// PROCITY Lane C — bible.js  [v7.0-beta wave 1, R32 — THE GUIDE + THE GEM (charter system #3)]
// The in-game price guide: thriftgod's BIBLE concept as a VALUE BAND per item. The band is the
// 90s guide book, not an oracle — it names a range ("guide $25–59"), never a verdict. A **gem**
// is an item ASKING under its band's low edge; spotting one is the player's skill, so nothing in
// any UI ever says "gem".
//
// THE DERIVATION RULING (R32): band NUMBERS mirror Lane E's pipeline thresholds
// (pipeline/build_stock_pack.py price_band(): record 8/25/60 · book 5/15/40 · toy 6/20/50 —
// duplicated verbatim in godverse_stock.py, validated by validate_pack.py). We derive ranges in
// JS from the band LABEL the packs already carry instead of re-baking band data into atlases —
// so charter risk #3 (a re-emitted pack orphaning owned skus) never opens. If E's thresholds
// move, this table moves with them in the same commit (the two files name each other).
//
// THE STRUCTURAL CONSEQUENCE (why the no-pump law survives the beta, LANE_C_PUB §9.1):
// real/mint pack items derive `price_band` FROM `price`, so real asking always sits INSIDE its
// band ⇒ bandLow ≤ asking ⇒ sellOffer(bandLow) ≤ bandLow − 1 < asking: every real round trip
// stays strictly negative with the basis swapped. Only PARODY stock (proceduralSleeves) rolls a
// seeded under-band gem — and per-day scarcity (the save's `pulls`) makes each gem profit ONCE.
// Growth is bounded by finds, not arbitrage loops — charter law #2, made structural.
//
// Zero DOM, zero draws, zero fetch, zero storage: a pure table + pure functions. ?classic=1 /
// ?dig=0 never import a caller, and importing this module alone has no effect at all.

// kind → band → [low, high]; `high: null` = open-ended (the card renders "$60+").
// Lows/highs are E's threshold edges: a band [t0, t1) renders as $t0–(t1−1).
export const BANDS = {
  record: { bargain: [2, 7], standard: [8, 24], collector: [25, 59], grail: [60, null] },
  book:   { bargain: [1, 4], standard: [5, 14], collector: [15, 39], grail: [40, null] },
  toy:    { bargain: [2, 5], standard: [6, 19], collector: [20, 49], grail: [50, null] },
};
export const BAND_ORDER = ['bargain', 'standard', 'collector', 'grail'];

// bandRange('record','collector') → [25, 59] | null on unknown kind/band (fail-closed: no range,
// no guide line, no basis swap — never an invented number).
export function bandRange(kind, band) {
  const k = BANDS[kind];
  const r = k && k[String(band || '').toLowerCase()];
  return r ? [r[0], r[1]] : null;
}

// The guide line for a card stamp — "guide $25–59" / "guide $60+" / '' when unknowable.
export function guideText(kind, band) {
  const r = bandRange(kind, band);
  if (!r) return '';
  return r[1] == null ? `guide $${r[0]}+` : `guide $${r[0]}–${r[1]}`;
}

// The sell basis for a collection entry (LANE_C_PUB §9.1, the pre-ratified beta swap): bandLow
// when the entry carries a band the BIBLE knows, else the alpha basis (pricePaid) — so every
// alpha-era find (no band field) sells exactly as it did before this round. The sellOffer()
// CLAMP SHAPE is sell.js's and survives untouched; this function only chooses the number fed in.
export function sellBasis(entry) {
  if (entry && entry.band) {
    const r = bandRange(entry.type, entry.band);
    if (r) return r[0];
  }
  return entry ? (entry.pricePaid != null ? entry.pricePaid : entry.price) : 0;
}