'use strict';

const _ = require('lodash');

const db = require('../database');
const privileges = require('../privileges');
const user = require('../user');
const categories = require('../categories');
const meta = require('../meta');
const plugins = require('../plugins');

module.exports = function (Topics) {
	Topics.getSortedTopics = async function (params) {
		const data = {
			nextStart: 0,
			topicCount: 0,
			topics: [],
		};

		params.term = params.term || 'alltime';
		params.sort = params.sort || 'recent';
		params.query = params.query || {};
		if (params.hasOwnProperty('cids') && params.cids && !Array.isArray(params.cids)) {
			params.cids = [params.cids];
		}
		params.tags = params.tags || [];
		if (params.tags && !Array.isArray(params.tags)) {
			params.tags = [params.tags];
		}
		data.tids = await getTids(params);
		data.tids = await sortTids(data.tids, params);
		data.tids = await filterTids(data.tids.slice(0, meta.config.recentMaxTopics), params);
		data.topicCount = data.tids.length;
		data.topics = await getTopics(data.tids, params);
		data.nextStart = params.stop + 1;
		return data;
	};

	async function getTids(params) {
		if (plugins.hooks.hasListeners('filter:topics.getSortedTids')) {
			const result = await plugins.hooks.fire('filter:topics.getSortedTids', { params: params, tids: [] });
			return result.tids;
		}
		let tids = [];
		if (params.term !== 'alltime') {
			tids = await Topics.getLatestTidsFromSet('topics:tid', 0, -1, params.term);
			if (params.filter === 'watched') {
				tids = await Topics.filterWatchedTids(tids, params.uid);
			}
		} else if (params.filter === 'watched') {
			tids = await db.getSortedSetRevRange(`uid:${params.uid}:followed_tids`, 0, -1);
		} else if (params.cids) {
			tids = await getCidTids(params);
		} else if (params.tags.length) {
			tids = await getTagTids(params);
		} else if (params.sort === 'old') {
			tids = await db.getSortedSetRange(`topics:recent`, 0, meta.config.recentMaxTopics - 1);
		} else {
			tids = await db.getSortedSetRevRange(`topics:${params.sort}`, 0, meta.config.recentMaxTopics - 1);
		}

		return tids;
	}

	async function getTagTids(params) {
		const sets = [
			params.sort === 'old' ?
				'topics:recent' :
				`topics:${params.sort}`,
			...params.tags.map(tag => `tag:${tag}:topics`),
		];
		const method = params.sort === 'old' ?
			'getSortedSetIntersect' :
			'getSortedSetRevIntersect';
		return await db[method]({
			sets: sets,
			start: 0,
			stop: meta.config.recentMaxTopics - 1,
			weights: sets.map((s, index) => (index ? 0 : 1)),
		});
	}

	async function getCidTids(params) {
		if (params.tags.length) {
			return _.intersection(...await Promise.all(params.tags.map(async (tag) => {
				const sets = params.cids.map(cid => `cid:${cid}:tag:${tag}:topics`);
				return await db.getSortedSetRevRange(sets, 0, -1);
			})));
		}

		const sets = [];
		const pinnedSets = [];
		params.cids.forEach((cid) => {
			if (params.sort === 'recent' || params.sort === 'old') {
				sets.push(`cid:${cid}:tids`);
			} else {
				sets.push(`cid:${cid}:tids${params.sort ? `:${params.sort}` : ''}`);
			}
			pinnedSets.push(`cid:${cid}:tids:pinned`);
		});
		let pinnedTids = await db.getSortedSetRevRange(pinnedSets, 0, -1);
		pinnedTids = await Topics.tools.checkPinExpiry(pinnedTids);
		const method = params.sort === 'old' ?
			'getSortedSetRange' :
			'getSortedSetRevRange';
		const tids = await db[method](sets, 0, meta.config.recentMaxTopics - 1);
		return pinnedTids.concat(tids);
	}

	async function sortTids(tids, params) {
		if (params.term === 'alltime' && !params.cids && !params.tags.length && params.filter !== 'watched' && !params.floatPinned) {
			return tids;
		}
		const topicData = await Topics.getTopicsFields(tids, ['tid', 'lastposttime', 'upvotes', 'downvotes', 'postcount', 'pinned']);
		const sortMap = {
			recent: sortRecent,
			old: sortOld,
			posts: sortPopular,
			votes: sortVotes,
		};
		const sortFn = sortMap[params.sort] || sortRecent;

		if (params.floatPinned) {
			floatPinned(topicData, sortFn);
		} else {
			topicData.sort(sortFn);
		}

		return topicData.map(topic => topic && topic.tid);
	}

	function floatPinned(topicData, sortFn) {
		topicData.sort((a, b) => (a.pinned !== b.pinned ? b.pinned - a.pinned : sortFn(a, b)));
	}

	function sortRecent(a, b) {
		return b.lastposttime - a.lastposttime;
	}

	function sortOld(a, b) {
		return a.lastposttime - b.lastposttime;
	}

	function sortVotes(a, b) {
		if (a.votes !== b.votes) {
			return b.votes - a.votes;
		}
		return b.postcount - a.postcount;
	}

	function sortPopular(a, b) {
		if (a.postcount !== b.postcount) {
			return b.postcount - a.postcount;
		}
		return b.viewcount - a.viewcount;
	}

	async function filterTids(tids, params) {
		const { filter } = params;
		const { uid } = params;

		if (filter === 'new') {
			tids = await Topics.filterNewTids(tids, uid);
		} else if (filter === 'unreplied') {
			tids = await Topics.filterUnrepliedTids(tids);
		} else {
			tids = await Topics.filterNotIgnoredTids(tids, uid);
		}

		tids = await privileges.topics.filterTids('topics:read', tids, uid);
		let topicData = await Topics.getTopicsFields(tids, ['uid', 'tid', 'cid']);
		const topicCids = _.uniq(topicData.map(topic => topic.cid)).filter(Boolean);

		async function getIgnoredCids() {
			if (params.cids || filter === 'watched' || meta.config.disableRecentCategoryFilter) {
				return [];
			}
			return await categories.isIgnored(topicCids, uid);
		}
		const [ignoredCids, filtered] = await Promise.all([
			getIgnoredCids(),
			user.blocks.filter(uid, topicData),
		]);

		const isCidIgnored = _.zipObject(topicCids, ignoredCids);
		topicData = filtered;

		const cids = params.cids && params.cids.map(String);
		tids = topicData.filter(t => (
			t &&
			t.cid &&
			!isCidIgnored[t.cid] &&
			(!cids || cids.includes(String(t.cid)))
		)).map(t => t.tid);

		const result = await plugins.hooks.fire('filter:topics.filterSortedTids', { tids: tids, params: params });
		return result.tids;
	}

	async function getTopics(tids, params) {
		tids = tids.slice(params.start, params.stop !== -1 ? params.stop + 1 : undefined);
		const topicData = await Topics.getTopicsByTids(tids, params);
		Topics.calculateTopicIndices(topicData, params.start);
		return topicData;
	}

	Topics.calculateTopicIndices = function (topicData, start) {
		topicData.forEach((topic, index) => {
			if (topic) {
				topic.index = start + index;
			}
		});
	};
};