3 files changed, 534 insertions, 0 deletions
diff --git a/src/features/account-usage/logic/types.ts b/src/features/account-usage/logic/types.ts
new file mode 100644
index 0000000..5bb4d00
--- /dev/null
+++ b/src/features/account-usage/logic/types.ts
@@ -0,0 +1,33 @@
+import type {
+  AccountUsageLimit,
+  AccountUsageProviderId,
+  AccountUsageReport,
+  AccountUsageResponse,
+  AccountUsageState,
+} from "@dispatch/transport-contract";
+
+/**
+ * Pure core types for the account-usage feature — zero DOM, zero effects.
+ *
+ * The backend (`account-usage` extension, transport-contract 0.25.0) polls the
+ * Claude + Codex subscription usage endpoints and caches them (5 min TTL,
+ * failure cooldowns, last-good retention). The FE reads `GET /usage`; a manual
+ * refresh sends `?refresh=1`, which the server still rate-limits.
+ */
+export type {
+  AccountUsageLimit,
+  AccountUsageProviderId,
+  AccountUsageReport,
+  AccountUsageResponse,
+  AccountUsageState,
+};
+
+/** Outcome of `GET /usage`. `unavailable` = the backend extension isn't loaded (503). */
+export type AccountUsageResult =
+  | { readonly ok: true; readonly usage: AccountUsageResponse }
+  | { readonly ok: false; readonly error: string; readonly unavailable?: boolean };
+
+/** Injected port: load the account usage (`refresh` asks the server to bypass its TTL). */
+export type LoadAccountUsage = (opts?: {
+  readonly refresh?: boolean;
+}) => Promise<AccountUsageResult>;
diff --git a/src/features/account-usage/logic/view-model.test.ts b/src/features/account-usage/logic/view-model.test.ts
new file mode 100644
index 0000000..943d047
--- /dev/null
+++ b/src/features/account-usage/logic/view-model.test.ts
@@ -0,0 +1,198 @@
+import type { AccountUsageLimit, AccountUsageReport } from "@dispatch/transport-contract";
+import { describe, expect, it } from "vitest";
+import {
+  elapsedFraction,
+  formatDuration,
+  normalizeAccountUsage,
+  viewProviderCard,
+  viewUsageBar,
+} from "./view-model";
+
+const HOUR = 3_600_000;
+const DAY = 24 * HOUR;
+const NOW = 1_760_000_000_000;
+
+function limit(over: Partial<AccountUsageLimit> = {}): AccountUsageLimit {
+  return {
+    id: "claude:5h",
+    label: "5 Hour",
+    kind: "window",
+    windowId: "5h",
+    shared: true,
+    tier: null,
+    durationMs: 5 * HOUR,
+    resetsAt: NOW + 2 * HOUR,
+    unit: "percent",
+    used: 40,
+    limit: 100,
+    remaining: 60,
+    usedFraction: 0.4,
+    remainingFraction: 0.6,
+    status: "ok",
+    ...over,
+  };
+}
+
+function report(over: Partial<AccountUsageReport> = {}): AccountUsageReport {
+  return {
+    provider: "claude",
+    label: "Claude",
+    state: "fresh",
+    account: { accountId: "a", email: "[email protected]", planType: "max" },
+    limits: [limit()],
+    limitReached: null,
+    canServe: null,
+    creditOverage: false,
+    credits: null,
+    fetchedAt: NOW - 3 * 60_000,
+    lastAttemptAt: NOW - 3 * 60_000,
+    nextRefreshAt: NOW + 2 * 60_000,
+    error: null,
+    ...over,
+  };
+}
+
+describe("pace marker (elapsedFraction)", () => {
+  it("is halfway two weeks into a four-week window", () => {
+    const resetsAt = NOW + 14 * DAY;
+    expect(elapsedFraction(28 * DAY, resetsAt, NOW)).toBeCloseTo(0.5);
+  });
+
+  it("clamps to 0..1 and is null when the window is unknown", () => {
+    expect(elapsedFraction(5 * HOUR, NOW + 10 * HOUR, NOW)).toBe(0);
+    expect(elapsedFraction(5 * HOUR, NOW - HOUR, NOW)).toBe(1);
+    expect(elapsedFraction(null, NOW, NOW)).toBeNull();
+    expect(elapsedFraction(5 * HOUR, null, NOW)).toBeNull();
+  });
+});
+
+describe("viewUsageBar", () => {
+  it("places the pace marker at elapsed % and labels ahead/under pace", () => {
+    // 5h window resetting in 2h ⇒ 3h elapsed ⇒ 60% pace; used 40% ⇒ 20% under.
+    const bar = viewUsageBar(limit(), NOW);
+    expect(bar.percent).toBe(40);
+    expect(bar.pacePercent).toBeCloseTo(60);
+    expect(bar.paceLabel).toBe("20% under pace");
+    expect(bar.aheadOfPace).toBe(false);
+    expect(bar.resetLabel).toBe("resets in 2h");
+    expect(bar.valueLabel).toBe("40%");
+    expect(bar.tone).toBe("success");
+
+    const ahead = viewUsageBar(limit({ used: 80, usedFraction: 0.8 }), NOW);
+    expect(ahead.paceLabel).toBe("20% ahead of pace");
+    expect(ahead.aheadOfPace).toBe(true);
+    expect(ahead.tone).toBe("warning");
+  });
+
+  it("has no pace marker for spend meters; formats dollars", () => {
+    const spend = viewUsageBar(
+      limit({
+        id: "claude:extra",
+        kind: "spend",
+        unit: "usd",
+        durationMs: null,
+        resetsAt: null,
+        used: 12.5,
+        limit: 50,
+        usedFraction: 0.25,
+      }),
+      NOW,
+    );
+    expect(spend.pacePercent).toBeNull();
+    expect(spend.valueLabel).toBe("$12.50 / $50.00");
+    const uncapped = viewUsageBar(
+      limit({
+        unit: "usd",
+        kind: "spend",
+        limit: null,
+        usedFraction: null,
+        used: 3,
+        durationMs: null,
+      }),
+      NOW,
+    );
+    expect(uncapped.valueLabel).toBe("$3.00 (no cap)");
+    expect(uncapped.percent).toBe(0);
+  });
+
+  it("exhausted → error tone", () => {
+    expect(viewUsageBar(limit({ used: 100, usedFraction: 1, status: "exhausted" }), NOW).tone).toBe(
+      "error",
+    );
+  });
+});
+
+describe("viewProviderCard", () => {
+  it("fresh card with subtitle and age", () => {
+    const c = viewProviderCard(report(), NOW);
+    expect(c.subtitle).toBe("Max · [email protected]");
+    expect(c.stateBadge).toBeNull();
+    expect(c.message).toBeNull();
+    expect(c.ageLabel).toBe("3m ago");
+    expect(c.bars).toHaveLength(1);
+  });
+
+  it("stale / not-configured / unsupported states", () => {
+    const stale = viewProviderCard(report({ state: "stale", error: "HTTP 429" }), NOW);
+    expect(stale.stateBadge).toBe("stale");
+    expect(stale.message).toContain("HTTP 429");
+    const nc = viewProviderCard(
+      report({
+        provider: "codex",
+        label: "Codex",
+        state: "not-configured",
+        limits: [],
+        account: null,
+      }),
+      NOW,
+    );
+    expect(nc.stateBadge).toBe("not configured");
+    expect(nc.message).toContain("Codex");
+    expect(nc.ageLabel).toBeNull();
+    const un = viewProviderCard(
+      report({ state: "unsupported", error: "api key", limits: [] }),
+      NOW,
+    );
+    expect(un.message).toBe("api key");
+  });
+
+  it("credit overage note", () => {
+    const c = viewProviderCard(
+      report({ creditOverage: true, limitReached: true, canServe: true }),
+      NOW,
+    );
+    expect(c.creditNote).toContain("credits");
+  });
+});
+
+describe("normalizeAccountUsage", () => {
+  it("coerces a well-formed body and drops malformed rows", () => {
+    const n = normalizeAccountUsage(
+      {
+        servedAt: 5,
+        providers: [
+          { ...report(), limits: [limit(), { id: "bad" }] },
+          { provider: "gemini" },
+          "junk",
+        ],
+      },
+      0,
+    );
+    expect(n.servedAt).toBe(5);
+    expect(n.providers).toHaveLength(1);
+    expect(n.providers[0]?.limits).toHaveLength(1);
+  });
+
+  it("malformed body → empty", () => {
+    expect(normalizeAccountUsage(null, 9)).toEqual({ providers: [], servedAt: 9 });
+  });
+});
+
+describe("formatDuration", () => {
+  it("formats", () => {
+    expect(formatDuration(30_000)).toBe("<1m");
+    expect(formatDuration(45 * 60_000)).toBe("45m");
+    expect(formatDuration(3 * HOUR + 12 * 60_000)).toBe("3h 12m");
+    expect(formatDuration(2 * DAY + 4 * HOUR)).toBe("2d 4h");
+  });
+});
diff --git a/src/features/account-usage/logic/view-model.ts b/src/features/account-usage/logic/view-model.ts
new file mode 100644
index 0000000..d6f3053
--- /dev/null
+++ b/src/features/account-usage/logic/view-model.ts
@@ -0,0 +1,303 @@
+import type {
+  AccountUsageCredits,
+  AccountUsageLimit,
+  AccountUsageLimitStatus,
+  AccountUsageProviderId,
+  AccountUsageReport,
+  AccountUsageResponse,
+  AccountUsageState,
+} from "@dispatch/transport-contract";
+
+/**
+ * Pure view-models for the account-usage feature — zero DOM, zero effects,
+ * zero Svelte. Coerces the untyped `GET /usage` JSON, and shapes each limit
+ * into a bar: fill %, colour, and the PACE MARKER — where usage "should" be
+ * to use the whole allowance exactly by the reset (elapsed fraction of the
+ * window: 2 weeks into a 4-week window ⇒ 50%).
+ */
+
+// ── Normalization (network seam) ──────────────────────────────────────────────
+
+function isRecord(v: unknown): v is Record<string, unknown> {
+  return typeof v === "object" && v !== null && !Array.isArray(v);
+}
+function num(v: unknown): number | null {
+  return typeof v === "number" && Number.isFinite(v) ? v : null;
+}
+function str(v: unknown): string | null {
+  return typeof v === "string" ? v : null;
+}
+function bool(v: unknown): boolean | null {
+  return typeof v === "boolean" ? v : null;
+}
+
+const STATES: readonly AccountUsageState[] = [
+  "fresh",
+  "stale",
+  "unavailable",
+  "unsupported",
+  "not-configured",
+];
+const STATUSES: readonly AccountUsageLimitStatus[] = ["ok", "warning", "exhausted", "unknown"];
+
+function normalizeLimit(r: Record<string, unknown>): AccountUsageLimit | null {
+  const id = str(r.id);
+  const used = num(r.used);
+  if (id === null || used === null) return null;
+  const status = STATUSES.find((s) => s === r.status) ?? "unknown";
+  return {
+    id,
+    label: str(r.label) ?? id,
+    kind: r.kind === "spend" ? "spend" : "window",
+    windowId: str(r.windowId) ?? "",
+    shared: r.shared === true,
+    tier: str(r.tier),
+    durationMs: num(r.durationMs),
+    resetsAt: num(r.resetsAt),
+    unit: r.unit === "usd" ? "usd" : "percent",
+    used,
+    limit: num(r.limit),
+    remaining: num(r.remaining),
+    usedFraction: num(r.usedFraction),
+    remainingFraction: num(r.remainingFraction),
+    status,
+  };
+}
+
+function normalizeCredits(v: unknown): AccountUsageCredits | null {
+  if (!isRecord(v)) return null;
+  return {
+    hasCredits: bool(v.hasCredits),
+    unlimited: bool(v.unlimited),
+    overageLimitReached: bool(v.overageLimitReached),
+    balance: num(v.balance),
+    spendControlReached: bool(v.spendControlReached),
+  };
+}
+
+function normalizeReport(r: Record<string, unknown>): AccountUsageReport | null {
+  const provider: AccountUsageProviderId | null =
+    r.provider === "claude" || r.provider === "codex" ? r.provider : null;
+  if (provider === null) return null;
+  const account = isRecord(r.account)
+    ? {
+        accountId: str(r.account.accountId),
+        email: str(r.account.email),
+        planType: str(r.account.planType),
+      }
+    : null;
+  const limits = Array.isArray(r.limits)
+    ? r.limits
+        .filter(isRecord)
+        .map(normalizeLimit)
+        .filter((l): l is AccountUsageLimit => l !== null)
+    : [];
+  return {
+    provider,
+    label: str(r.label) ?? (provider === "claude" ? "Claude" : "Codex"),
+    state: STATES.find((s) => s === r.state) ?? "unavailable",
+    account,
+    limits,
+    limitReached: bool(r.limitReached),
+    canServe: bool(r.canServe),
+    creditOverage: r.creditOverage === true,
+    credits: normalizeCredits(r.credits),
+    fetchedAt: num(r.fetchedAt),
+    lastAttemptAt: num(r.lastAttemptAt),
+    nextRefreshAt: num(r.nextRefreshAt),
+    error: str(r.error),
+  };
+}
+
+/** Coerce the untyped `GET /usage` body. Malformed → empty provider list. */
+export function normalizeAccountUsage(data: unknown, fallbackNow: number): AccountUsageResponse {
+  if (!isRecord(data)) return { providers: [], servedAt: fallbackNow };
+  const providers = Array.isArray(data.providers)
+    ? data.providers
+        .filter(isRecord)
+        .map(normalizeReport)
+        .filter((p): p is AccountUsageReport => p !== null)
+    : [];
+  return { providers, servedAt: num(data.servedAt) ?? fallbackNow };
+}
+
+// ── Formatting ────────────────────────────────────────────────────────────────
+
+/** "2d 4h" / "3h 12m" / "45m" / "<1m". */
+export function formatDuration(ms: number): string {
+  if (ms < 60_000) return "<1m";
+  const totalMin = Math.floor(ms / 60_000);
+  const d = Math.floor(totalMin / 1440);
+  const h = Math.floor((totalMin % 1440) / 60);
+  const m = totalMin % 60;
+  if (d > 0) return h > 0 ? `${d}d ${h}h` : `${d}d`;
+  if (h > 0) return m > 0 ? `${h}h ${m}m` : `${h}h`;
+  return `${m}m`;
+}
+
+/** "updated 3m ago" style age, or "just now". */
+export function formatAge(fetchedAt: number | null, now: number): string | null {
+  if (fetchedAt === null) return null;
+  const ms = now - fetchedAt;
+  return ms < 60_000 ? "just now" : `${formatDuration(ms)} ago`;
+}
+
+function formatUsd(v: number): string {
+  return `$${v.toFixed(2)}`;
+}
+
+// ── Bars ──────────────────────────────────────────────────────────────────────
+
+export type BarTone = "success" | "warning" | "error" | "neutral";
+
+export interface UsageBarView {
+  readonly id: string;
+  readonly label: string;
+  /** Fill 0..100 for the `<progress>` value. */
+  readonly percent: number;
+  /** "42%" or "$12.50 / $50.00". */
+  readonly valueLabel: string;
+  readonly tone: BarTone;
+  /**
+   * Pace marker position 0..100 (% of the window elapsed) — the usage level
+   * that would be "on track" to exactly use the allowance by the reset. Null
+   * when the window's start can't be determined (no duration/reset).
+   */
+  readonly pacePercent: number | null;
+  /** "+12% ahead of pace" / "8% under pace" / null. */
+  readonly paceLabel: string | null;
+  /** True when usage is ahead of the pace marker. */
+  readonly aheadOfPace: boolean;
+  /** "resets in 3h 12m" / null. */
+  readonly resetLabel: string | null;
+}
+
+/**
+ * Fraction (0..1) of the window elapsed at `now`. The window started at
+ * `resetsAt - durationMs`; returns null when either is unknown.
+ */
+export function elapsedFraction(
+  durationMs: number | null,
+  resetsAt: number | null,
+  now: number,
+): number | null {
+  if (durationMs === null || resetsAt === null || durationMs <= 0) return null;
+  const start = resetsAt - durationMs;
+  return Math.min(1, Math.max(0, (now - start) / durationMs));
+}
+
+function toneFor(status: AccountUsageLimitStatus, usedFraction: number | null): BarTone {
+  if (status === "exhausted") return "error";
+  if (status === "warning") return "warning";
+  if (status === "ok") return usedFraction !== null && usedFraction >= 0.75 ? "warning" : "success";
+  return "neutral";
+}
+
+export function viewUsageBar(limit: AccountUsageLimit, now: number): UsageBarView {
+  const fraction = limit.usedFraction;
+  const percent = fraction === null ? 0 : Math.min(100, Math.max(0, fraction * 100));
+  const valueLabel =
+    limit.unit === "usd"
+      ? limit.limit === null
+        ? `${formatUsd(limit.used)} (no cap)`
+        : `${formatUsd(limit.used)} / ${formatUsd(limit.limit)}`
+      : `${Math.round(limit.used)}%`;
+  const elapsed = elapsedFraction(limit.durationMs, limit.resetsAt, now);
+  const pacePercent = elapsed === null ? null : elapsed * 100;
+  let paceLabel: string | null = null;
+  let aheadOfPace = false;
+  if (pacePercent !== null && fraction !== null) {
+    const diff = Math.round(percent - pacePercent);
+    aheadOfPace = diff > 0;
+    paceLabel =
+      diff === 0 ? "on pace" : diff > 0 ? `${diff}% ahead of pace` : `${-diff}% under pace`;
+  }
+  const resetLabel =
+    limit.resetsAt === null
+      ? null
+      : limit.resetsAt <= now
+        ? "resetting"
+        : `resets in ${formatDuration(limit.resetsAt - now)}`;
+  return {
+    id: limit.id,
+    label: limit.label,
+    percent,
+    valueLabel,
+    tone: toneFor(limit.status, fraction),
+    pacePercent,
+    paceLabel,
+    aheadOfPace,
+    resetLabel,
+  };
+}
+
+// ── Provider cards ────────────────────────────────────────────────────────────
+
+export interface ProviderCardView {
+  readonly provider: AccountUsageProviderId;
+  readonly label: string;
+  /** "Pro · [email protected]" / null. */
+  readonly subtitle: string | null;
+  readonly state: AccountUsageState;
+  /** Badge text for non-fresh states ("stale", "unavailable", …) or null when fresh. */
+  readonly stateBadge: string | null;
+  /** Explanatory line for empty/non-fresh states, else null. */
+  readonly message: string | null;
+  readonly bars: readonly UsageBarView[];
+  /** "updated 3m ago" / null. */
+  readonly ageLabel: string | null;
+  /** Credit-overage note (Codex), or null. */
+  readonly creditNote: string | null;
+}
+
+function stateMessage(r: AccountUsageReport): string | null {
+  switch (r.state) {
+    case "fresh":
+      return r.limits.length === 0 ? "No quota windows reported." : null;
+    case "stale":
+      return `Showing last known usage — refresh failed${r.error ? ` (${r.error})` : ""}.`;
+    case "unavailable":
+      return `Usage unavailable${r.error ? `: ${r.error}` : "."}`;
+    case "unsupported":
+      return r.error ?? "This credential type can't report subscription usage.";
+    case "not-configured":
+      return r.provider === "claude"
+        ? "Not signed in to Claude (no OAuth credentials)."
+        : "Not signed in to Codex (no ChatGPT OAuth credentials).";
+  }
+}
+
+function capitalize(s: string): string {
+  return s.length === 0 ? s : s[0]?.toUpperCase() + s.slice(1);
+}
+
+export function viewProviderCard(r: AccountUsageReport, now: number): ProviderCardView {
+  const parts = [
+    r.account?.planType ? capitalize(r.account.planType) : null,
+    r.account?.email ?? null,
+  ].filter((p): p is string => p !== null && p !== "");
+  let creditNote: string | null = null;
+  if (r.creditOverage) {
+    creditNote = "Plan allowance used — requests are being funded by credits.";
+  } else if (r.limitReached === true && r.canServe === false) {
+    creditNote = "Plan limit reached — requests are blocked until reset.";
+  }
+  return {
+    provider: r.provider,
+    label: r.label,
+    subtitle: parts.length > 0 ? parts.join(" · ") : null,
+    state: r.state,
+    stateBadge: r.state === "fresh" ? null : r.state.replace("-", " "),
+    message: stateMessage(r),
+    bars: r.limits.map((l) => viewUsageBar(l, now)),
+    ageLabel: r.state === "fresh" || r.state === "stale" ? formatAge(r.fetchedAt, now) : null,
+    creditNote,
+  };
+}
+
+export function viewProviderCards(
+  usage: AccountUsageResponse,
+  now: number,
+): readonly ProviderCardView[] {
+  return usage.providers.map((p) => viewProviderCard(p, now));
+}