// @ts-nocheck — design-systems/ is not type-checked (see design-systems/CLAUDE.md). Strip this after a proper typing pass.
// ============================================================
// COMPONENT: Spinner
// 3×3 grid of square pixels with a "snake game" trail running
// clockwise around the perimeter. The 8 perimeter cells share a
// single keyframe; each cell's animation-delay is negative so all
// cells run on phase from the moment the spinner mounts. The
// center cell stays as a static dim square. Variants only colour
// the bright phase — the dim phase is always `text.faint`.
//
// Variants: default | accent | warning | fault
// Sizes:    sm (14px) | md (20px) | lg (28px)
// ============================================================

'use client';

import { forwardRef, useEffect } from 'react';
import { tokens } from '../tokens';
import { andromedaVars } from './lib/utils';

const STYLE_ID = 'andromeda-spinner-keyframes';
// 0-37.5% bright, 37.5-100% dim. The 37.6% stop snaps the colour change so
// the trail moves like discrete LCD pixels instead of fading. Over 1.2 ms
// of cycle the linear interpolation is imperceptible — it just looks crisp.
const KEYFRAMES = `
  @keyframes andromeda-spinner-snake {
    0%, 37.5%   { background: var(--andromeda-spinner-bright); }
    37.6%, 100% { background: var(--andromeda-spinner-dim); }
  }
`;

function ensureKeyframesInjected() {
  if (typeof document === 'undefined') return;
  if (document.getElementById(STYLE_ID)) return;
  const style = document.createElement('style');
  style.id = STYLE_ID;
  style.textContent = KEYFRAMES;
  document.head.appendChild(style);
}

const SIZE_MAP = {
  sm: { wrap: 14, cell: 4, gap: 1 },
  md: { wrap: 20, cell: 6, gap: 1 },
  lg: { wrap: 28, cell: 8, gap: 2 },
};

const colorByVariant = {
  default: tokens.color.text.primary,
  accent:  tokens.color.accent[300],
  warning: tokens.color.orange[300],
  fault:   tokens.color.red[300],
};

// Clockwise perimeter starting top-left. Center cell (1,1) is intentionally
// excluded — it stays statically dim like a snake-game arena interior.
const PERIMETER_ORDER = [
  [0, 0], [0, 1], [0, 2],
  [1, 2],
  [2, 2], [2, 1], [2, 0],
  [1, 0],
];

const DURATION_MS = 1200;
const STEPS = 8;
const STEP_MS = DURATION_MS / STEPS;

/**
 * @typedef {object} SpinnerProps
 * @property {'default'|'accent'|'warning'|'fault'} [variant='default']
 * @property {'sm'|'md'|'lg'} [size='md']
 * @property {string} [label='Loading'] Accessible label.
 * @property {string} [className]
 * @property {React.CSSProperties} [style]
 */

/** @type {React.ForwardRefExoticComponent<SpinnerProps & React.HTMLAttributes<HTMLSpanElement>>} */
export const Spinner = forwardRef(function Spinner(
  { className, variant = 'default', size = 'md', label = 'Loading', style, ...props },
  ref,
) {
  useEffect(() => { ensureKeyframesInjected(); }, []);
  ensureKeyframesInjected();

  const sz = SIZE_MAP[size] ?? SIZE_MAP.md;
  const bright = colorByVariant[variant] ?? colorByVariant.default;
  const dim = tokens.color.text.faint;

  const cells = [];
  for (let r = 0; r < 3; r++) {
    for (let c = 0; c < 3; c++) {
      const peri = PERIMETER_ORDER.findIndex(([pr, pc]) => pr === r && pc === c);
      const isCenter = peri === -1;
      // delay = -((STEPS - peri) % STEPS) * step — at t=0 cell `peri` is at
      // (peri/STEPS) of its cycle. peri=0 starts bright; the trail extends
      // backward from there (cells 7 and 6 are still inside the bright window).
      const delayMs = isCenter ? 0 : -((STEPS - peri) % STEPS) * STEP_MS;
      cells.push(
        <span
          key={`${r}-${c}`}
          aria-hidden
          style={{
            width:  `${sz.cell}px`,
            height: `${sz.cell}px`,
            background: dim,
            ...(isCenter ? null : {
              animation: `andromeda-spinner-snake ${DURATION_MS}ms linear infinite`,
              animationDelay: `${delayMs}ms`,
            }),
          }}
        />,
      );
    }
  }

  return (
    <span
      ref={ref}
      role="status"
      aria-label={label}
      className={className}
      style={{
        ...andromedaVars(),
        '--andromeda-spinner-bright': bright,
        '--andromeda-spinner-dim': dim,
        display: 'inline-grid',
        gridTemplateColumns: `repeat(3, ${sz.cell}px)`,
        gridTemplateRows: `repeat(3, ${sz.cell}px)`,
        gap: `${sz.gap}px`,
        width:  `${sz.wrap}px`,
        height: `${sz.wrap}px`,
        ...style,
      }}
      {...props}
    >
      {cells}
    </span>
  );
});
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