import type {Server, WebSocket} from "ws";
import {inviteWindow, createInviteWindow} from "./window";
/*
 MIT License

 Copyright (c) 2020-2022 Dawid Papiewski "SpacingBat3"

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */
async function wsLog(message: string, ...args: unknown[]) {
    console.log("[WebSocket] " + message, ...args);
}

/** Generates an inclusive range (as `Array`) from `start` to `end`. */
function range(start: number, end: number) {
    return Array.from({length: end - start + 1}, (_v, k) => start + k);
}

interface InviteResponse {
    /** Response type/command. */
    cmd: "INVITE_BROWSER";
    /** Response arguments. */
    args: {
        /** An invitation code. */
        code: string;
    };
    /** Nonce indentifying the communication. */
    nonce: string;
}

function isInviteResponse(data: unknown): data is InviteResponse {
    if (!(data instanceof Object)) return false;
    if ((data as Partial<InviteResponse>)?.cmd !== "INVITE_BROWSER") return false;
    if (typeof (data as Partial<InviteResponse>)?.args?.code !== "string") return false;
    if (typeof (data as Partial<InviteResponse>)?.nonce !== "string") return false;
    return true;
}

const messages = {
    /**
     * A fake, hard-coded Discord command to spoof the presence of
     * official Discord client (which makes browser to actually start a
     * communication with the ArmCord).
     */
    handShake: {
        /** Message command. */
        cmd: "DISPATCH",
        /** Message data. */
        data: {
            /** Message scheme version. */
            v: 1,
            /** Client properties. */
            config: {
                /** Discord CDN host (hard-coded for `dicscord.com` instance). */
                cdn_host: "cdn.discordapp.com",
                /** API endpoint (hard-coded for `dicscord.com` instance). */
                api_endpoint: "//discord.com/api",
                /** Client type. Can be (probably) `production` or `canary`. */
                environment: "production"
            }
        },
        evt: "READY",
        nonce: null
    }
};

/**
 * Tries to reserve the server at given port.
 *
 * @returns `Promise`, which always resolves (either to `Server<WebSocket>` on
 *          success or `null` on failure).
 */
async function getServer(port: number) {
    const {WebSocketServer} = await import("ws");
    return new Promise<Server<WebSocket> | null>((resolve) => {
        const wss = new WebSocketServer({host: "127.0.0.1", port});
        wss.once("listening", () => resolve(wss));
        wss.once("error", () => resolve(null));
    });
}

/**
 * Tries to start a WebSocket server at given port range. If it suceed, it will
 * listen to the browser requests which are meant to be sent to official
 * Discord client.
 *
 * Currently it supports only the invitation link requests.
 *
 */
export default async function startServer() {
    function isJsonSyntaxCorrect(string: string) {
        try {
            JSON.parse(string);
        } catch {
            return false;
        }
        return true;
    }
    /** Known Discord instances, including the official ones. */
    const knownInstancesList = [
        ["Discord", new URL("https://discord.com/app")],
        ["Discord Canary", new URL("https://canary.discord.com/app")],
        ["Discord PTB", new URL("https://ptb.discord.com/app")],
        ["Fosscord", new URL("https://dev.fosscord.com/app")]
    ] as const;

    let wss = null,
        wsPort = 6463;
    for (const port of range(6463, 6472)) {
        wss = await getServer(port);
        if (wss !== null) {
            void wsLog("ArmCord is listening at " + port.toString());
            wsPort = port;
            break;
        }
    }
    if (wss === null) return;
    let lock = false;
    wss.on("connection", (wss, request) => {
        const origin = request.headers.origin ?? "https://discord.com";
        let known = false;
        for (const instance of knownInstancesList) {
            if (instance[1].origin === origin) known = true;
        }
        if (!known) return;
        wss.send(JSON.stringify(messages.handShake));
        wss.once("message", (data, isBinary) => {
            if (lock) return;
            lock = true;
            let parsedData: unknown = data;
            if (!isBinary) parsedData = data.toString();
            if (isJsonSyntaxCorrect(parsedData as string)) parsedData = JSON.parse(parsedData as string);
            if (isInviteResponse(parsedData)) {
                // Replies to browser, so it finds the communication successful.
                wss.send(
                    JSON.stringify({
                        cmd: parsedData.cmd,
                        data: {
                            invite: null,
                            code: parsedData.args.code
                        },
                        evt: null,
                        nonce: parsedData.nonce
                    })
                );
                createInviteWindow();
                const child = inviteWindow;
                if (child === undefined) return;
                void child.loadURL(origin + "/invite/" + parsedData.args.code);
                child.webContents.once("did-finish-load", () => {
                    child.show();
                });
                child.webContents.once("will-navigate", () => {
                    lock = false;
                    child.close();
                });
                child.on("close", (e) => {
                    lock = false;
                });
                // Blocks requests to ArmCord's WS, to prevent loops.
                child.webContents.session.webRequest.onBeforeRequest(
                    {
                        urls: ["ws://127.0.0.1:" + wsPort.toString() + "/*"]
                    },
                    (_details, callback) => callback({cancel: true})
                );
            }
        });
    });
}