Add oracle rates

src/tui/hooks/index.ts

@@ -23,3 +23,5 @@ export {
   useBlockableInput,
   useIsInputCaptured,
 } from "./useInputLayer.js";
+export { useRate, useBchToFiatRate } from "./useRates.js";
+export { useSatoshisConversion } from "./useSatoshisConversion.js";

src/tui/hooks/useRates.tsx

@@ -0,0 +1,68 @@
+import { useCallback, useMemo, useSyncExternalStore } from 'react';
+import type { RatesServiceEventMap } from '../../services/rates.js';
+import { useAppContext } from './useAppContext.js';
+
+/**
+ * Reactive hook for a single market pair.
+ *
+ * Pair format is NUMERATOR / DENOMINATOR, e.g. USD / BCH.
+ */
+export function useRate(
+  numeratorUnitCode: string,
+  denominatorUnitCode: string,
+): number | null {
+  const { appService } = useAppContext();
+
+  const normalizedNumerator = useMemo(
+    () => numeratorUnitCode.toUpperCase(),
+    [numeratorUnitCode],
+  );
+  
+  const normalizedDenominator = useMemo(
+    () => denominatorUnitCode.toUpperCase(),
+    [denominatorUnitCode],
+  );
+
+  const subscribe = useCallback(
+    (callback: () => void) => {
+      if (!appService) {
+        return () => {};
+      }
+
+      const onRateUpdated = (event: RatesServiceEventMap['rate-updated']) => {
+        if (
+          event.numeratorUnitCode === normalizedNumerator &&
+          event.denominatorUnitCode === normalizedDenominator
+        ) {
+          callback();
+        }
+      };
+
+      const unsubscribe = appService.rates.on('rate-updated', onRateUpdated);
+
+      return () => {
+        unsubscribe();
+      };
+    },
+    [appService, normalizedNumerator, normalizedDenominator],
+  );
+
+  const getSnapshot = useCallback(() => {
+    if (!appService) {
+      return null;
+    }
+
+    return appService.rates.getRate(normalizedNumerator, normalizedDenominator);
+  }, [appService, normalizedNumerator, normalizedDenominator]);
+
+  return useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+}
+
+/**
+ * Convenience hook for BCH -> fiat market rates.
+ */
+export function useBchToFiatRate(
+  targetCurrency: string = 'USD',
+): number | null {
+  return useRate(targetCurrency, 'BCH');
+}

src/tui/hooks/useSatoshisConversion.tsx

@@ -0,0 +1,42 @@
+import { useCallback, useMemo } from 'react';
+import { useAppContext } from './useAppContext.js';
+import { useBchToFiatRate } from './useRates.js';
+
+/**
+ * Reactive BCH satoshis -> fiat conversion helpers for TUI screens.
+ *
+ * This hook subscribes to rate updates through `useBchToFiatRate`, so any
+ * component using it will re-render automatically when the selected pair
+ * receives a new quote.
+ */
+export function useSatoshisConversion(targetCurrency: string = 'USD') {
+  const { appService } = useAppContext();
+  const currencyCode = useMemo(() => targetCurrency.toUpperCase(), [targetCurrency]);
+  const fiatPerBchRate = useBchToFiatRate(currencyCode);
+
+  const formattedFiatPerBchRate = useMemo(() => {
+    if (!appService || fiatPerBchRate === null) {
+      return null;
+    }
+
+    return appService.rates.formatCurrency(fiatPerBchRate, currencyCode);
+  }, [appService, fiatPerBchRate, currencyCode]);
+
+  const formatSatoshisToFiat = useCallback(
+    (satoshis: bigint): string | null => {
+      if (!appService || fiatPerBchRate === null) {
+        return null;
+      }
+
+      return appService.rates.formatBchToFiat(satoshis, currencyCode);
+    },
+    [appService, fiatPerBchRate, currencyCode],
+  );
+
+  return {
+    currencyCode,
+    fiatPerBchRate,
+    formattedFiatPerBchRate,
+    formatSatoshisToFiat,
+  } as const;
+}