export type ImageScaleMode = 'contain' | 'cover' | 'fill';

export function readImageScaleMode(cfg: Record<string, unknown> | undefined | null): ImageScaleMode {
  const v = String(cfg?.scaleMode ?? cfg?.ScaleMode ?? 'contain')
    .trim()
    .toLowerCase();
  if (v === 'cover' || v === 'fill') return v;
  return 'contain';
}

/** Tailwind classes for &lt;img&gt; inside a fixed box */
export function imageScaleModeImgClassName(mode: ImageScaleMode): string {
  switch (mode) {
    case 'cover':
      return 'h-full w-full object-cover';
    case 'fill':
      return 'h-full w-full object-fill';
    default:
      return 'max-h-full max-w-full object-contain';
  }
}

export function computeImageDrawRect(
  boxW: number,
  boxH: number,
  sourceW: number,
  sourceH: number,
  scaleMode: string,
): { dx: number; dy: number; dw: number; dh: number } {
  const mode = String(scaleMode ?? 'contain').trim().toLowerCase();
  if (sourceW <= 0 || sourceH <= 0 || mode === 'fill') {
    return { dx: 0, dy: 0, dw: boxW, dh: boxH };
  }
  const ratio =
    mode === 'cover'
      ? Math.max(boxW / sourceW, boxH / sourceH)
      : Math.min(boxW / sourceW, boxH / sourceH);
  const dw = Math.max(1, Math.round(sourceW * ratio));
  const dh = Math.max(1, Math.round(sourceH * ratio));
  return {
    dx: Math.round((boxW - dw) / 2),
    dy: Math.round((boxH - dh) / 2),
    dw,
    dh,
  };
}