#!/usr/bin/env python3
"""Rebuild data/misc/loglevel.tsv from RFC 5424 and POSIX <syslog.h>.

    data-import/loglevel.py [--source URL_OR_FILE] [--posix URL_OR_FILE] [--cache DIR] [--out FILE]

Every severity in Table 2 ships, paired to POSIX's keywords by the order each source
lists them, which holds only because a keyword prefixes the severity RFC 5424 numbers
alike.
"""
import argparse
import html
import re
import sys
from pathlib import Path

import source
import tsv

SOURCE = "https://www.rfc-editor.org/rfc/rfc5424.txt"
POSIX = "https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/syslog.h.html"
OUT = Path(__file__).resolve().parent.parent / "data" / "misc" / "loglevel.tsv"
CACHE = Path(__file__).resolve().parent / "cache"
COLUMNS = ["code", "keyword", "severity"]
TABLE = re.compile(r"Table 1\.\s+Syslog Message Facilities(.*?)Table 2\.\s+Syslog Message Severities", re.S)
ROW = re.compile(r"^ +(\d) +([A-Z][a-z]+): ", re.M)
SECTION = re.compile(r"severity level portion of the.*?macros:(.*?)The following shall be declared as functions", re.S)
MACRO = re.compile(r"\bLOG_([A-Z]+)\b")
EXPECTED = 8


def severities(text):
    table = TABLE.search(text)
    if not table:
        sys.exit("the RFC holds no text between the facility and the severity caption; its tables have moved")
    return ROW.findall(table.group(1))


def keywords(page):
    section = SECTION.search(html.unescape(re.sub(r"<[^>]+>", "", page)))
    if not section:
        sys.exit("POSIX spells no severity list between its own caption and the function declarations; the page has moved")
    return [m.lower() for m in MACRO.findall(section.group(1))]


def main():
    p = argparse.ArgumentParser(description=__doc__.splitlines()[0])
    p.add_argument("--cache", default=str(CACHE))
    p.add_argument("--source", default=SOURCE)
    p.add_argument("--posix", default=POSIX)
    p.add_argument("--out", default=str(OUT))
    a = p.parse_args()
    table = sorted(severities(source.fetch(a.source, a.cache, "rfc5424.txt").decode("utf-8")))
    codes = [code for code, _ in table]
    if codes != [str(i) for i in range(EXPECTED)]:
        sys.exit(f"the severity table numbers {codes}, not 0 through {EXPECTED - 1}")
    words = keywords(source.fetch(a.posix, a.cache, "posix-syslog.h.html").decode("utf-8"))
    if len(words) != EXPECTED:
        sys.exit(f"POSIX lists {len(words)} severity macros, not {EXPECTED}: {words}")
    rows = []
    for (code, severity), keyword in zip(table, words):
        if not severity.lower().startswith(keyword):
            sys.exit(f"severity {code} is {severity} in the RFC and {keyword} in POSIX, which is no prefix of it")
        rows.append({"code": code, "keyword": keyword, "severity": severity})
    tsv.write(a.out, COLUMNS, rows)


if __name__ == "__main__":
    main()