Tags, links and where players came from

21def band_abbrev(band: str) -> str:
22    """'Grateful Dead' -> 'GD', 'String Cheese Incident' -> 'SCI', 'Phish' -> 'Phish'."""
23    words = [w for w in re.split(r"[^A-Za-z0-9]+", band) if w]
24    if words and words[0].lower() == "the" and len(words) > 1:
25        words = words[1:]
26    if not words:
27        return "X"
28    if len(words) == 1:
29        w = words[0]
30        return (w[0].upper() + w[1:])[:10]
31    return "".join(w[0].upper() for w in words)[:6]

34def base_tags(band: str, tours: list[dict]) -> list[str]:
35    """One tag per tour (``tours`` sorted by start date, each with a ``start`` ymd)."""
36    abbrev = band_abbrev(band)
37    seen: dict[str, int] = {}
38    out = []
39    for t in tours:
40        stem = f"TT{abbrev}{t['start'][2:4]}{_MONTHS[int(t['start'][5:7]) - 1]}"
41        seen[stem] = seen.get(stem, 0) + 1
42        out.append(stem + (str(seen[stem]) if seen[stem] > 1 else ""))
43    return out

66def register(store, base: str, info: dict) -> str:
67    """Record that ``base`` names this tour. If another band already owns the tag,
68    insert a letter after the band part until it is unique. Returns the tag to use."""
69    m = re.match(r"^TT(.+?)(\d{2}(?:" + "|".join(_MONTHS) + r")\d?)$", base)
70    stem, tail = (m.group(1), m.group(2)) if m else (base[2:], "")
71    for extra in [""] + list("BCDEFGHJKLMNPQRSTUVWYZ"):
72        candidate = f"TT{stem}{extra}{tail}"
73        key = "tag:" + candidate.lower()
74        if store.set_if_absent(key, info):
75            return candidate
76        existing = store.get(key) or {}
77        if existing.get("collection") == info["collection"] and existing.get("start") == info["start"]:
78            return candidate
79    return base

264    def tag_landing(tag: str) -> BaseResponse:
265        """A shared tour link: count where the visit came from, then open that tour."""
266        parts = tags.split(tag)
267        if not parts:
268            return redirect("/")
269        base, code = parts
270        code = dna.encode(dna.decode(request.args.get("dna") or code))
271        info = tour_info(base)
272        if not info:
273            return redirect("/")
274        base = info.get("tag", base)
275        full = tags.full_tag(base, code)
276        source = (request.args.get("utm_source") or "direct")[:40].lower()
277        store.zincr("src:" + full.lower(), source)
278        og = {
279            "title": f"#{full} - {info['band']} {info['year']} on Terrapin Trail",
280            "description": f"Drive the {info['band']} tour that started {info['start']}, "
281            "tape the shows, and beat the leaderboard. Real recordings from the Internet Archive.",
282            "type": "website",
283            "image": f"/og/{full}.png",
284        }
285        boot = {
286            "tag": base, "dna": code, "luck": request.args.get("luck"), "from": source,
287            "by": (request.args.get("utm_content") or "")[:24], "donate": DONATE_URL,
288        }