import { Inject, Injectable, NotFoundException } from "@nestjs/common";
import {
	ScheduleParser,
	ScheduleParseResult,
} from "./internal/schedule-parser/schedule-parser";
import { BasicXlsDownloader } from "./internal/xls-downloader/basic-xls-downloader";
import { XlsDownloaderCacheMode } from "./internal/xls-downloader/xls-downloader.base";
import {
	CacheStatusDto,
	GroupDto,
	GroupScheduleDto,
	ScheduleDto,
	ScheduleGroupsDto,
	SiteMainPageDto,
} from "../dto/schedule.dto";
import { Cache, CACHE_MANAGER } from "@nestjs/cache-manager";
import { instanceToPlain } from "class-transformer";
import { cacheGetOrFill } from "../utility/cache.util";
import * as crypto from "crypto";
import { ScheduleReplacerService } from "../schedule-replacer/schedule-replacer.service";

@Injectable()
export class ScheduleService {
	private readonly scheduleParser = new ScheduleParser(
		new BasicXlsDownloader(
			"https://politehnikum-eng.ru/index/raspisanie_zanjatij/0-409",
			XlsDownloaderCacheMode.SOFT,
		),
	);

	private cacheUpdatedAt: Date = new Date(0);
	private cacheHash: string = "0000000000000000000000000000000000000000";

	private lastChangedDays: Array<Array<number>> = [];
	private scheduleUpdatedAt: Date = new Date(0);

	constructor(
		@Inject(CACHE_MANAGER) private readonly cacheManager: Cache,
		private readonly scheduleReplacerService: ScheduleReplacerService,
	) {
		const xlsDownloader = this.scheduleParser.getXlsDownloader();

		if (xlsDownloader instanceof BasicXlsDownloader) {
			xlsDownloader.setScheduleReplacerService(
				this.scheduleReplacerService,
			);
		}
	}

	getCacheStatus(): CacheStatusDto {
		return {
			cacheHash: this.cacheHash,
			cacheUpdateRequired:
				(Date.now() - this.cacheUpdatedAt.valueOf()) / 1000 / 60 >= 5,
			lastCacheUpdate: this.cacheUpdatedAt.valueOf(),
			lastScheduleUpdate: this.scheduleUpdatedAt.valueOf(),
		};
	}

	async getSourceSchedule(): Promise<ScheduleParseResult> {
		return cacheGetOrFill(this.cacheManager, "sourceSchedule", async () => {
			const schedule = await this.scheduleParser.getSchedule();
			schedule.groups = ScheduleService.toObject(
				schedule.groups,
			) as Array<GroupDto>;

			this.cacheUpdatedAt = new Date();

			const oldHash = this.cacheHash;
			this.cacheHash = crypto
				.createHash("sha1")
				.update(
					JSON.stringify(schedule.groups, null, 0) + schedule.etag,
				)
				.digest("hex");

			if (
				this.scheduleUpdatedAt.valueOf() === 0 ||
				this.cacheHash !== oldHash
			)
				this.scheduleUpdatedAt = new Date();

			return schedule;
		});
	}

	private static toObject<T>(array: Array<T>): object {
		const object = {};

		for (const item in array) object[item] = array[item];

		return object;
	}

	async getSchedule(): Promise<ScheduleDto> {
		return cacheGetOrFill(
			this.cacheManager,
			"schedule",
			async (): Promise<ScheduleDto> => {
				const sourceSchedule = await this.getSourceSchedule();

				for (const groupName in sourceSchedule.affectedDays) {
					const affectedDays = sourceSchedule.affectedDays[groupName];

					if (affectedDays?.length !== 0)
						this.lastChangedDays[groupName] = affectedDays;
				}

				return {
					updatedAt: this.cacheUpdatedAt,
					groups: ScheduleService.toObject(sourceSchedule.groups),
					lastChangedDays: this.lastChangedDays,
				};
			},
		);
	}

	async getGroup(group: string): Promise<GroupScheduleDto> {
		const schedule = await this.getSourceSchedule();

		if ((schedule.groups as object)[group] === undefined) {
			throw new NotFoundException(
				"Группы с таким названием не существует!",
			);
		}

		return {
			updatedAt: this.cacheUpdatedAt,
			group: schedule.groups[group],
			lastChangedDays: this.lastChangedDays[group] ?? [],
		};
	}

	async getGroupNames(): Promise<ScheduleGroupsDto> {
		let groupNames: ScheduleGroupsDto | undefined =
			await this.cacheManager.get("groupNames");

		if (!groupNames) {
			const schedule = await this.getSourceSchedule();
			const names: Array<string> = [];

			for (const groupName in schedule.groups) names.push(groupName);

			groupNames = { names };
			await this.cacheManager.set(
				"groupNames",
				instanceToPlain(groupNames),
				24 * 60 * 60 * 1000,
			);
		}

		return groupNames;
	}

	async updateSiteMainPage(
		siteMainPageDto: SiteMainPageDto,
	): Promise<CacheStatusDto> {
		await this.scheduleParser
			.getXlsDownloader()
			.setPreparedData(siteMainPageDto.mainPage);
		await this.refreshCache();

		return this.getCacheStatus();
	}

	async refreshCache() {
		await this.cacheManager.reset();
		await this.getSourceSchedule();
	}
}