#!/usr/bin/env python3
"""Find CVEs that have identified diff URLs in NVD but no usable .diff file.

Walks every nvdcve-2.0-YYYY.json under dataset/nvd/data, collects the same
diff-bearing reference URLs that download.py would try to fetch, then
verifies that the expected file (data/<year>/<bucket>xxx/CVE-YYYY-NNNN.diff)
exists and contains real diff content.

Statuses:
    missing   no file on disk
    empty     file exists but is 0-byte
    invalid   file exists but contains no `diff --git ` and no
              git-format-patch header (likely HTML / 404 / JSON error)
    ok        file is a real diff (not reported)

Outputs (under <cve_diff>/.logs/, next to failures.tsv):
    missing.log  one line per (CVE, original URL): ts, status, cve, url
    missing.tsv  cve, status, expected_path, original_url, diff_url

Complements failures.tsv: failures.tsv lists per-URL fetch failures,
missing.tsv surfaces CVEs whose final .diff file is absent or invalid as
a whole — including cases the downloader silently skipped.

Usage:
    python missing.py
"""

from __future__ import annotations

import datetime as dt
import json
import pathlib
import sys


SCRIPT_DIR = pathlib.Path(__file__).resolve().parent
sys.path.insert(0, str(SCRIPT_DIR))

import download  # noqa: E402  reuse filter_url / to_diff_url / target_for


NVD_DIR = download.DATA_DIR
LOG_DIR = download.LOG_DIR


def extract_pairs():
    """Yield (cve_id, [url, ...]) for every CVE whose NVD references contain
    at least one URL that download.py would treat as a diff source."""
    for path in sorted(NVD_DIR.glob("nvdcve-2.0-*.json")):
        print(f"[scan] {path.name}", file=sys.stderr)
        try:
            with open(path, "rb") as fh:
                data = json.load(fh)
        except (OSError, json.JSONDecodeError) as e:
            print(f"[warn] failed to parse {path.name}: {e}", file=sys.stderr)
            continue
        for item in data.get("vulnerabilities", []):
            cve = item.get("cve") or {}
            cve_id = cve.get("id")
            if not cve_id:
                continue
            urls = []
            seen = set()
            for ref in cve.get("references") or []:
                url = ref.get("url")
                if url and url not in seen and download.filter_url(url):
                    urls.append(url)
                    seen.add(url)
            if urls:
                yield cve_id, urls


def classify(target: pathlib.Path) -> str:
    if not target.is_file():
        return "missing"
    try:
        body = target.read_bytes()
    except OSError:
        return "missing"
    if not body:
        return "empty"
    if not download.looks_like_diff(body):
        return "invalid"
    return "ok"


def main() -> int:
    if not NVD_DIR.is_dir():
        print(f"error: {NVD_DIR} is not a directory", file=sys.stderr)
        return 2

    LOG_DIR.mkdir(parents=True, exist_ok=True)
    log_path = LOG_DIR / "missing.log"
    tsv_path = LOG_DIR / "missing.tsv"

    n_total = 0
    counts = {"ok": 0, "missing": 0, "empty": 0, "invalid": 0}

    with open(log_path, "w", encoding="utf-8") as log, \
            open(tsv_path, "w", encoding="utf-8") as tsv:
        tsv.write("cve\tstatus\texpected_path\toriginal_url\tdiff_url\n")
        for cve_id, urls in extract_pairs():
            n_total += 1
            target = download.target_for(cve_id)
            status = classify(target)
            counts[status] += 1
            if status == "ok":
                continue
            try:
                rel_target = target.relative_to(SCRIPT_DIR)
            except ValueError:
                rel_target = target
            ts = dt.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
            for url in urls:
                diff_url = download.to_diff_url(url) or ""
                log.write(f"{ts}\t{status}\t{cve_id}\t{url}\n")
                tsv.write(
                    f"{cve_id}\t{status}\t{rel_target}\t{url}\t{diff_url}\n"
                )

    bad = counts["missing"] + counts["empty"] + counts["invalid"]
    print(f"[done] {n_total} CVE(s) with diff URLs", file=sys.stderr)
    print(
        f"       ok={counts['ok']}  missing={counts['missing']}  "
        f"empty={counts['empty']}  invalid={counts['invalid']}",
        file=sys.stderr,
    )
    print(f"       log={log_path}", file=sys.stderr)
    print(f"       tsv={tsv_path}", file=sys.stderr)
    return 1 if bad else 0


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