Add internationalization API to GUI

This commit intentionally fails one test, since that is for
functionality I intend to add later.

6 files changed, 97 insertions, 1 deletions

diff --git a/.classpath b/.classpath
index d4e759d..02a1f84 100644
--- a/.classpath
+++ b/.classpath
@@ -25,6 +25,6 @@
 			<attribute name="module" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
 	<classpathentry kind="output" path="bin/default"/>
 </classpath>
diff --git a/src/main/java/sevenUnitsGUI/Presenter.java b/src/main/java/sevenUnitsGUI/Presenter.java
index c46ee53..21f2951 100644
--- a/src/main/java/sevenUnitsGUI/Presenter.java
+++ b/src/main/java/sevenUnitsGUI/Presenter.java
@@ -22,6 +22,7 @@ import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -77,6 +78,15 @@ public final class Presenter {
 	/** A Predicate that returns true iff the argument is a full base unit */
 	private static final Predicate<Unit> IS_FULL_BASE = unit -> unit instanceof LinearUnit
 			&& ((LinearUnit) unit).isBase();
+	/** 
+	 * The default locale, used in two situations:
+	 * <ul>
+	 * <li> If no text is available in your locale,
+	 * uses text from this locale.
+	 * <li> Users are initialized with this locale.
+	 * </ul>
+	 */
+	static final String DEFAULT_LOCALE = "en";
 	
 	/**
 	 * Adds default units and dimensions to a database.
@@ -317,6 +327,12 @@ public final class Presenter {
 	 */
 	private final Set<String> metricExceptions;
 	
+	/** maps locale names (e.g. 'en') to key-text maps */
+	final Map<String, Map<String, String>> locales;
+	
+	/** name of locale in locales to use */
+	String userLocale;
+	
 	/**
 	 * If this is true, views that show units as a list will have metric units
 	 * removed from the From unit list and imperial/USC units removed from the To
@@ -375,6 +391,9 @@ public final class Presenter {
 					e);
 		}
 		
+		// TODO load locales
+		this.locales = new HashMap<>();
+		
 		// set default settings temporarily
 		if (Files.exists(CONFIG_FILE)) {
 			this.loadSettings(CONFIG_FILE);
@@ -736,6 +755,14 @@ public final class Presenter {
 	}
 	
 	/**
+	 * @return set of all locales available to select
+	 * @since 2025-02-21
+	 */
+	public final Set<String> getAvailableLocales() {
+		return this.locales.keySet();
+	}
+	
+	/**
 	 * Gets a name for this dimension using the database
 	 *
 	 * @param dimension dimension to name
@@ -751,6 +778,20 @@ public final class Presenter {
 	}
 	
 	/**
+	 * Gets the correct text for a provided ID.
+	 * If this text is available in the user's locale, that text is provided.
+	 * Otherwise, text is taken from the system default locale {@link #DEFAULT_LOCALE}.
+	 * 
+	 * @param textID ID of text to get (used in locale files)
+	 * @return text to be displayed
+	 */
+	public String getLocalizedText(String textID) {
+		final Map<String, String> userLocale = this.locales.get(this.userLocale);
+		final Map<String, String> defaultLocale = this.locales.get(DEFAULT_LOCALE);
+		return userLocale.getOrDefault(textID, defaultLocale.get(textID));
+	}
+	
+	/**
 	 * @return the rule that is used by this presenter to convert numbers into
 	 *         strings
 	 * @since 2022-04-10
@@ -786,6 +827,14 @@ public final class Presenter {
 	}
 	
 	/**
+	 * @return user's selected locale
+	 * @since 2025-02-21
+	 */
+	public String getUserLocale() {
+		return userLocale;
+	}
+	
+	/**
 	 * @return a search rule that shows all single prefixes
 	 * @since 2022-07-08
 	 */
@@ -1100,6 +1149,15 @@ public final class Presenter {
 		this.updateView();
 	}
 	
+	/**
+	 * Sets the user's locale, updating the view.
+	 * @param userLocale locale to use
+	 */
+	public void setUserLocale(String userLocale) {
+		this.userLocale = userLocale;
+		this.view.updateText();
+	}
+	
 	private List<Map.Entry<String, String>> settingsFromFile(Path settingsFile) {
 		try (Stream<String> lines = Files.lines(settingsFile)) {
 			return lines.map(Presenter::withoutComments)
diff --git a/src/main/java/sevenUnitsGUI/TabbedView.java b/src/main/java/sevenUnitsGUI/TabbedView.java
index 6542541..493fc10 100644
--- a/src/main/java/sevenUnitsGUI/TabbedView.java
+++ b/src/main/java/sevenUnitsGUI/TabbedView.java
@@ -827,4 +827,9 @@ final class TabbedView implements ExpressionConversionView, UnitConversionView {
 		this.presenter.setNumberDisplayRule(roundingRule);
 		this.presenter.saveSettings();
 	}
+
+	@Override
+	public void updateText() {
+		// TODO Auto-generated method stub
+	}
 }
diff --git a/src/main/java/sevenUnitsGUI/View.java b/src/main/java/sevenUnitsGUI/View.java
index 7dd0c44..4140992 100644
--- a/src/main/java/sevenUnitsGUI/View.java
+++ b/src/main/java/sevenUnitsGUI/View.java
@@ -112,4 +112,11 @@ public interface View {
 	 */
 	void showUnit(NameSymbol name, String definition, String dimensionName,
 			UnitType type);
+	
+	/**
+	 * Updates the view's text to reflect the presenter's locale.
+	 * 
+	 * This method <b>must not</b> call {@link Presenter#setUserLocale(String)}.
+	 */
+	void updateText();
 }
diff --git a/src/main/java/sevenUnitsGUI/ViewBot.java b/src/main/java/sevenUnitsGUI/ViewBot.java
index e6593fb..8fff46d 100644
--- a/src/main/java/sevenUnitsGUI/ViewBot.java
+++ b/src/main/java/sevenUnitsGUI/ViewBot.java
@@ -505,4 +505,9 @@ public final class ViewBot
 	public List<UnitViewingRecord> unitViewList() {
 		return Collections.unmodifiableList(this.unitViewingRecords);
 	}
+
+	@Override
+	public void updateText() {
+		// do nothing, since ViewBot is not localized
+	}
 }
diff --git a/src/test/java/sevenUnitsGUI/I18nTest.java b/src/test/java/sevenUnitsGUI/I18nTest.java
new file mode 100644
index 0000000..73bd727
--- /dev/null
+++ b/src/test/java/sevenUnitsGUI/I18nTest.java
@@ -0,0 +1,21 @@
+package sevenUnitsGUI;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+
+class I18nTest {
+
+	/**
+	 * Tests that the default locale exists.
+	 * 
+	 * Currently this test fails.
+	 */
+	@Test
+	void testDefaultLocale() {
+		Presenter p = new Presenter(new ViewBot());
+		assertNotNull(p.locales.get(Presenter.DEFAULT_LOCALE),
+				"Default locale does not exist.");
+	}
+
+}