Implement mattertimesync: one-shot Matter time synchronization CLIHEADmain

A standalone CLI Matter controller that joins Matter devices' existing
setups as a secondary administrator (multi-admin) and sets their clocks
via the standard Time Synchronization cluster. Built on matter.js 0.17.6
using the CommissioningController API. One-shot runs from a systemd
timer, no daemon: being a secondary controller is fabric membership, not
a running process, so each invocation loads the persisted keys,
discovers the device via operational DNS-SD, opens a fresh CASE session,
does its work, and exits.

- TypeScript scaffold: strict tsc, oxlint, prettier, vitest (66 tests:
  Matter epoch conversion, config validation, IANA timezone offsets and
  exact DST transition search, atomic state writes, pairing-code
  parsing, clock-delta reporting, capability planning against the
  captured device fixture)
- Validated JSON configuration with bigint-safe values; unknown fields
  rejected loudly
- Persistent controller fabric with the same identity across restarts.
  The fabric doubles as the device registry: every node commissioned
  onto it is kept in sync, and membership changes only through
  commission and decommission, so no separate device list can drift
- On-network multi-admin commissioning from a manual or QR pairing code;
  any number of devices, one per-device pairing code each. A device
  already on the fabric rejects re-commissioning via fabric conflict
- sync, validated against real hardware (IKEA ALPSTUGA air quality
  monitor over Thread, commissioned alongside Apple Home): refuses to
  run unless the host is NTP-synchronized, then per node reads utcTime,
  reports the correction with direction ("device clock was 1m 23s
  behind", handling unset clocks in exact bigint microseconds), writes
  SetUTCTime, SetTimeZone (standard offset plus IANA name), and
  SetDSTOffset (transition list bounded by the device's capacity), and
  verifies by reading the clock back. Capability-driven throughout:
  UTC-only devices degrade gracefully, cluster-less devices are skipped
  with a warning. Devices whose firmware encodes Unix-epoch time on the
  wire are detected by the exact 946684800s shift and reported
  corrected. Note matter.js's TlvEpochUs API convention: values are
  Unix-epoch microseconds at the API boundary; the library converts to
  Matter epoch on the wire
- Commands: nodes, inspect (human/JSON; also reads the fabric table
  fabric-unfiltered, matching our own entry by fabric ID plus root
  public key and flagging likely-stale orphans; strictly read-only,
  since this tool never uses its admin rights against other fabrics'
  entries), status, and decommission (each device drops our fabric
  while staying paired to its primary ecosystem; targets all devices
  unless --node narrows it)
- Logs (service and matter.js library, plain format) go to stderr;
  stdout carries only command output, so --json (available on nodes,
  inspect, sync, status, fabrics) is always clean parseable JSON with
  64-bit values as decimal strings. Node's node:sqlite
  ExperimentalWarning is filtered before matter.js loads
- systemd oneshot service (dedicated non-root user, hardening) plus
  hourly timer with randomized delay
- Deployment as a single esbuild bundle (mattertimesync.mjs, ~4.5 MB):
  all runtime deps are pure JavaScript, so the target needs only
  Node 20+, with no npm, registry access, or build toolchain. The Bun
  sqlite driver stays external behind its runtime guard and node:sqlite
  is aliased to a lazy shim so the bundle runs under plain Node. npm
  pack remains an alternative install path

1 files changed, 99 insertions, 0 deletions

diff --git a/src/config.ts b/src/config.ts
new file mode 100644
index 0000000..14dbd4f
--- /dev/null
+++ b/src/config.ts
@@ -0,0 +1,99 @@
+import { readFileSync } from "node:fs";
+import { isLogLevel, type LogLevel } from "./logging.js";
+import { isValidTimeZone } from "./timezone.js";
+
+export const DEFAULT_CONFIG_PATH = "/etc/mattertimesync/config.json";
+
+export interface Config {
+  /** Directory holding persistent Matter fabric state and service state. Contains secrets. */
+  storagePath: string;
+  /** IANA time-zone name, e.g. "America/Chicago". Never a fixed UTC offset. */
+  timezone: string;
+  logLevel: LogLevel;
+}
+
+export class ConfigError extends Error {}
+
+const DEFAULTS = {
+  timezone: "America/Chicago",
+  logLevel: "info" as LogLevel,
+};
+
+export function loadConfig(path: string): Config {
+  let raw: string;
+  try {
+    raw = readFileSync(path, "utf8");
+  } catch (cause) {
+    throw new ConfigError(
+      `Cannot read configuration file ${path}: ${cause instanceof Error ? cause.message : String(cause)}`,
+    );
+  }
+
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(raw);
+  } catch (cause) {
+    throw new ConfigError(
+      `Configuration file ${path} is not valid JSON: ${cause instanceof Error ? cause.message : String(cause)}`,
+    );
+  }
+
+  return validateConfig(parsed, path);
+}
+
+export function validateConfig(parsed: unknown, source = "configuration"): Config {
+  if (typeof parsed !== "object" || parsed === null || Array.isArray(parsed)) {
+    throw new ConfigError(`${source}: top-level value must be a JSON object`);
+  }
+  const record = parsed as Record<string, unknown>;
+
+  // Device membership lives in controller storage, not the configuration, so
+  // there is deliberately no nodeId field; commands take --node instead.
+  const known = new Set(["storagePath", "timezone", "logLevel"]);
+  for (const key of Object.keys(record)) {
+    if (!known.has(key)) {
+      throw new ConfigError(`${source}: unknown field "${key}"`);
+    }
+  }
+
+  const storagePath = record["storagePath"];
+  if (typeof storagePath !== "string" || storagePath.length === 0) {
+    throw new ConfigError(`${source}: "storagePath" is required and must be a non-empty string`);
+  }
+
+  const timezone = record["timezone"] === undefined ? DEFAULTS.timezone : record["timezone"];
+  if (typeof timezone !== "string" || !isValidTimeZone(timezone)) {
+    throw new ConfigError(
+      `${source}: "timezone" must be a valid IANA time-zone name (got ${JSON.stringify(timezone)})`,
+    );
+  }
+
+  const logLevel = record["logLevel"] === undefined ? DEFAULTS.logLevel : record["logLevel"];
+  if (!isLogLevel(logLevel)) {
+    throw new ConfigError(`${source}: "logLevel" must be one of debug, info, warn, error`);
+  }
+
+  return { storagePath, timezone, logLevel };
+}
+
+/**
+ * Parses a node ID given on the command line (--node). Node IDs are 64-bit
+ * values; they are carried as decimal strings so they never pass through a
+ * lossy JavaScript number.
+ */
+export function parseNodeId(value: unknown, source = "--node"): bigint {
+  if (typeof value === "string" && /^\d+$/.test(value)) {
+    return toNodeId(BigInt(value), source);
+  }
+  if (typeof value === "number" && Number.isSafeInteger(value) && value >= 0) {
+    return toNodeId(BigInt(value), source);
+  }
+  throw new ConfigError(`${source}: node ID must be a decimal string; got ${JSON.stringify(value)}`);
+}
+
+function toNodeId(value: bigint, source: string): bigint {
+  if (value < 0n || value >= 1n << 64n) {
+    throw new ConfigError(`${source}: node ID must fit in an unsigned 64-bit integer`);
+  }
+  return value;
+}