feat: replace MaxMind ASN with iptoasn.com TSV backend

Drop GeoLite2-ASN.mmdb dependency (required license key) in favor of
iptoasn.com ip2asn-v4.tsv (no auth, public domain).  Bisect-based
lookup in pure stdlib, downloaded via SOCKS5 in update-data.sh.
Adds 30 test cases covering load, lookup, and command handler.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_asn.py

@@ -0,0 +1,258 @@
+"""Tests for the ASN lookup plugin (iptoasn.com TSV backend)."""
+
+import asyncio
+import importlib.util
+import sys
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+from derp.irc import Message
+
+# plugins/ is not a Python package -- load the module from file path
+_spec = importlib.util.spec_from_file_location(
+    "plugins.asn", Path(__file__).resolve().parent.parent / "plugins" / "asn.py",
+)
+_mod = importlib.util.module_from_spec(_spec)
+sys.modules[_spec.name] = _mod
+_spec.loader.exec_module(_mod)
+
+from plugins.asn import (  # noqa: E402
+    _ip_to_int,
+    _load_db,
+    _lookup,
+    cmd_asn,
+)
+
+# -- Sample TSV data ---------------------------------------------------------
+
+SAMPLE_TSV = """\
+1.0.0.0\t1.0.0.255\t13335\tUS\tCLOUDFLARENET
+1.0.1.0\t1.0.3.255\t0\tNone\tNot routed
+1.0.4.0\t1.0.7.255\t56203\tAU\tGTELECOM
+8.8.8.0\t8.8.8.255\t15169\tUS\tGOOGLE
+"""
+
+
+# -- Helpers -----------------------------------------------------------------
+
+class _FakeBot:
+    def __init__(self):
+        self.replied: list[str] = []
+
+    async def reply(self, message, text: str) -> None:
+        self.replied.append(text)
+
+
+def _msg(text: str, nick: str = "alice", target: str = "#test") -> Message:
+    return Message(
+        raw="", prefix=f"{nick}!~{nick}@host", nick=nick,
+        command="PRIVMSG", params=[target, text], tags={},
+    )
+
+
+def _reset_db():
+    """Clear module-level DB state between tests."""
+    _mod._starts.clear()
+    _mod._ends.clear()
+    _mod._asns.clear()
+    _mod._countries.clear()
+    _mod._orgs.clear()
+    _mod._loaded = False
+
+
+def _load_sample(tsv: str = SAMPLE_TSV) -> Path:
+    """Write TSV to a temp file, load it, return the path."""
+    _reset_db()
+    tmp = tempfile.NamedTemporaryFile(mode="w", suffix=".tsv", delete=False)
+    tmp.write(tsv)
+    tmp.flush()
+    tmp.close()
+    p = Path(tmp.name)
+    _load_db(p)
+    return p
+
+
+# ---------------------------------------------------------------------------
+# TestIpToInt
+# ---------------------------------------------------------------------------
+
+class TestIpToInt:
+    def test_zero(self):
+        assert _ip_to_int("0.0.0.0") == 0
+
+    def test_one(self):
+        assert _ip_to_int("0.0.0.1") == 1
+
+    def test_max(self):
+        assert _ip_to_int("255.255.255.255") == 0xFFFFFFFF
+
+    def test_known(self):
+        assert _ip_to_int("1.0.0.0") == 0x01000000
+
+    def test_google_dns(self):
+        assert _ip_to_int("8.8.8.8") == 0x08080808
+
+
+# ---------------------------------------------------------------------------
+# TestLoad
+# ---------------------------------------------------------------------------
+
+class TestLoad:
+    def test_loads_rows(self):
+        _load_sample()
+        # 4 rows in TSV, but ASN 0 is skipped -> 3 entries
+        assert len(_mod._starts) == 3
+
+    def test_skips_asn_zero(self):
+        _load_sample()
+        for asn in _mod._asns:
+            assert asn != "AS0"
+
+    def test_first_entry(self):
+        _load_sample()
+        assert _mod._asns[0] == "AS13335"
+        assert _mod._orgs[0] == "CLOUDFLARENET"
+        assert _mod._countries[0] == "US"
+
+    def test_missing_file_returns_false(self):
+        _reset_db()
+        result = _load_db(Path("/nonexistent/path.tsv"))
+        assert result is False
+        assert not _mod._loaded
+
+    def test_empty_file(self):
+        _reset_db()
+        tmp = tempfile.NamedTemporaryFile(mode="w", suffix=".tsv", delete=False)
+        tmp.write("")
+        tmp.close()
+        result = _load_db(Path(tmp.name))
+        assert result is True
+        assert len(_mod._starts) == 0
+
+    def test_skips_comments_and_blanks(self):
+        tsv = "# comment\n\n1.0.0.0\t1.0.0.255\t13335\tUS\tCLOUD\n"
+        _load_sample(tsv)
+        assert len(_mod._starts) == 1
+
+    def test_skips_malformed_rows(self):
+        tsv = "bad\tdata\n1.0.0.0\t1.0.0.255\t13335\tUS\tCLOUD\n"
+        _load_sample(tsv)
+        assert len(_mod._starts) == 1
+
+
+# ---------------------------------------------------------------------------
+# TestLookup
+# ---------------------------------------------------------------------------
+
+class TestLookup:
+    def setup_method(self):
+        _load_sample()
+
+    def test_exact_start(self):
+        result = _lookup("1.0.0.0")
+        assert result is not None
+        asn, org, country = result
+        assert asn == "AS13335"
+        assert org == "CLOUDFLARENET"
+        assert country == "US"
+
+    def test_mid_range(self):
+        result = _lookup("1.0.0.128")
+        assert result is not None
+        assert result[0] == "AS13335"
+
+    def test_exact_end(self):
+        result = _lookup("1.0.0.255")
+        assert result is not None
+        assert result[0] == "AS13335"
+
+    def test_second_range(self):
+        result = _lookup("1.0.5.0")
+        assert result is not None
+        assert result[0] == "AS56203"
+        assert result[2] == "AU"
+
+    def test_google_dns(self):
+        result = _lookup("8.8.8.8")
+        assert result is not None
+        assert result[0] == "AS15169"
+        assert result[1] == "GOOGLE"
+
+    def test_miss_gap(self):
+        """IP in the not-routed gap (ASN 0 range) returns None."""
+        result = _lookup("1.0.1.0")
+        assert result is None
+
+    def test_miss_below_first(self):
+        result = _lookup("0.255.255.255")
+        assert result is None
+
+    def test_miss_above_last(self):
+        result = _lookup("8.8.9.0")
+        assert result is None
+
+    def test_db_not_loaded(self):
+        _reset_db()
+        with patch.object(_mod, "_DB_PATH", Path("/nonexistent")):
+            result = _lookup("1.0.0.0")
+        assert result is None
+
+
+# ---------------------------------------------------------------------------
+# TestCommand
+# ---------------------------------------------------------------------------
+
+class TestCommand:
+    def setup_method(self):
+        _load_sample()
+
+    def test_valid_ip(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 1.0.0.1")))
+        assert "AS13335" in bot.replied[0]
+        assert "CLOUDFLARENET" in bot.replied[0]
+        assert "(US)" in bot.replied[0]
+
+    def test_google_dns(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 8.8.8.8")))
+        assert "AS15169" in bot.replied[0]
+        assert "GOOGLE" in bot.replied[0]
+
+    def test_private_ip(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 192.168.1.1")))
+        assert "private/loopback" in bot.replied[0]
+
+    def test_loopback(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 127.0.0.1")))
+        assert "private/loopback" in bot.replied[0]
+
+    def test_invalid_input(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn notanip")))
+        assert "Invalid IP" in bot.replied[0]
+
+    def test_no_args(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn")))
+        assert "Usage:" in bot.replied[0]
+
+    def test_ipv6_rejected(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 2606:4700::1")))
+        assert "only IPv4" in bot.replied[0]
+
+    def test_no_match(self):
+        bot = _FakeBot()
+        asyncio.run(cmd_asn(bot, _msg("!asn 200.200.200.200")))
+        assert "no ASN data" in bot.replied[0]
+
+    def test_db_missing(self):
+        _reset_db()
+        bot = _FakeBot()
+        with patch.object(_mod, "_DB_PATH", Path("/nonexistent")):
+            asyncio.run(cmd_asn(bot, _msg("!asn 1.0.0.1")))
+        assert "not available" in bot.replied[0]