added cidr list merge algorithm

cidr4_merger.py

@@ -0,0 +1,45 @@
+from copy import deepcopy
+from typing import List
+
+from netaddr import IPNetwork, cidr_merge
+
+
+def get_ips(input_file) -> List[IPNetwork]:
+    with open(input_file, "r") as file:
+        data = file.read().splitlines()
+    return [IPNetwork(line) for line in data]
+
+
+def reduce_prefixlen(ip: IPNetwork, step=1) -> IPNetwork:
+    """Reduce the CIDR prefix len by step"""
+    new_ip = IPNetwork(ip)
+    new_ip.prefixlen -= step
+    return IPNetwork(new_ip.cidr)
+
+
+def merge_ips(ips_to_reduce: List[IPNetwork], max_len, step=1) -> List[IPNetwork]:
+    ips = deepcopy(ips_to_reduce)
+    reduction_limit_reached = False
+    while len(ips) > max_len and not reduction_limit_reached:
+        reduced_ips = map(reduce_prefixlen, ips)
+        merged_ips = cidr_merge(reduced_ips)
+        if len(merged_ips) > 1:
+            ips = merged_ips
+        else:
+            reduction_limit_reached = True
+            print("The reduction limit has been reached")
+    return ips
+
+
+def main():
+    file = "cidr4.txt"
+    ips = get_ips(file)
+    print(f"{len(ips)=}")
+    merged_ips = merge_ips(ips, 10)
+    print(f"{len(merged_ips)=}")
+    print(", ".join([str(x) for x in merged_ips]))
+
+
+if __name__ == "__main__":
+    assert reduce_prefixlen(IPNetwork("4.78.139.0/24")) == IPNetwork("4.78.138.0/23")
+    main()