#!/usr/bin/env python3
"""Generate the narrowly guarded mDNS 1.12.0 membership overlay; never edit upstream."""
import argparse
import hashlib
from pathlib import Path
import re

SOURCE_SHA256 = "adc139fa504a925ab644f21f8dce3659927f534e390a176b72b0ae3206c6a3ea"
OLD_DEINIT = """    s_interfaces[tcpip_if].proto &= ~(ip_protocol == MDNS_IP_PROTOCOL_V4 ? PROTO_IPV4 : PROTO_IPV6);
    if (s_interfaces[tcpip_if].proto == 0) {
        s_interfaces[tcpip_if].ready = false;
        join_group(tcpip_if, ip_protocol, false);
"""
NEW_DEINIT = """    int proto = (ip_protocol == MDNS_IP_PROTOCOL_V4 ? PROTO_IPV4 : PROTO_IPV6);
    if (!(s_interfaces[tcpip_if].proto & proto)) {
        return;
    }
    join_group(tcpip_if, ip_protocol, false);
    s_interfaces[tcpip_if].proto &= ~proto;
    if (s_interfaces[tcpip_if].proto == 0) {
        s_interfaces[tcpip_if].ready = false;
"""
OLD_INIT = """    err = pcb_init();
    if (err) {
        return err;
    }
"""
NEW_INIT = """    err = pcb_init();
    if (err) {
        join_group(tcpip_if, ip_protocol, false);
        return err;
    }
"""


def generate(component: Path, output: Path) -> None:
    manifest = (component / "idf_component.yml").read_text()
    if re.findall(r"^version:\s*(\S+)\s*$", manifest, re.MULTILINE) != ["1.12.0"]:
        raise ValueError("mDNS membership overlay requires exactly version 1.12.0; review upstream")
    original = (component / "mdns_networking_lwip.c").read_bytes()
    if hashlib.sha256(original).hexdigest() != SOURCE_SHA256:
        raise ValueError("mDNS networking source SHA-256 mismatch; review upstream, do not bypass guard")
    patched = original.decode("utf-8")
    for old, new in ((OLD_DEINIT, NEW_DEINIT), (OLD_INIT, NEW_INIT)):
        if patched.count(old) != 1:
            raise ValueError("mDNS membership replacement must match exactly once")
        patched = patched.replace(old, new, 1)
    result = patched.encode("utf-8")
    output.parent.mkdir(parents=True, exist_ok=True)
    if not output.exists() or output.read_bytes() != result:
        output.write_bytes(result)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("component", type=Path)
    parser.add_argument("output", type=Path)
    args = parser.parse_args()
    try:
        generate(args.component, args.output)
    except (OSError, ValueError) as error:
        parser.exit(1, f"mDNS membership overlay: {error}\n")