// VirtualGrid's column-count policy, extracted as a pure function so the viewport contract's UPPER
// end is unit-testable without a layout engine (the lower end, the 768-wide tablet floor, needs no policy —
// the grid simply drops to the columns that fit).
//
// An auto-fill grid answers "more room" with more columns, never bigger ones, so it always settles
// just above its minimum column width no matter how wide the screen is. Measured at 3440px,
// the feed laid out 11 columns of 264px — a diluted feed is as bad a failure of the viewport contract
// as a broken one, so `maxCols` stops the multiplication and lets the leftover width flow into the
// items instead. The cap can only bind ABOVE the width at which that many columns already fit, so the
// 1024px floor and everything near it is unchanged. How far up that reaches is per view: the feed's
// small cards (`feedView.cardsSmall`, 11) are already capped at 2560 with the filter rail collapsed —
// 12 would fit there — while the regular cards stay uncapped up to 2560.

/** The grid's gutter in px; the column maths has to net it out on both sides of the division. */
export const GRID_GAP = 16;

/** Columns that fit `width` (never more than `maxCols`), or 1 for the single-column layout
 *  (`minCol == null`). */
export function columnsFor(
  minCol: number | null,
  width: number,
  maxCols: number | null = null,
): number {
  if (minCol == null) return 1;
  const fit = Math.max(1, Math.floor((width + GRID_GAP) / (minCol + GRID_GAP)));
  return maxCols == null ? fit : Math.min(fit, maxCols);
}

/** The px width one item gets once `columnsFor` has chosen the count — i.e. where the width saved by
 *  the cap actually goes. */
export function itemWidthFor(width: number, cols: number): number {
  return Math.floor((width - GRID_GAP * (cols - 1)) / cols);
}