Get SQL databases working again

.gitignore

@@ -164,6 +164,9 @@ fabric.properties
 
 .idea/
 
+### VS Code ###
+.vscode/
+
 # Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-249601023
 
 # Exception for the icon

build.gradle

@@ -45,6 +45,10 @@ dependencies {
 		exclude group: 'org.bukkit', module: 'bukkit'
 	}
 
+	// Libraries that are installed at runtime. See plugin.yml 'libraries' section.
+	implementation group: 'com.h2database', name: 'h2', version: project.property('h2.version')
+	implementation group: 'com.zaxxer', name: 'HikariCP', version: project.property('hikaricp.version')
+
 	implementation fileTree(dir: 'lib', include: '*.jar')
 
 	testShadow group: 'junit', name: 'junit', version: '4.13.2'
@@ -289,6 +293,15 @@ tasks.register('JUnit') {
 	dependsOn JUnitJava17, JUnitJava21
 }
 
+// Generic replace tokens, e.g: '@version@'
+tasks.withType(Copy).configureEach {
+	filter(ReplaceTokens, tokens: [
+		'today'            : '' + LocalTime.now(),
+		'h2.version'       : project.property('h2.version'),
+		'hikaricp.version' : project.property('hikaricp.version')
+	])
+}
+
 // Build flavor configurations
 task githubResources(type: ProcessResources) {
 	from 'src/main/resources', {
@@ -299,7 +312,6 @@ task githubResources(type: ProcessResources) {
 			channel = 'prerelease'
 		filter ReplaceTokens, tokens: [
 			'version'         : version,
-			'today'           : '' + LocalTime.now(),
 			'release-flavor'  : 'skriptlang-github', // SkriptLang build, distributed on Github
 			'release-channel' : channel, // Release channel, see above
 			'release-updater' : 'ch.njol.skript.update.GithubChecker', // Github API client
@@ -332,7 +344,6 @@ task spigotResources(type: ProcessResources) {
 			channel = 'prerelease'
 		filter ReplaceTokens, tokens: [
 			'version'         : version,
-			'today'           : '' + LocalTime.now(),
 			'release-flavor'  : 'skriptlang-spigot', // SkriptLang build, distributed on Spigot resources
 			'release-channel' : channel, // Release channel, see above
 			'release-updater' : 'ch.njol.skript.update.GithubChecker', // Github API client
@@ -363,7 +374,6 @@ task nightlyResources(type: ProcessResources) {
 		version = project.property('version') + '-nightly-' + hash
 		filter ReplaceTokens, tokens: [
 			'version'         : version,
-			'today'           : '' + LocalTime.now(),
 			'release-flavor'  : 'skriptlang-nightly', // SkriptLang build, automatically done by CI
 			'release-channel' : 'prerelease', // No update checking, but these are VERY unstable
 			'release-updater' : 'ch.njol.skript.update.NoUpdateChecker', // No auto updates for now

gradle.properties

@@ -9,3 +9,6 @@ version=2.10.2
 jarName=Skript.jar
 testEnv=java21/paper-1.21.4
 testEnvJavaVersion=21
+
+hikaricp.version=5.1.0
+h2.version=2.3.232

src/main/java/ch/njol/skript/SkriptAddon.java

@@ -6,13 +6,14 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-import org.bukkit.Bukkit;
-import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.java.JavaPlugin;
 import org.jetbrains.annotations.Nullable;
 
 import ch.njol.skript.util.Utils;
 import ch.njol.skript.util.Version;
+import ch.njol.skript.variables.VariableStorage;
+import ch.njol.skript.variables.Variables;
+
 import org.jetbrains.annotations.ApiStatus;
 import org.skriptlang.skript.localization.Localizer;
 import org.skriptlang.skript.registration.SyntaxRegistry;
@@ -76,6 +77,20 @@ public SkriptAddon loadClasses(String basePackage, String... subPackages) throws
 		return this;
 	}
 
+	/**
+	 * Register a VariableStorage class for Skript to create if the user config value matches.
+	 * 
+	 * @param <T> A class to extend VariableStorage.
+	 * @param storage The class of the VariableStorage implementation.
+	 * @param names The names used in the config of Skript to select this VariableStorage.
+	 * @return This SkriptAddon for method chaining.
+	 * @throws SkriptAPIException if the operation was not successful because the storage class is already registered.
+	 */
+	public <T extends VariableStorage> SkriptAddon registerStorage(Class<T> storage, String... names) throws SkriptAPIException {
+		Variables.registerStorage(this, storage, names);
+		return this;
+	}
+
 	/**
 	 * Makes Skript load language files from the specified directory, e.g. "lang" or "skript lang" if you have a lang folder yourself. Localised files will be read from the
 	 * plugin's jar and the plugin's data folder, but the default English file is only taken from the jar and <b>must</b> exist!

src/main/java/ch/njol/skript/lang/Variable.java

@@ -4,8 +4,6 @@
 import java.util.*;
 import java.util.Map.Entry;
 import java.util.regex.Pattern;
-import java.util.NoSuchElementException;
-import java.util.TreeMap;
 import java.util.function.Predicate;
 import java.util.function.Function;
 
@@ -16,7 +14,7 @@
 import ch.njol.skript.classes.Changer.ChangeMode;
 import ch.njol.skript.classes.Changer.ChangerUtils;
 import ch.njol.skript.classes.ClassInfo;
-import ch.njol.skript.variables.VariablesStorage;
+import ch.njol.skript.variables.VariableStorage;
 import org.skriptlang.skript.lang.arithmetic.Arithmetics;
 import org.skriptlang.skript.lang.arithmetic.OperationInfo;
 import org.skriptlang.skript.lang.arithmetic.Operator;
@@ -41,21 +39,12 @@
 import org.bukkit.event.Event;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.skriptlang.skript.lang.arithmetic.Arithmetics;
-import org.skriptlang.skript.lang.arithmetic.OperationInfo;
-import org.skriptlang.skript.lang.arithmetic.Operator;
 import org.skriptlang.skript.lang.comparator.Comparators;
 import org.skriptlang.skript.lang.comparator.Relation;
 import org.skriptlang.skript.lang.converter.Converters;
 import org.skriptlang.skript.lang.script.Script;
 import org.skriptlang.skript.lang.script.ScriptWarning;
 
-import java.lang.reflect.Array;
-import java.util.*;
-import java.util.Map.Entry;
-import java.util.function.Function;
-import java.util.function.Predicate;
-
 public class Variable<T> implements Expression<T>, KeyReceiverExpression<T>, KeyProviderExpression<T> {
 
 	private final static String SINGLE_SEPARATOR_CHAR = ":";
@@ -120,8 +109,8 @@ public static boolean isValidVariableName(String name, boolean allowListVariable
 				A lot of people already use '-' so we want to skip this warning iff they're using it here
 				*/
 				if (first == '-') {
-					for (VariablesStorage store : Variables.getStores()) {
-						@Nullable Pattern pattern = store.getNamePattern();
+					for (VariableStorage storage : Variables.getLoadedStorages()) {
+						@Nullable Pattern pattern = storage.getNamePattern();
 						if (pattern != null && pattern.pattern().equals("(?!-).*"))
 							continue check_reserved_tokens;
 					}

src/main/java/ch/njol/skript/registrations/Classes.java

@@ -41,7 +41,7 @@
 import ch.njol.skript.log.ParseLogHandler;
 import ch.njol.skript.log.SkriptLogger;
 import ch.njol.skript.util.StringMode;
-import ch.njol.skript.variables.SQLStorage;
+import ch.njol.skript.variables.JdbcStorage;
 import ch.njol.skript.variables.SerializedVariable;
 import ch.njol.skript.variables.Variables;
 import ch.njol.util.Kleenean;
@@ -79,8 +79,8 @@ public static <T> void registerClass(final ClassInfo<T> info) {
 				throw new IllegalArgumentException("Can't register " + info.getC().getName() + " with the code name " + info.getCodeName() + " because that name is already used by " + classInfosByCodeName.get(info.getCodeName()));
 			if (exactClassInfos.containsKey(info.getC()))
 				throw new IllegalArgumentException("Can't register the class info " + info.getCodeName() + " because the class " + info.getC().getName() + " is already registered");
-			if (info.getCodeName().length() > SQLStorage.MAX_CLASS_CODENAME_LENGTH)
-				throw new IllegalArgumentException("The codename '" + info.getCodeName() + "' is too long to be saved in a database, the maximum length allowed is " + SQLStorage.MAX_CLASS_CODENAME_LENGTH);
+			if (info.getCodeName().length() > JdbcStorage.MAX_CLASS_CODENAME_LENGTH)
+				throw new IllegalArgumentException("The codename '" + info.getCodeName() + "' is too long to be saved in a database, the maximum length allowed is " + JdbcStorage.MAX_CLASS_CODENAME_LENGTH);
 			exactClassInfos.put(info.getC(), info);
 			classInfosByCodeName.put(info.getCodeName(), info);
 			tempClassInfos.add(info);

src/main/java/ch/njol/skript/variables/FlatFileStorage.java

@@ -1,6 +1,7 @@
 package ch.njol.skript.variables;
 
 import ch.njol.skript.Skript;
+import ch.njol.skript.SkriptAddon;
 import ch.njol.skript.config.SectionNode;
 import ch.njol.skript.lang.Variable;
 import ch.njol.skript.log.SkriptLogger;
@@ -40,7 +41,7 @@
  *  accessed. (rem: print a warning when Skript starts)
  *  rem: store null variables (in memory) to prevent looking up the same variables over and over again
  */
-public class FlatFileStorage extends VariablesStorage {
+public class FlatFileStorage extends VariableStorage {
 
 	/**
 	 * The {@link Charset} used in the CSV storage file.
@@ -108,21 +109,22 @@ public class FlatFileStorage extends VariablesStorage {
 	/**
 	 * Create a new CSV storage of the given name.
 	 *
+	 * @param source the source of this storage.
 	 * @param type the databse type i.e. CSV.
 	 */
-	FlatFileStorage(String type) {
-		super(type);
+	FlatFileStorage(SkriptAddon source, String type) {
+		super(source, type);
 	}
 
 	/**
 	 * Loads the variables in the CSV file.
 	 * <p>
 	 * Doesn't lock the connection, as required by
-	 * {@link Variables#variableLoaded(String, Object, VariablesStorage)}.
+	 * {@link Variables#variableLoaded(String, Object, VariableStorage)}.
 	 */
-	@SuppressWarnings("deprecation")
 	@Override
-	protected boolean load_i(SectionNode sectionNode) {
+	@SuppressWarnings("deprecation")
+	protected final boolean load(SectionNode sectionNode) {
 		SkriptLogger.setNode(null);
 
 		if (file == null) {
@@ -464,16 +466,16 @@ private void save(PrintWriter pw, String parent, TreeMap<String, Object> map) {
 			if (childNode == null)
 				continue; // Leaf node
 
-			if (childNode instanceof TreeMap) {
+			if (childNode instanceof TreeMap multiVariable) {
 				// TreeMap found, recurse
-				save(pw, parent + childKey + Variable.SEPARATOR, (TreeMap<String, Object>) childNode);
+				save(pw, parent + childKey + Variable.SEPARATOR, multiVariable);
 			} else {
 				// Remove variable separator if needed
 				String name = childKey == null ? parent.substring(0, parent.length() - Variable.SEPARATOR.length()) : parent + childKey;
 
 				try {
 					// Loop over storages to make sure this variable is ours to store
-					for (VariablesStorage storage : Variables.STORAGES) {
+					for (VariableStorage storage : Variables.STORAGES) {
 						if (storage.accept(name)) {
 							if (storage == this) {
 								// Serialize the value