lab-report

#!/usr/bin/env node

const path = require("path");
const {
  promises: { readdir, readFile },
} = require("fs");

const noFormat = process.env.NO_FORMAT;
const noColor = process.env.NO_COLOR;

const padValue = (key, value = key) => {
  if (noFormat) {
    return value;
  }

  const widths = {
    TBT: "99,999 ms".length,
    CLS: "0.999".length,
    Timestamp: "2021-03-19 21:48:49".length,
    score: "Score".length,
    "total-blocking-time": "99,999 ms".length,
    default: "99.9 s".length,
  };
  const width = widths[key] || widths.default;

  const isHeading = key === value;
  return isHeading ? value.padEnd(width, " ") : value.padStart(width, " ");
};

const formatMetric = ({ id, score, displayValue, numericValue }) => {
  const colorReset = () => (noColor ? "" : "\x1b[0m");

  const scoreColor = (score) => {
    if (noColor) {
      return "";
    }
    if (score < 0.5) {
      return "\x1b[31m"; // red
    }
    if (score < 0.9) {
      return "\x1b[33m"; // yellow
    }
    return "\x1b[32m"; // green
  };

  const metricValue = noFormat ? numericValue : padValue(id, displayValue);

  return `${scoreColor(score)}${metricValue}${colorReset()}`;
};

const formatTimeStamp = (isoDateString) =>
  noFormat
    ? isoDateString
    : isoDateString.replace("T", " ").replace(/\..*/, "");

const formatNameOrPath = ({
  name,
  requestedUrl,
  requestedOrigin,
  requestedPath,
  finalUrl,
  finalOrigin,
  finalPath,
}) => {
  const requestedNameOrPath = name ? name : requestedPath;
  if (requestedUrl === finalUrl) {
    return requestedNameOrPath;
  } else {
    if (requestedOrigin === finalOrigin) {
      return `${requestedNameOrPath} -> ${finalPath}`;
    } else {
      return `${requestedNameOrPath} -> ${finalUrl}`;
    }
  }
};

async function* getFiles(dir) {
  const dirents = await readdir(path.resolve(__dirname, dir), {
    withFileTypes: true,
  });
  for (const dirent of dirents) {
    const res = path.join(dir, dirent.name);
    if (dirent.isDirectory()) {
      yield* getFiles(res);
    } else {
      yield res;
    }
  }
}

const origin = (url) => new URL(url).origin;

const stripOrigin = (url) => url.replace(origin(url), "");

const getPaths = ({ requestedUrl, finalUrl }) => ({
  requestedOrigin: origin(requestedUrl),
  requestedPath: stripOrigin(requestedUrl),
  finalOrigin: origin(requestedUrl),
  finalPath: stripOrigin(finalUrl),
});

const AUDITS = {
  FCP: "first-contentful-paint",
  LCP: "largest-contentful-paint",
  CLS: "cumulative-layout-shift",
  TBT: "total-blocking-time",
};

const HEADINGS = ["Timestamp", ...Object.keys(AUDITS), "Score", "URL"];

const getScoreAsMetric = ({ categories: { performance } }) => ({
  id: "score",
  score: performance.score,
  displayValue: Math.floor(performance.score * 100).toString(),
  numericValue: Math.floor(performance.score * 100),
});

(async () => {
  const [, , snapshotsPath = "", filter] = process.argv;

  console.log(HEADINGS.map((key) => padValue(key)).join("\t"));

  for await (const resultPath of getFiles(snapshotsPath)) {
    if (!resultPath.endsWith(".json")) {
      continue;
    }

    try {
      const absoluteResultPath = path.resolve(__dirname, resultPath);
      const psiResult = JSON.parse(await readFile(absoluteResultPath, "utf-8"));
      const { name, error, lighthouseResult } = psiResult;

      if (error) {
        console.error(`${resultPath}:`, error.code || error.message);
        continue;
      }

      const paths = getPaths(lighthouseResult);

      if (
        filter &&
        filter !== name &&
        filter !== lighthouseResult.requestedUrl &&
        filter !== paths.requestedPath
      ) {
        continue;
      }

      const audits = Object.values(AUDITS).map(
        (key) => lighthouseResult.audits[key]
      );
      const score = getScoreAsMetric(lighthouseResult);
      const timeStamp = psiResult.analysisUTCTimestamp;

      console.log(
        [
          formatTimeStamp(timeStamp),
          ...[...audits, score].map(formatMetric),
          formatNameOrPath({ name, ...lighthouseResult, ...paths }),
        ].join("\t")
      );
    } catch (e) {
      console.error(`${resultPath}:`, e.message);
      continue;
    }
  }
})();