#!/usr/bin/env python3
import os
import re
import sys
import collections
import ipaddress

# This script requires python3.7 or higher!

def parse_ipv4_filter_rules(registry_path):
    with open(registry_path + '/data/filter.txt') as f:
        filter_data = f.read()
    filter_regex = re.compile(r'(?P<filter_num>\d+)(\s+)(?P<route_allowed>permit|deny)(\s+)(?P<network>\d+\.\d+\.\d+\.\d+\/\d+)(\s+)(?P<min_length>\d+)(\s+)(?P<max_length>\d+)(\s+)#(\s+)(?P<comment>.*)')
    ipv4_rules = collections.OrderedDict()
    for filter_line in filter_data.split('\n'):
        if filter_line.startswith('#'): continue
        filter_rule = filter_regex.match(filter_line)
        if filter_rule == None: continue
        parsed_rule = {
            'filter_num': int(filter_rule.group('filter_num')),
            'route_allowed': (True if filter_rule.group('route_allowed') == 'permit' else False),
            'network': filter_rule.group('network'),
            'min_length': int(filter_rule.group('min_length')),
            'max_length': int(filter_rule.group('max_length')),
            'comment': filter_rule.group('comment')
        }
        ipv4_rules[parsed_rule['filter_num']] = parsed_rule
    return ipv4_rules

def parse_ipv6_filter_rules(registry_path):
    with open(registry_path + '/data/filter6.txt') as f:
        filter_data = f.read()
    filter_regex = re.compile(r'(?P<filter_num>\d+)(\s+)(?P<route_allowed>permit|deny)(\s+)(?P<network>([0-9a-f:]*)\/\d+)(\s+)(?P<min_length>\d+)(\s+)(?P<max_length>\d+)(\s+)#(\s+)(?P<comment>.*)')
    ipv6_rules = collections.OrderedDict()
    for filter_line in filter_data.split('\n'):
        if filter_line.startswith('#'): continue
        filter_rule = filter_regex.match(filter_line)
        if filter_rule == None: continue
        parsed_rule = {
            'filter_num': int(filter_rule.group('filter_num')),
            'route_allowed': (True if filter_rule.group('route_allowed') == 'permit' else False),
            'network': filter_rule.group('network'),
            'min_length': int(filter_rule.group('min_length')),
            'max_length': int(filter_rule.group('max_length')),
            'comment': filter_rule.group('comment')
        }
        ipv6_rules[parsed_rule['filter_num']] = parsed_rule
    return ipv6_rules

def parse_route_objects(folder_path):
    route_objects = []
    for root, dirs, files in os.walk(folder_path):
        for filename in files:
            current_file = str(root) + str(filename)
            route_object = read_schema_object_file(current_file)
            route_objects.append(route_object)
    return route_objects

def read_schema_object_file(file_path):
    with open(file_path) as f:
        data = f.read()
    schema_object = {}
    current_key = None
    current_value = None
    for line in data.split('\n'):
        # Ignore completely empty lines
        if line == '': continue
        # If a new key/value pair comes up (meaning there's a : within the first 20 chars)
        if ':' in line[0:20]:
            # Write last processed key/value-pair into schema_object if needed
            if current_key != None:
                if current_key in schema_object.keys():
                    if isinstance(schema_object[current_key], list):
                        schema_object[current_key].append(current_value)
                    else:
                        schema_object[current_key] = [schema_object[current_key], current_value]
                else:
                    schema_object[current_key] = current_value
            # Then begin parsing the next one
            items = line.split(':', 1)
            current_key = items[0].strip()
            current_value = items[1].strip()
        else:
            # This denotes a linebreak in a multiline value
            if line[0] == '+':
                current_value += '\n'
            elif line.startswith(' ' * 20):
                # This is an additional line in a multiline value
                current_value += line[20:] + '\n'
    return schema_object

def create_roa_entries(route_objects, filter_rules, mode, f):
    for route_object in route_objects:
        # Convert single value origin attribute to list
        if not isinstance(route_object['origin'], list):
            route_object['origin'] = [route_object['origin']]
        # Check if route is permitted by filter rules
        if mode == 'ipv4':
            route_network = ipaddress.IPv4Network(route_object['route'])
        elif mode == 'ipv6':
            route_network = ipaddress.IPv6Network(route_object['route6'])
        matching_filter_rule = None
        for id, filter_rule in filter_rules.items():
            if mode == 'ipv4':
                filter_network = ipaddress.IPv4Network(filter_rule['network'])
            elif mode == 'ipv6':
                filter_network = ipaddress.IPv6Network(filter_rule['network'])
            if route_network.subnet_of(filter_network):
                # First final rule match. Take it and leave!
                #print('# ' + str(filter_rule) + ' matched for ' + str(route_object))
                matching_filter_rule = filter_rule
                break
        # Now check if it permits or denies
        if matching_filter_rule['route_allowed'] == False:
            # Skip non-permitted routes
            f.write('# DENIED' + str(route_object) + ' by filter rule: ' + str(matching_filter_rule) + '\n')
            continue
        # Check if min-length fits filter requirements
        if matching_filter_rule['min_length'] > route_network.prefixlen:
            # Drop route objects which do not satisfy min_length requirement of matching filter rule
            f.write('# FAILED minimum prefix length requirement exceeded: ' + str(route_object) + ' against filter rule: ' + str(matching_filter_rule) + '\n')
            continue
        # Figure out max-length (filter rule wins over route object)
        if 'max-length' in route_object.keys():
            allowed_max_len = min(int(matching_filter_rule['max_length']), int(route_object['max-length']))
        else:
            allowed_max_len = int(matching_filter_rule['max_length'])
        if allowed_max_len < route_network.prefixlen:
            # Drop route objects which do not satisfy max_length requirement of matching filter rule
            f.write('# FAILED maximum prefix length exceeded: ' + str(route_object) + ' against filter rule: ' + str(matching_filter_rule) + '\n')
            continue
        # Create roa for every origin of this route
        for origin in route_object['origin']:
           # Make sure to strip "AS" prefix from AS value
           origin = origin.lstrip('AS')
           if mode == 'ipv4':
               f.write('route ' + route_object['route'] + ' max ' + str(allowed_max_len) + ' as ' + origin + ';' + "\n")
           elif mode == 'ipv6':
               f.write('route ' + route_object['route6'] + ' max ' + str(allowed_max_len) + ' as ' + origin + ';' + "\n")

def create_valid_network_function(filter_rules, mode, f):
    f.write('function dn42_is_valid_' + mode + '_network() {\n')
    f.write('  return net ~ [\n')
    first_line_written = False
    for id, filter_rule in filter_rules.items():
        if filter_rule['route_allowed']:
            if first_line_written:
                f.write(',\n')
            f.write('    ' + filter_rule['network'] + '{' + str(filter_rule['min_length']) + ',' + str(filter_rule['max_length']) + '}')
            if not first_line_written:
                first_line_written = True
    f.write('\n  ];\n')
    f.write('}\n')

if __name__ == '__main__':
    # Get registry path over commandline argument
    registry_path = sys.argv[1]

    # Uncomment this block to test the parser against that evil file in the registry.
    #print(read_schema_object_file(registry_path + '/data/schema/SCHEMA-SCHEMA'))
    #exit

    # Read filter rules
    ipv4_filter_rules = parse_ipv4_filter_rules(registry_path)
    ipv6_filter_rules = parse_ipv6_filter_rules(registry_path)
    # Read all route objects
    ipv4_route_objects = parse_route_objects(registry_path + '/data/route/')
    ipv6_route_objects = parse_route_objects(registry_path + '/data/route6/')
    # Create routes out of ipv4 route objects
    with open('./dn42_roa_ipv4.conf', 'w') as target_file:
        create_roa_entries(ipv4_route_objects, ipv4_filter_rules, 'ipv4', target_file)
    # Create routes out of ipv6 route objects
    with open('./dn42_roa_ipv6.conf', 'w') as target_file:
        create_roa_entries(ipv6_route_objects, ipv6_filter_rules, 'ipv6', target_file)
    # Create ipv4 network validation function
    with open('./dn42_valid_ipv4.conf', 'w') as target_file:
        create_valid_network_function(ipv4_filter_rules, 'ipv4', target_file)
    # Create ipv6 network validation function
    with open('./dn42_valid_ipv6.conf', 'w') as target_file:
        create_valid_network_function(ipv6_filter_rules, 'ipv6', target_file)