'use strict';

const Promise = require('bluebird');
const moment = require('moment');

const argv = require('./argv');
const logger = require('./logger')(__filename);
const knex = require('./knex');
const { curateRelease } = require('./releases');
const include = require('./utils/argv-include')(argv);
const scrapers = require('./scrapers/scrapers');
const { fetchIncludedEntities } = require('./entities');

const emptyReleases = { uniqueReleases: [], duplicateReleases: [] };

async function filterUniqueReleases(latestReleases, accReleases) {
	const latestReleaseIdentifiers = latestReleases
		.map(release => [release.entity.id, release.entryId]);

	const duplicateReleaseEntries = await knex('releases')
		.select(knex.raw('releases.*, row_to_json(entities) as entity'))
		.leftJoin('entities', 'entities.id', 'releases.entity_id')
		.whereIn(['entity_id', 'entry_id'], latestReleaseIdentifiers);

	const duplicateReleases = duplicateReleaseEntries.map(release => curateRelease(release));

	// add entry IDs of accumulated releases to prevent an infinite scrape loop
	// when one page contains the same release as the previous
	const duplicateReleasesSiteIdAndEntryIds = duplicateReleases
		.concat(accReleases)
		.reduce((acc, release) => {
			const entityId = release.entityId || release.entity.id;
			const entryId = release.entryId || release.entryId;

			if (!acc[entityId]) acc[entityId] = {};
			acc[entityId][entryId] = true;

			return acc;
		}, {});

	const uniqueReleases = latestReleases.filter(release => !duplicateReleasesSiteIdAndEntryIds[release.entity.id]?.[release.entryId]);

	return { uniqueReleases, duplicateReleases };
}

function needNextPage(releases, uniqueReleases, totalReleases, hasDates, upcoming) {
	if (upcoming && uniqueReleases.length > 0) {
		return argv.paginateUpcoming;
	}

	if (argv.last) {
		return releases.length > 0 && totalReleases + releases.length < argv.last;
	}

	if (!hasDates) {
		return totalReleases + releases.length < argv.nullDateLimit;
	}

	if (uniqueReleases.length === 0) {
		return false;
	}

	const oldestReleaseOnPage = releases
		.sort((releaseA, releaseB) => releaseB.date - releaseA.date)
		.slice(-1)[0];

	if (moment(oldestReleaseOnPage.date).isAfter(argv.after)) {
		// oldest release on page is newer than the specified date cut-off
		return true;
	}

	return false;
}

async function scrapeReleases(scraper, entity, preData, upcoming = false, page = 1, acc = emptyReleases, totalReleases = 0) {
	const releases = upcoming
		? await scraper.fetchUpcoming(entity, page, include, preData)
		: await scraper.fetchLatest(entity, page, include, preData);

	if (!Array.isArray(releases)) {
		// scraper is unable to fetch the releases and returned a HTTP code or null
		logger.warn(`Scraper returned ${releases} when fetching latest from '${entity.name}' (${entity.parent?.name})`);
		return acc;
	}

	const releasesWithEntity = releases.map(release => ({
		...release,
		entity: release.entity || entity, // allow override
	})); // attach entity the release is assigned to when stored

	const hasDates = releasesWithEntity.every(release => !!release.date);

	const limitedReleases = (argv.last && releasesWithEntity.slice(0, Math.max(argv.last - totalReleases, 0)))
		|| (hasDates && releasesWithEntity.filter(release => moment(release.date).isAfter(argv.after)))
		|| releasesWithEntity.slice(0, Math.max(argv.nullDateLimit - totalReleases, 0));

	const { uniqueReleases, duplicateReleases } = argv.force
		? { uniqueReleases: limitedReleases, duplicateReleases: [] }
		: await filterUniqueReleases(limitedReleases, acc.uniqueReleases);

	const accReleases = {
		uniqueReleases: acc.uniqueReleases.concat(uniqueReleases),
		duplicateReleases: acc.duplicateReleases.concat(duplicateReleases),
	};

	if (needNextPage(releases, uniqueReleases, totalReleases, hasDates, upcoming)) {
		return scrapeReleases(scraper, entity, preData, upcoming, page + 1, accReleases, totalReleases + releases.length);
	}

	return accReleases;
}

async function scrapeLatestReleases(scraper, entity, preData) {
	if ((!argv.latest && !argv.last && !argv.after) || !scraper.fetchLatest) {
		return emptyReleases;
	}

	try {
		return await scrapeReleases(scraper, entity, preData, false, argv.page || 1);
	} catch (error) {
		if (argv.debug) {
			console.trace(error);
		}

		logger.warn(`Failed to scrape latest updates for '${entity.slug}' (${entity.parent?.slug}): ${error.message}`);
	}

	return emptyReleases;
}

async function scrapeUpcomingReleases(scraper, entity, preData) {
	if (!argv.upcoming || !scraper.fetchUpcoming) {
		return emptyReleases;
	}

	try {
		return await scrapeReleases(scraper, entity, preData, true);
	} catch (error) {
		if (argv.debug) {
			console.trace(error);
		}

		logger.warn(`Failed to scrape upcoming updates for '${entity.slug}' (${entity.parent?.slug}): ${error.message}`);
	}

	return emptyReleases;
}

async function scrapeMovies(scraper, entity) {
	if (!argv.movies || !scraper.fetchMovies) {
		return [];
	}

	try {
		// return await scrapeReleases(scraper, entity, preData, true);
		return await scraper.fetchMovies(entity);
	} catch (error) {
		logger.warn(`Failed to scrape movies for '${entity.slug}' (${entity.parent?.slug}): ${error.message}`);
	}

	return [];
}

async function scrapeChannelReleases(scraper, channelEntity, preData) {
	const [latestReleases, upcomingReleases] = await Promise.all([
		scrapeLatestReleases(scraper, channelEntity, preData),
		scrapeUpcomingReleases(scraper, channelEntity, preData),
		scrapeMovies(scraper, channelEntity, preData),
	]);

	logger.info(`Fetching ${latestReleases.uniqueReleases.length} latest and ${upcomingReleases.uniqueReleases.length} upcoming updates for '${channelEntity.name}' (${channelEntity.parent?.name})`);

	return {
		uniqueReleases: [...latestReleases.uniqueReleases, ...upcomingReleases.uniqueReleases],
		duplicateReleases: [...latestReleases.duplicateReleases, ...upcomingReleases.duplicateReleases],
	};
}

async function scrapeChannel(channelEntity, accNetworkReleases) {
	const scraper = scrapers.releases[channelEntity.slug]
        || scrapers.releases[channelEntity.parent?.slug]
        || scrapers.releases[channelEntity.parent?.parent?.slug];

	if (!scraper) {
		logger.warn(`No scraper found for '${channelEntity.name}' (${channelEntity.parent?.name})`);
		return emptyReleases;
	}

	try {
		const beforeFetchLatest = await scraper.beforeFetchLatest?.(channelEntity);

		return await scrapeChannelReleases(scraper, channelEntity, {
			...accNetworkReleases,
			beforeFetchLatest,
		});
	} catch (error) {
		logger.error(`Failed to scrape releases from ${channelEntity.name} using ${scraper.slug}: ${error.message}`);

		return emptyReleases;
	}
}

async function scrapeNetworkSequential(networkEntity) {
	const releases = await Promise.reduce(
		networkEntity.children,
		async (chain, channelEntity) => {
			const accNetworkReleases = await chain;
			const { uniqueReleases, duplicateReleases } = await scrapeChannel(channelEntity, accNetworkReleases);

			return {
				uniqueReleases: accNetworkReleases.uniqueReleases.concat(uniqueReleases),
				duplicateReleases: accNetworkReleases.duplicateReleases.concat(duplicateReleases),
			};
		},
		Promise.resolve(emptyReleases),
	);

	return releases.uniqueReleases;
}

async function scrapeNetworkParallel(networkEntity) {
	return Promise.map(
		networkEntity.children,
		async (channelEntity) => {
			const { uniqueReleases } = await scrapeChannel(channelEntity, networkEntity);

			return uniqueReleases;
		},
		{ concurrency: 3 },
	);
}

async function fetchUpdates() {
	const includedNetworks = await fetchIncludedEntities();

	const scrapedNetworks = await Promise.map(
		includedNetworks,
		async networkEntity => (networkEntity.parameters?.sequential
			? scrapeNetworkSequential(networkEntity)
			: scrapeNetworkParallel(networkEntity)),
		{ concurrency: 5 },
	);

	const releases = scrapedNetworks.flat(2);

	return releases;
}

module.exports = fetchUpdates;