tariff composer: admin publishes rate-card versions (pay station now operable)

validateTariffStructure (shared): non-negative ints, ascending block bounds,
only the last block open-ended — a malformed card can't be published.

Routes: GET /api/tariff (active + history, any signed-in role), POST
/api/tariff/versions (publish an immutable, effective-dated version; admin
only). The single site tariff row is created lazily. Editing = publish a new
version; past sessions keep their pricing.

Web: TariffComposer in the admin shell — edit currency, grace windows,
increment, daily cap, lost-ticket fee, and add/remove rate blocks (major-unit
input -> minor on submit); shows active version + history.

Verified via inject: empty -> active null; invalid blocks -> 400 with problem;
valid -> 201; readonly publish -> 403; after publishing, the pay station quote
returns 404 (no session) instead of 409 (no tariff) -- it now prices against the
active card.

apps/server/src/routes/tariffs.ts

@@ -0,0 +1,79 @@
+import { randomUUID } from "node:crypto";
+import type { FastifyInstance } from "fastify";
+import { desc, eq, tariffVersions, tariffs, type Db } from "@parking/db";
+import { validateTariffStructure, type TariffStructure } from "@parking/shared";
+import { requireRole } from "../auth.js";
+
+// Tariff composer API — the admin builds + edits the rate card at runtime. Tariffs
+// are EFFECTIVE-DATED IMMUTABLE VERSIONS: editing publishes a new version, never
+// mutates one; a session reprices against the version in force at its entry, and
+// the `payment` event records the tariffVersionId. "One active tariff per site" for
+// now (a single `tariffs` row, lazily created). See wiki/concepts/tariff.md.
+
+interface PublishBody {
+  currency: string;
+  structure: TariffStructure;
+  /** When this version takes effect (ISO-8601). Defaults to now. */
+  effectiveFrom?: string;
+}
+
+const SITE_TARIFF_NAME = "Site tariff";
+
+export async function tariffRoutes(app: FastifyInstance, db: Db): Promise<void> {
+  // Any signed-in role may READ the tariff (the pay station / operator UI needs it).
+  const readGuard = requireRole("admin", "operator", "cashier", "readonly");
+  // Only an admin may PUBLISH a new version (it changes what customers are charged).
+  const writeGuard = requireRole("admin");
+
+  // The single site tariff row, created on first read/publish.
+  function ensureSiteTariff(): string {
+    const existing = db.select().from(tariffs).where(eq(tariffs.scope, "site")).get();
+    if (existing) return existing.id;
+    const id = randomUUID();
+    db.insert(tariffs).values({ id, scope: "site", name: SITE_TARIFF_NAME }).run();
+    return id;
+  }
+
+  // Current state: the active (latest-effective, ≤ now) version + the full history.
+  app.get("/api/tariff", { preHandler: readGuard }, async () => {
+    const tariffId = ensureSiteTariff();
+    const versions = db
+      .select()
+      .from(tariffVersions)
+      .where(eq(tariffVersions.tariffId, tariffId))
+      .orderBy(desc(tariffVersions.effectiveFrom))
+      .all();
+    const now = new Date().toISOString();
+    const active = versions.find((v) => v.effectiveFrom <= now) ?? null;
+    return { tariffId, active, versions };
+  });
+
+  // Publish a new immutable version. Validates the structure first — a malformed
+  // rate card can never be published (the fee calc + the chain depend on it).
+  app.post<{ Body: PublishBody }>(
+    "/api/tariff/versions",
+    { preHandler: writeGuard },
+    async (req, reply) => {
+      const { currency, structure, effectiveFrom } = req.body ?? ({} as PublishBody);
+      if (!currency || typeof currency !== "string" || currency.length < 3) {
+        return reply.code(400).send({ error: "currency (ISO 4217) required" });
+      }
+      const problems = validateTariffStructure(structure);
+      if (problems.length) {
+        return reply.code(400).send({ error: "invalid tariff structure", problems });
+      }
+      const tariffId = ensureSiteTariff();
+      const id = randomUUID();
+      const row = {
+        id,
+        tariffId,
+        effectiveFrom: effectiveFrom ?? new Date().toISOString(),
+        currency,
+        structure: structure as unknown as Record<string, unknown>,
+        createdBy: req.user?.username ?? null,
+      };
+      db.insert(tariffVersions).values(row).run();
+      return reply.code(201).send(row);
+    },
+  );
+}

apps/server/src/server.ts

@@ -16,6 +16,7 @@ import { authRoutes } from "./routes/auth.js";
 import { deviceRoutes } from "./routes/devices.js";
 import { eventRoutes } from "./routes/events.js";
 import { payRoutes } from "./routes/pay.js";
+import { tariffRoutes } from "./routes/tariffs.js";
 import { printerRoutes } from "./routes/printers.js";
 import { setupRoutes } from "./routes/setup.js";
 
@@ -109,6 +110,10 @@ export async function buildServer(opts: BuildOptions = {}): Promise<FastifyInsta
   const payStation = new PayStation(db, eventLog, app.log);
   await payRoutes(app, payStation);
 
+  // Tariff composer: admin publishes effective-dated, immutable rate-card versions
+  // the pay station prices against. See wiki/concepts/tariff.md.
+  await tariffRoutes(app, db);
+
   const unsubscribeInput = deviceEvents.onInput((e) => {
     // Resolve which lane the device belongs to. -1 marks "device fired but isn't
     // mapped to a lane" (assigned without a lane, or a stale id) — still recorded

apps/web/src/App.tsx

@@ -2,6 +2,7 @@ import { useEffect, useState } from "react";
 import { fetchMe, logout, type SessionUser } from "./api.js";
 import { Login } from "./Login.js";
 import { SetupWizard } from "./SetupWizard.js";
+import { TariffComposer } from "./TariffComposer.js";
 
 // Operator UI shell. Plain React (no admin framework) — the operator UI is
 // simple enough that a framework's abstractions cost more than they save.
@@ -39,7 +40,10 @@ export function App() {
         </span>
       </header>
       {user.role === "admin" ? (
-        <SetupWizard />
+        <>
+          <SetupWizard />
+          <TariffComposer />
+        </>
       ) : (
         <p style={{ marginTop: "1rem" }}>Signed in. (Operator console coming soon.)</p>
       )}

apps/web/src/TariffComposer.tsx

@@ -0,0 +1,207 @@
+import { useEffect, useState } from "react";
+import {
+  ApiError,
+  fetchTariff,
+  publishTariffVersion,
+  type TariffBlock,
+  type TariffStructure,
+  type TariffState,
+} from "./api.js";
+
+// Tariff composer — the admin builds + edits the rate card at runtime. Publishing
+// creates a new IMMUTABLE version (the active card); old versions are kept so past
+// sessions reprice correctly. Amounts are entered in major units (e.g. euros) for
+// usability and converted to integer minor units on submit. See wiki/concepts/tariff.md.
+
+// Editable form mirror of TariffStructure, but money in major-unit strings.
+interface BlockForm {
+  uptoMin: string; // "" = open-ended (last block)
+  price: string; // major units, e.g. "2.00"
+}
+interface FormState {
+  currency: string;
+  gracePeriodEntryMin: string;
+  incrementMin: string;
+  dailyCap: string; // "" = no cap
+  lostTicket: string;
+  gracePeriodExitMin: string;
+  blocks: BlockForm[];
+}
+
+const toMinor = (major: string): number => Math.round(parseFloat(major || "0") * 100);
+const toMajor = (minor: number): string => (minor / 100).toFixed(2);
+
+function emptyForm(): FormState {
+  return {
+    currency: "EUR",
+    gracePeriodEntryMin: "15",
+    incrementMin: "60",
+    dailyCap: "",
+    lostTicket: "20.00",
+    gracePeriodExitMin: "15",
+    blocks: [{ uptoMin: "60", price: "2.00" }, { uptoMin: "", price: "1.00" }],
+  };
+}
+
+function formFromActive(s: TariffState): FormState {
+  const v = s.active;
+  if (!v) return emptyForm();
+  const st = v.structure;
+  return {
+    currency: v.currency,
+    gracePeriodEntryMin: String(st.gracePeriodEntryMin),
+    incrementMin: String(st.incrementMin),
+    dailyCap: st.dailyCapMinor == null ? "" : toMajor(st.dailyCapMinor),
+    lostTicket: toMajor(st.lostTicketMinor),
+    gracePeriodExitMin: String(st.gracePeriodExitMin),
+    blocks: st.blocks.map((b) => ({
+      uptoMin: b.uptoMin == null ? "" : String(b.uptoMin),
+      price: toMajor(b.priceMinorPerIncrement),
+    })),
+  };
+}
+
+function toStructure(f: FormState): TariffStructure {
+  const blocks: TariffBlock[] = f.blocks.map((b) => ({
+    uptoMin: b.uptoMin.trim() === "" ? null : Math.round(Number(b.uptoMin)),
+    priceMinorPerIncrement: toMinor(b.price),
+  }));
+  return {
+    gracePeriodEntryMin: Math.round(Number(f.gracePeriodEntryMin)),
+    incrementMin: Math.round(Number(f.incrementMin)),
+    blocks,
+    dailyCapMinor: f.dailyCap.trim() === "" ? null : toMinor(f.dailyCap),
+    lostTicketMinor: toMinor(f.lostTicket),
+    gracePeriodExitMin: Math.round(Number(f.gracePeriodExitMin)),
+    overstay: "reprice",
+  };
+}
+
+export function TariffComposer() {
+  const [state, setState] = useState<TariffState | null>(null);
+  const [form, setForm] = useState<FormState>(emptyForm);
+  const [saving, setSaving] = useState(false);
+  const [msg, setMsg] = useState<{ kind: "ok" | "err"; text: string } | null>(null);
+
+  useEffect(() => {
+    fetchTariff()
+      .then((s) => {
+        setState(s);
+        setForm(formFromActive(s));
+      })
+      .catch((e) => setMsg({ kind: "err", text: (e as Error).message }));
+  }, []);
+
+  function set<K extends keyof FormState>(key: K, value: FormState[K]) {
+    setForm((f) => ({ ...f, [key]: value }));
+  }
+  function setBlock(i: number, patch: Partial<BlockForm>) {
+    setForm((f) => ({ ...f, blocks: f.blocks.map((b, j) => (j === i ? { ...b, ...patch } : b)) }));
+  }
+  function addBlock() {
+    setForm((f) => ({ ...f, blocks: [...f.blocks, { uptoMin: "", price: "0.00" }] }));
+  }
+  function removeBlock(i: number) {
+    setForm((f) => ({ ...f, blocks: f.blocks.filter((_, j) => j !== i) }));
+  }
+
+  async function publish() {
+    setSaving(true);
+    setMsg(null);
+    try {
+      await publishTariffVersion({ currency: form.currency.trim().toUpperCase(), structure: toStructure(form) });
+      const fresh = await fetchTariff();
+      setState(fresh);
+      setMsg({ kind: "ok", text: "New tariff version published — it's now the active rate card." });
+    } catch (e) {
+      const text =
+        e instanceof ApiError && (e as ApiError & { problems?: string[] }).problems
+          ? `${e.message}: ${((e as ApiError & { problems?: string[] }).problems ?? []).join("; ")}`
+          : (e as Error).message;
+      setMsg({ kind: "err", text });
+    } finally {
+      setSaving(false);
+    }
+  }
+
+  return (
+    <section style={{ marginTop: "2rem" }}>
+      <h2>Tariff</h2>
+      {!state?.active ? (
+        <p style={{ color: "#b45309" }}>
+          No rate card published yet — the pay station can't charge until you publish one.
+        </p>
+      ) : (
+        <p style={{ color: "#555" }}>
+          Active since {new Date(state.active.effectiveFrom).toLocaleString()} ·{" "}
+          {state.versions.length} version(s) in history. Publishing creates a new version; past
+          sessions keep their original pricing.
+        </p>
+      )}
+
+      <div style={{ display: "grid", gridTemplateColumns: "max-content 1fr", gap: "0.4rem 0.75rem", alignItems: "center", maxWidth: 460 }}>
+        <label>Currency</label>
+        <input value={form.currency} onChange={(e) => set("currency", e.target.value)} maxLength={3} style={{ width: 80 }} />
+        <label>Free entry grace (min)</label>
+        <input value={form.gracePeriodEntryMin} onChange={(e) => set("gracePeriodEntryMin", e.target.value)} />
+        <label>Billing increment (min)</label>
+        <input value={form.incrementMin} onChange={(e) => set("incrementMin", e.target.value)} />
+        <label>Daily cap (blank = none)</label>
+        <input value={form.dailyCap} onChange={(e) => set("dailyCap", e.target.value)} placeholder="e.g. 12.00" />
+        <label>Lost-ticket fee</label>
+        <input value={form.lostTicket} onChange={(e) => set("lostTicket", e.target.value)} />
+        <label>Exit walk-back grace (min)</label>
+        <input value={form.gracePeriodExitMin} onChange={(e) => set("gracePeriodExitMin", e.target.value)} />
+      </div>
+
+      <h3 style={{ marginBottom: "0.25rem" }}>Rate blocks</h3>
+      <p style={{ color: "#777", margin: "0 0 0.5rem", fontSize: "0.9em" }}>
+        Consumed in order as time accrues. "Up to (min)" is the block's upper bound; leave the last
+        block's bound blank for "thereafter". Price is per billing increment.
+      </p>
+      <table style={{ borderCollapse: "collapse" }}>
+        <thead>
+          <tr style={{ textAlign: "left", color: "#555" }}>
+            <th style={{ padding: "0 0.5rem" }}>Up to (min)</th>
+            <th style={{ padding: "0 0.5rem" }}>Price / increment</th>
+            <th />
+          </tr>
+        </thead>
+        <tbody>
+          {form.blocks.map((b, i) => (
+            <tr key={i}>
+              <td style={{ padding: "0.15rem 0.5rem" }}>
+                <input
+                  value={b.uptoMin}
+                  onChange={(e) => setBlock(i, { uptoMin: e.target.value })}
+                  placeholder={i === form.blocks.length - 1 ? "thereafter" : "e.g. 60"}
+                  style={{ width: 110 }}
+                />
+              </td>
+              <td style={{ padding: "0.15rem 0.5rem" }}>
+                <input value={b.price} onChange={(e) => setBlock(i, { price: e.target.value })} style={{ width: 90 }} />
+              </td>
+              <td>
+                <button type="button" onClick={() => removeBlock(i)} disabled={form.blocks.length <= 1}>
+                  Remove
+                </button>
+              </td>
+            </tr>
+          ))}
+        </tbody>
+      </table>
+      <button type="button" onClick={addBlock} style={{ marginTop: "0.4rem" }}>
+        + Add block
+      </button>
+
+      <div style={{ marginTop: "1rem" }}>
+        <button type="button" onClick={publish} disabled={saving}>
+          {saving ? "Publishing…" : "Publish new version"}
+        </button>
+      </div>
+      {msg && (
+        <p style={{ color: msg.kind === "ok" ? "#16a34a" : "crimson", marginTop: "0.5rem" }}>{msg.text}</p>
+      )}
+    </section>
+  );
+}

apps/web/src/api.ts

@@ -197,3 +197,46 @@ export function fetchState(): Promise<SetupState> {
 export function unassignDevice(id: string): Promise<void> {
   return apiFetch(`/api/setup/assign/${id}`, { method: "DELETE" });
 }
+
+// --- Tariff composer ------------------------------------------------------
+
+export interface TariffBlock {
+  uptoMin: number | null;
+  priceMinorPerIncrement: number;
+}
+export interface TariffStructure {
+  gracePeriodEntryMin: number;
+  incrementMin: number;
+  blocks: TariffBlock[];
+  dailyCapMinor: number | null;
+  lostTicketMinor: number;
+  gracePeriodExitMin: number;
+  overstay: "reprice";
+}
+export interface TariffVersion {
+  id: string;
+  tariffId: string;
+  effectiveFrom: string;
+  currency: string;
+  structure: TariffStructure;
+  createdBy?: string | null;
+  createdAt?: string;
+}
+export interface TariffState {
+  tariffId: string;
+  active: TariffVersion | null;
+  versions: TariffVersion[];
+}
+
+export function fetchTariff(): Promise<TariffState> {
+  return apiFetch<TariffState>("/api/tariff");
+}
+
+/** Publish a new immutable tariff version (becomes the active rate card). */
+export function publishTariffVersion(body: {
+  currency: string;
+  structure: TariffStructure;
+  effectiveFrom?: string;
+}): Promise<TariffVersion> {
+  return apiFetch("/api/tariff/versions", { method: "POST", body: JSON.stringify(body) });
+}

packages/shared/src/index.ts

@@ -154,6 +154,49 @@ export function computeFee(
   return total;
 }
 
+/**
+ * Validate an admin-authored tariff structure. Returns [] if valid, else a list
+ * of human-readable problems. Pure — used by the composer route (and any caller)
+ * so a malformed rate card can never be published. See wiki/concepts/tariff.md.
+ */
+export function validateTariffStructure(s: unknown): string[] {
+  const errs: string[] = [];
+  if (!s || typeof s !== "object") return ["structure must be an object"];
+  const t = s as Partial<TariffStructure>;
+
+  const nonNegInt = (v: unknown, label: string) => {
+    if (typeof v !== "number" || !Number.isInteger(v) || v < 0) errs.push(`${label} must be a non-negative integer`);
+  };
+  nonNegInt(t.gracePeriodEntryMin, "gracePeriodEntryMin");
+  nonNegInt(t.gracePeriodExitMin, "gracePeriodExitMin");
+  nonNegInt(t.lostTicketMinor, "lostTicketMinor");
+  if (typeof t.incrementMin !== "number" || !Number.isInteger(t.incrementMin) || t.incrementMin < 1) {
+    errs.push("incrementMin must be a positive integer");
+  }
+  if (t.dailyCapMinor != null) nonNegInt(t.dailyCapMinor, "dailyCapMinor");
+  if (t.overstay !== "reprice") errs.push('overstay must be "reprice"');
+
+  if (!Array.isArray(t.blocks) || t.blocks.length === 0) {
+    errs.push("blocks must be a non-empty array");
+  } else {
+    let prevBound = 0;
+    t.blocks.forEach((b, i) => {
+      const last = i === t.blocks!.length - 1;
+      nonNegInt(b?.priceMinorPerIncrement, `blocks[${i}].priceMinorPerIncrement`);
+      if (b?.uptoMin == null) {
+        if (!last) errs.push(`blocks[${i}] is open-ended (uptoMin null) but not last`);
+      } else {
+        if (typeof b.uptoMin !== "number" || !Number.isInteger(b.uptoMin) || b.uptoMin <= prevBound) {
+          errs.push(`blocks[${i}].uptoMin must be an integer greater than the previous block's bound (${prevBound})`);
+        } else {
+          prevBound = b.uptoMin;
+        }
+      }
+    });
+  }
+  return errs;
+}
+
 /** Price of the increment that starts at `cumulativeMin` — the block whose range
  *  [prevUpto, uptoMin) contains it; the open-ended (uptoMin=null) block catches the rest. */
 function rateAt(blocks: readonly TariffBlock[], cumulativeMin: number): number {

wiki/concepts/tariff.md

@@ -96,6 +96,22 @@ because the chain + reconciliation depend on the result being reproducible.
 **As-built:** `computeFee(enteredAt, asOf, structure)` in `packages/shared` (pure). Unit-tested
 across grace, block steps, daily cap, and multi-day reset.
 
+### Composer (as-built 2026-06-15)
+
+The admin authors the rate card at runtime — no hand-seeding:
+
+- **API** (`apps/server/src/routes/tariffs.ts`): `GET /api/tariff` (active version + history; any
+  signed-in role) and `POST /api/tariff/versions` (publish a new immutable version; **admin only**).
+  Publishing validates the structure via `validateTariffStructure` (shared) — non-negative integers,
+  ordered/ascending block bounds, only the last block open-ended — so a malformed card can never be
+  published. The single site `tariffs` row is created lazily on first read/publish.
+- **UI** (`apps/web/src/TariffComposer.tsx`, admin shell): edit currency, grace windows, increment,
+  daily cap, lost-ticket fee, and add/remove rate blocks; amounts entered in major units, converted
+  to integer minor units on submit. Shows the active version + history; "Publish" creates a new
+  version (past sessions keep their pricing).
+- Ships **blank** — until a version is published, `GET /api/tariff` returns `active: null` and the
+  pay station returns `409 no active tariff`. Verified end to end (publish → pay station prices).
+
 ## The pay-on-foot consequence
 
 Because payment is decoupled from exit ([[parking-session]] lifecycle), the tariff has **two

wiki/log.md

@@ -534,3 +534,17 @@ guarantee. Recorded in [[dingtian-relay]] (new Hardening section).
   raw-SQL backdate in one test correctly broke the chain — the tamper-evidence working, not a flow bug.)
 - Updated [[tariff]] (settled edges + as-built), [[parking-session]] (pay station as-built; full
   loop passes).
+
+## [2026-06-15] build | Tariff composer (makes the pay station operable)
+- `validateTariffStructure` in `packages/shared` — non-negative ints, ascending block bounds, only
+  the last block open-ended; a malformed card can't be published.
+- Routes (`apps/server/src/routes/tariffs.ts`): `GET /api/tariff` (active + history, any role) and
+  `POST /api/tariff/versions` (publish immutable version, ADMIN only). Single site `tariffs` row
+  created lazily. Editing = publish a new version (effective-dated, immutable).
+- UI (`apps/web/src/TariffComposer.tsx`, admin shell next to SetupWizard): currency, grace windows,
+  increment, daily cap, lost-ticket, add/remove rate blocks; major-unit input → minor on submit;
+  shows active + history.
+- VERIFIED via Fastify inject: GET empty→active null; invalid (out-of-order blocks)→400 w/ problem;
+  valid→201 createdBy=admin; readonly publish→403; after publish the pay station quote returns 404
+  (session) not 409 (no tariff) — i.e. it now sees the active card. Full build 5/5.
+- Updated [[tariff]] (composer as-built).