Loading spinner

'use client';

import { cn, formatPercent, round, useLocale, useTexts } from '@/lib/kit';

/*
 * Spinners: small signs that something is working. Six drawn loaders in one
 * family, every one built on the same 24 px grid so they swap without
 * shifting the layout. With reduced motion each one stands still as a
 * readable picture (an open ring, three dots in rising strength, bars of
 * different height) and the label carries the message.
 */

export type SpinnerType = 'ring' | 'dots' | 'bars' | 'pulse' | 'orbit' | 'spokes';
export type SpinnerSize = 'xs' | 'sm' | 'md' | 'lg' | 'xl';
export type SpinnerTone = 'current' | 'accent' | 'muted';

const PX: Record<SpinnerSize, number> = { xs: 14, sm: 18, md: 24, lg: 36, xl: 48 };
const TEXT: Record<SpinnerSize, string> = { xs: 'text-[12px]', sm: 'text-[13px]', md: 'text-sm', lg: 'text-[15px]', xl: 'text-base' };
const TONE: Record<SpinnerTone, string> = {
  current: 'text-current',
  accent: 'text-primary',
  muted: 'text-muted-foreground',
};

const TEXTS = {
  en: { loading: 'Loading', progress: 'Progress' },
  de: { loading: 'Wird geladen', progress: 'Fortschritt' },
};
type SpinnerTexts = (typeof TEXTS)['en'];

/* All motion lives in one style sheet, keyed by the kitfx-sp prefix. Reduced motion stops every loop. */
const STYLES =
  '.kitfx-sp-spin{animation:kitfx-sp-spin .85s linear infinite}' +
  '.kitfx-sp-steps{animation:kitfx-sp-spin .9s steps(8) infinite}' +
  '.kitfx-sp-orbit{animation:kitfx-sp-spin 1.3s cubic-bezier(.45,.05,.55,.95) infinite}' +
  '@keyframes kitfx-sp-spin{to{transform:rotate(360deg)}}' +
  '.kitfx-sp-dot{transform-box:fill-box;transform-origin:center;animation:kitfx-sp-dot 1.05s ease-in-out infinite;animation-delay:calc(var(--i) * 150ms)}' +
  '@keyframes kitfx-sp-dot{0%,80%,100%{opacity:.3;transform:translateY(0)}40%{opacity:1;transform:translateY(-3px)}}' +
  '.kitfx-sp-bar{transform-box:fill-box;transform-origin:center;animation:kitfx-sp-bar 1s ease-in-out infinite;animation-delay:calc(var(--i) * 120ms)}' +
  '@keyframes kitfx-sp-bar{0%,70%,100%{transform:scaleY(.4);opacity:.45}35%{transform:scaleY(1);opacity:1}}' +
  '.kitfx-sp-wave{transform-box:fill-box;transform-origin:center;animation:kitfx-sp-wave 1.6s cubic-bezier(.2,.7,.2,1) infinite;animation-delay:calc(var(--i) * 800ms)}' +
  '@keyframes kitfx-sp-wave{0%{transform:scale(.45);opacity:.7}100%{transform:scale(1);opacity:0}}' +
  '.kitfx-sp-core{transform-box:fill-box;transform-origin:center;animation:kitfx-sp-core 1.6s ease-in-out infinite}' +
  '@keyframes kitfx-sp-core{50%{transform:scale(.82)}}' +
  '@media (prefers-reduced-motion:reduce){.kitfx-sp-spin,.kitfx-sp-steps,.kitfx-sp-orbit,.kitfx-sp-dot,.kitfx-sp-bar,.kitfx-sp-core{animation:none}.kitfx-sp-wave{animation:none;opacity:.35;transform:scale(.8)}.kitfx-sp-wave[style*="--i:1"]{opacity:0}}';

function Styles() {
  return (
    <style href="kitfx-sp" precedence="default">
      {STYLES}
    </style>
  );
}

/** The drawing of one loader, 24 by 24, in currentColor */
function Drawing({ type, px }: { type: SpinnerType; px: number }) {
  const common = { width: px, height: px, viewBox: '0 0 24 24', fill: 'none', 'aria-hidden': true as const, className: 'block shrink-0 overflow-visible' };
  // Thin strokes look heavy at small sizes and faint at large ones, so the stroke follows the size
  const sw = px <= 18 ? 2.6 : px >= 40 ? 1.8 : 2.2;
  switch (type) {
    case 'ring':
      return (
        <svg {...common} className={cn(common.className, 'kitfx-sp-spin')}>
          <circle cx="12" cy="12" r="9.5" stroke="currentColor" strokeOpacity="0.18" strokeWidth={sw} />
          <path d="M12 2.5a9.5 9.5 0 0 1 9.5 9.5" stroke="currentColor" strokeWidth={sw} strokeLinecap="round" />
        </svg>
      );
    case 'dots':
      return (
        <svg {...common}>
          {[5, 12, 19].map((cx, i) => (
            <circle key={cx} cx={cx} cy="12" r="2.4" fill="currentColor" className="kitfx-sp-dot" style={{ '--i': i, opacity: [0.35, 0.65, 1][i] } as React.CSSProperties} />
          ))}
        </svg>
      );
    case 'bars':
      return (
        <svg {...common}>
          {[3.5, 8.5, 13.5, 18.5].map((x, i) => {
            const h = [10, 16, 13, 7][i];
            return <rect key={x} x={x - 0.5} y={12 - h / 2} width="3" height={h} rx="1.5" fill="currentColor" className="kitfx-sp-bar" style={{ '--i': i, transform: 'none' } as React.CSSProperties} />;
          })}
        </svg>
      );
    case 'pulse':
      return (
        <svg {...common}>
          {[0, 1].map((i) => (
            <circle key={i} cx="12" cy="12" r="10.5" stroke="currentColor" strokeWidth={px <= 18 ? 2 : 1.6} className="kitfx-sp-wave" style={{ '--i': i } as React.CSSProperties} />
          ))}
          <circle cx="12" cy="12" r="4.2" fill="currentColor" className="kitfx-sp-core" />
        </svg>
      );
    case 'orbit':
      return (
        <svg {...common} className={cn(common.className, 'kitfx-sp-orbit')}>
          <circle cx="12" cy="12" r="9" stroke="currentColor" strokeOpacity="0.18" strokeWidth={sw * 0.8} />
          <circle cx="12" cy="3" r="2.6" fill="currentColor" />
          <circle cx={round(12 + 9 * Math.sin(-0.62))} cy={round(12 - 9 * Math.cos(-0.62))} r="1.7" fill="currentColor" opacity="0.5" />
          <circle cx={round(12 + 9 * Math.sin(-1.12))} cy={round(12 - 9 * Math.cos(-1.12))} r="1.1" fill="currentColor" opacity="0.25" />
        </svg>
      );
    case 'spokes':
      return (
        <svg {...common} className={cn(common.className, 'kitfx-sp-steps')}>
          {Array.from({ length: 8 }, (_, i) => {
            const a = (i * Math.PI) / 4;
            return (
              <line
                key={i}
                x1={round(12 + 5 * Math.sin(a))}
                y1={round(12 - 5 * Math.cos(a))}
                x2={round(12 + 9.5 * Math.sin(a))}
                y2={round(12 - 9.5 * Math.cos(a))}
                stroke="currentColor"
                strokeWidth={sw}
                strokeLinecap="round"
                opacity={round(1 - ((8 - i) % 8) * 0.105, 3)}
              />
            );
          })}
        </svg>
      );
  }
}

export interface SpinnerProps {
  type?: SpinnerType;
  size?: SpinnerSize;
  tone?: SpinnerTone;
  /** What is happening, e.g. "Saving draft". Read out by screen readers, shown when showLabel is set. */
  label?: string;
  /** Write the label next to the loader */
  showLabel?: boolean;
  /** Label below the loader instead of beside it, for empty panels */
  stacked?: boolean;
  /**
   * Announce the loader as a live status. Turn it off inside a button or a
   * region that already says it is busy (aria-busy), so nothing is read twice.
   */
  announce?: boolean;
  labels?: Partial<SpinnerTexts>;
  className?: string;
}

/**
 * A loader that shows that something is working, with a label for screen readers (role="status").
 *   <Spinner type="dots" label="Saving draft" showLabel />
 */
export function Spinner({ type = 'ring', size = 'md', tone = 'current', label, showLabel, stacked, announce = true, labels, className }: SpinnerProps) {
  const t = useTexts(TEXTS, labels);
  const text = label ?? t.loading;
  return (
    <span
      role={announce ? 'status' : undefined}
      aria-live={announce ? 'polite' : undefined}
      className={cn('inline-flex items-center', stacked ? 'flex-col gap-3 text-center' : 'gap-2.5', TONE[tone], className)}
    >
      <Styles />
      <Drawing type={type} px={PX[size]} />
      <span className={cn(showLabel ? cn('font-medium text-muted-foreground', TEXT[size]) : 'sr-only')}>{text}</span>
    </span>
  );
}

export interface ProgressSpinnerProps {
  /** 0 to 100 */
  value: number;
  /** Diameter in px, 32 to 120 */
  size?: number;
  tone?: Exclude<SpinnerTone, 'current'>;
  /** Write the percentage in the middle (from 40 px on) */
  showValue?: boolean;
  /** Accessible name, e.g. "Upload of plan.pdf" */
  label?: string;
  /** Turn into a running ring while the total is still unknown */
  indeterminate?: boolean;
  labels?: Partial<SpinnerTexts>;
  className?: string;
}

/**
 * A ring that fills with the progress and writes the percentage in its middle.
 * Before the total is known it runs like a spinner (indeterminate), then it fills.
 */
export function ProgressSpinner({ value, size = 56, tone = 'accent', showValue = true, label, indeterminate, labels, className }: ProgressSpinnerProps) {
  const t = useTexts(TEXTS, labels);
  const locale = useLocale();
  const v = Math.min(100, Math.max(0, value));
  const stroke = size >= 72 ? 5 : size >= 48 ? 4 : 3;
  const r = (size - stroke) / 2;
  const c = 2 * Math.PI * r;
  return (
    <span
      role="progressbar"
      aria-label={label ?? t.progress}
      aria-valuemin={0}
      aria-valuemax={100}
      aria-valuenow={indeterminate ? undefined : round(v, 0)}
      aria-valuetext={indeterminate ? t.loading : formatPercent(round(v, 0), locale)}
      className={cn('relative inline-grid shrink-0 place-items-center', className)}
      style={{ width: size, height: size }}
    >
      <Styles />
      <svg width={size} height={size} viewBox={`0 0 ${size} ${size}`} fill="none" aria-hidden className={cn('absolute inset-0 -rotate-90', indeterminate && 'kitfx-sp-spin')}>
        <circle cx={size / 2} cy={size / 2} r={round(r)} stroke="var(--track)" strokeWidth={stroke} />
        <circle
          cx={size / 2}
          cy={size / 2}
          r={round(r)}
          stroke="currentColor"
          strokeWidth={stroke}
          strokeLinecap="round"
          strokeDasharray={round(c)}
          strokeDashoffset={round(indeterminate ? c * 0.72 : c * (1 - v / 100))}
          className={cn(TONE[tone], 'transition-[stroke-dashoffset] duration-500 ease-[var(--ease-kit)] motion-reduce:transition-none')}
        />
      </svg>
      {showValue && size >= 40 && !indeterminate && (
        <span className={cn('relative font-semibold tabular-nums tracking-[-0.02em] text-foreground', size >= 88 ? 'text-xl' : size >= 64 ? 'text-[15px]' : size >= 52 ? 'text-[12px]' : 'text-[10px] tracking-[-0.04em]')}>
          {formatPercent(round(v, 0), locale)}
        </span>
      )}
    </span>
  );
}