import { ReviewLog } from '../models/ReviewLog.js';
import { StudyItem } from '../models/StudyItem.js';
import { getDaysDiff, getSRSDate } from '../utils/dateUtils.js';

export const processReview = async (user, subjectId, success) => {
	if (!user.stats) user.stats = { totalReviews: 0, correctReviews: 0, currentStreak: 0, maxStreak: 0 };
	user.stats.totalReviews += 1;
	if (success) user.stats.correctReviews += 1;

	const todayStr = new Date().toISOString().split('T')[0];
	const lastStudyStr = user.stats.lastStudyDate;

	if (lastStudyStr !== todayStr) {
		if (!lastStudyStr) {
			user.stats.currentStreak = 1;
		} else {
			const diff = getDaysDiff(lastStudyStr, todayStr);
			if (diff === 1) {
				user.stats.currentStreak += 1;
			} else if (diff > 1) {
				const lastFreeze = user.stats.lastFreezeDate ? new Date(user.stats.lastFreezeDate) : null;
				let daysSinceFreeze = 999;
				if (lastFreeze) daysSinceFreeze = getDaysDiff(lastFreeze.toISOString().split('T')[0], todayStr);

				const canUseShield = daysSinceFreeze >= 7;

				if (canUseShield && diff === 2) {
					console.log(`User ${user._id} saved by Zen Shield!`);
					user.stats.lastFreezeDate = new Date();
					user.stats.currentStreak += 1;
				} else {
					user.stats.currentStreak = 1;
				}
			}
		}
		user.stats.lastStudyDate = todayStr;
		if (user.stats.currentStreak > user.stats.maxStreak) user.stats.maxStreak = user.stats.currentStreak;
	}
	await user.save();

	await ReviewLog.findOneAndUpdate(
		{ userId: user._id, date: todayStr },
		{ $inc: { count: 1 } },
		{ upsert: true, new: true }
	);

	const item = await StudyItem.findOne({ userId: user._id, wkSubjectId: subjectId });
	if (!item) throw new Error('Item not found');

	if (!item.stats) item.stats = { correct: 0, total: 0 };
	item.stats.total += 1;
	if (success) item.stats.correct += 1;

	if (success) {
		const nextLevel = Math.min(item.srsLevel + 1, 10);
		item.srsLevel = nextLevel;
		item.nextReview = getSRSDate(nextLevel);
	} else {
		item.srsLevel = Math.max(1, item.srsLevel - 1);
		item.nextReview = Date.now();
	}

	await item.save();
	return { nextReview: item.nextReview, srsLevel: item.srsLevel };
};

export const getQueue = async (user, limit = 100, sortMode) => {
	const query = {
		userId: user._id,
		srsLevel: { $lt: 10, $gt: 0 },
		nextReview: { $lte: new Date() }
	};

	let dueItems;
	if (sortMode === 'priority') {
		dueItems = await StudyItem.find(query).sort({ srsLevel: 1, level: 1 }).limit(limit);
	} else {
		dueItems = await StudyItem.find(query).limit(limit);
		for (let i = dueItems.length - 1; i > 0; i--) {
			const j = Math.floor(Math.random() * (i + 1));
			[dueItems[i], dueItems[j]] = [dueItems[j], dueItems[i]];
		}
	}
	return dueItems;
};

export const getLessonQueue = async (user, limit = 100) => {
	const query = {
		userId: user._id,
		srsLevel: 0
	};
	return await StudyItem.find(query).sort({ level: 1, wkSubjectId: 1 }).limit(limit);
};

export const processLesson = async (user, subjectId) => {
	const item = await StudyItem.findOne({ userId: user._id, wkSubjectId: subjectId });
	if (!item) throw new Error('Item not found');

	item.srsLevel = 1;
	item.nextReview = getSRSDate(1);

	await item.save();
	return { success: true, item };
};