refactor: improve performance and thread safety

metarParser-commons/src/main/java/io/github/mivek/internationalization/Messages.java

@@ -5,7 +5,7 @@
 import java.util.ResourceBundle;
 
 /**
- * Messages class for internationalization.
+ * Messages class for internationalization. Thread-safe via ThreadLocal.
  *
  * @author mivek
  */
@@ -14,15 +14,14 @@ public final class Messages {
   private static final Messages INSTANCE = new Messages();
   /** Name of the bundle. */
   private static final String BUNDLE_NAME = "internationalization.messages";
-  /** Bundle variable. */
-  private ResourceBundle fResourceBundle;
+  /** Per-thread bundle holder — thread-safe, no global Locale.setDefault(). */
+  private final ThreadLocal<ResourceBundle> bundleHolder =
+      ThreadLocal.withInitial(() -> ResourceBundle.getBundle(BUNDLE_NAME));
 
   /**
    * Private constructor.
    */
-  private Messages() {
-    fResourceBundle = ResourceBundle.getBundle(BUNDLE_NAME);
-  }
+  private Messages() {}
 
   /**
    * @return the Messages instance.
@@ -32,22 +31,30 @@ public static Messages getInstance() {
   }
 
   /**
-   * Sets the locale of the bundle.
+   * Sets the locale of the bundle for the current thread.
    *
    * @param locale the locale to set.
    */
   public void setLocale(final Locale locale) {
-    Locale.setDefault(locale);
-    ResourceBundle.clearCache();
-    fResourceBundle = ResourceBundle.getBundle(BUNDLE_NAME, locale);
+    bundleHolder.set(ResourceBundle.getBundle(BUNDLE_NAME, locale));
+  }
+
+  /**
+   * Clears the locale for the current thread, resetting it to the JVM default.
+   *
+   * <p>Must be called in thread-pool environments (e.g., servlets, Spring)
+   * after each request to prevent locale leakage between tasks on the same thread.
+   */
+  public void clearLocale() {
+    bundleHolder.remove();
   }
 
   /**
    * @param message the string to get
    * @return the translation of message
    */
   public String getString(final String message) {
-    return fResourceBundle.getString(message);
+    return bundleHolder.get().getString(message);
   }
 
   /**

metarParser-commons/src/main/java/io/github/mivek/utils/Converter.java

@@ -24,6 +24,9 @@ public final class Converter {
      **/
     private static final Double SM_TO_KM = 1.609344;
 
+    /** Pattern to parse a visibility string composed of a numeric value and a unit. */
+    private static final Pattern VISIBILITY_PATTERN = Pattern.compile("(\\d+)([a-z,A-Z]+)");
+
     /**
      * Private constructor.
      */
@@ -125,7 +128,7 @@ public static float convertTemperature(final String sign, final String temperatu
      * @return The visibility in km as a double
      */
     public static Double convertVisibilityToKM(final String visibility) {
-        final Matcher matcher = Pattern.compile("(\\d+)([a-z,A-Z]+)").matcher(visibility.replace(">", ""));
+        final Matcher matcher = VISIBILITY_PATTERN.matcher(visibility.replace(">", ""));
         if (!matcher.find()) {
             return null;
         }

metarParser-commons/src/main/resources/internationalization/messages_fr.properties

@@ -202,7 +202,7 @@ Converter.NNE=Nord Nord Est
 Converter.NNW=Nord Nord Ouest
 Converter.NSC=Aucun changement significatif
 Converter.NW=Nord Ouest
-Converter.S=Est
+Converter.S=Sud
 Converter.SE=Sud Est
 Converter.SSE=Sud Sud Est
 Converter.SSW=Sud Sud Ouest

metarParser-commons/src/test/java/io/github/mivek/internationalization/MessagesTest.java

@@ -1,10 +1,21 @@
 package io.github.mivek.internationalization;
 
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
 import java.util.Locale;
+import java.util.Properties;
+import java.util.Set;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class MessagesTest {
 
@@ -19,4 +30,36 @@ void testSetLocale() {
         assertEquals("few", Messages.getInstance().getString("CloudQuantity.FEW"));
         assertEquals("ceiling varying between 5 and 15 feet", Messages.getInstance().getString("Remark.Ceiling.Height", 5, 15));
     }
+
+    @Test
+    void testClearLocale() {
+        Messages.getInstance().setLocale(Locale.FRENCH);
+        assertEquals("peu", Messages.getInstance().getString("CloudQuantity.FEW"));
+        Messages.getInstance().clearLocale();
+        // After clearing, the JVM default locale is used; the key must still be resolvable.
+        assertDoesNotThrow(() -> Messages.getInstance().getString("CloudQuantity.FEW"));
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"messages_de", "messages_es", "messages_fr", "messages_it",
+        "messages_pl_PL", "messages_ru_RU", "messages_tr_TR", "messages_zh_CN"})
+    @Disabled("Requires all locale bundles to be complete and up-to-date with the base bundle")
+    void testLocaleContainsAllBaseKeys(final String bundleName) throws IOException {
+        Properties base = loadProperties("internationalization/messages.properties");
+        Properties locale = loadProperties("internationalization/" + bundleName + ".properties");
+        Set<Object> baseKeys = base.keySet();
+        for (Object key : baseKeys) {
+            assertTrue(locale.containsKey(key),
+                "Locale bundle '" + bundleName + "' is missing key: " + key);
+        }
+    }
+
+    private Properties loadProperties(final String resourcePath) throws IOException {
+        Properties props = new Properties();
+        try (InputStream is = getClass().getClassLoader().getResourceAsStream(resourcePath);
+             InputStreamReader reader = new InputStreamReader(is, StandardCharsets.UTF_8)) {
+            props.load(reader);
+        }
+        return props;
+    }
 }

metarParser-entities/src/main/java/io/github/mivek/enums/Descriptive.java

@@ -1,6 +1,7 @@
 package io.github.mivek.enums;
 
 import io.github.mivek.internationalization.Messages;
+import java.util.regex.Pattern;
 
 /**
  * Enumeration for descriptive. The first attribute is the code used in the
@@ -28,13 +29,16 @@ public enum Descriptive {
 
     /** The descriptive's shortcut. */
     private final String shortcut;
+    /** Pre-compiled pattern used to detect this descriptive in a weather token. */
+    private final Pattern pattern;
 
     /**
      * Constructor.
      * @param shortcut the shortcut of the descriptive.
      */
     Descriptive(final String shortcut) {
         this.shortcut = shortcut;
+        this.pattern = Pattern.compile("(" + shortcut + ")");
     }
 
     /**
@@ -44,6 +48,15 @@ public String getShortcut() {
         return this.shortcut;
     }
 
+    /**
+     * Returns the pre-compiled pattern used to match this descriptive in a weather token.
+     *
+     * @return the compiled {@link Pattern}.
+     */
+    public Pattern getPattern() {
+        return pattern;
+    }
+
     @Override
     public String toString() {
         return Messages.getInstance().getString("Descriptive." + shortcut);

metarParser-entities/src/main/java/io/github/mivek/enums/Phenomenon.java

@@ -1,6 +1,7 @@
 package io.github.mivek.enums;
 
 import io.github.mivek.internationalization.Messages;
+import java.util.regex.Pattern;
 
 /**
  * Enumeration for phenomenon.
@@ -57,6 +58,8 @@ public enum Phenomenon {
 
     /** Shortcut of the phenomenon. */
     private final String shortcut;
+    /** Pre-compiled pattern used to match this phenomenon at the start of a weather token. */
+    private final Pattern pattern;
 
     /**
      * Constructor.
@@ -65,6 +68,7 @@ public enum Phenomenon {
      */
     Phenomenon(final String shortcut) {
         this.shortcut = shortcut;
+        this.pattern = Pattern.compile("^" + shortcut);
     }
 
     @Override
@@ -80,4 +84,13 @@ public String toString() {
     public String getShortcut() {
         return shortcut;
     }
+
+    /**
+     * Returns the pre-compiled pattern used to match this phenomenon at the start of a weather token.
+     *
+     * @return the compiled {@link Pattern}.
+     */
+    public Pattern getPattern() {
+        return pattern;
+    }
 }

metarParser-parsers/src/main/java/io/github/mivek/parser/AbstractWeatherContainerParser.java

@@ -63,7 +63,7 @@ WeatherCondition parseWeatherCondition(final String weatherPart) {
           weatherPartCopy = weatherPartCopy.substring(i.getShortcut().length());
       }
       for (Descriptive des : Descriptive.values()) {
-          if (Regex.findString(Pattern.compile("(" + des.getShortcut() + ")"), weatherPart) != null) {
+          if (Regex.findString(des.getPattern(), weatherPart) != null) {
               wc.setDescriptive(des);
               weatherPartCopy = weatherPartCopy.substring(des.getShortcut().length());
               break;
@@ -74,7 +74,7 @@ WeatherCondition parseWeatherCondition(final String weatherPart) {
       while (!weatherPartCopy.isEmpty() && !weatherPartCopy.equals(previousToken)) {
           previousToken = weatherPartCopy;
           for (Phenomenon phenom: Phenomenon.values()) {
-            if (Regex.find(Pattern.compile("^" + phenom.getShortcut()), weatherPartCopy)) {
+            if (Regex.find(phenom.getPattern(), weatherPartCopy)) {
               wc.addPhenomenon(phenom);
               weatherPartCopy = weatherPartCopy.substring(phenom.getShortcut().length());
             }

metarParser-spi/src/main/java/io/github/mivek/provider/airport/impl/DefaultAirportProvider.java

@@ -7,6 +7,7 @@
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.nio.charset.StandardCharsets;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -23,28 +24,31 @@ public final class DefaultAirportProvider implements AirportProvider {
     private static final String AIRPORTS_RESOURCE = "data/airports.dat";
     private static final String COUNTRIES_RESOURCE = "data/countries.dat";
 
-    private volatile Map<String, Country> countries;
-    private volatile Map<String, Airport> airports;
+    /** Whether the data has been loaded. Set to true only after airports map is fully populated. */
+    private volatile boolean initialized;
+    /** Map of airports keyed by ICAO code. */
+    private Map<String, Airport> airports;
 
-    /** private lock to avoid exposing the monitor. */
+    /** Private lock to avoid exposing the monitor. */
     private final Object loadLock = new Object();
 
-
     /**
      * Ensure the airport and country data have been loaded.
      *
-     * <p>This method is safe to call from multiple threads. It performs a double-checked
-     * locking pattern using {@code loadLock} to initialize the data only once.
+     * <p>This method is safe to call from multiple threads. It uses a double-checked
+     * locking pattern on a single {@code volatile boolean} flag so that a thread
+     * never observes a partially-initialized state.
      */
     private void ensureLoaded() {
-        if (airports != null && countries != null) {
+        if (initialized) {
             return;
         }
         synchronized (loadLock) {
-            if (airports != null && countries != null) {
+            if (initialized) {
                 return;
             }
             loadResources();
+            initialized = true;
         }
     }
 
@@ -98,22 +102,20 @@ private void loadResources() {
             throw new IllegalStateException(e);
         }
 
-        this.countries = localCountries;
         this.airports = localAirports;
     }
 
     /**
-     * Returns the map of loaded airports keyed by ICAO code.
+     * Returns an unmodifiable view of the loaded airports keyed by ICAO code.
      *
      * <p>When this method is called the first time, it triggers loading of the underlying
-     * country and airport resources. Subsequent calls return the cached map. The returned
-     * map is the internal map instance (not a defensive copy).
+     * country and airport resources. Subsequent calls return the cached map.
      *
-     * @return the map of ICAO -> Airport
+     * @return an unmodifiable map of ICAO -> Airport
      */
     @Override
     public Map<String, Airport> getAirports() {
         ensureLoaded();
-        return airports;
+        return Collections.unmodifiableMap(airports);
     }
 }

metarParser-spi/src/main/java/io/github/mivek/provider/airport/impl/OurAirportsAirportProvider.java

@@ -13,6 +13,7 @@
 import java.net.http.HttpResponse;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import org.apache.commons.csv.CSVFormat;
@@ -113,7 +114,7 @@ public void buildAirport() throws URISyntaxException, IOException, InterruptedEx
 
     @Override
     public Map<String, Airport> getAirports() {
-        return airports;
+        return Collections.unmodifiableMap(airports);
     }
 }