rewrite ratelimiting and api route builder (#1667)

* rewrite ratelimiting and api route builder

* more stuff

* let people pass their own handlers

* Update burst.js

* Update RequestHandler.js

* Update burst.js

* Update sequential.js

* Update RequestHandler.js

src/client/rest/RequestHandlers/Sequential.js

@@ -1,98 +0,0 @@
-const RequestHandler = require('./RequestHandler');
-const DiscordAPIError = require('../DiscordAPIError');
-
-/**
- * Handles API Requests sequentially, i.e. we wait until the current request is finished before moving onto
- * the next. This plays a _lot_ nicer in terms of avoiding 429's when there is more than one session of the account,
- * but it can be slower.
- * @extends {RequestHandler}
- * @private
- */
-class SequentialRequestHandler extends RequestHandler {
-  /**
-   * @param {RESTManager} restManager The REST manager to use
-   * @param {string} endpoint The endpoint to handle
-   */
-  constructor(restManager, endpoint) {
-    super(restManager, endpoint);
-
-    /**
-     * The endpoint that this handler is handling
-     * @type {string}
-     */
-    this.endpoint = endpoint;
-
-    /**
-     * The time difference between Discord's Dates and the local computer's Dates. A positive number means the local
-     * computer's time is ahead of Discord's
-     * @type {number}
-     */
-    this.timeDifference = 0;
-
-    /**
-     * Whether the queue is being processed or not
-     * @type {boolean}
-     */
-    this.busy = false;
-  }
-
-  push(request) {
-    super.push(request);
-    this.handle();
-  }
-
-  /**
-   * Performs a request then resolves a promise to indicate its readiness for a new request.
-   * @param {APIRequest} item The item to execute
-   * @returns {Promise<?Object|Error>}
-   */
-  execute(item) {
-    this.busy = true;
-    return new Promise(resolve => {
-      item.request.gen().end((err, res) => {
-        if (res && res.headers) {
-          this.requestLimit = Number(res.headers['x-ratelimit-limit']);
-          this.requestResetTime = Number(res.headers['x-ratelimit-reset']) * 1000;
-          this.requestRemaining = Number(res.headers['x-ratelimit-remaining']);
-          this.timeDifference = Date.now() - new Date(res.headers.date).getTime();
-        }
-        if (err) {
-          if (err.status === 429) {
-            this.queue.unshift(item);
-            this.restManager.client.setTimeout(() => {
-              this.globalLimit = false;
-              resolve();
-            }, Number(res.headers['retry-after']) + this.restManager.client.options.restTimeOffset);
-            if (res.headers['x-ratelimit-global']) this.globalLimit = true;
-          } else {
-            item.reject(err.status >= 400 && err.status < 500 ? new DiscordAPIError(res.request.path, res.body) : err);
-            resolve(err);
-          }
-        } else {
-          this.globalLimit = false;
-          const data = res && res.body ? res.body : {};
-          item.resolve(data);
-          if (this.requestRemaining === 0) {
-            this.restManager.client.setTimeout(
-              () => resolve(data),
-              this.requestResetTime - Date.now() + this.timeDifference + this.restManager.client.options.restTimeOffset
-            );
-          } else {
-            resolve(data);
-          }
-        }
-      });
-    });
-  }
-
-  handle() {
-    super.handle();
-    if (this.busy || this.remaining === 0 || this.queue.length === 0 || this.globalLimit) return;
-    this.execute(this.queue.shift()).then(() => {
-      this.busy = false;
-      this.handle();
-    });
-  }
-}
-
-module.exports = SequentialRequestHandler;