import { get } from "svelte/store";
import type { Media } from "../../../../Data/AniList/media";
import settings from "$stores/settings";
import type { SubsPlease } from "$lib/Media/Anime/Airing/Subtitled/subsPlease";
import stringSimilarity from "string-similarity";
import excludeMatch from "$lib/Data/Static/matchExclude.json";
import { season } from "../../season";

export interface Time {
	title: string;
	time: string;
	day: string;
}

interface IndexedTime {
	time: Time;
	normalizedTitle: string;
	tokens: string[];
}

interface DayScheduleIndex {
	entries: IndexedTime[];
	exactTitleIndex: Map<string, number[]>;
	tokenIndex: Map<string, number[]>;
}

interface ScheduleIndex {
	byDay: Map<string, DayScheduleIndex>;
	version: string;
}

const secondsUntil = (targetTime: string, targetDay: string) => {
	const now = new Date();
	const [targetHour, targetMinute] = targetTime.split(":").map(Number);
	let dayDifference =
		[
			"Sunday",
			"Monday",
			"Tuesday",
			"Wednesday",
			"Thursday",
			"Friday",
			"Saturday",
		].indexOf(targetDay) - now.getDay();

	if (dayDifference < 0) dayDifference += 7;

	const targetDate = new Date(now);

	targetDate.setDate(now.getDate() + dayDifference);
	targetDate.setHours(targetHour, targetMinute, 0, 0);

	const secondsDifference = (Number(targetDate) - Number(now)) / 1000;

	return secondsDifference > 0
		? secondsDifference
		: secondsDifference + 7 * 24 * 60 * 60;
};

const preprocessTitle = (title: string): string => {
	return title
		.toLowerCase()
		.replace(/\b(season|s|part|cour)\b/g, " ")
		.replace(/[^a-z0-9\s]/gi, "")
		.trim()
		.split(/\s+/)
		.join(" ");
};

const NON_DISTINCTIVE_TOKENS = new Set([
	"a",
	"and",
	"de",
	"e",
	"for",
	"ga",
	"in",
	"na",
	"ni",
	"no",
	"o",
	"of",
	"on",
	"the",
	"to",
	"wa",
	"wo",
]);

const isMeaningfulToken = (token: string): boolean =>
	/^\d+$/.test(token) ||
	(token.length >= 3 && !NON_DISTINCTIVE_TOKENS.has(token));

const MIN_MATCH_SCORE = 0.3;
const MIN_TOKEN_OVERLAP = 2;
const MIN_MATCH_MARGIN = 0.08;
const FALLBACK_MIN_SCORE = 0.82;
const FALLBACK_MIN_MARGIN = 0.08;
const MAX_MATCH_CACHE_ENTRIES = 10_000;
const MAX_INJECT_CACHE_ENTRIES = 10_000;
const STALE_AIRING_GRACE_SECONDS = 5 * 60;
const MAX_EPISODE_SHIFT_WINDOW_SECONDS = 36 * 60 * 60;

interface SimilarityAnalysis {
	score: number;
	tokenOverlap: number;
	numericTokenOverlap: number;
}

const calculateWeightedSimilarity = (
	title1: string,
	title2: string,
): SimilarityAnalysis => {
	const tokens1 = title1.split(" ").filter(isMeaningfulToken);
	const tokens2 = title2.split(" ").filter(isMeaningfulToken);

	if (tokens1.length === 0 || tokens2.length === 0)
		return {
			score: 0,
			tokenOverlap: 0,
			numericTokenOverlap: 0,
		};

	const set2 = new Set(tokens2);
	let score = 0;
	let tokenOverlap = 0;
	let numericTokenOverlap = 0;
	const numericTokens1 = tokens1.filter((token) => /^\d+$/.test(token));
	const numericTokens2 = tokens2.filter((token) => /^\d+$/.test(token));

	tokens1.forEach((token) => {
		if (set2.has(token)) {
			tokenOverlap += 1;

			if (/^\d+$/.test(token)) numericTokenOverlap += 1;

			score += /^\d+$/.test(token) ? 2 : 1;
		}
	});

	let finalScore =
		(score / ((Math.max(tokens1.length, tokens2.length) || 1) * 2)) * 0.7 +
		stringSimilarity.compareTwoStrings(title1, title2) * 0.3;

	if (
		numericTokens1.length > 0 &&
		numericTokens2.length > 0 &&
		numericTokenOverlap === 0
	)
		finalScore *= 0.5;

	return {
		score: finalScore,
		tokenOverlap,
		numericTokenOverlap,
	};
};

const indexPush = (
	index: Map<string, number[]>,
	key: string,
	entryIndex: number,
) => {
	const existing = index.get(key);

	if (existing) existing.push(entryIndex);
	else index.set(key, [entryIndex]);
};

const scheduleIndexCache = new WeakMap<SubsPlease, ScheduleIndex>();
const closestMatchCache = new Map<string, Time | null>();
const injectAiringTimeCache = new Map<string, Media>();

const hashString = (input: string): string => {
	let hash = 2166136261;

	for (let index = 0; index < input.length; index += 1) {
		hash ^= input.charCodeAt(index);
		hash = Math.imul(hash, 16777619);
	}

	return (hash >>> 0).toString(36);
};

const setBoundedCacheValue = <T>(
	cache: Map<string, T>,
	key: string,
	value: T,
	maxEntries: number,
) => {
	if (cache.size >= maxEntries) cache.clear();

	cache.set(key, value);
};

const animeTitleFingerprint = (anime: Media) =>
	[anime.title.romaji, anime.title.english, ...anime.synonyms]
		.filter(Boolean)
		.map(preprocessTitle)
		.join("|");

const localTimeZone = () =>
	Intl.DateTimeFormat().resolvedOptions().timeZone || "local";

const airingDayOf = (airingAt: number | undefined) =>
	new Date((airingAt || 0) * 1000).toLocaleString("en-US", { weekday: "long" });

const fallbackClosestMatch = (
	dayIndex: DayScheduleIndex,
	searchTitles: string[],
): Time | null => {
	let bestMatch: Time | null = null;
	let bestScore = 0;
	let secondBestScore = 0;

	for (const searchTitle of searchTitles) {
		if (searchTitle.includes("OVA") || searchTitle.includes("Special"))
			continue;

		const normalizedSearchTitle = preprocessTitle(searchTitle);

		for (const candidateEntry of dayIndex.entries) {
			const score = stringSimilarity.compareTwoStrings(
				normalizedSearchTitle,
				candidateEntry.normalizedTitle,
			);

			if (score > bestScore) {
				secondBestScore = bestScore;
				bestScore = score;
				bestMatch = candidateEntry.time;
			} else if (score > secondBestScore) {
				secondBestScore = score;
			}
		}
	}

	if (bestScore < FALLBACK_MIN_SCORE) return null;
	if (bestScore - secondBestScore < FALLBACK_MIN_MARGIN) return null;

	return bestMatch;
};

const buildScheduleIndex = (subsPlease: SubsPlease): ScheduleIndex => {
	const byDay = new Map<string, DayScheduleIndex>();
	const versionParts: string[] = [];

	for (const [day, value] of Object.entries(subsPlease.schedule)) {
		const flattenedValue = Array.isArray(value) ? value.flat() : [];

		versionParts.push(day);

		const dayIndex: DayScheduleIndex = {
			entries: [],
			exactTitleIndex: new Map<string, number[]>(),
			tokenIndex: new Map<string, number[]>(),
		};

		for (const scheduleTime of flattenedValue) {
			const time = {
				title: scheduleTime.title,
				time: scheduleTime.time,
				day,
			};

			versionParts.push(`${day}\u001f${time.title}\u001f${time.time}`);

			const normalizedTitle = preprocessTitle(time.title);
			const tokens = normalizedTitle.split(" ").filter(isMeaningfulToken);
			const entryIndex = dayIndex.entries.length;

			dayIndex.entries.push({
				time,
				normalizedTitle,
				tokens,
			});
			indexPush(dayIndex.exactTitleIndex, normalizedTitle, entryIndex);

			for (const token of tokens)
				indexPush(dayIndex.tokenIndex, token, entryIndex);
		}

		byDay.set(day, dayIndex);
	}

	return {
		byDay,
		version: hashString(`${subsPlease.tz}\u001e${versionParts.join("\u001d")}`),
	};
};

export const findClosestMatch = (
	scheduleIndex: ScheduleIndex,
	anime: Media,
): Time | null => {
	if (excludeMatch.includes(anime.id)) {
		setBoundedCacheValue(
			closestMatchCache,
			`${anime.id}:excluded`,
			null,
			MAX_MATCH_CACHE_ENTRIES,
		);

		return null;
	}

	const airingDay = airingDayOf(anime.nextAiringEpisode?.airingAt);
	const cacheKey = `${anime.id}:${anime.nextAiringEpisode?.airingAt || 0}:${animeTitleFingerprint(
		anime,
	)}:${airingDay}:${localTimeZone()}:${scheduleIndex.version}`;
	const cached = closestMatchCache.get(cacheKey);

	if (cached !== undefined) return cached;
	const dayIndex = scheduleIndex.byDay.get(airingDay);

	if (!dayIndex || dayIndex.entries.length === 0) {
		setBoundedCacheValue(
			closestMatchCache,
			cacheKey,
			null,
			MAX_MATCH_CACHE_ENTRIES,
		);

		return null;
	}

	let bestMatch: Time | null = null;
	let bestScore = 0;
	let secondBestScore = 0;
	let bestTokenOverlap = 0;
	let bestNumericTokenOverlap = 0;
	const searchTitles = [
		anime.title.romaji,
		anime.title.english,
		...anime.synonyms,
	].filter(Boolean);

	for (const searchTitle of searchTitles) {
		if (searchTitle.includes("OVA") || searchTitle.includes("Special"))
			continue;

		const normalizedSearchTitle = preprocessTitle(searchTitle);
		const exactMatchIndexes = dayIndex.exactTitleIndex.get(
			normalizedSearchTitle,
		);

		if (exactMatchIndexes && exactMatchIndexes.length > 0) {
			const exactMatch = dayIndex.entries[exactMatchIndexes[0]];

			if (exactMatch) {
				setBoundedCacheValue(
					closestMatchCache,
					cacheKey,
					exactMatch.time,
					MAX_MATCH_CACHE_ENTRIES,
				);

				return exactMatch.time;
			}
		}

		const searchTokens = normalizedSearchTitle
			.split(" ")
			.filter(isMeaningfulToken);
		const candidateIndexSet = new Set<number>();

		for (const token of searchTokens) {
			for (const candidateIndex of dayIndex.tokenIndex.get(token) || [])
				candidateIndexSet.add(candidateIndex);
		}

		const candidateIndexes =
			candidateIndexSet.size > 0
				? [...candidateIndexSet]
				: dayIndex.entries.map((_, entryIndex) => entryIndex);

		for (const candidateIndex of candidateIndexes) {
			const candidateEntry = dayIndex.entries[candidateIndex];
			const similarity = calculateWeightedSimilarity(
				normalizedSearchTitle,
				candidateEntry.normalizedTitle,
			);

			if (similarity.score > bestScore) {
				secondBestScore = bestScore;
				bestScore = similarity.score;
				bestTokenOverlap = similarity.tokenOverlap;
				bestNumericTokenOverlap = similarity.numericTokenOverlap;
				bestMatch = candidateEntry.time;
			} else if (similarity.score > secondBestScore) {
				secondBestScore = similarity.score;
			}
		}
	}

	if (bestScore < MIN_MATCH_SCORE) {
		const fallbackMatch = fallbackClosestMatch(dayIndex, searchTitles);

		setBoundedCacheValue(
			closestMatchCache,
			cacheKey,
			fallbackMatch,
			MAX_MATCH_CACHE_ENTRIES,
		);

		return fallbackMatch;
	}

	if (bestScore - secondBestScore < MIN_MATCH_MARGIN) {
		const fallbackMatch = fallbackClosestMatch(dayIndex, searchTitles);

		setBoundedCacheValue(
			closestMatchCache,
			cacheKey,
			fallbackMatch,
			MAX_MATCH_CACHE_ENTRIES,
		);

		return fallbackMatch;
	}

	if (bestNumericTokenOverlap === 0 && bestTokenOverlap < MIN_TOKEN_OVERLAP) {
		const fallbackMatch = fallbackClosestMatch(dayIndex, searchTitles);

		setBoundedCacheValue(
			closestMatchCache,
			cacheKey,
			fallbackMatch,
			MAX_MATCH_CACHE_ENTRIES,
		);

		return fallbackMatch;
	}

	setBoundedCacheValue(
		closestMatchCache,
		cacheKey,
		bestMatch,
		MAX_MATCH_CACHE_ENTRIES,
	);

	return bestMatch;
};

const normalizeTitle = (title: string | null) =>
	(title || "")
		.toLowerCase()
		.replace(/\b(s|season|part|cour)\s*\d+/g, "")
		.replace(/[\W_]+/g, " ")
		.trim();

const findClosestMediaCache = new Map<string, Media | null>();

export const findClosestMedia = (media: Media[], matchFor: string) => {
	if (!matchFor) return null;

	const cached = findClosestMediaCache.get(matchFor);

	if (cached !== undefined) return cached;

	const normalisedMatchFor = normalizeTitle(matchFor);
	const matchForWords = normalisedMatchFor.split(" ");
	let bestFitMedia: Media | null = null;
	let bestDistance = -Infinity;

	for (const m of media) {
		const titles = [m.title.romaji, m.title.english, ...m.synonyms].filter(
			Boolean,
		);

		if (
			titles.some(
				(title) =>
					title.toLowerCase().includes("special") ||
					title.toLowerCase().includes("ova"),
			)
		)
			continue;

		const normalisedTitles = titles.map(normalizeTitle);

		for (const normalisedTitle of normalisedTitles) {
			const distance = stringSimilarity.compareTwoStrings(
				normalisedMatchFor,
				normalisedTitle,
			);

			if (distance <= bestDistance) continue;

			const wordMatch =
				matchForWords.every((word) =>
					normalisedTitles.some((t) => t.includes(word)),
				) || normalisedTitles.some((t) => t.includes(normalisedMatchFor));

			if (wordMatch) {
				bestDistance = distance;
				bestFitMedia = m;

				if (distance === 1) break;
			}
		}

		if (bestDistance === 1) break;
	}

	findClosestMediaCache.set(matchFor, bestFitMedia);

	return bestFitMedia as Media | null;
};

export const clearClosestMediaCache = () => findClosestMediaCache.clear();

const getScheduleIndex = (subsPlease: SubsPlease): ScheduleIndex => {
	const cached = scheduleIndexCache.get(subsPlease);

	if (cached) return cached;

	const built = buildScheduleIndex(subsPlease);

	scheduleIndexCache.set(subsPlease, built);

	return built;
};

const buildInjectAiringTimeCacheKey = (
	anime: Media,
	scheduleVersion: string,
	displayNativeCountdown: boolean,
) =>
	[
		anime.id,
		anime.status,
		anime.mediaListEntry?.status || "",
		anime.mediaListEntry?.progress || 0,
		anime.mediaListEntry?.updatedAt || 0,
		anime.nextAiringEpisode?.episode || 0,
		anime.nextAiringEpisode?.airingAt || 0,
		displayNativeCountdown ? 1 : 0,
		scheduleVersion,
		animeTitleFingerprint(anime),
	].join(":");

const cloneInjectedMedia = (media: Media): Media =>
	({
		...media,
		mediaListEntry: media.mediaListEntry
			? {
					...media.mediaListEntry,
					startedAt: { ...media.mediaListEntry.startedAt },
					completedAt: { ...media.mediaListEntry.completedAt },
					customLists: { ...media.mediaListEntry.customLists },
				}
			: undefined,
		nextAiringEpisode: media.nextAiringEpisode
			? { ...media.nextAiringEpisode }
			: undefined,
	}) as Media;

export const injectAiringTime = (
	anime: Media,
	subsPlease: SubsPlease | null,
) => {
	if (season() !== anime.season) return anime;

	const displayNativeCountdown = get(settings).displayNativeCountdown;
	const scheduleVersion = subsPlease
		? getScheduleIndex(subsPlease).version
		: "native-only";
	const cacheKey = buildInjectAiringTimeCacheKey(
		anime,
		scheduleVersion,
		displayNativeCountdown,
	);
	const cached = injectAiringTimeCache.get(cacheKey);

	if (cached) return cloneInjectedMedia(cached);

	const airingAt = anime.nextAiringEpisode?.airingAt;
	const now = new Date();
	// const nativeUntilAiring = airingAt
	// 	? Math.round((airingAt - Date.now() / 1000) * 100) / 100
	// 	: undefined;
	const nativeTime = new Date(airingAt ? airingAt * 1000 : 0);
	let untilAiring: number | undefined;
	let time = new Date(airingAt ? airingAt * 1000 : 0);
	let nextEpisode = anime.nextAiringEpisode?.episode || 0;

	if (!(displayNativeCountdown || !subsPlease)) {
		const scheduleIndex = getScheduleIndex(subsPlease);

		if ((anime.nextAiringEpisode?.episode || 0) > 1) {
			const foundTime: Time | null = findClosestMatch(scheduleIndex, anime);

			if (foundTime) {
				untilAiring = secondsUntil(
					(foundTime as Time).time,
					(foundTime as Time).day,
				);
				time = new Date(Date.now() + untilAiring * 1000);
			}
		}
	}

	const SEVEN_DAYS = 7 * 24 * 60 * 60 * 1000;

	const nowEpochSeconds = Date.now() / 1000;
	const nativeAheadSeconds =
		nativeTime.getTime() / 1000 - time.getTime() / 1000;

	if (
		nativeAheadSeconds > 0 &&
		nativeAheadSeconds <= MAX_EPISODE_SHIFT_WINDOW_SECONDS &&
		nativeTime.getTime() / 1000 > nowEpochSeconds + STALE_AIRING_GRACE_SECONDS
	) {
		nextEpisode -= 1;
	}

	if (nativeTime.getTime() - now.getTime() > SEVEN_DAYS) {
		const beforeTime = time;

		time = nativeTime;

		time.setHours(beforeTime.getHours());
		time.setMinutes(beforeTime.getMinutes());
	}

	const injected = {
		...anime,
		nextAiringEpisode: {
			episode: nextEpisode,
			airingAt: time.getTime() / 1000,
			nativeAiringAt: nativeTime.getTime() / 1000,
			nativeEpisode: anime.nextAiringEpisode?.episode || 0,
		},
	} as Media;

	const cachedValue = cloneInjectedMedia(injected);

	setBoundedCacheValue(
		injectAiringTimeCache,
		cacheKey,
		cachedValue,
		MAX_INJECT_CACHE_ENTRIES,
	);

	return cloneInjectedMedia(cachedValue);
};

export const clearInjectAiringTimeCache = () => injectAiringTimeCache.clear();