import argparse
from math import log2
import os

HEADW = 0xFA6A8001  # work file
HEADERSIZE=156

def bytes_to_num(byte_data):    
    return int.from_bytes(byte_data, byteorder='little')
    

def checkhead(wf):
    head = bytes_to_num(wf.read(4))
    if head==HEADW:
        return head
    else:
        print('HEADER ERROR %08x %08x' % (head, HEADW))
        return False

def workinfo(workfile):    
    wf = open(workfile, 'rb')
    head = checkhead(wf)
    if not head:
        print('Invalid WorkFile Header')
        return False
    version = bytes_to_num(bytes(wf.read(4)))
    dp1 = bytes_to_num(bytes(wf.read(4)))
    RangeStart = bytes_to_num(bytes(wf.read(32)))
    RangeEnd = bytes_to_num(bytes(wf.read(32)))
    x = bytes_to_num(bytes(wf.read(32)))
    y = bytes_to_num(bytes(wf.read(32)))
    count = bytes_to_num(bytes(wf.read(8)))
    time = bytes_to_num(bytes(wf.read(8)))
    print(
        f'Header     : {head:08x}'
        f'\nVersion    : {version:d}'
        f'\nDP Bits    : {dp1}'
        f'\nStart      : {RangeStart:032x}'
        f'\nStop       : {RangeEnd:032x}'
        f'\nPubKey X   : {x:032x}'
        f'\nPubKey Y   : {y:032x}'
        f'\nCount      : 2^{log2(count):.3f}'       
        )      
    wf.close()
    return True
        
def getuncompressedpub(compressed_key):    
    p=2**256 - 2**32 - 977
    y_parity = int(compressed_key[:2],16) - 2 
    if y_parity>1:      
      x = int(compressed_key[2:66], 16) 
      y = int(compressed_key[66:130], 16) 
      return (x,y)     
    x = int(compressed_key[2:], 16)
    a = (pow(x, 3, p) + 7) % p
    y = pow(a, (p+1)//4, p)    
    if y % 2 != y_parity:
        y = -y % p        
    return (x,y)
    
def MakeChanges(workfile, NewPubCompressed, NewRB, NewRE):
    if os.path.exists(f'{workfile}'):
        print('Old header:')
        if workinfo(workfile):        
            #make some changes
            (x,y)= getuncompressedpub(NewPubCompressed)    
            with open(workfile, 'r+b') as wf:            
                try:
                    wf.seek(12)
                    wf.write(NewRB.to_bytes(32, byteorder='little'))
                    wf.write(NewRE.to_bytes(32, byteorder='little'))
                    wf.write(x.to_bytes(32, byteorder='little'))
                    wf.write(y.to_bytes(32, byteorder='little'))  
                except Exception as e:
                    print(f'File error {e}')       
            print('New header:')
            workinfo(workfile)        
    else:
        print(f'File {workfile} is not exist')
        return


        
if __name__ == '__main__':    
    parser = argparse.ArgumentParser()
    parser.add_argument('-f', dest='workfile', type=str, required=True, help='WorkFile path')
    parser.add_argument('-pub', dest='pub', required=True, type=str, help='Compressed public key')
    parser.add_argument('-rb', dest='rb', required=True, type=str, help='Begin range')
    parser.add_argument('-re', dest='re', required=True, type=str, help='End range')
    args = parser.parse_args()

    if args.workfile:
        print(f'Workfile {args.workfile}')
        MakeChanges(args.workfile, args.pub, int(args.rb,16), int(args.re,16))