#!/usr/bin/env -S deno run --allow-env --allow-net

import { Mutex } from "https://deno.land/x/async@v2.1.0/mutex.ts";

// Reference:
// * https://docs.deno.com/runtime/reference/env_variables/
// * https://docs.deno.com/runtime/fundamentals/http_server/

const TOKEN = Deno.env.get("TOKEN");
const listen = {
    port: Deno.env.get("LISTEN_PORT") || 3000,
    hostname: Deno.env.get("LISTEN_HOSTNAME") || "127.0.0.1",
};
const startTime = new Date().getTime();

// IP: Add time
const globalIpAddressMap = {};
const globalIpAddressMapMutex = new Mutex();

async function addIpAddress(ip: string): Promise<void> {
    await globalIpAddressMapMutex.acquire();
    try {
        globalIpAddressMap[ip] = new Date().getTime();
    } finally {
        globalIpAddressMapMutex.release();
    }
}

async function cleanAndGetIpAddresses(): Promise<Array<string>> {
    await globalIpAddressMapMutex.acquire();
    try {
        const currentTimeMillis = new Date().getTime();
        const invalidKeys = [];
        const validKeys = [];
        for (let k in globalIpAddressMap) {
            const t = globalIpAddressMap[k];
            if ((currentTimeMillis - t) > 60 * 60 * 1000) {
                invalidKeys.push(k);
            } else {
                validKeys.push(k);
            }
        }
        for (let i = 0; i < invalidKeys.length; i++) {
            delete globalIpAddressMap[invalidKeys[i]];
        }
        return validKeys;
    } finally {
        globalIpAddressMapMutex.release();
    }
}

const globalFilters: any[] = [];
const globalHandlerMap = {};

type RequestHandler = (url: URL, req: any) => Promise<Response>;

function registerFilter(handler: RequestHandler) {
    globalFilters.push(handler);
}

function registerHandler(
    method: string,
    path: string,
    handler: RequestHandler,
) {
    const requestIdent = `${method}::${path}`;
    if (globalHandlerMap[requestIdent] != null) {
        throw `Handler for ${method} ${path} exists.`;
    }
    globalHandlerMap[requestIdent] = handler;
}

function buildJsonResponse(status: number, body: any): Response {
    return new Response(JSON.stringify(body, null, "    "), {
        status: status,
        headers: {
            "content-type": "application/json; charset=utf-8",
        },
    });
}

function buildOkJsonResponse(body: any): Response {
    return buildJsonResponse(200, body);
}

function notFoundHandler(url: URL, req: any): Response {
    return buildJsonResponse(404, {
        "error": "not_found",
        "message": "Resource not found.",
    });
}

registerFilter(async (url: URL, req: any) => {
    if (url.pathname == "/version") {
        return null;
    }
    if (TOKEN == null) {
        return buildJsonResponse(500, {
            "error": "bad_token",
            "message": "Bad token.",
        });
    }
    const token = url.searchParams.get("__token");
    if (TOKEN !== token) {
        return buildJsonResponse(401, {
            "error": "invalid_token",
            "message": "Invalid token.",
        });
    }
    return null;
});

function formatHumanTime(time: number): string {
    const t = [];
    const leftMs = time % 1000;
    if (leftMs > 0) {
        t.push(`${leftMs}ms`);
    }
    const secs = Math.floor(time / 1000);
    const leftSecs = secs % 60;
    if (leftSecs > 0) {
        t.push(`${leftSecs}s`);
    }
    const mins = Math.floor(secs / 60);
    const leftMins = mins % 60;
    if (leftMins > 0) {
        t.push(`${leftMins}min`);
    }
    const hours = Math.floor(mins / 60);
    const leftHours = hours % 24;
    if (leftHours > 0) {
        t.push(`${leftHours}hour`);
    }
    const days = Math.floor(hours / 24);
    if (days > 0) {
        t.push(`${days}day`);
    }
    return t.reverse().join(" ");
}

registerHandler("GET", "/version", async (url, req) => {
    return buildOkJsonResponse({
        "version": "0.0.1",
        "uptime": formatHumanTime(new Date().getTime() - startTime),
    });
});

interface AddIpAddressRequest {
    ip: string;
}

registerHandler("POST", "/ip_addresses", async (url, req) => {
    let addIpAddressRequest: AddIpAddressRequest;
    try {
        addIpAddressRequest = await req.json();
    } catch (e) {
        return buildJsonResponse(400, {
            "error": "bad_request",
            "message": "Bad request.",
        });
    }
    await addIpAddress(addIpAddressRequest.ip);
    return buildOkJsonResponse({});
});

registerHandler("GET", "/ip_addresses", async (url, req) => {
    const ipAddresses = await cleanAndGetIpAddresses();
    return buildOkJsonResponse({
        ipAddresses: ipAddresses,
    });
});

registerHandler("*", "/check_ip_address", async (url, req) => {
    const clientIp = req.headers.get("x-real-ip");
    if (clientIp == null) {
        return buildJsonResponse(400, {
            "error": "bad_request",
            "message": "Bad request: no client IP",
        });
    }
    const ipAddresses = await cleanAndGetIpAddresses();
    if (ipAddresses.indexOf(clientIp) >= 0) {
        return buildOkJsonResponse({});
    }
    return buildJsonResponse(401, {
        "error": "access_denied",
        "message": "Access denied: not allowed IP",
    });
});

Deno.serve(listen, async (req) => {
    const url = new URL(req.url);
    for (let i = 0; i < globalFilters.length; i++) {
        const response = await globalFilters[i](url, req);
        if (response != null) {
            return response;
        }
    }
    console.log("Handler request:", req.method, url.pathname);
    const req1 = `${req.method}::${url.pathname}`;
    const req2 = `*::${url.pathname}`;
    const req_handler = globalHandlerMap[req1] || globalHandlerMap[req2] ||
        notFoundHandler;
    return await req_handler(url, req);
});

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