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import json from "json-stable-stringify";
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import { EventEmitter } from "events";
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import type { JSONValue } from "@cocalc/util/types";
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import { ConatError } from "@cocalc/conat/core/client";
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import { getLogger } from "@cocalc/conat/client";
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const logger = getLogger("monitor:usage");
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interface Options {
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  resource: string;
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  maxPerUser?: number;
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  max?: number;
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  log?: (...args) => void;
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}
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export class UsageMonitor extends EventEmitter {
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  private options: Options;
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  private total = 0;
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  private perUser: { [user: string]: number } = {};
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  constructor(options: Options) {
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    super();
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    this.options = options;
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    logger.debug("creating usage monitor", this.options);
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    this.initLogging();
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  }
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  stats = () => {
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    return { total: this.total, perUser: this.perUser };
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  };
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  close = () => {
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    this.removeAllListeners();
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    this.perUser = {};
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  };
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  private toJson = (user: JSONValue) => json(user) ?? "";
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  private initLogging = () => {
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    const { log } = this.options;
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    if (log == null) {
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      return;
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    }
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    this.on("total", (total, limit) => {
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      log("usage", this.options.resource, { total, limit });
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    });
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    this.on("add", (user, count, limit) => {
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      log("usage", this.options.resource, "add", { user, count, limit });
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    });
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    this.on("delete", (user, count, limit) => {
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      log("usage", this.options.resource, "delete", { user, count, limit });
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    });
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    this.on("deny", (user, limit, type) => {
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      log("usage", this.options.resource, "not allowed due to hitting limit", {
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        type,
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        user,
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        limit,
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      });
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    });
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  };
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  add = (user: JSONValue) => {
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    const u = this.toJson(user);
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    let count = this.perUser[u] ?? 0;
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    if (this.options.max && this.total >= this.options.max) {
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      this.emit("deny", user, this.options.max, "global");
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      throw new ConatError(
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        `There is a global limit of ${this.options.max} ${this.options.resource}.   Please close browser tabs or files or come back later.`,
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        // http error code "429 Too Many Requests."
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        { code: 429 },
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      );
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    }
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    if (this.options.maxPerUser && count >= this.options.maxPerUser) {
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      this.emit("deny", this.options.maxPerUser, "per-user");
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      throw new ConatError(
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        `There is a per user limit of ${this.options.maxPerUser} ${this.options.resource}.   Please close browser tabs or files or come back later.`,
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        // http error code "429 Too Many Requests."
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        { code: 429 },
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      );
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    }
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    this.total += 1;
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    count++;
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    this.perUser[u] = count;
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    this.emit("total", this.total, this.options.max);
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    this.emit("add", user, count, this.options.maxPerUser);
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  };
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  delete = (user: JSONValue) => {
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    this.total -= 1;
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    const u = this.toJson(user);
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    let count = (this.perUser[u] ?? 0) - 1;
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    if (count <= 0) {
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      delete this.perUser[u];
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    } else {
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      this.perUser[u] = count;
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    }
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    this.emit("total", this.total);
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    this.emit("delete", user, count);
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  };
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}
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