/*
        Spacebar: A FOSS re-implementation and extension of the Discord.com backend.
        Copyright (C) 2023 Spacebar and Spacebar Contributors

        This program is free software: you can redistribute it and/or modify
        it under the terms of the GNU Affero General Public License as published
        by the Free Software Foundation, either version 3 of the License, or
        (at your option) any later version.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU Affero General Public License for more details.

        You should have received a copy of the GNU Affero General Public License
        along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

import { Config, JimpType } from "@spacebar/util";
import { Request, Response } from "express";
import { yellow } from "picocolors";
import crypto from "crypto";

let sharp: undefined | false | { default: typeof import("sharp") } = undefined;

let Jimp: JimpType | undefined = undefined;
try {
    Jimp = require("jimp") as JimpType;
} catch {
    // empty
}

let sentImageProxyWarning = false;

const sharpSupported = new Set(["image/jpeg", "image/png", "image/bmp", "image/tiff", "image/gif", "image/webp", "image/avif", "image/svg+xml"]);
const jimpSupported = new Set(["image/jpeg", "image/png", "image/bmp", "image/tiff", "image/gif"]);
const resizeSupported = new Set([...sharpSupported, ...jimpSupported]);

export async function ImageProxy(req: Request, res: Response) {
    const path = req.originalUrl.split("/").slice(2);

    // src/api/util/utility/EmbedHandlers.ts getProxyUrl
    const hash = crypto.createHmac("sha1", Config.get().security.requestSignature).update(path.slice(1).join("/")).digest("base64").replace(/\+/g, "-").replace(/\//g, "_");

    try {
        if (!crypto.timingSafeEqual(Buffer.from(hash), Buffer.from(path[0]))) throw new Error("Invalid signature");
    } catch {
        console.log("[ImageProxy] Invalid signature, expected " + hash + " but got " + path[0]);
        res.status(403).send("Invalid signature");
        return;
    }

    const abort = new AbortController();
    setTimeout(() => abort.abort(), 5000);

    const request = await fetch("https://" + path.slice(2).join("/"), {
        headers: {
            "User-Agent": "SpacebarImageProxy/1.0.0 (https://spacebar.chat)",
        },
        signal: abort.signal,
    }).catch((e) => {
        if (e.name === "AbortError") res.status(504).send("Request timed out");
        else res.status(500).send("Unable to proxy origin: " + e.message);
    });
    if (!request) return;

    if (request.status !== 200) {
        res.status(request.status).send("Origin failed to respond: " + request.status + " " + request.statusText);
        return;
    }

    if (!request.headers.get("Content-Type") || !request.headers.get("Content-Length")) {
        res.status(500).send("Origin did not provide a Content-Type or Content-Length header");
        return;
    }

    // @ts-expect-error TS doesn't believe that the header cannot be null (it's checked for falsiness above)
    if (parseInt(request.headers.get("Content-Length")) > 1024 * 1024 * 10) {
        res.status(500).send("Origin provided a Content-Length header that is too large");
        return;
    }

    // @ts-expect-error TS doesn't believe that the header cannot be null (it's checked for falsiness above)
    let contentType: string = request.headers.get("Content-Type");

    const arrayBuffer = await request.arrayBuffer();
    let resultBuffer = Buffer.from(arrayBuffer);

    if (!sentImageProxyWarning && resizeSupported.has(contentType) && /^\d+x\d+$/.test(path[1])) {
        if (sharp !== false) {
            try {
                sharp = await import("sharp");
            } catch {
                sharp = false;
            }
        }

        if (sharp === false && !Jimp) {
            try {
                // eslint-disable-next-line @typescript-eslint/ban-ts-comment
                // @ts-ignore Typings don't fit
                Jimp = await import("jimp");
            } catch {
                sentImageProxyWarning = true;
                console.log(`[ImageProxy] ${yellow('Neither "sharp" or "jimp" NPM packages are installed, image resizing will be disabled')}`);
            }
        }

        const [width, height] = path[1].split("x").map((x) => parseInt(x));

        const buffer = Buffer.from(arrayBuffer);
        if (sharp && sharpSupported.has(contentType)) {
            resultBuffer = Buffer.from(
                await sharp
                    .default(buffer)
                    // Sharp doesn't support "scaleToFit"
                    .resize(width)
                    .toBuffer(),
            );
        } else if (Jimp && jimpSupported.has(contentType)) {
            resultBuffer = await Jimp.read(buffer).then((image) => {
                contentType = image.getMIME();
                return (
                    image
                        .scaleToFit(width, height)
                        // @ts-expect-error Jimp is defined at this point
                        .getBufferAsync(Jimp.AUTO)
                );
            });
        }
    }

    res.header("Content-Type", contentType);
    res.setHeader("Cache-Control", "public, max-age=" + Config.get().cdn.proxyCacheHeaderSeconds);

    res.send(resultBuffer);
}
