#!/usr/bin/env python3
"""Link liveness sweep for Markdown files (stdlib only).

Usage:
    python linkcheck.py <file.md> [<file2.md> ...] [--workers N] [--timeout S]

Checks every http(s) URL found in the markdown files.
- 403/405 are reported as BOTWALL (bot wall — site is alive, not dead)
- Other HTTP errors are reported with their code
- Network errors/timeouts are reported as DEAD

Output line format: CHECK <status> <url>
Exit code is always 0; the report is the output. Diagnostics go to stderr.
"""
import argparse
import concurrent.futures
import re
import ssl
import sys
import urllib.error
import urllib.request

URL_RE = re.compile(r"https?://[^\s()<>{}|\"'`]+")
UA = ("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
      "(KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36")


def probe(url, method, timeout, ctx):
    req = urllib.request.Request(url, headers={"User-Agent": UA}, method=method)
    try:
        with urllib.request.urlopen(req, timeout=timeout, context=ctx) as resp:
            return resp.status
    except urllib.error.HTTPError as e:
        return e.code
    except Exception:
        return None


def check(url, timeout):
    url = url.rstrip(".,;:!?)]}")
    ctx = ssl.create_default_context()
    ctx.check_hostname = False
    ctx.verify_mode = ssl.CERT_NONE
    for method in ("HEAD", "GET"):
        status = probe(url, method, timeout, ctx)
        if status is not None and status != 999:
            if status in (403, 405):
                return f"CHECK BOTWALL {status} {url}"
            if status < 400:
                return f"CHECK {status} {url}"
            # 4xx/5xx from HEAD could be server refusing HEAD; try GET first
            if method == "GET":
                return f"CHECK {status} {url}"
            continue
        if method == "GET":
            break
    return f"CHECK DEAD {url}"


def collect_urls(files):
    urls, seen = [], set()
    for path in files:
        try:
            text = open(path, encoding="utf-8").read()
        except OSError as e:
            print(f"ERR cannot read {path}: {e}", file=sys.stderr)
            continue
        for u in URL_RE.findall(text):
            if u not in seen:
                seen.add(u)
                urls.append(u)
    return urls


def main():
    ap = argparse.ArgumentParser(description="Link liveness sweep for Markdown files.")
    ap.add_argument("files", nargs="+", metavar="file.md")
    ap.add_argument("--workers", type=int, default=24, help="parallel workers (default: 24)")
    ap.add_argument("--timeout", type=float, default=15.0, help="per-request timeout in s (default: 15)")
    args = ap.parse_args()

    urls = collect_urls(args.files)
    if not urls:
        print("CHECK NONE (no URLs found)")
        return 0

    with concurrent.futures.ThreadPoolExecutor(max_workers=args.workers) as pool:
        for result in pool.map(lambda u: check(u, args.timeout), urls):
            print(result)
    return 0


if __name__ == "__main__":
    sys.exit(main())