indicate historical rates support in exchange source drop-down

src/main/java/com/sparrowwallet/sparrow/net/ExchangeSource.java

@@ -21,7 +21,7 @@ import java.util.*;
 import java.util.stream.Collectors;
 
 public enum ExchangeSource {
-    NONE("None") {
+    NONE("None", null) {
         @Override
         public List<Currency> getSupportedCurrencies() {
             return Collections.emptyList();
@@ -37,7 +37,7 @@ public enum ExchangeSource {
             return Collections.emptyMap();
         }
     },
-    COINBASE("Coinbase") {
+    COINBASE("Coinbase", "No historical rates") {
         @Override
         public List<Currency> getSupportedCurrencies() {
             return getRates().data.rates.keySet().stream().filter(code -> isValidISO4217Code(code.toUpperCase(Locale.ROOT)))
@@ -121,7 +121,7 @@ public enum ExchangeSource {
             return historicalRates;
         }
     },
-    COINGECKO("Coingecko") {
+    COINGECKO("Coingecko", "No historical rates") {
         @Override
         public List<Currency> getSupportedCurrencies() {
             return getRates().rates.entrySet().stream().filter(rate -> "fiat".equals(rate.getValue().type) && isValidISO4217Code(rate.getKey().toUpperCase(Locale.ROOT)))
@@ -189,7 +189,7 @@ public enum ExchangeSource {
             return historicalRates;
         }
     },
-    MEMPOOL_SPACE("mempool.space") {
+    MEMPOOL_SPACE("mempool.space", "Historical rates from Apr 2023") {
         @Override
         public List<Currency> getSupportedCurrencies() {
             return getRates().rates.entrySet().stream().filter(price -> isValidISO4217Code(price.getKey().toUpperCase(Locale.ROOT)))
@@ -262,9 +262,11 @@ public enum ExchangeSource {
     private static final Logger log = LoggerFactory.getLogger(ExchangeSource.class);
 
     private final String name;
+    private final String description;
 
-    ExchangeSource(String name) {
+    ExchangeSource(String name, String description) {
         this.name = name;
+        this.description = description;
     }
 
     public abstract List<Currency> getSupportedCurrencies();
@@ -282,6 +284,14 @@ public enum ExchangeSource {
         }
     }
 
+    public String getName() {
+        return name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
     @Override
     public String toString() {
         return name;

src/main/java/com/sparrowwallet/sparrow/settings/GeneralSettingsController.java

@@ -19,6 +19,7 @@ import javafx.collections.ObservableList;
 import javafx.fxml.FXML;
 import javafx.scene.control.ComboBox;
 import javafx.scene.control.Label;
+import javafx.scene.control.ListCell;
 import javafx.util.StringConverter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -158,6 +159,9 @@ public class GeneralSettingsController extends SettingsDetailController {
             config.setExchangeSource(exchangeSource.getValue());
         }
 
+        exchangeSource.setButtonCell(new ExchangeSourceButtonCell());
+        exchangeSource.setCellFactory(_ -> new ExchangeSourceListCell());
+
         exchangeSource.valueProperty().addListener((observable, oldValue, source) -> {
             config.setExchangeSource(source);
             updateCurrencies(source);
@@ -253,4 +257,32 @@ public class GeneralSettingsController extends SettingsDetailController {
 
         fiatCurrency.valueProperty().addListener(fiatCurrencyListener);
     }
+
+    private static class ExchangeSourceButtonCell extends ListCell<ExchangeSource> {
+        @Override
+        protected void updateItem(ExchangeSource exchangeSource, boolean empty) {
+            super.updateItem(exchangeSource, empty);
+            if(exchangeSource == null || empty) {
+                setText("");
+            } else {
+                setText(exchangeSource.getName());
+            }
+        }
+    }
+
+    private static class ExchangeSourceListCell extends ListCell<ExchangeSource> {
+        @Override
+        protected void updateItem(ExchangeSource exchangeSource, boolean empty) {
+            super.updateItem(exchangeSource, empty);
+            if(exchangeSource == null || empty) {
+                setText("");
+            } else {
+                String text = exchangeSource.getName();
+                if(exchangeSource.getDescription() != null && !exchangeSource.getDescription().isEmpty()) {
+                    text += " (" + exchangeSource.getDescription() + ")";
+                }
+                setText(text);
+            }
+        }
+    }
 }

src/main/resources/com/sparrowwallet/sparrow/settings/general.fxml

@@ -52,7 +52,7 @@
                 <ComboBox fx:id="fiatCurrency" />
             </Field>
             <Field text="Exchange rate source:">
-                <ComboBox fx:id="exchangeSource">
+                <ComboBox fx:id="exchangeSource" prefWidth="150">
                     <items>
                         <FXCollections fx:factory="observableArrayList">
                             <ExchangeSource fx:constant="NONE" />