestamp, # Already in PST format
"Transactions": block.transactions,
"Previous Hash": block.previous_hash,
"Hash": block.hash,
})
# Validate Blockchain
if st.button("Validate Blockchain"):
if blockchain.is_chain_valid():
st.success("Blockchain is valid!")
else:
st.error("Blockchain is invalid!")
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