#!/usr/bin/env python3
# Convert a TSV file to a asn.txt
# Source:
# range_start range_end AS_number country_code AS_description
# Result:
# subnet/mask AS_number AS_description country_code
# 1.0.0.0/24      13335 eetc US
# 1.0.4.0/22      38803 etc AU

import sys
import ipaddress
import csv

def calculate_subnets(line_list):
    subnets = []
    while True:
        # Calculate from diff of range_start and range_end subnet size
        # 1.1.1.0 1.1.2.0 = 256
        subnet1_uint32 = int(ipaddress.IPv4Address(line_list[0]))
        subnet2_uint32 = int(ipaddress.IPv4Address(line_list[1]))
        subnet_size = subnet2_uint32 - subnet1_uint32
        # calculate bitmask
        subnet_mask = 32 - subnet_size.bit_length()
        # is subnet not exact size of 2^n? verify using subnet_mask
        p2 = (2**(32-subnet_mask))-1
        if subnet_size != p2:
            #print(f'Error: {line} is not a power of 2 {subnet_size} {subnet_mask} {p2}')
            # Calculate next subnet
            subnet_mask = subnet_mask + 1
            subnets.append(f'{line_list[0]}/{subnet_mask}')
            #print(f'Adding {line_list[0]}/{subnet_mask}')            
            # Calculate next subnet
            subnet1_uint32 = subnet1_uint32 + (2**(32-subnet_mask))
            printable_subnet = str(ipaddress.IPv4Address(subnet1_uint32))
            #print(f'Next subnet {printable_subnet}')
            # if next subnet is not in range, break
            if subnet1_uint32 > subnet2_uint32:
                print(f'Error: Subnet {subnet1_uint32} is not in range {subnet2_uint32}')
                break
            line_list[0] = str(ipaddress.IPv4Address(subnet1_uint32))            
        else:
            # Add subnet to subnets
            subnets.append(f'{line_list[0]}/{subnet_mask}')
            break
    return subnets 


def main():
    # argv[1] is the input file
    # argv[2] is the output file
    if len(sys.argv) != 3:
        print("Usage: convert_tsv.py <input_file> <output_file>")
        sys.exit(1)

    # Open the input file
    try:
        input_file = open(sys.argv[1], 'r')
    except IOError:
        print("Error: Cannot open input file")
        sys.exit(1)

    # Open the output file
    try:
        output_file = csv.writer(open(sys.argv[2], 'w'), delimiter=',',doublequote=True,quoting=csv.QUOTE_ALL)
    except IOError:
        print("Error: Cannot open output file")
        sys.exit(1)

    # Read the input file line by line
    for line in input_file:
        # strip the newline at the end of the line
        line = line.rstrip('\n')
        # Split the line into a list by tabs
        line_list = line.split('\t')
        subnets = calculate_subnets(line_list)
        for subnet in subnets:
            #print(line_list[2] + '\t' + line_list[4] + '\t' + line_list[3] + '\t' + subnet)
            # CSV
            output_file.writerow([subnet, line_list[2], line_list[4], line_list[3]])
        

        # Write the output file
        #output_file.write(str(subnet) + '\t' + line_list[2] + '\t' + line_list[4] + '\t' + line_list[3] + '\n')


    input_file.close()

if __name__ == '__main__':
    main()