import { writable } from 'svelte/store';

// Small global toast queue.
//
// Any part of the UI can drop a message and it appears in the corner for a
// couple of seconds, then quietly dismisses. Replaces the ad-hoc "flash"
// strings scattered across pages when the message doesn't need to live inline
// with a form.

export type ToastVariant = 'info' | 'success' | 'warning' | 'danger';

export interface Toast {
    id: number;
    message: string;
    variant: ToastVariant;
    ttl: number;
    href?: string;
}

export const toasts = writable<Toast[]>([]);
export interface Notice extends Toast { createdAt: string; read: boolean; }
export const notificationHistory = writable<Notice[]>([]);
const historyKey = 'electric-cherry:notifications';

export function startNotificationHistory(): () => void {
    try {
        const saved: unknown = JSON.parse(sessionStorage.getItem(historyKey) ?? '[]');
        if (Array.isArray(saved)) {
            const valid = saved.filter((item): item is Notice => item && typeof item.id === 'number' && Number.isSafeInteger(item.id)
                && typeof item.message === 'string' && ['info', 'success', 'warning', 'danger'].includes(item.variant)
                && typeof item.createdAt === 'string' && Number.isFinite(Date.parse(item.createdAt))
                && typeof item.read === 'boolean' && (!item.href || (typeof item.href === 'string' && item.href.startsWith('/') && !item.href.startsWith('//')))).slice(0, 50);
            notificationHistory.set(valid);
            nextId = Math.max(nextId, ...valid.map(item => item.id + 1));
        }
    } catch { /* Notifications still work when browser storage is unavailable. */ }
    return notificationHistory.subscribe(items => { try { sessionStorage.setItem(historyKey, JSON.stringify(items)); } catch { /* Optional persistence. */ } });
}

export function markNotificationsRead() { notificationHistory.update(items => items.map(item => ({ ...item, read: true }))); }
export function clearNotifications() { notificationHistory.set([]); }

let nextId = 1;

export function toast(
    message: string,
    opts: { variant?: ToastVariant; ttl?: number; href?: string } = {}
): void {
    const t: Toast = {
        id: nextId++,
        message,
        variant: opts.variant ?? 'info',
        ttl: opts.ttl ?? 3500,
        href: opts.href
    };
    toasts.update((arr) => [...arr, t]);
    if (t.href || t.ttl === 0 || t.variant !== 'info') {
        notificationHistory.update(items => [{ ...t, createdAt: new Date().toISOString(), read: false }, ...items].slice(0, 50));
    }
    if (t.ttl > 0) {
        setTimeout(() => dismiss(t.id), t.ttl);
    }
}

export function dismiss(id: number): void {
    toasts.update((arr) => arr.filter((t) => t.id !== id));
}