// Pure log-scale mapping helpers for the time-scale slider (v0.9.1) — no game logic,
// unit-testable in node. Slider position t ∈ [0,1] ↔ scale = round(60^t), so equal
// distances on the slider correspond to equal multiplicative steps: 1× at t=0, ~8×
// mid-slider, 60× at t=1 (matching POST /api/sim's clamp range).

export const MIN_SCALE = 1;
export const MAX_SCALE = 60;

const clamp = (v: number, lo: number, hi: number) => Math.min(hi, Math.max(lo, v));

// t → scale. Exact at the endpoints: sliderToScale(0) === 1, sliderToScale(1) === 60.
export function sliderToScale(t: number): number {
  const tt = clamp(Number.isFinite(t) ? t : 0, 0, 1);
  return Math.round(clamp(Math.pow(MAX_SCALE, tt), MIN_SCALE, MAX_SCALE));
}

// scale → t (inverse of the pre-rounding mapping). Exact at the endpoints:
// scaleToSlider(1) === 0, scaleToSlider(60) === 1. Round-trips every integer 1..60.
export function scaleToSlider(scale: number): number {
  const s = clamp(Number.isFinite(scale) ? scale : MIN_SCALE, MIN_SCALE, MAX_SCALE);
  return Math.log(s) / Math.log(MAX_SCALE);
}