import { useEffect, useRef, useState, type PointerEvent } from "react";
import { useNavigate } from "react-router";
import { clientConfig } from "../client-config";
import { reducedMotionOn, usePreferences } from "../state/preferences";
import { useToasts, type Toast } from "../state/toasts";
import { Icon } from "../ui";

const { durationMs, maxVisible, desktopMinWidthPx } = clientConfig.toasts;
/** A sideways drag this far dismisses a toast. */
const SWIPE_PX = 60;

/** The viewport's width, kept current on resize. */
function useViewportWidth(): number {
  const [width, setWidth] = useState(() => window.innerWidth);
  useEffect(() => {
    const onResize = () => setWidth(window.innerWidth);
    window.addEventListener("resize", onResize);
    return () => window.removeEventListener("resize", onResize);
  }, []);
  return width;
}

const TONES: Record<Toast["tone"], string> = {
  good: "border-emerald-400/40 text-emerald-50",
  info: "border-glass-line text-ink-50",
  warn: "border-action/50 text-ink-50",
};

/**
 * One toast: closes after 5 s, paused while hovered or touched; ✕ or a swipe
 * closes it early; tapping opens its screen (decision 0.5.161).
 */
function ToastItem({
  toast,
  motion,
  desktop,
}: {
  toast: Toast;
  motion: boolean;
  desktop: boolean;
}) {
  const dismiss = useToasts((s) => s.dismiss);
  const navigate = useNavigate();
  const [paused, setPaused] = useState(false);
  const left = useRef<number>(durationMs);
  const swipe = useRef<{ x: number; moved: boolean } | null>(null);

  useEffect(() => {
    if (paused) return;
    const started = Date.now();
    const timer = window.setTimeout(() => dismiss(toast.id), left.current);
    return () => {
      window.clearTimeout(timer);
      left.current = Math.max(0, left.current - (Date.now() - started));
    };
  }, [paused, dismiss, toast.id]);

  const onPointerDown = (e: PointerEvent) => {
    swipe.current = { x: e.clientX, moved: false };
  };
  const onPointerUp = (e: PointerEvent) => {
    const start = swipe.current;
    if (start && Math.abs(e.clientX - start.x) >= SWIPE_PX) {
      start.moved = true;
      dismiss(toast.id);
    }
  };
  const open = () => {
    if (swipe.current?.moved) return;
    dismiss(toast.id);
    void navigate(toast.to);
  };

  return (
    <li
      data-toast
      onMouseEnter={() => setPaused(true)}
      onMouseLeave={() => setPaused(false)}
      onTouchStart={() => setPaused(true)}
      onTouchEnd={() => setPaused(false)}
      onPointerDown={onPointerDown}
      onPointerUp={onPointerUp}
      className={`pointer-events-auto flex items-start gap-2 rounded-xl border bg-white/5 py-2 pr-1.5 pl-3 text-sm shadow-panel backdrop-blur ${TONES[toast.tone]} ${motion ? (desktop ? "animate-slide" : "animate-rise") : ""}`}
    >
      <button type="button" onClick={open} className="min-w-0 flex-1 py-0.5 text-left">
        {toast.text}
      </button>
      <button
        type="button"
        aria-label="Dismiss"
        onClick={() => dismiss(toast.id)}
        className="grid size-7 shrink-0 place-items-center rounded-lg text-ink-400 hover:bg-space-700 hover:text-ink-100"
      >
        <Icon name="close" className="size-4" />
      </button>
    </li>
  );
}

/**
 * The toasts on screen (decision 0.5.161): top-right on desktop, top-center
 * below the safe area on phones; the newest on top, at most 3, and the rest as
 * "+N more", which opens the Logbook. Announced politely; no sliding with
 * reduced motion.
 */
export function Toasts() {
  const toasts = useToasts((s) => s.toasts);
  const dropOverflow = useToasts((s) => s.dropOverflow);
  const navigate = useNavigate();
  const motion = !usePreferences(reducedMotionOn);
  const desktop = useViewportWidth() >= desktopMinWidthPx;
  const shown = toasts.slice(0, maxVisible);
  const more = toasts.length - shown.length;

  return (
    <section
      aria-label="Notifications"
      aria-live="polite"
      data-placement={desktop ? "top-right" : "top-center"}
      data-motion={motion ? "slide" : "none"}
      className={`pointer-events-none fixed z-[60] flex flex-col gap-2 ${
        desktop
          ? "top-[calc(env(safe-area-inset-top)+4rem)] right-4 w-80"
          : "inset-x-0 top-[calc(env(safe-area-inset-top)+4rem)] mx-auto w-[min(24rem,calc(100%-2rem))]"
      }`}
    >
      <ul className="flex flex-col gap-2">
        {shown.map((toast) => (
          <ToastItem key={toast.id} toast={toast} motion={motion} desktop={desktop} />
        ))}
      </ul>
      {more > 0 && (
        <button
          type="button"
          onClick={() => {
            dropOverflow();
            void navigate("/logbook");
          }}
          className="pointer-events-auto self-end rounded-full border border-glass-line bg-white/5 px-3 py-1 font-display text-xs text-ink-200 shadow-panel"
        >
          +{more} more
        </button>
      )}
    </section>
  );
}