/**
 * Choosing a type size that fits the space available.
 *
 * The panel cannot scroll and cannot reflow gracefully: text that does not fit
 * is text that spills over a neighbour or falls off the bottom edge. The shop
 * can legitimately enter three opening periods in a day, none of them on a
 * round hour, and write a long message on top — a combination that overflowed
 * both the week strip and the bottom banner before this existed.
 *
 * The width estimate is deliberately crude. Measuring glyphs properly would
 * mean loading the font here and would still be an estimate, because the
 * renderer applies its own kerning. Erring small costs a point of type; erring
 * large costs a broken screen.
 */

/** Average glyph width as a fraction of the type size, for Inter's digits and lowercase. */
const WIDTH_RATIO = 0.54;

export type FitOptions = {
  /** The width the text has to live in, in pixels. */
  available: number;
  /** The size to use when the text is short enough. */
  preferred: number;
  /** Never go below this: smaller stops being readable from the pavement. */
  minimum: number;
};

export function fitFontSize(text: string, { available, preferred, minimum }: FitOptions): number {
  if (text.length === 0) {
    return preferred;
  }
  const fitting = available / (text.length * WIDTH_RATIO);
  return Math.max(minimum, Math.min(preferred, Math.floor(fitting)));
}