Add some localisation

Implemented with a big bad singleton. It features namespaces, though.

build.gradle

@@ -16,6 +16,7 @@ dependencies {
     compile group: 'com.github.stefanbirkner', name: 'fishbowl', version: '1.4.0'
     compile group: 'net.sourceforge.argparse4j', name: 'argparse4j', version: '0.7.0'
     compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.5'
+    compile group: 'com.google.guava', name: 'guava', version: '20.0'
 
     compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.21'
     runtime group: 'org.slf4j', name: 'slf4j-simple', version: '1.7.21'
@@ -72,13 +73,18 @@ javadoc {
 }
 
 import org.apache.tools.ant.filters.ReplaceTokens
-processResources {
-   filter(ReplaceTokens, tokens: [
-      "version": version,
-      "built.at": (new Date()).format("yyyy-MM-dd HH:mm:ssZ"),
-      "built.by": System.getProperty('user.name'),
-      "build.JDK": System.getProperty('java.version')
-   ])
+import org.apache.tools.ant.filters.EscapeUnicode
+tasks.withType(ProcessResources).each { task ->
+    task.from(task.getSource()) {
+        include '**/*.properties'
+        filter(EscapeUnicode)
+        filter(ReplaceTokens, tokens: [
+            "version": version,
+            "built.at": (new Date()).format("yyyy-MM-dd HH:mm:ssZ"),
+            "built.by": System.getProperty('user.name'),
+            "build.JDK": System.getProperty('java.version')
+        ])
+    }
 }
 
 run {

src/main/java/ppke/itk/xplang/common/Messages.java

@@ -0,0 +1,7 @@
+package ppke.itk.xplang.common;
+
+/**
+ * A big bad singleton encapsulating a resource bundle.
+ */
+public class Messages {
+}

src/main/java/ppke/itk/xplang/common/Translator.java

@@ -0,0 +1,55 @@
+package ppke.itk.xplang.common;
+
+import java.util.*;
+
+import static java.util.Arrays.asList;
+
+public final class Translator {
+    private final static Set<String> LANGUAGES = new HashSet<>(asList("", "hu", "en"));
+    private final static String DEFAULT_LANGUAGE = "";
+
+    private static final Map<String, Translator> instances = new HashMap<>();
+    private static String language = DEFAULT_LANGUAGE;
+
+    private ResourceBundle messages;
+    private Translator(String namespace) {
+        reset(namespace);
+    }
+
+    private void reset(String namespace) {
+        Locale locale = new Locale(language);
+        messages = ResourceBundle.getBundle(
+            String.format("messages.%s", namespace),
+            locale,
+            ResourceBundle.Control.getNoFallbackControl(ResourceBundle.Control.FORMAT_PROPERTIES)
+        );
+    }
+
+    public String translate(String key) {
+        return messages.getString(key);
+    }
+
+    public String translate(String key, Object... args) {
+        return String.format(messages.getString(key), args);
+    }
+
+    public static Translator getInstance(String namespace) {
+        namespace = namespace.toLowerCase();
+        if(!instances.containsKey(namespace)) {
+            instances.put(namespace, new Translator(namespace));
+        }
+
+        return instances.get(namespace);
+    }
+
+    public static void setLanguage(String newLanguage) {
+        if(!LANGUAGES.contains(newLanguage)) {
+            throw new IllegalStateException(String.format("Language '%s' is not supported", language));
+        }
+        language = newLanguage;
+
+        for(Map.Entry<String, Translator> instance : instances.entrySet()) {
+            instance.getValue().reset(instance.getKey());
+        }
+    }
+}

src/main/java/ppke/itk/xplang/lang/PlangGrammar.java

@@ -3,6 +3,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import ppke.itk.xplang.ast.*;
+import ppke.itk.xplang.common.Translator;
 import ppke.itk.xplang.parser.*;
 
 import java.util.ArrayList;
@@ -11,6 +12,7 @@
 import java.util.stream.Stream;
 
 public class PlangGrammar extends Grammar {
+    private final static Translator translator = Translator.getInstance("Plang");
     private final static Logger log = LoggerFactory.getLogger("Root.Parser.Grammar");
 
     public PlangGrammar() {
@@ -60,8 +62,10 @@ public void setup(Context ctx) {
      */
     protected Program program(Parser parser) throws ParseError {
         log.debug("Program");
-        parser.accept("PROGRAM", "A programnak a PROGRAM kulcsszóval kell keződnie!");
-        Token nameToken = parser.accept("IDENTIFIER", "Hiányzik a program neve (egy azonosító).");
+        parser.accept("PROGRAM",
+            translator.translate("plang.program_keyword_missing", "PROGRAM"));
+        Token nameToken = parser.accept("IDENTIFIER",
+            translator.translate("plang.missing_program_name"));
 
         if(parser.actual().symbol().equals(parser.context().lookup("DECLARE"))) {
             declarations(parser);
@@ -80,7 +84,8 @@ protected Program program(Parser parser) throws ParseError {
             }
         } while(!stoppers.contains(parser.actual().symbol()));
 
-        parser.accept("END_PROGRAM", "A programot a PROGRAM_VÉGE kulcsszóval kell lezárni.");
+        parser.accept("END_PROGRAM",
+            translator.translate("plang.missing_end_program", "PROGRAM_VÉGE"));
         Scope scope = parser.context().closeScope();
         Sequence sequence = new Sequence(statementList);
 
@@ -92,8 +97,10 @@ protected Program program(Parser parser) throws ParseError {
      */
     protected void declarations(Parser parser) throws ParseError {
         log.debug("Declarations");
-        parser.accept("DECLARE", "Hiányzik a VÁLTOZÓK kulcsszó");
-        parser.accept("COLON", "Hiányzik a VÁLTOZÓK kulcsszó után a kettőspont.");
+        parser.accept("DECLARE",
+            translator.translate("plang.missing_declarations_keyword", "VÁLTOZÓK"));
+        parser.accept("COLON",
+            translator.translate("plang.missing_colon_after_declarations_keyword", "VÁLTOZÓK"));
 
         variableDeclaration(parser);
         while(parser.actual().symbol().equals(parser.context().lookup("COMMA"))) {

src/main/java/ppke/itk/xplang/parser/LexerError.java

@@ -1,15 +1,19 @@
 package ppke.itk.xplang.parser;
 
+import ppke.itk.xplang.common.Translator;
+
 /**
  * An error of the {@link Lexer}. Thrown when the Lexer encounters a piece of text it cannot match to any of the
  * {@link Symbol}s it knows.
  */
 public class LexerError extends ParseError {
+    private final static Translator translator = Translator.getInstance("parser");
+
     /**
      * Signal a lexing error.
      * @param token Lexer is supposed to return the rest of the line, starting from the point of error.
      */
     LexerError(Token token) {
-        super(String.format("Could not tokenize '%s'", token.lexeme()), token.location());
+        super(translator.translate("parser.LexerError.message", token.lexeme()), token.location());
     }
 }

src/main/java/ppke/itk/xplang/parser/NameClashError.java

@@ -1,13 +1,15 @@
 package ppke.itk.xplang.parser;
 
+import ppke.itk.xplang.common.Translator;
+
 /**
  * Thrown when you try to declare something by a name, but that name is already taken in that scope.
  */
 public class NameClashError extends SemanticError {
-    private final static String NAME_CLASH_MESSAGE = "Could not declare '%s': name already taken.";
+    private final static Translator translator = Translator.getInstance("parser");
 
     NameClashError(Token token) {
-        this(NAME_CLASH_MESSAGE, token);
+        this(translator.translate("parser.NameClashError.message"), token);
     }
 
     NameClashError(String message, Token token) {

src/main/java/ppke/itk/xplang/parser/NameError.java

@@ -1,10 +1,12 @@
 package ppke.itk.xplang.parser;
 
+import ppke.itk.xplang.common.Translator;
+
 public class NameError extends SemanticError {
-    private final static String NAME_ERROR_MESSAGE = "'%s' does not exist.";
+    private final static Translator translator = Translator.getInstance("parser");
 
     NameError(Token token) {
-        this(NAME_ERROR_MESSAGE, token);
+        this(translator.translate("parser.NameError.message"), token);
     }
 
     NameError(String message, Token token) {

src/main/java/ppke/itk/xplang/parser/SyntaxError.java

@@ -1,15 +1,16 @@
 package ppke.itk.xplang.parser;
 
 
+import ppke.itk.xplang.common.Translator;
+
 import java.util.Collection;
 import java.util.Collections;
 
 /**
  * Thrown when the source code does not conform the expected structure of the language.
  */
 public class SyntaxError extends ParseError {
-    private static final String EXPECT_MANY_MSG = "Expected any symbol of %s, encountered %s";
-    private static final String EXPECT_ONE_MSG  = "Expected symbol %s, encountered %s";
+    private final static Translator translator = Translator.getInstance("parser");
 
     /**
      * Signal a syntax error with the given message.
@@ -33,7 +34,10 @@ public SyntaxError(String message, Collection<Symbol> expected, Symbol actual, T
      * @param token The token causing the error.
      */
     public SyntaxError(Collection<Symbol> expected, Symbol actual, Token token) {
-        this(expected.size() > 1? EXPECT_MANY_MSG : EXPECT_ONE_MSG, expected, actual, token);
+        this(translator.translate(expected.size() > 1?
+                "parser.SyntaxError.message.expectMany" :
+                "parser.SyntaxError.message.expectOne"
+            ), expected, actual, token);
     }
 
     /**
@@ -43,7 +47,7 @@ public SyntaxError(Collection<Symbol> expected, Symbol actual, Token token) {
      * @param token The token causing the error.
      */
     public SyntaxError(Symbol expected, Symbol actual, Token token) {
-        this(EXPECT_ONE_MSG, expected, actual, token);
+        this(translator.translate("parser.SyntaxError.message.expectOne"), expected, actual, token);
     }
 
     /**

src/main/resources/messages/parser.properties

@@ -0,0 +1,6 @@
+parser.NameClashError.message=Could not declare '%s': name already taken.
+parser.LexerError.message=Could not tokenize '%s'
+parser.NameError.message='%s' does not exist.
+parser.SyntaxError.message.expectMany=Expected any symbol of %s, encountered %s
+parser.SyntaxError.message.expectOne=Expected symbol %s, encountered %s
+

src/main/resources/messages/parser_hu.properties

@@ -0,0 +1,6 @@
+parser.NameClashError.message=A '%s' név már használatban van.
+parser.LexerError.message=Ismeretlen szimbólum: '%s'
+parser.NameError.message='%s' nevű objektum nem létezik.
+parser.SyntaxError.message.expectMany=A következő szimbólumok valamelyikére számítottam: %s, helyette azt kaptam, hogy %s
+parser.SyntaxError.message.expectOne=Arra a szimbólura számítottam, hogy %s, de azt kaptam, hogy %s
+

src/main/resources/messages/plang.properties

@@ -0,0 +1,5 @@
+plang.program_keyword_missing=The program must start with the %s keyword
+plang.missing_program_name=The name of the program (an identifier) is missing.
+plang.missing_end_program=The program must end with the %s keyword
+plang.missing_declarations_keyword=The %s keyword is missing
+plang.missing_colon_after_declarations_keyword=Missing colon after the %s keyword

src/main/resources/messages/plang_hu.properties

@@ -0,0 +1,5 @@
+plang.program_keyword_missing=A programnak a %s kulcsszóval kell keződnie!
+plang.missing_program_name=Hiányzik a program neve (egy azonosító).
+plang.missing_end_program=A programot a %s kulcsszóval kell lezárni.
+plang.missing_declarations_keyword=Hiányzik a %s kulcsszó
+plang.missing_colon_after_declarations_keyword=Hiányzik a %s kulcsszó után a kettőspont.

src/test/java/ppke/itk/xplang/common/TranslatorTest.java

@@ -0,0 +1,28 @@
+package ppke.itk.xplang.common;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class TranslatorTest {
+    @Test public void translatorShouldParametrizeMessage() {
+        Translator.setLanguage("");
+        Translator translator = Translator.getInstance("test");
+        assertEquals("TEST 1", translator.translate("parser.parametrized.message", 1));
+    }
+
+    @Test public void translatorShouldFallBackToDefault() {
+        Translator.setLanguage("hu");
+        Translator translator = Translator.getInstance("test");
+
+        assertEquals("TEST_FALLBACK", translator.translate("parser.missing.message"));
+    }
+
+    @Test public void switchingLanguagesShouldChangeInstances() {
+        Translator.setLanguage("");
+        Translator translator = Translator.getInstance("test");
+
+        Translator.setLanguage("hu");
+        assertEquals("DIFO_HU", translator.translate("parser.simple.message"));
+    }
+}

src/test/resources/messages/test.properties

@@ -0,0 +1,3 @@
+parser.simple.message=DIFO
+parser.parametrized.message=TEST %s
+parser.missing.message=TEST_FALLBACK

src/test/resources/messages/test_hu.properties

@@ -0,0 +1,2 @@
+parser.simple.message=DIFO_HU
+parser.parametrized.message=TEST HU %s