shim.js

/* Static-deployment shim.
 *
 * Hugging Face static Spaces serve files, not Python, so the page has no
 * backend. This intercepts the app's own API routes and answers them in the
 * browser: NAB is fetched straight from the upstream GitHub raw endpoint
 * (which sends `access-control-allow-origin: *`) and every detector and metric
 * is recomputed locally by web/outliar.js — the same code the Python↔Node
 * parity test pins to the NumPy implementation.
 *
 * Two detectors do not survive the trip and the page says so rather than
 * quietly serving different numbers: `iforest` needs scikit-learn's fitted
 * trees, and `random` uses NumPy's PCG64, which a JS PRNG cannot reproduce
 * bit-for-bit (it is still uniform noise, which is the entire point of it).
 */
(function () {
  "use strict";

  const NAB = "https://raw.githubusercontent.com/numenta/NAB/master";
  const REAL_CORPORA = new Set([
    "realAWSCloudwatch", "realAdExchange", "realKnownCause", "realTraffic", "realTweets",
  ]);
  const N_GRID = 120;

  const cache = { labels: null, series: new Map(), scores: new Map(), sweeps: new Map() };

  const SAMPLES = [
    {
      series: "realKnownCause/nyc_taxi.csv",
      detector: "random",
      note: "Uniform noise on NYC taxi demand, at its own point-adjusted optimum.",
    },
    {
      series: "realKnownCause/machine_temperature_system_failure.csv",
      detector: "window_pca",
      note: "A real detector on a real machine failure — the honest case.",
    },
    {
      series: "realAWSCloudwatch/ec2_cpu_utilization_5f5533.csv",
      detector: "random",
      note: "Noise again, on EC2 CPU utilisation.",
    },
    {
      series: "realTraffic/speed_7578.csv",
      detector: "seasonal",
      note: "A seasonal-profile detector on highway speeds.",
    },
  ];

  async function labels() {
    if (!cache.labels) {
      const response = await fetch(`${NAB}/labels/combined_windows.json`);
      if (!response.ok) throw new Error(`could not reach NAB (${response.status})`);
      cache.labels = await response.json();
    }
    return cache.labels;
  }

  async function series(key) {
    if (cache.series.has(key)) return cache.series.get(key);
    const [all, response] = await Promise.all([
      labels(), fetch(`${NAB}/data/${key}`),
    ]);
    if (!response.ok) throw new Error(`could not load ${key} (${response.status})`);
    const parsed = outliar.parseCsv(await response.text());
    const windows = outliar.windowsToIndices(parsed.timestamps, all[key] || []);
    const value = {
      key,
      name: key.split("/")[1].replace(/\.csv$/, ""),
      corpus: key.split("/")[0],
      timestamps: parsed.timestamps,
      values: parsed.values,
      windows,
      n: parsed.values.length,
      samplingMinutes: outliar.samplingMinutes(parsed.timestamps),
    };
    cache.series.set(key, value);
    return value;
  }

  function scores(s, detector) {
    const id = `${s.key}::${detector}`;
    if (!cache.scores.has(id)) {
      cache.scores.set(id, outliar.DETECTORS[detector](s, 7));
    }
    return cache.scores.get(id);
  }

  async function evaluate(key, detector, threshold) {
    const s = await series(key);
    const raw = scores(s, detector);
    const probation = outliar.probationLength(s.n);

    const scored = Array.from(raw.slice(probation));
    const yTrue = outliar.pointLabels(s.n, s.windows).slice(probation);

    const sweepId = `${key}::${detector}`;
    if (!cache.sweeps.has(sweepId)) {
      cache.sweeps.set(sweepId, outliar.sweep(yTrue, scored, N_GRID));
    }
    const best = cache.sweeps.get(sweepId);
    const paOptimal = best.pa[0];
    if (threshold === null || threshold === undefined) threshold = paOptimal;

    const yPred = scored.map((v) => v >= threshold);
    const protocols = outliar.allProtocols(yTrue, yPred);
    const [caught, missed] = outliar.eventRecall(yTrue, yPred);

    let alarms = 0, inside = 0;
    for (let i = 0; i < yPred.length; i++) {
      if (yPred[i]) { alarms++; if (yTrue[i]) inside++; }
    }
    const credited = outliar.adjustPredictions(yTrue, yPred).reduce((a, b) => a + (b ? 1 : 0), 0);

    const step = Math.max(1, Math.floor(s.n / 2400));
    const timestamps = [], values = [], drawn = [];
    for (let i = 0; i < s.n; i += step) {
      timestamps.push(s.timestamps[i]);
      values.push(s.values[i]);
      drawn.push(raw[i]);
    }

    const finite = scored.filter(Number.isFinite);
    return {
      series: key,
      name: s.name,
      detector,
      is_control: outliar.CONTROLS.has(detector),
      description: outliar.DESCRIPTIONS[detector],
      threshold,
      pa_optimal_threshold: paOptimal,
      composite_optimal_threshold: best.composite[0],
      score_range: [Math.min(...finite), outliar.quantile(finite, 0.999)],
      probation,
      n: s.n,
      timestamps,
      values,
      scores: drawn,
      windows: s.windows,
      metrics: protocols,
      alarms,
      alarms_inside: inside,
      pa_credited: credited,
      windows_caught: caught,
      windows_total: caught + missed,
      false_alarms_per_day: outliar.falseAlarmsPerDay(yTrue, yPred, s.samplingMinutes),
    };
  }

  async function catalog() {
    const all = await labels();
    const keys = Object.keys(all).filter((k) => REAL_CORPORA.has(k.split("/")[0])).sort();
    return {
      series: keys.map((k) => ({
        key: k,
        name: k.split("/")[1].replace(/\.csv$/, ""),
        corpus: k.split("/")[0],
        windows: all[k].length,
      })),
      detectors: Object.keys(outliar.DETECTORS).map((name) => ({
        name,
        description: outliar.DESCRIPTIONS[name],
        is_control: outliar.CONTROLS.has(name),
      })),
      n_samples: SAMPLES.length,
    };
  }

  function json(payload) {
    return new Response(JSON.stringify(payload), {
      status: 200, headers: { "content-type": "application/json" },
    });
  }

  const original = window.fetch.bind(window);

  window.fetch = async function (input, init) {
    const url = typeof input === "string" ? input : input.url;
    // Only the app's own routes are intercepted; NAB requests pass through.
    if (!/^\/(api\/|sample|healthz)/.test(url)) return original(input, init);

    const parsed = new URL(url, location.origin);
    const path = parsed.pathname;
    const query = parsed.searchParams;

    try {
      if (path === "/api/catalog") return json(await catalog());
      if (path === "/healthz") return json({ status: "ok", static: true });
      if (path === "/api/findings") {
        const response = await original("findings.json");
        if (!response.ok) throw new Error("findings.json missing");
        return json(await response.json());
      }
      if (path === "/api/evaluate") {
        const threshold = query.has("threshold") ? parseFloat(query.get("threshold")) : null;
        return json(await evaluate(query.get("series"), query.get("detector"), threshold));
      }
      if (path === "/sample") {
        const choice = SAMPLES[(parseInt(query.get("index") || "0", 10) || 0) % SAMPLES.length];
        const payload = await evaluate(choice.series, choice.detector, null);
        payload.note = choice.note;
        return json(payload);
      }
    } catch (err) {
      return new Response(String(err && err.message ? err.message : err), { status: 502 });
    }
    return new Response("not found", { status: 404 });
  };
})();