MoonSignalKit

MoonSignalKit is a MoonBit-native library for streaming telemetry and compact time-series analysis. It is intended for device metrics, sensor pipelines, service health signals, edge processing, and WebAssembly monitoring views. The same dependency-free API runs on Native, JavaScript, Wasm, and Wasm-GC.

Why this library exists

MoonBit provides portable numeric and collection primitives, but application authors still need bounded windows, online statistics, robust smoothing, timestamp-quality checks, and sustained-change detection. MoonSignalKit turns those recurring pieces into a typed, tested library rather than requiring every application to reimplement them.

Install

Add the published package to a MoonBit project:

moon add cn-wn/moonsignalkit

Then import it from the package that consumes it:

import {
  "cn-wn/moonsignalkit" @signal,
}

Minimal call

This example keeps the newest three samples and asks for the median. It is a complete black-box test body that can be copied into a consuming package.

///|
test {
  let window = @signal.RollingWindow::new(3)
  window.push(@signal.Sample::new(100, 41.0))
  window.push(@signal.Sample::new(101, 43.0))
  window.push(@signal.Sample::new(102, 42.0))
  assert_eq(window.median(), 42.0)
}

Production-oriented capabilities

• Batch series analysis: summaries, normalization, moving average, EMA, difference, rate of change, peaks, and Z-score outliers.
• Bounded rolling windows with chronological eviction, exact nearest-rank quantiles, median, and stable summaries.
• Constant-memory Welford online moments and two-sided CUSUM level-shift detection for unbounded streams.
• EWMA smoothing and bounded median filtering for noisy measurements.
• TimestampMonitor for deterministic late-sample and sampling-gap detection; late arrivals never move the accepted timing baseline backwards.
• Portable time,value CSV import/export with explicit malformed-input errors.

Runnable examples

The repository contains a deterministic telemetry walkthrough and a 100,000-sample operation-count benchmark:

moon run cmd/main
moon run cmd/bench

The benchmark intentionally retains a bounded 256-sample rolling window. Its retained_samples column is therefore 256, while online statistics and CUSUM remain constant-memory. See examples/pipeline.md and benchmark notes for the reproducible scenario.

Verification

moon fmt --check
moon check --deny-warn --target all
moon info && git diff --exit-code -- '*.mbti'
moon test --deny-warn --target all

MoonBit 0.10.4 no longer accepts moon fmt --deny-warn or moon info --deny-warn. The non-mutating equivalents above are used locally; CI detects and uses those flags on toolchains that still provide them.

Scope

MoonSignalKit is not an audio DSP engine, FFT suite, reactive UI framework, or platform I/O layer. It focuses on portable numerical telemetry primitives that applications can compose with their own transports and storage. Related work, license, and acceptance evidence are documented in README.mbt.md, docs/RELATED_WORK.md, and docs/ACCEPTANCE.md.

Licensed under Apache-2.0.