// components/Toast.tsx
// Tiny in-app toast system. Each toast is a row in a vertical stack
// anchored to the bottom-right. Auto-dismiss after 5s (configurable).
// Includes a 3-second coalesce window — bursty events (e.g. 20 tasks
// flipping to done at once) only show one toast.

"use client";

import {
  createContext,
  useCallback,
  useContext,
  useEffect,
  useRef,
  useState,
  type ReactNode,
} from "react";

export type ToastKind = "info" | "success" | "error" | "warn";

export interface Toast {
  id: string;
  kind: ToastKind;
  title: string;
  body?: string;
  /** Optional click target — e.g. open a task detail panel. */
  onClick?: () => void;
  /** Auto-dismiss in ms. 0 = sticky. Default 5000. */
  duration?: number;
}

interface ToastContextValue {
  toast: (t: Omit<Toast, "id">) => void;
  dismiss: (id: string) => void;
}

const ToastContext = createContext<ToastContextValue | null>(null);

const COALESCE_MS = 3000;
const MAX_VISIBLE = 4;

export function ToastProvider({ children }: { children: ReactNode }) {
  const [toasts, setToasts] = useState<Toast[]>([]);
  const lastFiredRef = useRef<{ key: string; at: number } | null>(null);

  const dismiss = useCallback((id: string) => {
    setToasts((prev) => prev.filter((t) => t.id !== id));
  }, []);

  const toast = useCallback((t: Omit<Toast, "id">) => {
    const key = `${t.kind}|${t.title}|${t.body ?? ""}`;
    const now = Date.now();
    if (lastFiredRef.current && lastFiredRef.current.key === key && now - lastFiredRef.current.at < COALESCE_MS) {
      return;
    }
    lastFiredRef.current = { key, at: now };

    const id = `${now}-${Math.random().toString(36).slice(2, 8)}`;
    setToasts((prev) => {
      const next = [...prev, { ...t, id }];
      return next.slice(-MAX_VISIBLE);
    });
  }, []);

  return (
    <ToastContext.Provider value={{ toast, dismiss }}>
      {children}
      <ToastViewport toasts={toasts} onDismiss={dismiss} />
    </ToastContext.Provider>
  );
}

export function useToast(): ToastContextValue {
  const ctx = useContext(ToastContext);
  if (!ctx) {
    // Safe no-op so non-provider contexts (e.g. tests) don't crash.
    return { toast: () => {}, dismiss: () => {} };
  }
  return ctx;
}

function ToastViewport({
  toasts,
  onDismiss,
}: {
  toasts: Toast[];
  onDismiss: (id: string) => void;
}) {
  return (
    <div
      aria-live="polite"
      aria-atomic="true"
      className="fixed bottom-4 right-4 z-50 flex flex-col gap-2 w-[min(360px,calc(100vw-2rem))]"
    >
      {toasts.map((t) => (
        <ToastItem key={t.id} toast={t} onDismiss={() => onDismiss(t.id)} />
      ))}
    </div>
  );
}

function ToastItem({ toast, onDismiss }: { toast: Toast; onDismiss: () => void }) {
  const duration = toast.duration ?? 5000;
  useEffect(() => {
    if (duration <= 0) return;
    const t = setTimeout(onDismiss, duration);
    return () => clearTimeout(t);
  }, [duration, onDismiss]);

  const palette = {
    info: "border-blue-300 bg-blue-50 text-blue-900",
    success: "border-green-300 bg-green-50 text-green-900",
    error: "border-red-300 bg-red-50 text-red-900",
    warn: "border-amber-300 bg-amber-50 text-amber-900",
  }[toast.kind];

  const icon = {
    info: "ℹ",
    success: "✅",
    error: "❌",
    warn: "⚠",
  }[toast.kind];

  const inner = (
    <div
      role={toast.onClick ? "button" : undefined}
      onClick={toast.onClick}
      className={`rounded-md border ${palette} px-4 py-3 shadow-sm text-sm flex gap-3 items-start ${toast.onClick ? "cursor-pointer hover:shadow-md transition-shadow" : ""}`}
    >
      <span className="text-base leading-tight">{icon}</span>
      <div className="flex-1 min-w-0">
        <p className="font-semibold">{toast.title}</p>
        {toast.body ? <p className="text-xs mt-0.5 opacity-80">{toast.body}</p> : null}
      </div>
      <button
        type="button"
        onClick={(e) => {
          e.stopPropagation();
          onDismiss();
        }}
        aria-label="Dismiss"
        className="text-xs opacity-60 hover:opacity-100"
      >
        ✕
      </button>
    </div>
  );
  return inner;
}

// ─────────────────────────────────────────────────────────────────
// Browser notifications — request permission on first prompt.
// ─────────────────────────────────────────────────────────────────

export async function maybeRequestNotificationPermission(): Promise<boolean> {
  if (typeof window === "undefined") return false;
  if (!("Notification" in window)) return false;
  if (Notification.permission === "granted") return true;
  if (Notification.permission === "denied") return false;
  const result = await Notification.requestPermission();
  return result === "granted";
}

export function fireBrowserNotification(title: string, options: NotificationOptions = {}) {
  if (typeof window === "undefined") return;
  if (!("Notification" in window)) return;
  if (Notification.permission !== "granted") return;
  try {
    new Notification(title, options);
  } catch {
    // Some browsers throw on focus-tab notifications — ignore.
  }
}