feat(default-exts): Implement read fallback extension

tweed5/default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/readfallback/api/ReadFallbackExtension.java

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+package de.siphalor.tweed5.defaultextensions.readfallback.api;
+
+import de.siphalor.tweed5.core.api.extension.TweedExtension;
+import de.siphalor.tweed5.defaultextensions.readfallback.impl.ReadFallbackExtensionImpl;
+
+public interface ReadFallbackExtension extends TweedExtension {
+	Class<? extends ReadFallbackExtension> DEFAULT = ReadFallbackExtensionImpl.class;
+	String EXTENSION_ID = "read-fallback";
+
+	@Override
+	default String getId() {
+		return EXTENSION_ID;
+	}
+}

tweed5/default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/readfallback/impl/ReadFallbackExtensionImpl.java

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+package de.siphalor.tweed5.defaultextensions.readfallback.impl;
+
+import de.siphalor.tweed5.core.api.container.ConfigContainer;
+import de.siphalor.tweed5.core.api.entry.ConfigEntry;
+import de.siphalor.tweed5.core.api.middleware.Middleware;
+import de.siphalor.tweed5.defaultextensions.readfallback.api.ReadFallbackExtension;
+import de.siphalor.tweed5.data.extension.api.TweedEntryReadException;
+import de.siphalor.tweed5.data.extension.api.TweedEntryReader;
+import de.siphalor.tweed5.data.extension.api.extension.ReadWriteExtensionSetupContext;
+import de.siphalor.tweed5.data.extension.api.extension.ReadWriteRelatedExtension;
+import de.siphalor.tweed5.defaultextensions.presets.api.PresetsExtension;
+import lombok.extern.apachecommons.CommonsLog;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
+
+import java.util.Collections;
+import java.util.Set;
+
+@CommonsLog
+public class ReadFallbackExtensionImpl implements ReadFallbackExtension, ReadWriteRelatedExtension {
+	private final ConfigContainer<?> configContainer;
+	private @Nullable PresetsExtension presetsExtension;
+
+	public ReadFallbackExtensionImpl(ConfigContainer<?> configContainer) {
+		this.configContainer = configContainer;
+	}
+
+	@Override
+	public void extensionsFinalized() {
+		presetsExtension = configContainer.extension(PresetsExtension.class)
+				.orElseThrow(() -> new IllegalStateException(getClass().getSimpleName()
+						+ " requires " + ReadFallbackExtension.class.getSimpleName()));
+	}
+
+	@Override
+	public void setupReadWriteExtension(ReadWriteExtensionSetupContext context) {
+		assert presetsExtension != null;
+
+		context.registerReaderMiddleware(new Middleware<TweedEntryReader<?, ?>>() {
+			@Override
+			public String id() {
+				return EXTENSION_ID;
+			}
+
+			@Override
+			public Set<String> mustComeBefore() {
+				return Collections.singleton(DEFAULT_START);
+			}
+
+			@Override
+			public Set<String> mustComeAfter() {
+				return Collections.emptySet();
+			}
+
+			@Override
+			public TweedEntryReader<?, ?> process(TweedEntryReader<?, ?> inner) {
+				//noinspection unchecked
+				TweedEntryReader<Object, ConfigEntry<Object>> castedInner =
+						(TweedEntryReader<Object, @NonNull ConfigEntry<Object>>) inner;
+				return (TweedEntryReader<Object, @NonNull ConfigEntry<Object>>) (reader, entry, context1) -> {
+					try {
+						return castedInner.read(reader, entry, context1);
+					} catch (TweedEntryReadException e) {
+						log.error("Failed to read entry: " + e.getMessage(), e);
+						return presetsExtension.presetValue(entry, PresetsExtension.DEFAULT_PRESET_NAME);
+					}
+				};
+			}
+		});
+	}
+}

tweed5/default-extensions/src/test/java/de/siphalor/tweed5/defaultextensions/readfallback/impl/ReadFallbackExtensionImplTest.java

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+package de.siphalor.tweed5.defaultextensions.readfallback.impl;
+
+import de.siphalor.tweed5.core.api.entry.ConfigEntry;
+import de.siphalor.tweed5.core.impl.DefaultConfigContainer;
+import de.siphalor.tweed5.core.impl.entry.SimpleConfigEntryImpl;
+import de.siphalor.tweed5.data.extension.api.ReadWriteExtension;
+import de.siphalor.tweed5.data.extension.api.TweedEntryReadException;
+import de.siphalor.tweed5.data.extension.api.TweedReadContext;
+import de.siphalor.tweed5.data.extension.api.TweedWriteContext;
+import de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriter;
+import de.siphalor.tweed5.data.hjson.HjsonLexer;
+import de.siphalor.tweed5.data.hjson.HjsonReader;
+import de.siphalor.tweed5.dataapi.api.*;
+import de.siphalor.tweed5.defaultextensions.presets.api.PresetsExtension;
+import de.siphalor.tweed5.defaultextensions.readfallback.api.ReadFallbackExtension;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+import org.junit.jupiter.api.Test;
+
+import java.io.StringReader;
+
+import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.entryReaderWriter;
+import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.read;
+import static de.siphalor.tweed5.defaultextensions.presets.api.PresetsExtension.presetValue;
+import static org.assertj.core.api.Assertions.assertThat;
+
+@NullMarked
+class ReadFallbackExtensionImplTest {
+	@Test
+	void test() {
+		DefaultConfigContainer<Integer> configContainer = new DefaultConfigContainer<>();
+		configContainer.registerExtension(ReadWriteExtension.class);
+		configContainer.registerExtension(PresetsExtension.class);
+		configContainer.registerExtension(ReadFallbackExtension.DEFAULT);
+		configContainer.finishExtensionSetup();
+
+		ConfigEntry<Integer> entry = new SimpleConfigEntryImpl<>(configContainer, Integer.class)
+				.apply(presetValue(PresetsExtension.DEFAULT_PRESET_NAME, -1))
+				.apply(entryReaderWriter(new TweedEntryReaderWriter<>() {
+					@Override
+					public Integer read(
+							TweedDataReader reader,
+							ConfigEntry<Integer> entry,
+							TweedReadContext context
+					) throws TweedEntryReadException {
+						int value;
+						try {
+							value = reader.readToken().readAsInt();
+						} catch (TweedDataReadException e) {
+							throw new IllegalStateException("Should not be called", e);
+						}
+						if (value % 2 == 0) {
+							return value;
+						} else {
+							throw new TweedEntryReadException("Value is not even", context);
+						}
+					}
+
+					@Override
+					public void write(
+							TweedDataVisitor writer,
+							@Nullable Integer value,
+							ConfigEntry<Integer> entry,
+							TweedWriteContext context
+					) throws TweedDataWriteException {
+						throw new IllegalStateException("Should not be called");
+					}
+				}));
+
+		configContainer.attachTree(entry);
+		configContainer.initialize();
+
+		assertThat(entry.call(read(new HjsonReader(new HjsonLexer(new StringReader("12")))))).isEqualTo(12);
+		assertThat(entry.call(read(new HjsonReader(new HjsonLexer(new StringReader("13")))))).isEqualTo(-1);
+	}
+}