#! /usr/bin/env python3

import sys, time

def prepare_message(bin_message):
    length = 32
    while length > 0 and bin_message[length-1] == 0:
        length -= 1
    bin_message = bin_message[0:length]
    for byte in bin_message:
        if byte < 32:
            return "<some binary blob>"
    try:
        return bin_message.decode()
    except UnicodeDecodeError:
        return "<some binary blob>"

def main():
    try:
        with open("blockchain", "rb") as f:
            while True:
                block = f.read(293)
                if len(block) != 293:
                    break
                if block[0] == 3:
                    # Reveal Transaction, skip the associated data
                    f.read(5376)
                timestamp = int.from_bytes(block[245:253], "big")
                time_info = time.strftime("%d.%m.%Y %H:%M:%S", time.localtime(timestamp))
                message = prepare_message(block[149:181])
                print(f"[{time_info}] {message}")
    except FileNotFoundError:
        print("Found no blockchain file", file=sys.stderr)
        exit(1)

if __name__ == '__main__':
    main()