historical rates: 1000 USD in EUR on 2024-01-01 via frankfurter.app

src-tauri/src/main.rs

@@ -315,6 +315,60 @@ async fn fetch_market_data(
     Ok(prices)
 }
 
+// ---------- historical rates (frankfurter.app, cached permanently per date)
+
+fn valid_date_str(date: &str) -> bool {
+    let parts: Vec<&str> = date.split('-').collect();
+    parts.len() == 3
+        && parts[0].len() == 4
+        && parts[1].len() == 2
+        && parts[2].len() == 2
+        && parts.iter().all(|p| p.chars().all(|c| c.is_ascii_digit()))
+}
+
+#[tauri::command]
+async fn fetch_historical_rates(
+    app: AppHandle,
+    date: String,
+) -> Result<std::collections::HashMap<String, f64>, String> {
+    if !valid_date_str(&date) {
+        return Err("invalid date format".into());
+    }
+    let cache_path = data_dir(&app).join(format!("rates-{}.json", date));
+    if let Ok(raw) = fs::read_to_string(&cache_path) {
+        if let Ok(cached) = serde_json::from_str::<std::collections::HashMap<String, f64>>(&raw) {
+            return Ok(cached);
+        }
+    }
+    let client = reqwest::Client::builder()
+        .timeout(std::time::Duration::from_secs(15))
+        .build()
+        .map_err(|e| e.to_string())?;
+    let url = format!("https://api.frankfurter.app/{}?from=USD", date);
+    let body: serde_json::Value = client
+        .get(&url)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?
+        .json()
+        .await
+        .map_err(|e| e.to_string())?;
+    let raw_rates = body["rates"].as_object().ok_or("no rates in response")?;
+    let mut rates = std::collections::HashMap::new();
+    rates.insert("USD".to_string(), 1.0_f64);
+    for (code, val) in raw_rates {
+        if let Some(v) = val.as_f64() {
+            if v > 0.0 {
+                rates.insert(code.to_uppercase(), v);
+            }
+        }
+    }
+    if let Ok(serialized) = serde_json::to_string(&rates) {
+        write_atomic(&cache_path, &serialized).ok();
+    }
+    Ok(rates)
+}
+
 // ---------- documents in the (possibly custom) data folder
 
 #[tauri::command]
@@ -636,6 +690,7 @@ fn main() {
             data_dir_has_documents,
             migrate_data_dir,
             fetch_rates,
+            fetch_historical_rates,
             fetch_market_data,
             load_extensions,
             open_extensions_folder,

src-tauri/tauri.conf.json

@@ -23,7 +23,7 @@
       }
     ],
     "security": {
-      "csp": "default-src 'self'; script-src 'self' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self' data:; connect-src ipc: http://ipc.localhost https://open.er-api.com https://api.coingecko.com https://query1.finance.yahoo.com https://query2.finance.yahoo.com"
+      "csp": "default-src 'self'; script-src 'self' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self' data:; connect-src ipc: http://ipc.localhost https://open.er-api.com https://api.coingecko.com https://query1.finance.yahoo.com https://query2.finance.yahoo.com https://api.frankfurter.app"
     }
   },
   "bundle": {

src/engine/engine.test.ts

@@ -302,6 +302,16 @@ describe("dates", () => {
   });
 });
 
+describe("historical rates", () => {
+  it("in EUR on date uses injected historical rate", () => {
+    eng.setHistoricalRates("2024-01-01", { EUR: 0.9, USD: 1 });
+    expect(calc("1000 USD in EUR on 2024-01-01")).toBe("€ 900");
+  });
+  it("missing historical date returns null", () => {
+    expect(calc("500 USD in EUR on 1800-01-01")).toBeNull();
+  });
+});
+
 describe("goal seek", () => {
   it("? * 1.2 = 1000", () => expect(calc("? * 1.2 = 1000")).toBe("833.33"));
   it("? + 50 = 200", () => expect(calc("? + 50 = 200")).toBe("150"));

src/engine/evaluator.ts

@@ -19,6 +19,8 @@ export interface EvalCtx {
   reg: Registry;
   vars: Map<string, Value>;
   line: LineCtx;
+  /** date → { code → rate-per-usd } */
+  historicalRates?: Map<string, Map<string, number>>;
 }
 
 const PI = new Decimal("3.14159265358979323846264338327950288419716939937510");
@@ -332,8 +334,16 @@ function evalConv(v: Value, target: ConvTarget, ctx: EvalCtx): Value {
       return convertQ(v, target.unit);
     }
     case "currency": {
-      const unit = ctx.reg.makeCurrencyUnit(target.code);
-      if (!unit) throw new EvalError(`no rate for ${target.code}`);
+      let unit;
+      if (target.onDate) {
+        const dateRates = ctx.historicalRates?.get(target.onDate);
+        const rate = dateRates?.get(target.code);
+        if (rate === undefined) throw new EvalError(`no historical rate for ${target.code} on ${target.onDate}`);
+        unit = ctx.reg.makeCurrencyUnitFromRate(target.code, new Decimal(rate));
+      } else {
+        unit = ctx.reg.makeCurrencyUnit(target.code);
+        if (!unit) throw new EvalError(`no rate for ${target.code}`);
+      }
       if (v.kind !== "quantity") throw new EvalError("cannot convert to currency");
       if (!v.unit) return qty(v.value, unit);
       return convertQ(v, unit);

src/engine/index.ts

@@ -39,8 +39,8 @@ export interface ExtensionValue {
 export class SumEngine {
   reg: Registry;
   settings: EngineSettings;
-  /** variables defined by extensions, persist across evaluations */
   private globals = new Map<string, Value>();
+  private historicalRates = new Map<string, Map<string, number>>();
 
   constructor(settings: Partial<EngineSettings> = {}) {
     this.settings = { ...defaultSettings, ...settings };
@@ -49,10 +49,19 @@ export class SumEngine {
   }
 
   setRates(rates: Record<string, number | string>): void {
-    // snapshot fills codes the live API doesn't return (e.g. crypto when CoinGecko fails)
     this.reg.setRates({ ...snapshot.rates, ...cryptoSnapshot, ...rates });
   }
 
+  setHistoricalRates(date: string, rates: Record<string, number>): void {
+    const m = new Map<string, number>();
+    for (const [k, v] of Object.entries(rates)) m.set(k.toUpperCase(), v);
+    this.historicalRates.set(date, m);
+  }
+
+  hasHistoricalRates(date: string): boolean {
+    return this.historicalRates.has(date);
+  }
+
   updateSettings(patch: Partial<EngineSettings>): void {
     this.settings = { ...this.settings, ...patch };
   }
@@ -98,6 +107,7 @@ export class SumEngine {
           reg: this.reg,
           vars,
           line: { lineValues, lineKinds, index: i, lineText: rawLine },
+          historicalRates: this.historicalRates,
         };
         try {
           value = evaluate(parsed.expr, ctx);

src/engine/parser.ts

@@ -7,7 +7,7 @@ import { PctOp, DateWord, BitOp } from "./registry";
 
 export type ConvTarget =
   | { type: "unit"; unit: Unit }
-  | { type: "currency"; code: string }
+  | { type: "currency"; code: string; onDate?: string }
   | { type: "repr"; repr: NumeralRepr }
   | { type: "tz"; words: string[] }
   | { type: "scale"; mult: Decimal; label: string }
@@ -115,7 +115,7 @@ class Parser {
         this.i++;
         const target = this.parseTarget();
         if (target) {
-          items = [{ k: "conv", x: mk(), target }];
+          items = [{ k: "conv", x: mk(), target: this.tryHistoricalDate(target) }];
           continue;
         }
         this.i = save + 1; // drop the conversion word, it was noise
@@ -195,7 +195,7 @@ class Parser {
           this.i = save;
           break;
         }
-        l = { k: "conv", x: l, target };
+        l = { k: "conv", x: l, target: this.tryHistoricalDate(target) };
       } else if (tk?.t === "pctop" && (tk.op.startsWith("as_pct") || tk.op.endsWith("what_is"))) {
         this.i++;
         const r = this.parseAdd();
@@ -208,6 +208,24 @@ class Parser {
     return l;
   }
 
+  /** If the current token is `pctop(on)` + `datelit`, consume them and attach `onDate`. */
+  private tryHistoricalDate(target: ConvTarget): ConvTarget {
+    if (target.type !== "currency") return target;
+    const nx = this.peek();
+    if (nx?.t !== "pctop" || nx.op !== "on") return target;
+    const save = this.i;
+    this.i++;
+    const dk = this.peek();
+    if (dk?.t === "datelit") {
+      this.i++;
+      const d = new Date(dk.ms);
+      const onDate = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-${String(d.getDate()).padStart(2, "0")}`;
+      return { ...target, onDate };
+    }
+    this.i = save;
+    return target;
+  }
+
   private parseTarget(): ConvTarget | null {
     const tk = this.peek();
     if (!tk) return null;

src/engine/registry.ts

@@ -134,10 +134,14 @@ export class Registry {
   makeCurrencyUnit(code: string): Unit | null {
     const rate = this.rates.get(code);
     if (!rate) return null;
+    return this.makeCurrencyUnitFromRate(code, rate);
+  }
+
+  makeCurrencyUnitFromRate(code: string, ratePerUsd: Decimal): Unit {
     return {
       id: code,
       dimension: "currency",
-      ratio: new Decimal(1).div(rate), // USD per 1 unit
+      ratio: new Decimal(1).div(ratePerUsd), // USD per 1 unit
       format: this.currencyFormat.get(code) ?? `{} ${code}`,
     };
   }

src/main.ts

@@ -5,7 +5,7 @@ import { SumEditor } from "./ui/editor";
 import {
   AppData, DocMeta, SettingsData, defaultSettingsData,
   loadAppData, saveAppData, flushAppData, onAppQuit, loadSettings, saveSettings,
-  fetchRates, fetchMarketData, writeImageFile, loadExtensionScripts, openExtensionsFolder, isTauri,
+  fetchRates, fetchMarketData, fetchHistoricalRates, writeImageFile, loadExtensionScripts, openExtensionsFolder, isTauri,
   getLaunchFile, onOpenFile, onFileDrop,
   setDataDir, runBackups, backupDeletedSheet, openBackupsFolder,
   chooseFolder, dataDirHasDocuments, migrateDataDir,
@@ -143,11 +143,13 @@ function renderDocList(): void {
 
 function switchDoc(id: string): void {
   data.activeId = id;
-  editor.setText(data.contents[id] ?? "");
+  const text = data.contents[id] ?? "";
+  editor.setText(text);
   syncTitleField();
   renderDocList();
   saveAppData(data);
   editor.focus();
+  void fetchNeededHistoricalRates(text);
 }
 
 function newDoc(content = ""): void {
@@ -572,6 +574,23 @@ async function refreshMarket(force = false): Promise<void> {
   renderMarketInfo();
 }
 
+// ---------- historical rates
+
+const HIST_DATE_RE = /(?:on|на)\s+(\d{4}-\d{2}-\d{2})/gi;
+
+async function fetchNeededHistoricalRates(text: string): Promise<void> {
+  const dates = new Set<string>();
+  for (const m of text.matchAll(HIST_DATE_RE)) dates.add(m[1]!);
+  let fetched = false;
+  for (const date of dates) {
+    if (!engine.hasHistoricalRates(date)) {
+      const rates = await fetchHistoricalRates(date);
+      if (rates) { engine.setHistoricalRates(date, rates); fetched = true; }
+    }
+  }
+  if (fetched) editor.refresh();
+}
+
 function renderMarketInfo(): void {
   const el = $("#market-info") as HTMLElement;
   if (marketFetchedAt === 0) { el.style.display = "none"; return; }
@@ -770,6 +789,7 @@ async function boot(): Promise<void> {
         }
         renderDocList();
         saveAppData(data);
+        void fetchNeededHistoricalRates(text);
       },
       onCopy(text) {
         void navigator.clipboard.writeText(text);

src/storage.ts

@@ -205,6 +205,27 @@ export async function fetchRates(force = false): Promise<RatesPayload | null> {
   return null;
 }
 
+// ---------- historical rates
+
+export async function fetchHistoricalRates(date: string): Promise<Record<string, number> | null> {
+  try {
+    if (isTauri()) {
+      return await invoke<Record<string, number>>("fetch_historical_rates", { date });
+    }
+    const res = await fetch(`https://api.frankfurter.app/${date}?from=USD`);
+    const json = await res.json();
+    if (!json?.rates) return null;
+    const out: Record<string, number> = { USD: 1 };
+    for (const [k, v] of Object.entries(json.rates as Record<string, number>)) {
+      if (v > 0) out[k.toUpperCase()] = v;
+    }
+    return out;
+  } catch (e) {
+    console.warn("fetchHistoricalRates failed", date, e);
+    return null;
+  }
+}
+
 // ---------- image export
 
 export async function writeImageFile(path: string, dataBase64: string): Promise<void> {