import { useEffect, useState, type ButtonHTMLAttributes, type CSSProperties, type ReactNode } from 'react';
import { ChevronRight, RotateCw } from 'lucide-react';
import { SeyarMascot } from '@/mascots/SeyarMascot';
import type { SeyarChar, SeyarMood } from '@/mascots/seyar';
import { friendlyError } from '@/lib/errors';
import { useNav } from '@/nav/Navigator';
import { onWhite, shade } from '@/lib/color';

/* ─── سربرگِ رنگیِ صفحه ──────────────────────────────────────────────────── */

export function ScreenHeader({
  title,
  subtitle,
  color,
  back = false,
  mascot,
  children,
}: {
  title: ReactNode;
  subtitle?: ReactNode;
  color: string;
  /** دکمه‌ی بازگشت؛ true یعنی صفحه‌ی قبل در پشته. */
  back?: boolean | (() => void);
  mascot?: { char: SeyarChar; mood?: SeyarMood; size?: number };
  children?: ReactNode;
}) {
  const nav = useNav();
  const onBack = typeof back === 'function' ? back : nav.back;
  const bg = onWhite(color);
  return (
    <header
      className="relative flex-shrink-0 overflow-hidden rounded-b-[32px] px-5 pb-6 pt-safe text-white"
      style={{ backgroundColor: bg, backgroundImage: `linear-gradient(160deg, ${shade(bg, 0.12)} 0%, ${bg} 55%, ${shade(bg, -0.06)} 100%)` }}
    >
      <div className="pointer-events-none absolute -left-12 -top-12 h-40 w-40 rounded-full bg-white/10" />
      <div className="pointer-events-none absolute -right-10 top-10 h-28 w-28 rounded-full bg-white/10" />
      <div className="relative z-10 pt-6">
        {back && (typeof back === 'function' || nav.canGoBack) && (
          <IconButton label="بازگشت" onClick={onBack} className="mb-3 bg-white/15">
            <ChevronRight size={18} strokeWidth={2.5} />
          </IconButton>
        )}
        <div className="flex items-center justify-between gap-3">
          <div className="min-w-0 flex-1">
            <h1 className="text-xl font-black leading-snug">{title}</h1>
            {subtitle && <div className="mt-1 text-xs text-white/75">{subtitle}</div>}
          </div>
          {mascot && <SeyarMascot char={mascot.char} mood={mascot.mood ?? 'happy'} size={mascot.size ?? 64} />}
        </div>
        {children}
      </div>
    </header>
  );
}

/* ─── دکمه‌ها ──────────────────────────────────────────────────────────────── */

export function IconButton({
  label,
  className = '',
  children,
  ...rest
}: ButtonHTMLAttributes<HTMLButtonElement> & { label: string }) {
  return (
    <button
      type="button"
      aria-label={label}
      title={label}
      className={`flex h-9 w-9 flex-shrink-0 items-center justify-center rounded-full transition-transform active:scale-90 ${className}`}
      {...rest}
    >
      {children}
    </button>
  );
}

export function PrimaryButton({
  color = '#ED6956',
  loading = false,
  className = '',
  style,
  children,
  disabled,
  ...rest
}: ButtonHTMLAttributes<HTMLButtonElement> & { color?: string; loading?: boolean }) {
  return (
    <button
      type="button"
      disabled={disabled || loading}
      className={`flex w-full items-center justify-center gap-2 rounded-2xl py-4 text-base font-black text-white transition-[transform,box-shadow] active:translate-y-[3px] active:shadow-none disabled:opacity-50 disabled:active:translate-y-0 ${className}`}
      style={{ backgroundColor: color, boxShadow: `0 4px 0 ${shade(color, -0.22)}`, ...style }}
      {...rest}
    >
      {loading ? <Spinner /> : children}
    </button>
  );
}

export function SecondaryButton({ className = '', children, ...rest }: ButtonHTMLAttributes<HTMLButtonElement>) {
  return (
    <button
      type="button"
      className={`flex w-full items-center justify-center gap-2 rounded-2xl border-2 border-b-4 border-line bg-white py-3.5 text-sm font-bold text-body transition-transform active:translate-y-[2px] active:border-b-2 disabled:opacity-50 ${className}`}
      {...rest}
    >
      {children}
    </button>
  );
}

export function Spinner({ size = 20, className = '' }: { size?: number; className?: string }) {
  return (
    <span
      role="status"
      aria-label="در حالِ بارگذاری"
      className={`inline-block animate-spin rounded-full border-2 border-current border-t-transparent ${className}`}
      style={{ width: size, height: size }}
    />
  );
}

/* ─── حالت‌های بارگذاری / خطا / خالی ───────────────────────────────────────── */

function StateBox({ char, mood, text, children }: { char: SeyarChar; mood: SeyarMood; text: ReactNode; children?: ReactNode }) {
  return (
    <div className="flex flex-col items-center justify-center gap-3 px-8 py-16 text-center">
      <SeyarMascot char={char} mood={mood} size={72} />
      <p className="text-sm leading-7 text-muted">{text}</p>
      {children}
    </div>
  );
}

/**
 * لودر فقط بعد از `delayMs` دیده می‌شود. پاسخِ API معمولاً زیرِ ۳۰۰ms می‌رسد و نشان دادنِ لودر برای
 * همان چند فریم، پرشِ ریزِ «لودر ← محتوا» می‌ساخت؛ حالا تا آن لحظه جای خالی می‌ماند. اگر پاسخ
 * کند باشد کاربر باز هم لودر را می‌بیند. در مرورگر با شبکه‌ی کند آزموده نشده.
 */
export function LoadingState({ text = 'یه لحظه صبر کن…', char = 'sigma' as SeyarChar, delayMs = 300 }) {
  const [show, setShow] = useState(delayMs <= 0);
  useEffect(() => {
    if (delayMs <= 0) return;
    const t = setTimeout(() => setShow(true), delayMs);
    return () => clearTimeout(t);
  }, [delayMs]);
  return show ? <StateBox char={char} mood="idle" text={text} /> : null;
}

export function ErrorState({ error, onRetry, text }: { error?: unknown; onRetry?: () => void; text?: string }) {
  return (
    <StateBox char="pi" mood="sad" text={text ?? friendlyError(error)}>
      {onRetry && (
        <button
          type="button"
          onClick={onRetry}
          className="flex items-center gap-1.5 rounded-full bg-white px-4 py-2 text-xs font-bold text-coral shadow-sm ring-1 ring-line"
        >
          <RotateCw size={13} /> دوباره امتحان کن
        </button>
      )}
    </StateBox>
  );
}

export function EmptyState({ text, char = 'pi' as SeyarChar }: { text: string; char?: SeyarChar }) {
  return <StateBox char={char} mood="idle" text={text} />;
}

/**
 * جداکننده‌ی میانِ دو تکه‌ی متن. «·» کنارِ صفرِ فارسی (که خودش یک نقطه است)
 * خوانده نمی‌شد: «فصلِ ۱ · ۰ از ۴» شبیهِ «۱۰۰» دیده می‌شد.
 */
export function Sep() {
  return <span aria-hidden className="mx-1.5 inline-block h-2.5 w-px bg-current align-middle opacity-40" />;
}

export function InlineError({ children }: { children: ReactNode }) {
  return (
    <div role="alert" className="rounded-xl border border-red-200 bg-red-50 px-3 py-2.5 text-xs leading-6 text-red-600">
      {children}
    </div>
  );
}

/* ─── چیزهای کوچک ──────────────────────────────────────────────────────────── */

export function ProgressBar({ percent, color, track = '#eae7ff', height = 8 }: { percent: number; color: string; track?: string; height?: number }) {
  return (
    <div className="w-full overflow-hidden rounded-full" style={{ height, backgroundColor: track }}>
      <div
        className="h-full rounded-full transition-[width] duration-700 ease-out"
        style={{ width: `${Math.max(0, Math.min(100, percent))}%`, backgroundColor: color }}
      />
    </div>
  );
}

export function Card({ className = '', style, children, onClick }: { className?: string; style?: CSSProperties; children: ReactNode; onClick?: () => void }) {
  const Tag = onClick ? 'button' : 'div';
  return (
    <Tag
      type={onClick ? 'button' : undefined}
      onClick={onClick}
      style={style}
      className={`rounded-3xl border border-line bg-white p-4 text-right shadow-sm ${onClick ? 'transition-transform active:scale-[0.98]' : ''} ${className}`}
    >
      {children}
    </Tag>
  );
}

/** بدنه‌ی اسکرول‌شونده‌ی صفحه، زیرِ سربرگ. */
export function ScreenBody({ className = '', children }: { className?: string; children: ReactNode }) {
  return <div className={`flex-1 overflow-y-auto px-4 py-5 ${className}`}>{children}</div>;
}

export function Screen({ className = 'bg-page', children }: { className?: string; children: ReactNode }) {
  return <div className={`flex h-full flex-col ${className}`}>{children}</div>;
}