Re-format the NACL change output from Terraform to make changes easier to spot.

comparenacl.py

import re
import argparse

PROTOCOLS = {
        "1": "icmp",
        "6": "tcp",
        "17": "udp",
}

ap = argparse.ArgumentParser()
ap.add_argument("--rule-indent", type=int, default=10)
ap.add_argument("--field-indent", type=int, default=14)
ap.add_argument("plan_txt")

args = ap.parse_args()

RULE_RE = re.compile(r"^ {%d}(.) {$" % args.rule_indent)
FIELD_RE = re.compile(r"^ {%d}(.) ([0-9a-z_]+) += (.*)$" % args.field_indent)

# Parse the NACL rule changes.  The parser is pretty stupid, so the regexes
# may need fiddling or the file have some 'massaging' in a text editor.
rules = []
for line in open(args.plan_txt, "r"):
    m = RULE_RE.match(line)
    if m:
        rule = {"addremove": m.group(1)}
        rules.append(rule)
        continue
    m = FIELD_RE.match(line)
    if m:
        (addrem, field, value) = m.groups()
        assert (
            addrem == rule["addremove"]
        ), "rule %r does not match field %r" % (rule, line)
        rule[field] = value
        continue
    rule = None

for r in rules:
    r["rule_no"] = int(r["rule_no"])

    protocol = r["protocol"][1:-1]
    if protocol in PROTOCOLS:
        protocol = PROTOCOLS[protocol]
    r["protocol"] = protocol

    for f in ("cidr_block", "ipv6_cidr_block"):
        if r[f] in ('""', 'null'):
            r[f] = None

rules.sort(
    key=lambda r: (
        r["rule_no"],
        r["cidr_block"],
        r["ipv6_cidr_block"],
        r["from_port"],
        r["to_port"],
        r["protocol"],
        r["action"],
        r["addremove"],
    )
)
print(
    "\n".join(
        [
            (
                "%(addremove)s %(rule_no)3d %(action)-5s %(cidr_block)-24s "
                "%(ipv6_cidr_block)-44s %(protocol)-4s "
                "%(from_port)8s %(to_port)8s"
            )
            % r
            for r in rules
        ]
    )
)