influxLineProtocolFormatter.ts

import debug from "debug";

import type { Sensor } from "./types";

let dbg = debug("sauter:LineProtocol");
// Log to stdout instead of stderr by default
dbg.log = console.log.bind(console);

// Escape special chars depending on the field (see https://is.gd/wdaALB)
const escape = {
  mesurement: (s: string) => s.replace(/[,\s]/g, "\\$&"),
  tagKeyOrValue: (s: string) => s.replace(/[,=\s]/g, "\\$&"),
  fieldKey: (s: string) => s.replace(/[,=\s]/g, "\\$&"),
  fieldValue: (s: string) => s.replace(/["\\]/g, "\\$&"),
};

// Formatter helper for the Line Protocol used by InfluxDB as data point input format
// (reference: https://is.gd/B4LclV)
export default class LineProtocol {
  private mesurement: string;

  constructor(mesurement: string) {
    this.mesurement = escape.mesurement(mesurement);
  }

  // Format a sensor object into a line protocol string
  format({ id, code, category, unit, name, longName, value }: Sensor): string {
    if (value === undefined) throw new Error("value cannot be undefined!");

    // Escape all fields based on their role in the line protocol string
    code = escape.tagKeyOrValue(code);
    category = escape.tagKeyOrValue(category);
    let sensor_id: string = escape.tagKeyOrValue(id.toString());

    if (typeof value === "string") value = `"${value}"`;
    value = escape.fieldValue(value.toString());

    let unitField = "";
    // Create a unit field if it exists
    if (unit !== undefined) unitField = `,unit=${escape.tagKeyOrValue(unit)}`;

    return (
      `${this.mesurement},sensor_id=${sensor_id},sensor_code=${code},category=${category}${unitField}` +
      ` value=${value} ${Date.now()}`
    );
  }
}

// sauter,sensor_id=1107,sensor_code=SM01-MTE01.M01_SS09-HPE,category=EXTRACTEUR\ HFO,unit=°C value=22.5 1722357994543