Compile downloaded DNS blocklists for a home DNS sinkhole (hosts, adblock and plain formats, IDN, allow exceptions, minimal output)

# Compile downloaded DNS blocklists for a home DNS sinkhole Our home network's DNS sinkhole takes one merged list. `lists/` holds downloaded lists in three styles. Rewrite `blocklist.py` (Python 3 stdlib only) so that `compile_lists(folder)` returns the merged, minimal result described below, `is_blocked(result, domain)` answers queries, and `python blocklist.py [folder]` (default `lists`) writes the result to `report.json`. ## Reading lines 1. Read every file in `folder` whose name ends in `.txt`, in sorted filename order, as UTF-8; lines are numbered from 1 in each file. Each line is stripped. Skip blank lines and lines starting with `!` or `#`. Then cut a trailing comment: everything from the first whitespace character that is followed by `#`. 2. A line containing `$` (adblock options) is **unsupported**. 3. `||D^` is a **wildcard block** of D (D and all subdomains); `@@||D^` is a **wildcard allow**. (D must not contain `|`, `^` or `/`.) 4. Any other line that starts with `@@` or `|`, or contains `/` or `^`, is **unsupported**. 5. A single word `*.D` is a wildcard block of D; any other single word D is an **exact block** of D only. 6. Several words: if the first is one of `0.0.0.0`, `127.0.0.1`, `::`, `::1`, each following word is an exact block. Lines starting with any other word (e.g. `192.168.1.20 nas.home.arpa`, a local name override) are ignored without a report. 7. Unsupported lines are reported as `[filename, line_number, original_line]` where original_line is the line without its trailing newline (not stripped). ## Domains 8. Before validation: strip, lowercase and remove one or more trailing dots. If the result is one of `localhost`, `localhost.localdomain`, `broadcasthost`, `local`, `ip6-localhost`, `ip6-loopback`, `0.0.0.0`, skip it silently. 9. Convert with Python's built-in `idna` codec (`d.encode("idna").decode("ascii")`; `UnicodeError` = invalid). The result is valid if it is at most 253 characters, has at least 2 labels, the last label is not all digits, and every label is 1-63 characters of `a-z 0-9 -` not starting or ending with `-`. 10. Each invalid domain adds `[filename, line_number, original_line]` to `invalid` (once per invalid domain, so a hosts line with two invalid domains appears twice). ## Result (all lists sorted ascending, no duplicates) 11. "A covers B" means B equals A or ends with `"." + A`. 12. `wildcard`: wildcard-block domains not covered by another wildcard-block domain (other than themselves) and not covered by any wildcard-allow domain. 13. `exact`: exact-block domains not covered by any domain in the final `wildcard` list and not covered by any wildcard-allow domain. 14. `allow`: wildcard-allow domains that are covered by some domain in the final `wildcard` list (allows that unblock nothing are dropped), then minus those covered by another kept allow domain. 15. `invalid` and `unsupported`: in reading order. 16. `is_blocked(result, domain)`: normalise `domain` as in rules 8-9 (an invalid domain is not blocked); it is not blocked if any `allow` domain covers it; otherwise it is blocked if it is in `exact` or covered by a `wildcard` domain. For `lists/` here the correct `wildcard` is `["doubleclick.example", "telemetry.example", "xn--bcher-ads-q9a.example"]`. ## Scoring Hidden checks (partial credit = fraction passed; all must pass): on a hidden folder of 4 lists (~300 lines) `wildcard_exact`, `exact_exact`, `allow_exact`, `invalid_exact`, `unsupported_exact` (each key equal), `is_blocked_queries` (400 queries), `fresh_lists_exact` (all five keys on a second hidden folder) and `cli_report` (`python blocklist.py lists` writes `report.json` equal to the result for `lists/`).