discourse/app/assets/javascripts/admin/components/admin-backups-logs.js.es6

import debounce from "discourse/lib/debounce";
import { renderSpinner } from "discourse/helpers/loading-spinner";
import { escapeExpression } from "discourse/lib/utilities";
import { bufferedRender } from "discourse-common/lib/buffered-render";

export default Ember.Component.extend(
  bufferedRender({
    classNames: ["admin-backups-logs"],

    init() {
      this._super();
      this._reset();
    },

    _reset() {
      this.setProperties({ formattedLogs: "", index: 0 });
    },

    _scrollDown() {
      const $div = this.$()[0];
      $div.scrollTop = $div.scrollHeight;
    },

    _updateFormattedLogs: debounce(function() {
      const logs = this.get("logs");
      if (logs.length === 0) {
        this._reset(); // reset the cached logs whenever the model is reset
      } else {
        // do the log formatting only once for HELLish performance
        let formattedLogs = this.get("formattedLogs");
        for (let i = this.get("index"), length = logs.length; i < length; i++) {
          const date = logs[i].get("timestamp"),
            message = escapeExpression(logs[i].get("message"));
          formattedLogs += "[" + date + "] " + message + "\n";
        }
        // update the formatted logs & cache index
        this.setProperties({
          formattedLogs: formattedLogs,
          index: logs.length
        });
        // force rerender
        this.rerenderBuffer();
      }
      Ember.run.scheduleOnce("afterRender", this, this._scrollDown);
    }, 150)
      .observes("logs.[]")
      .on("init"),

    buildBuffer(buffer) {
      const formattedLogs = this.get("formattedLogs");
      if (formattedLogs && formattedLogs.length > 0) {
        buffer.push("<pre>");
        buffer.push(formattedLogs);
        buffer.push("</pre>");
      } else {
        buffer.push("<p>" + I18n.t("admin.backups.logs.none") + "</p>");
      }
      // add a loading indicator
      if (this.get("status.isOperationRunning")) {
        buffer.push(renderSpinner("small"));
      }
    }
  })
);