import { randomUUID } from 'node:crypto';
import { getDatabase } from '$lib/server/database';
import { createNotification } from '$lib/server/notifications';

export const OVERSIGHT_NOTIFICATION_CATEGORIES = [
	{ id: 'data_changes', label: 'DATA CHANGES', permission: 'data.approve', link: '/isac/data-moderation' },
	{ id: 'avatars', label: 'AVATAR REVIEW', permission: 'avatars.review', link: '/isac/avatar-oversight' }
] as const;

export const OVERSIGHT_NOTIFICATION_FREQUENCIES = ['immediate', '15_minutes', '1_hour', 'daily'] as const;
export type OversightNotificationCategory = (typeof OVERSIGHT_NOTIFICATION_CATEGORIES)[number]['id'];
export type OversightNotificationFrequency = (typeof OVERSIGHT_NOTIFICATION_FREQUENCIES)[number];

function easternParts(date: Date) {
	const parts = new Intl.DateTimeFormat('en-CA', {
		timeZone: 'America/New_York',
		year: 'numeric', month: '2-digit', day: '2-digit', hour: '2-digit', minute: '2-digit',
		hourCycle: 'h23'
	}).formatToParts(date);
	return Object.fromEntries(parts.map((part) => [part.type, Number(part.value)])) as Record<string, number>;
}

function easternInstant(year: number, month: number, day: number, hour: number) {
	for (const offset of [4, 5]) {
		const candidate = new Date(Date.UTC(year, month - 1, day, hour + offset));
		const parts = easternParts(candidate);
		if (parts.year === year && parts.month === month && parts.day === day && parts.hour === hour) return candidate;
	}
	throw new Error('Unable to resolve Eastern delivery time.');
}

function deliveryTime(frequency: Exclude<OversightNotificationFrequency, 'immediate'>, now: Date) {
	if (frequency !== 'daily') {
		const window = frequency === '15_minutes' ? 15 * 60_000 : 60 * 60_000;
		return new Date(Math.floor(now.getTime() / window) * window + window);
	}
	const parts = easternParts(now);
	const localDate = new Date(Date.UTC(parts.year, parts.month - 1, parts.day));
	if (parts.hour >= 10) localDate.setUTCDate(localDate.getUTCDate() + 1);
	return easternInstant(localDate.getUTCFullYear(), localDate.getUTCMonth() + 1, localDate.getUTCDate(), 10);
}

async function eligibleReviewers(permission: string) {
	const database = await getDatabase();
	return (await database.prepare(`
		SELECT DISTINCT users.id
		FROM users
		LEFT JOIN deleted_accounts deleted ON deleted.user_id=users.id
		LEFT JOIN user_status status ON status.user_id=users.id
		LEFT JOIN user_roles ON user_roles.user_id=users.id
		LEFT JOIN role_permissions ON role_permissions.role_id=user_roles.role_id
		LEFT JOIN permissions role_permission ON role_permission.id=role_permissions.permission_id
		LEFT JOIN user_permissions ON user_permissions.user_id=users.id
		LEFT JOIN permissions direct_permission ON direct_permission.id=user_permissions.permission_id
		WHERE deleted.user_id IS NULL AND status.blocked_at IS NULL
			AND (status.banned_until IS NULL OR status.banned_until<=?)
			AND (users.role='admin' OR role_permission.name IN (?, 'system.admin') OR direct_permission.name IN (?, 'system.admin'))
	`)).all(new Date().toISOString(), permission, permission);
}

export async function notifyOversightReview(input: {
	category: OversightNotificationCategory;
	itemId: string;
	title: string;
	summary: string;
	link?: string;
}) {
	const definition = OVERSIGHT_NOTIFICATION_CATEGORIES.find((item) => item.id === input.category);
	if (!definition) throw new Error('Unknown Oversight notification category.');
	const database = await getDatabase();
	const now = new Date();
	for (const reviewer of await eligibleReviewers(definition.permission)) {
		const userId = String(reviewer.id);
		const preference = await (await database.prepare(
			'SELECT frequency FROM oversight_notification_preferences WHERE user_id=? AND oversight_category=?'
		)).get(userId, input.category);
		const frequency = String(preference?.frequency ?? 'immediate') as OversightNotificationFrequency;
		if (frequency === 'immediate') {
			await createNotification({
				userId,
				category: 'isac',
				source: 'ISAC OVERSIGHT NETWORK',
				title: input.title,
				body: input.summary,
				link: input.link ?? definition.link,
				mandatory: true
			});
			continue;
		}
		await (await database.prepare(`INSERT INTO oversight_notification_queue
			(id,user_id,oversight_category,review_item_id,title,summary,link,frequency,created_at,deliver_after)
			VALUES(?,?,?,?,?,?,?,?,?,?)`)).run(
			randomUUID(), userId, input.category, input.itemId, input.title.slice(0, 140),
			input.summary.slice(0, 2000), input.link ?? definition.link, frequency,
			now.toISOString(), deliveryTime(frequency, now).toISOString()
		);
	}
}