'use client';

import { useCallback, useRef, useState } from 'react';

// ISS-008 (v0.17.0): transient toast notifications — a bottom-right stack for action errors
// and game events derived from snapshot diffs. Each toast auto-dismisses after TOAST_TTL_MS;
// the queue is capped at MAX_TOASTS (oldest dropped) so an event burst can't fill the corner.

export type ToastKind = 'error' | 'info';

export interface Toast {
  id: number;
  kind: ToastKind;
  message: string;
}

export const TOAST_TTL_MS = 5_000;
export const MAX_TOASTS = 4;

// Pure core (unit-tested): append a toast, dropping the oldest beyond the cap.
export function pushToast(toasts: Toast[], toast: Toast): Toast[] {
  return [...toasts, toast].slice(-MAX_TOASTS);
}

export interface UseToastsResult {
  toasts: Toast[];
  push: (kind: ToastKind, message: string) => void;
  dismiss: (id: number) => void;
}

export function useToasts(): UseToastsResult {
  const [toasts, setToasts] = useState<Toast[]>([]);
  const nextIdRef = useRef(1);

  // Functional update — a late timer for an already-dismissed/dropped id is a no-op.
  const dismiss = useCallback((id: number) => {
    setToasts((current) => current.filter((t) => t.id !== id));
  }, []);

  const push = useCallback(
    (kind: ToastKind, message: string) => {
      const toast: Toast = { id: nextIdRef.current++, kind, message };
      setToasts((current) => pushToast(current, toast));
      setTimeout(() => dismiss(toast.id), TOAST_TTL_MS);
    },
    [dismiss],
  );

  return { toasts, push, dismiss };
}