/*
 * SPDX-FileCopyrightText: syuilo and misskey-project
 * SPDX-License-Identifier: AGPL-3.0-only
 */

import { Inject, Injectable } from '@nestjs/common';
import RE2 from 're2';
import { summaly } from '@misskey-dev/summaly';
import { SummalyResult } from '@misskey-dev/summaly/built/summary.js';
import { DI } from '@/di-symbols.js';
import type { Config } from '@/config.js';
import { MetaService } from '@/core/MetaService.js';
import { HttpRequestService } from '@/core/HttpRequestService.js';
import type Logger from '@/logger.js';
import { query } from '@/misc/prelude/url.js';
import { LoggerService } from '@/core/LoggerService.js';
import { bindThis } from '@/decorators.js';
import { ApiError } from '@/server/api/error.js';
import { MiMeta } from '@/models/Meta.js';
import type { FastifyRequest, FastifyReply } from 'fastify';

@Injectable()
export class UrlPreviewService {
	private logger: Logger;

	constructor(
		@Inject(DI.config)
		private config: Config,

		private metaService: MetaService,
		private httpRequestService: HttpRequestService,
		private loggerService: LoggerService,
	) {
		this.logger = this.loggerService.getLogger('url-preview');
	}

	@bindThis
	private wrap(url?: string | null): string | null {
		return url != null
			? url.match(/^https?:\/\//)
				? `${this.config.mediaProxy}/preview.webp?${query({
					url,
					preview: '1',
				})}`
				: url
			: null;
	}

	@bindThis
	public async handle(
		request: FastifyRequest<{ Querystring: { url: string; lang?: string; } }>,
		reply: FastifyReply,
	): Promise<object | undefined> {
		const url = request.query.url;
		if (typeof url !== 'string') {
			reply.code(400);
			return;
		}

		const lang = request.query.lang;
		if (Array.isArray(lang)) {
			reply.code(400);
			return;
		}

		const meta = await this.metaService.fetch();

		if (!meta.urlPreviewEnabled) {
			reply.code(403);
			return {
				error: new ApiError({
					message: 'URL preview is disabled',
					code: 'URL_PREVIEW_DISABLED',
					id: '58b36e13-d2f5-0323-b0c6-76aa9dabefb8',
				}),
			};
		}

		this.logger.info(meta.urlPreviewSummaryProxyUrl
			? `(Proxy) Getting preview of ${url}@${lang} ...`
			: `Getting preview of ${url}@${lang} ...`);

		try {
			const summary = meta.urlPreviewSummaryProxyUrl
				? await this.fetchSummaryFromProxy(url, meta, lang)
				: await this.fetchSummary(url, meta, lang);

			this.logger.succ(`Got preview of ${url}: ${summary.title}`);

			if (!(summary.url.startsWith('http://') || summary.url.startsWith('https://'))) {
				throw new Error('unsupported schema included');
			}

			if (summary.player.url && !(summary.player.url.startsWith('http://') || summary.player.url.startsWith('https://'))) {
				throw new Error('unsupported schema included');
			}

			summary.icon = this.wrap(summary.icon);
			summary.thumbnail = this.wrap(summary.thumbnail);

			const includeDenyList = meta.urlPreviewDenyList.some(filter => {
				// represents RegExp
				const regexp = /^\/(.+)\/(.*)$/.exec(filter);
				// This should never happen due to input sanitisation.
				if (!regexp) {
					const words = filter.split(' ');
					return words.every(keyword => summary.url.includes(keyword));
				}
				try {
					return new RE2(regexp[1], regexp[2]).test(summary.url);
				} catch (err) {
					// This should never happen due to input sanitisation.
					return false;
				}
			});
			if (includeDenyList) summary.sensitive = true;

			// Cache 7days
			reply.header('Cache-Control', 'max-age=604800, immutable');

			return summary;
		} catch (err) {
			this.logger.warn(`Failed to get preview of ${url}: ${err}`);

			reply.code(422);
			reply.header('Cache-Control', 'max-age=86400, immutable');
			return {
				error: new ApiError({
					message: 'Failed to get preview',
					code: 'URL_PREVIEW_FAILED',
					id: '09d01cb5-53b9-4856-82e5-38a50c290a3b',
				}),
			};
		}
	}

	private fetchSummary(url: string, meta: MiMeta, lang?: string): Promise<SummalyResult> {
		const agent = this.config.proxy
			? {
				http: this.httpRequestService.httpAgent,
				https: this.httpRequestService.httpsAgent,
			}
			: undefined;

		return summaly(url, {
			followRedirects: false,
			lang: lang ?? 'ja-JP',
			agent: agent,
			userAgent: meta.urlPreviewUserAgent ?? undefined,
			operationTimeout: meta.urlPreviewTimeout,
			contentLengthLimit: meta.urlPreviewMaximumContentLength,
			contentLengthRequired: meta.urlPreviewRequireContentLength,
		});
	}

	private fetchSummaryFromProxy(url: string, meta: MiMeta, lang?: string): Promise<SummalyResult> {
		const proxy = meta.urlPreviewSummaryProxyUrl!;
		const queryStr = query({
			url: url,
			lang: lang ?? 'ja-JP',
			userAgent: meta.urlPreviewUserAgent ?? undefined,
			operationTimeout: meta.urlPreviewTimeout,
			contentLengthLimit: meta.urlPreviewMaximumContentLength,
			contentLengthRequired: meta.urlPreviewRequireContentLength,
		});

		return this.httpRequestService.getJson<SummalyResult>(`${proxy}?${queryStr}`);
	}
}
