feat: show every amount in one currency, chosen in the header, $ toggles it

A selector in the header and the palette's Currency group pick the
currency, the primary one by default; the choice persists between pages
and $ switches it on and off. Rates come from Firefly's exchange rates,
then from the owner's own transactions with a foreign amount, walking
through other currencies when there is no direct pair. Amount converts
with a ≈ and keeps the original in its title; Money sums several
currencies into one converted amount.

src/lib/components/Amount.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
   import { formatMoney, type Money, toNumber } from "#lib/format.js";
+  import { display } from "#lib/money/display.svelte.js";
 
   export type Tone = "income" | "expense" | "transfer" | "neutral" | "auto";
 
@@ -10,10 +11,31 @@
     decimals,
     tone = "auto",
     signed = false,
+    approx = false,
+    exact = false,
     class: className = "",
-  }: Money & { tone?: Tone; signed?: boolean; class?: string } = $props();
+  }: Money & {
+    tone?: Tone;
+    signed?: boolean;
+    approx?: boolean;
+    exact?: boolean;
+    class?: string;
+  } = $props();
 
   const value = $derived(toNumber(amount));
+  const converted = $derived(
+    exact || !code || code === display.code
+      ? null
+      : display.convert(value, code)
+  );
+  const original = $derived(
+    formatMoney({ amount, code, decimals, symbol }, signed)
+  );
+  const shown = $derived(
+    converted === null
+      ? original
+      : formatMoney({ ...display.target, amount: converted }, signed)
+  );
   const resolved = $derived.by(() => {
     if (tone !== "auto") {
       return tone;
@@ -33,6 +55,8 @@
   );
 </script>
 
-<span class="num font-medium {color} {className}"
-  >{formatMoney({ amount, code, decimals, symbol }, signed)}</span
+<span
+  class="num font-medium {color} {className}"
+  title={converted === null ? undefined : original}
+  >{approx || converted !== null ? "≈" : ""}{shown}</span
 >

src/lib/components/Money.svelte

@@ -0,0 +1,45 @@
+<script lang="ts">
+  import type { Money } from "#lib/format.js";
+  import { display } from "#lib/money/display.svelte.js";
+  import Amount, { type Tone } from "./Amount.svelte";
+
+  let {
+    parts,
+    tone = "auto",
+    signed = false,
+    inline = false,
+    class: className = "",
+  }: {
+    parts: Money[];
+    tone?: Tone;
+    signed?: boolean;
+    inline?: boolean;
+    class?: string;
+  } = $props();
+
+  const total = $derived(display.total(parts));
+</script>
+
+{#if total}
+  <Amount
+    amount={total.amount}
+    approx={total.converted}
+    class={className}
+    code={total.code}
+    decimals={total.decimals}
+    {signed}
+    symbol={total.symbol}
+    {tone}
+  />
+{:else if inline}
+  {#each parts as part, index (part.code ?? index)}
+    {#if index > 0}
+      <span class="text-cladd-fg-softer"> + </span>
+    {/if}
+    <Amount {...part} class={className} {signed} {tone} />
+  {/each}
+{:else}
+  {#each parts as part, index (part.code ?? index)}
+    <div><Amount {...part} class={className} {signed} {tone} /></div>
+  {/each}
+{/if}

src/lib/components/shell/Palette.svelte

@@ -4,6 +4,7 @@
   import { lists } from "#lib/api/lists.js";
   import { fuzzyFilter } from "#lib/fuzzy.js";
   import { keys, prettyKeys } from "#lib/keys.svelte.js";
+  import { display } from "#lib/money/display.svelte.js";
   import { allLinks, CREATE_LINKS } from "#lib/nav.js";
   import { searches } from "#lib/transactions/searches.svelte.js";
   import { ui } from "#lib/ui.svelte.js";
@@ -227,10 +228,26 @@
       : []
   );
 
+  const currencyEntries = $derived<Entry[]>([
+    {
+      group: "Currency",
+      id: "currency:own",
+      label: "Show amounts in their own currencies",
+      run: () => display.show(null),
+    },
+    ...display.options.map((currency) => ({
+      group: "Currency",
+      id: `currency:${currency.code}`,
+      label: `Show everything in ${currency.code} (${currency.symbol})`,
+      run: () => display.show(currency.code),
+    })),
+  ]);
+
   const entries = $derived([
     ...pageEntries,
     ...searchEntries,
     ...staticEntries,
+    ...currencyEntries,
     ...commandEntries,
     ...entityEntries,
   ]);

src/lib/dashboard/primary.svelte.ts

@@ -2,9 +2,9 @@ import { api } from "#lib/api/client.js";
 import { all } from "#lib/api/lists.js";
 import type { ExchangeRate, Page, TransactionGroup } from "#lib/api/types.js";
 import { formatMoney, toNumber } from "#lib/format.js";
+import { display } from "#lib/money/display.svelte.js";
 import { session } from "#lib/session.svelte.js";
 
-const KEY = "ffui.dashboard.in-primary";
 const OWN_SAMPLE = 100;
 const HOUR_MS = 3_600_000;
 
@@ -25,13 +25,12 @@ export function median(values: number[]): number {
 }
 
 class InPrimary {
-  on = $state(
-    typeof localStorage !== "undefined" && localStorage.getItem(KEY) === "1"
-  );
+  get on() {
+    return display.on && display.code === session.primary?.code;
+  }
 
   toggle() {
-    this.on = !this.on;
-    localStorage.setItem(KEY, this.on ? "1" : "0");
+    display.toggle();
   }
 }
 

src/lib/money/display.svelte.ts

@@ -0,0 +1,220 @@
+import { api } from "#lib/api/client.js";
+import { all, queryClient } from "#lib/api/lists.js";
+import type { ExchangeRate, Page, TransactionGroup } from "#lib/api/types.js";
+import { formatMoney, type Money, toNumber } from "#lib/format.js";
+import { session } from "#lib/session.svelte.js";
+
+const KEY = "ffui.display";
+const OWN_SAMPLE = 200;
+const HOUR_MS = 3_600_000;
+
+type Graph = Map<string, Map<string, number>>;
+
+export interface Total {
+  amount: number;
+  code: string;
+  converted: boolean;
+  decimals: number;
+  symbol: string;
+}
+
+function link(graph: Graph, from: string, to: string, rate: number) {
+  if (!(rate > 0 && Number.isFinite(rate)) || from === to) {
+    return;
+  }
+  const row = graph.get(from) ?? new Map<string, number>();
+  if (!row.has(to)) {
+    row.set(to, rate);
+  }
+  graph.set(from, row);
+}
+
+function listed(rates: { attributes: ExchangeRate }[], graph: Graph) {
+  const latest = new Map<string, { date: string; rate: number }>();
+  for (const { attributes: r } of rates) {
+    const from = r.from_currency_code;
+    const to = r.to_currency_code;
+    const rate = toNumber(r.rate);
+    const date = r.date ?? "";
+    const key = `${from}>${to}`;
+    if (from && to && rate && date >= (latest.get(key)?.date ?? "")) {
+      latest.set(key, { date, rate });
+    }
+  }
+  for (const [key, { rate }] of latest) {
+    const [from, to] = key.split(">");
+    link(graph, from, to, rate);
+    link(graph, to, from, 1 / rate);
+  }
+}
+
+function implied(groups: { attributes: TransactionGroup }[], graph: Graph) {
+  const sums = new Map<string, [number, number]>();
+  for (const split of groups.flatMap((g) => g.attributes.transactions)) {
+    const from = split.currency_code;
+    const to = split.foreign_currency_code;
+    const x = Math.abs(toNumber(split.amount));
+    const y = Math.abs(toNumber(split.foreign_amount));
+    if (from && to && from !== to && x > 0 && y > 0) {
+      const pair = sums.get(`${from}>${to}`) ?? [0, 0];
+      sums.set(`${from}>${to}`, [pair[0] + x, pair[1] + y]);
+    }
+  }
+  for (const [key, [x, y]] of sums) {
+    const [from, to] = key.split(">");
+    link(graph, from, to, y / x);
+    link(graph, to, from, x / y);
+  }
+}
+
+async function loadGraph(): Promise<Graph> {
+  const [rates, own] = await Promise.all([
+    all<ExchangeRate>("/v1/exchange-rates").catch(() => []),
+    api<Page<TransactionGroup>>("/v1/search/transactions", {
+      query: { limit: OWN_SAMPLE, query: "has_foreign_amount:true" },
+    }).catch(() => ({ data: [] })),
+  ]);
+  const graph: Graph = new Map();
+  listed(rates, graph);
+  implied(own.data, graph);
+  return graph;
+}
+
+function rateIn(graph: Graph, from: string, to: string): number | null {
+  if (from === to) {
+    return 1;
+  }
+  const rates = new Map([[from, 1]]);
+  const queue = [from];
+  for (const code of queue) {
+    const base = rates.get(code) ?? 1;
+    for (const [next, rate] of graph.get(code) ?? []) {
+      if (!rates.has(next)) {
+        rates.set(next, base * rate);
+        queue.push(next);
+      }
+    }
+    if (rates.has(to)) {
+      return rates.get(to) ?? null;
+    }
+  }
+  return null;
+}
+
+function read(): { code: string | null; on: boolean } {
+  try {
+    return JSON.parse(localStorage.getItem(KEY) ?? "") ?? {};
+  } catch {
+    return { code: null, on: false };
+  }
+}
+
+class Display {
+  on = $state(false);
+  chosen = $state<string | null>(null);
+  graph = $state.raw<Graph | null>(null);
+
+  constructor() {
+    if (typeof localStorage !== "undefined") {
+      const saved = read();
+      this.on = saved.on === true;
+      this.chosen = saved.code ?? null;
+    }
+  }
+
+  get code(): string {
+    return this.chosen ?? session.primary?.code ?? "";
+  }
+
+  get target() {
+    const { code } = this;
+    const found = session.currencies.find((c) => c.attributes.code === code);
+    return {
+      code,
+      decimals: found?.attributes.decimal_places ?? 2,
+      symbol: found?.attributes.symbol ?? code,
+    };
+  }
+
+  get active(): boolean {
+    return this.on && this.graph !== null && this.code !== "";
+  }
+
+  get options() {
+    return session.currencies
+      .filter((c) => c.attributes.enabled)
+      .map((c) => c.attributes);
+  }
+
+  private save() {
+    localStorage.setItem(
+      KEY,
+      JSON.stringify({ code: this.chosen, on: this.on })
+    );
+  }
+
+  async load() {
+    if (this.graph) {
+      return;
+    }
+    this.graph = await queryClient.fetchQuery({
+      queryFn: loadGraph,
+      queryKey: ["display-rates"],
+      staleTime: HOUR_MS,
+    });
+  }
+
+  show(code: string | null) {
+    if (code === null) {
+      this.on = false;
+    } else {
+      this.chosen = code;
+      this.on = true;
+      this.load().catch(() => undefined);
+    }
+    this.save();
+  }
+
+  toggle() {
+    this.show(this.on ? null : this.code);
+  }
+
+  rate(from: string | null | undefined): number | null {
+    if (!(this.active && this.graph && from)) {
+      return null;
+    }
+    return rateIn(this.graph, from, this.code);
+  }
+
+  convert(amount: number, from: string | null | undefined): number | null {
+    const rate = this.rate(from);
+    return rate === null ? null : amount * rate;
+  }
+
+  total(parts: Money[]): Total | null {
+    if (!this.active || parts.length === 0) {
+      return null;
+    }
+    let amount = 0;
+    let converted = false;
+    for (const part of parts) {
+      const value = this.convert(toNumber(part.amount), part.code);
+      if (value === null) {
+        return null;
+      }
+      amount += value;
+      converted ||= part.code !== this.code;
+    }
+    return { ...this.target, amount, converted };
+  }
+
+  text(parts: Money[], signed = false, separator = " + "): string {
+    const sum = this.total(parts);
+    if (sum) {
+      return `${sum.converted ? "≈" : ""}${formatMoney(sum, signed)}`;
+    }
+    return parts.map((part) => formatMoney(part, signed)).join(separator);
+  }
+}
+
+export const display = new Display();

src/routes/+page.svelte

@@ -14,30 +14,11 @@
   import PiggyBanksBox from "#lib/components/dashboard/PiggyBanksBox.svelte";
   import SubscriptionsBox from "#lib/components/dashboard/SubscriptionsBox.svelte";
   import PageHeader from "#lib/components/shell/PageHeader.svelte";
-  import Checkbox from "#lib/components/ui/checkbox/checkbox.svelte";
   import { provideColumn } from "#lib/dashboard/column.svelte.js";
-  import { inPrimary, ratesQuery } from "#lib/dashboard/primary.svelte.js";
-  import { useKeys } from "#lib/keys.svelte.js";
   import { period } from "#lib/period.svelte.js";
-  import { session } from "#lib/session.svelte.js";
 
   provideColumn();
 
-  const rates = createQuery(() => ratesQuery());
-  const primary = $derived(session.primary?.code ?? "");
-  const ownRates = $derived(
-    inPrimary.on && Object.values(rates.data ?? {}).some((r) => r.own)
-  );
-
-  useKeys(() => [
-    {
-      group: "Dashboard",
-      keys: "$",
-      label: `Show totals in ${primary}`,
-      run: () => inPrimary.toggle(),
-    },
-  ]);
-
   const assets = createQuery(() =>
     accountsQuery("asset", period.start, period.end)
   );
@@ -49,22 +30,7 @@
   });
 </script>
 
-<PageHeader subtitle="What's playing?" title="Dashboard">
-  {#snippet actions()}
-    <div class="flex items-center gap-1.5 text-[12px] text-cladd-fg-soft">
-      <Checkbox
-        checked={inPrimary.on}
-        id="in-primary"
-        onCheckedChange={() => inPrimary.toggle()}
-      />
-      <label for="in-primary">Show in {primary}</label>
-      <span class="hidden sm:inline"><span class="kbd">$</span></span>
-      {#if ownRates}
-        <span>≈ from your own exchanges</span>
-      {/if}
-    </div>
-  {/snippet}
-</PageHeader>
+<PageHeader subtitle="What's playing?" title="Dashboard" />
 
 <InfoBoxes />