discordeno/module/requestManager.ts

import { RequestMethod } from "../types/fetch.ts";
import { authorization } from "./client.ts";
import { sleep } from "../utils/utils.ts";

const ratelimitedPaths = new Map<string, RateLimitedPath>();

export interface RateLimitedPath {
  url: string;
  resetTimestamp: number;
}

setInterval(() => {
  const now = Date.now();
  ratelimitedPaths.forEach((value, key) => {
    if (value.resetTimestamp > now) return;
    ratelimitedPaths.delete(key);
  });
}, 1000);

export const RequestManager = {
  // Something off about using runMethod with get breaks when using fetch
  get: async (url: string, body?: unknown) => {
    await checkRatelimits(url);

    const result = await fetch(url, createRequestBody(body));
    processHeaders(url, result.headers);

    return result.json();
  },
  post: (url: string, body?: unknown) => {
    return runMethod(RequestMethod.Post, url, body);
  },
  delete: (url: string, body?: unknown) => {
    return runMethod(RequestMethod.Delete, url, body);
  },
  patch: (url: string, body?: unknown) => {
    return runMethod(RequestMethod.Patch, url, body);
  },
  put: (url: string, body?: unknown) => {
    return runMethod(RequestMethod.Put, url, body);
  },
};

const createRequestBody = (body: any, method?: RequestMethod) => {
  return {
    headers: {
      Authorization: authorization,
      "User-Agent":
        `DiscordBot (https://github.com/skillz4killz/discordeno, 0.0.1)`,
      "Content-Type": "application/json",
      "X-Audit-Log-Reason": body ? encodeURIComponent(body.reason) : "",
    },
    body: JSON.stringify(body),
    method: method?.toUpperCase(),
  };
};

const runMethod = async (
  method: RequestMethod,
  url: string,
  body?: unknown,
) => {
  await checkRatelimits(url);
  const response = await fetch(url, createRequestBody(body, method));
  processHeaders(url, response.headers);

  // Sometimes Discord returns an empty 204 response that can't be made to JSON.
  if (response.status === 204) return;

  return await response.json();
};

const checkRatelimits = async (url: string) => {
  const ratelimited = ratelimitedPaths.get(url);
  const global = ratelimitedPaths.get("global");

  const now = Date.now();
  if (ratelimited && now < ratelimited.resetTimestamp) {
    await sleep(now - ratelimited.resetTimestamp);
  }
  if (global && now < global.resetTimestamp) {
    await sleep(now - global.resetTimestamp);
  }
};

const processHeaders = (url: string, headers: Headers) => {
  // If a rate limit response is encountered this will become true and returned
  let ratelimited = false;

  // Get all useful headers
  const remaining = headers.get("x-ratelimit-remaining");
  const resetTimestamp = headers.get("x-ratelimit-reset");
  const retryAfter = headers.get("retry-after");
  const global = headers.get("x-ratelimit-global");

  // If there is no remaining rate limit for this endpoint, we save it in cache
  if (remaining && remaining === "0") {
    ratelimited = true;

    ratelimitedPaths.set(url, {
      url,
      resetTimestamp: Number(resetTimestamp),
    });
  }

  // If there is no remaining global limit, we save it in cache
  if (global) {
    ratelimited = true;

    ratelimitedPaths.set("global", {
      url: "global",
      resetTimestamp: Date.now() + Number(retryAfter),
    });
  }

  // Returns a boolean to check if we need to request again once the rate limit resets
  return ratelimited;
};