feat(labs): unit conversion, analyte registry, marker normalization

server/src/lib/units.ts

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+// Lab unit conversion. Two transform kinds: dimensional scaling (prefix/volume,
+// analyte-independent) and the mass<->mole bridge, which requires the analyte's
+// molar mass. %, ratios, IU, and cell counts never bridge to mass or mole.
+type Kind = "mass" | "mole" | "count" | "iu" | "percent" | "ratio" | "other";
+
+const AMOUNT: Record<string, [Kind, number]> = {
+  g: ["mass", 1], mg: ["mass", 1e-3], ug: ["mass", 1e-6], mcg: ["mass", 1e-6],
+  "µg": ["mass", 1e-6], ng: ["mass", 1e-9], pg: ["mass", 1e-12],
+  mol: ["mole", 1], mmol: ["mole", 1e-3], umol: ["mole", 1e-6], "µmol": ["mole", 1e-6],
+  nmol: ["mole", 1e-9], pmol: ["mole", 1e-12],
+  cells: ["count", 1], k: ["count", 1e3], thousand: ["count", 1e3],
+  million: ["count", 1e6], "x10^9": ["count", 1e9], "x10^12": ["count", 1e12],
+  iu: ["iu", 1], miu: ["iu", 1e-3], uiu: ["iu", 1e-6], "µiu": ["iu", 1e-6], u: ["iu", 1],
+};
+const VOLUME: Record<string, number> = { l: 1, dl: 0.1, ml: 1e-3, ul: 1e-6, "µl": 1e-6 };
+
+const clean = (u: string) => u.toLowerCase().replace(/\s+/g, "").replace("μ", "µ");
+
+interface Parsed { kind: Kind; amountFactor: number; volumeFactor: number }
+
+export function parseUnit(unit: string): Parsed | null {
+  const u = clean(unit);
+  if (u === "%") return { kind: "percent", amountFactor: 1, volumeFactor: 1 };
+  if (u === "" || u === "ratio" || u === "index") return { kind: "ratio", amountFactor: 1, volumeFactor: 1 };
+  const m = u.match(/^([a-zµ0-9^]+)\/([a-zµ0-9.]+)$/);
+  if (m) {
+    const amtEntry = AMOUNT[m[1]];
+    const volFactor = VOLUME[m[2]];
+    if (amtEntry && volFactor) return { kind: amtEntry[0], amountFactor: amtEntry[1], volumeFactor: volFactor };
+  }
+  return { kind: "other", amountFactor: 1, volumeFactor: 1 };
+}
+
+export function convert(value: number, fromUnit: string, toUnit: string, molarMass?: number | null): number | null {
+  const from = parseUnit(fromUnit);
+  const to = parseUnit(toUnit);
+  if (!from || !to) return null;
+  if (clean(fromUnit) === clean(toUnit)) return value;
+  if (from.kind === "other" || to.kind === "other") return null;
+
+  const fromBasePerL = (value * from.amountFactor) / from.volumeFactor;
+  let toBasePerL = fromBasePerL;
+  if (from.kind !== to.kind) {
+    const bridge = (from.kind === "mass" && to.kind === "mole") || (from.kind === "mole" && to.kind === "mass");
+    if (!bridge || !molarMass) return null;
+    toBasePerL = from.kind === "mass" ? fromBasePerL / molarMass : fromBasePerL * molarMass;
+  }
+  return (toBasePerL * to.volumeFactor) / to.amountFactor;
+}