'use strict';

const config = require('config');
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: [] };

function mapReleasesToEntityIdAndEntryId(acc, release) {
	const entityId = release.entityId || release.entity.id;
	const entryId = release.entryId || release.entryId;

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

	return acc;
}

function filterLocalUniqueReleases(releases, accReleases) {
	const localDuplicateReleasesBySiteIdAndEntryId = accReleases.reduce(mapReleasesToEntityIdAndEntryId, {});

	const localUniqueReleases = releases.filter(release => !localDuplicateReleasesBySiteIdAndEntryId[release.entity.id]?.[release.entryId]);
	const localDuplicateReleases = releases.filter(release => localDuplicateReleasesBySiteIdAndEntryId[release.entity.id]?.[release.entryId]);

	return {
		localUniqueReleases,
		localDuplicateReleases,
	};
}

async function filterUniqueReleases(releases) {
	const releaseIdentifiers = releases
		.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'], releaseIdentifiers);

	const duplicateReleases = duplicateReleaseEntries.map(release => curateRelease(release));
	const duplicateReleasesByEntityIdAndEntryId = duplicateReleases.reduce(mapReleasesToEntityIdAndEntryId, {});

	const internalUniqueReleasesByEntityIdAndEntryId = releases.reduce((acc, release) => mapReleasesToEntityIdAndEntryId(acc, release), {});
	const internalUniqueReleases = Object.values(internalUniqueReleasesByEntityIdAndEntryId).map(releasesByEntryId => Object.values(releasesByEntryId)).flat();

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

	return { uniqueReleases, duplicateReleases };
}

function needNextPage(pageReleases, accReleases, isUpcoming) {
	const { localUniqueReleases: uniquePageReleases } = filterLocalUniqueReleases(pageReleases, accReleases);

	if (uniquePageReleases.length === 0) {
		// page is empty, or only contains scenes from previous page
		return false;
	}

	if (isUpcoming) {
		return uniquePageReleases.length > 0 && argv.paginateUpcoming;
	}

	if (uniquePageReleases.length > 0) {
		if (argv.last) {
			return accReleases.length + pageReleases.length < argv.last;
		}

		if (!pageReleases.every(release => !!release.date)) { // some scenes don't have dates
			return accReleases.length + pageReleases.length < argv.missingDateLimit;
		}

		if (argv.after) {
			const oldestReleaseOnPage = pageReleases
				.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, isUpcoming) {
	async function scrapeReleasesPage(page, accReleases) {
		const options = {
			...config.options[scraper.slug],
			...include,
		};

		const pageReleases = isUpcoming
			? await scraper.fetchUpcoming(entity, page, options, preData)
			: await scraper.fetchLatest(entity, page, options, preData);

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

		const validPageReleases = pageReleases.filter(release => release?.entryId); // filter out empty and unidentified releases
		const pageReleasesWithEntity = validPageReleases.map(release => ({ ...release, entity: release.entity || entity }));

		if (pageReleases.length > validPageReleases.length) {
			logger.warn(`Found ${pageReleases.length - validPageReleases.length} empty or unidentified releases on page ${page} for '${entity.name}'`);
		}

		if (needNextPage(pageReleasesWithEntity, accReleases, isUpcoming)) {
			return scrapeReleasesPage(page + 1, accReleases.concat(pageReleasesWithEntity), isUpcoming);
		}

		return accReleases.concat(pageReleasesWithEntity);
	}

	const releases = await scrapeReleasesPage(argv.page || 1, []);

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

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

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

	return { uniqueReleases, duplicateReleases };
}

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

	try {
		return await scrapeReleases(scraper, entity, preData, false);
	} 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;