/**
 * How much of a leaf's bottom is covered by something the operator cannot
 * move: Obsidian's desktop status bar, a phone's navbar (which paints over a
 * leaf rather than shortening it), and the software keyboard, which shrinks
 * the visual viewport while the layout keeps its full height.
 *
 * Pure on purpose - the view feeds it live rectangles, the tests feed it the
 * numbers a phone actually reports.
 */

export interface Rect {
  bottom: number;
  height: number;
  left: number;
  right: number;
  top: number;
}

export interface Visible {
  /** `visualViewport.height`: what is left once the keyboard is up. */
  height: number;
  /** `visualViewport.offsetTop`: where the visible area starts. */
  offsetTop: number;
}

export function insetFor(
  leaf: Rect,
  bars: Rect[],
  visible: Visible | null
): number {
  if (leaf.height <= 0) {
    return 0;
  }
  let overlap = 0;
  for (const bar of bars) {
    // A bar that does not sit over this leaf horizontally covers nothing of
    // it - the desktop status bar next to a left-hand sidedock, say.
    if (bar.height > 0 && bar.left < leaf.right && bar.right > leaf.left) {
      overlap = Math.max(overlap, leaf.bottom - bar.top);
    }
  }
  if (visible) {
    const floor = visible.offsetTop + visible.height;
    overlap = Math.max(overlap, leaf.bottom - floor);
  }
  return Math.max(0, Math.round(overlap));
}