Added worldgen catalog model

- Added the platform-neutral worldgen catalog records, index and atomic JSON store
- Added the mod ingest request, report, item and tier types

core/src/main/java/art/arcane/iris/pack/ingest/ModIngestItem.java

@@ -0,0 +1,33 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest;
+
+import java.util.Objects;
+
+public record ModIngestItem(String namespace, String sourceKey, String kind, ModIngestTier tier, String target, String reason) {
+    public ModIngestItem {
+        Objects.requireNonNull(namespace, "namespace");
+        Objects.requireNonNull(sourceKey, "sourceKey");
+        Objects.requireNonNull(kind, "kind");
+        Objects.requireNonNull(tier, "tier");
+        Objects.requireNonNull(target, "target");
+        Objects.requireNonNull(reason, "reason");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/ModIngestReport.java

@@ -0,0 +1,32 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest;
+
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Objects;
+
+public record ModIngestReport(Path targetPack, List<ModIngestItem> items, List<String> summaryLines) {
+    public ModIngestReport {
+        Objects.requireNonNull(targetPack, "targetPack");
+        items = List.copyOf(Objects.requireNonNull(items, "items"));
+        summaryLines = List.copyOf(Objects.requireNonNull(summaryLines, "summaryLines"));
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/ModIngestRequest.java

@@ -0,0 +1,36 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest;
+
+import art.arcane.iris.pack.ingest.catalog.WorldgenCatalog;
+
+import java.nio.file.Path;
+import java.util.Objects;
+import java.util.Set;
+
+public record ModIngestRequest(Path sourcePack, Path targetPack, String dimensionKey, WorldgenCatalog catalog, Set<String> namespaces, boolean replaceTarget) {
+    public ModIngestRequest {
+        Objects.requireNonNull(sourcePack, "sourcePack");
+        Objects.requireNonNull(targetPack, "targetPack");
+        Objects.requireNonNull(dimensionKey, "dimensionKey");
+        Objects.requireNonNull(catalog, "catalog");
+        namespaces = Set.copyOf(Objects.requireNonNull(namespaces, "namespaces"));
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/ModIngestTier.java

@@ -0,0 +1,27 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest;
+
+public enum ModIngestTier {
+    NATIVE,
+    ADOPTED,
+    PASSTHROUGH,
+    SKIPPED
+}

core/src/main/java/art/arcane/iris/pack/ingest/ModIngester.java

@@ -0,0 +1,31 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest;
+
+import java.io.IOException;
+
+public final class ModIngester {
+    private ModIngester() {
+    }
+
+    public static ModIngestReport ingest(ModIngestRequest request) throws IOException {
+        throw new UnsupportedOperationException("Mod ingest is not implemented yet");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogBiome.java

@@ -0,0 +1,42 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.JsonElement;
+
+import java.util.List;
+import java.util.Objects;
+
+public record CatalogBiome(
+        String key,
+        float temperature,
+        float downfall,
+        boolean hasPrecipitation,
+        List<String> tags,
+        List<List<String>> featureSteps,
+        List<CatalogSpawn> spawns,
+        JsonElement definition) {
+    public CatalogBiome {
+        Objects.requireNonNull(key, "key");
+        tags = List.copyOf(Objects.requireNonNull(tags, "tags"));
+        featureSteps = Objects.requireNonNull(featureSteps, "featureSteps").stream().map(List::copyOf).toList();
+        spawns = List.copyOf(Objects.requireNonNull(spawns, "spawns"));
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogDimensionType.java

@@ -0,0 +1,30 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.JsonElement;
+
+import java.util.Objects;
+
+public record CatalogDimensionType(String key, int minY, int height, int logicalHeight, JsonElement definition) {
+    public CatalogDimensionType {
+        Objects.requireNonNull(key, "key");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogLevelStem.java

@@ -0,0 +1,38 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.JsonElement;
+
+import java.util.Objects;
+
+public record CatalogLevelStem(
+        String key,
+        String dimensionType,
+        String generatorType,
+        String biomeSourceType,
+        JsonElement generator) {
+    public CatalogLevelStem {
+        Objects.requireNonNull(key, "key");
+        Objects.requireNonNull(dimensionType, "dimensionType");
+        Objects.requireNonNull(generatorType, "generatorType");
+        Objects.requireNonNull(biomeSourceType, "biomeSourceType");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogNamespace.java

@@ -0,0 +1,30 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import java.util.Objects;
+
+public record CatalogNamespace(String namespace, String displayName, String version) {
+    public CatalogNamespace {
+        Objects.requireNonNull(namespace, "namespace");
+        Objects.requireNonNull(displayName, "displayName");
+        Objects.requireNonNull(version, "version");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogPlacedFeature.java

@@ -0,0 +1,37 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.JsonElement;
+
+import java.util.Objects;
+
+public record CatalogPlacedFeature(
+        String key,
+        String configuredFeature,
+        String featureType,
+        JsonElement config,
+        JsonElement placement) {
+    public CatalogPlacedFeature {
+        Objects.requireNonNull(key, "key");
+        Objects.requireNonNull(configuredFeature, "configuredFeature");
+        Objects.requireNonNull(featureType, "featureType");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogSpawn.java

@@ -0,0 +1,29 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import java.util.Objects;
+
+public record CatalogSpawn(String category, String entity, int weight, int minCount, int maxCount) {
+    public CatalogSpawn {
+        Objects.requireNonNull(category, "category");
+        Objects.requireNonNull(entity, "entity");
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/CatalogStructure.java

@@ -0,0 +1,42 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import java.util.List;
+import java.util.Objects;
+
+public record CatalogStructure(
+        String key,
+        String type,
+        String step,
+        String terrainAdaptation,
+        String biomeTag,
+        List<String> biomes,
+        List<String> structureSets) {
+    public CatalogStructure {
+        Objects.requireNonNull(key, "key");
+        Objects.requireNonNull(type, "type");
+        Objects.requireNonNull(step, "step");
+        Objects.requireNonNull(terrainAdaptation, "terrainAdaptation");
+        Objects.requireNonNull(biomeTag, "biomeTag");
+        biomes = List.copyOf(Objects.requireNonNull(biomes, "biomes"));
+        structureSets = List.copyOf(Objects.requireNonNull(structureSets, "structureSets"));
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/WorldgenCatalog.java

@@ -0,0 +1,50 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import java.util.List;
+import java.util.Objects;
+
+public record WorldgenCatalog(
+        int format,
+        String minecraftVersion,
+        String platform,
+        long capturedAtEpochMillis,
+        String contentFingerprint,
+        List<CatalogNamespace> namespaces,
+        List<CatalogBiome> biomes,
+        List<CatalogPlacedFeature> placedFeatures,
+        List<CatalogStructure> structures,
+        List<CatalogDimensionType> dimensionTypes,
+        List<CatalogLevelStem> levelStems) {
+    public static final int FORMAT = 1;
+
+    public WorldgenCatalog {
+        Objects.requireNonNull(minecraftVersion, "minecraftVersion");
+        Objects.requireNonNull(platform, "platform");
+        Objects.requireNonNull(contentFingerprint, "contentFingerprint");
+        namespaces = List.copyOf(Objects.requireNonNull(namespaces, "namespaces"));
+        biomes = List.copyOf(Objects.requireNonNull(biomes, "biomes"));
+        placedFeatures = List.copyOf(Objects.requireNonNull(placedFeatures, "placedFeatures"));
+        structures = List.copyOf(Objects.requireNonNull(structures, "structures"));
+        dimensionTypes = List.copyOf(Objects.requireNonNull(dimensionTypes, "dimensionTypes"));
+        levelStems = List.copyOf(Objects.requireNonNull(levelStems, "levelStems"));
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/WorldgenCatalogIndex.java

@@ -0,0 +1,111 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Function;
+
+public final class WorldgenCatalogIndex {
+    private final WorldgenCatalog catalog;
+    private final Map<String, CatalogBiome> biomes;
+    private final Map<String, CatalogPlacedFeature> placedFeatures;
+    private final Map<String, CatalogStructure> structures;
+    private final Map<String, CatalogDimensionType> dimensionTypes;
+    private final Map<String, CatalogLevelStem> levelStems;
+
+    private WorldgenCatalogIndex(WorldgenCatalog catalog) {
+        this.catalog = catalog;
+        this.biomes = index(catalog.biomes(), CatalogBiome::key);
+        this.placedFeatures = index(catalog.placedFeatures(), CatalogPlacedFeature::key);
+        this.structures = index(catalog.structures(), CatalogStructure::key);
+        this.dimensionTypes = index(catalog.dimensionTypes(), CatalogDimensionType::key);
+        this.levelStems = index(catalog.levelStems(), CatalogLevelStem::key);
+    }
+
+    public static WorldgenCatalogIndex of(WorldgenCatalog catalog) {
+        return new WorldgenCatalogIndex(Objects.requireNonNull(catalog, "catalog"));
+    }
+
+    public static String namespaceOf(String key) {
+        int colon = key.indexOf(':');
+        return colon < 0 ? "minecraft" : key.substring(0, colon);
+    }
+
+    public WorldgenCatalog catalog() {
+        return catalog;
+    }
+
+    public Optional<CatalogBiome> biome(String key) {
+        return Optional.ofNullable(biomes.get(key));
+    }
+
+    public Optional<CatalogPlacedFeature> placedFeature(String key) {
+        return Optional.ofNullable(placedFeatures.get(key));
+    }
+
+    public Optional<CatalogStructure> structure(String key) {
+        return Optional.ofNullable(structures.get(key));
+    }
+
+    public Optional<CatalogDimensionType> dimensionType(String key) {
+        return Optional.ofNullable(dimensionTypes.get(key));
+    }
+
+    public Optional<CatalogLevelStem> levelStem(String key) {
+        return Optional.ofNullable(levelStems.get(key));
+    }
+
+    public List<CatalogBiome> biomesIn(String namespace) {
+        List<CatalogBiome> result = new ArrayList<>();
+        for (CatalogBiome biome : catalog.biomes()) {
+            if (namespaceOf(biome.key()).equals(namespace)) {
+                result.add(biome);
+            }
+        }
+        return Collections.unmodifiableList(result);
+    }
+
+    public List<CatalogBiome> biomesDeclaring(String placedFeatureKey) {
+        List<CatalogBiome> result = new ArrayList<>();
+        for (CatalogBiome biome : catalog.biomes()) {
+            for (List<String> step : biome.featureSteps()) {
+                if (step.contains(placedFeatureKey)) {
+                    result.add(biome);
+                    break;
+                }
+            }
+        }
+        return Collections.unmodifiableList(result);
+    }
+
+    private static <T> Map<String, T> index(List<T> values, Function<T, String> key) {
+        Map<String, T> result = new LinkedHashMap<>(Math.max(16, values.size() * 2));
+        for (T value : values) {
+            result.put(key.apply(value), value);
+        }
+        return Collections.unmodifiableMap(result);
+    }
+}

core/src/main/java/art/arcane/iris/pack/ingest/catalog/WorldgenCatalogStore.java

@@ -0,0 +1,70 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.Writer;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.Objects;
+
+public final class WorldgenCatalogStore {
+    public static final String FILE_NAME = "worldgen-catalog.json";
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().create();
+
+    private WorldgenCatalogStore() {
+    }
+
+    public static WorldgenCatalog read(Path file) throws IOException {
+        Objects.requireNonNull(file, "file");
+        try (Reader reader = Files.newBufferedReader(file, StandardCharsets.UTF_8)) {
+            WorldgenCatalog catalog = GSON.fromJson(reader, WorldgenCatalog.class);
+            if (catalog == null) {
+                throw new IOException("Worldgen catalog is empty: " + file);
+            }
+            if (catalog.format() != WorldgenCatalog.FORMAT) {
+                throw new IOException("Worldgen catalog " + file + " has format " + catalog.format() + ", expected " + WorldgenCatalog.FORMAT);
+            }
+            return catalog;
+        }
+    }
+
+    public static void write(Path file, WorldgenCatalog catalog) throws IOException {
+        Objects.requireNonNull(file, "file");
+        Objects.requireNonNull(catalog, "catalog");
+        Path parent = file.toAbsolutePath().getParent();
+        Files.createDirectories(parent);
+        Path temp = Files.createTempFile(parent, FILE_NAME, ".tmp");
+        try {
+            try (Writer writer = Files.newBufferedWriter(temp, StandardCharsets.UTF_8)) {
+                GSON.toJson(catalog, writer);
+            }
+            Files.move(temp, file, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
+        } finally {
+            Files.deleteIfExists(temp);
+        }
+    }
+}

core/src/test/java/art/arcane/iris/pack/ingest/catalog/WorldgenCatalogStoreTest.java

@@ -0,0 +1,83 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+package art.arcane.iris.pack.ingest.catalog;
+
+import com.google.gson.JsonObject;
+import com.google.gson.JsonPrimitive;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class WorldgenCatalogStoreTest {
+    @Rule
+    public TemporaryFolder folder = new TemporaryFolder();
+
+    @Test
+    public void writeThenReadPreservesEveryRecord() throws IOException {
+        JsonObject config = new JsonObject();
+        config.add("size", new JsonPrimitive(9));
+        WorldgenCatalog catalog = new WorldgenCatalog(
+                WorldgenCatalog.FORMAT,
+                "26.3",
+                "neoforge",
+                1234L,
+                "abc",
+                List.of(new CatalogNamespace("examplemod", "Example Mod", "1.0.0")),
+                List.of(new CatalogBiome("examplemod:glade", 0.7F, 0.8F, true, List.of("minecraft:is_overworld"),
+                        List.of(List.of(), List.of("examplemod:ore_glimmer")),
+                        List.of(new CatalogSpawn("creature", "minecraft:sheep", 12, 2, 4)), new JsonObject())),
+                List.of(new CatalogPlacedFeature("examplemod:ore_glimmer", "examplemod:ore_glimmer", "minecraft:ore", config, null)),
+                List.of(new CatalogStructure("examplemod:tower", "minecraft:jigsaw", "surface_structures", "none",
+                        "examplemod:has_tower", List.of("examplemod:glade"), List.of("examplemod:towers"))),
+                List.of(new CatalogDimensionType("examplemod:sky", 0, 256, 256, new JsonObject())),
+                List.of(new CatalogLevelStem("examplemod:sky", "examplemod:sky", "minecraft:noise", "minecraft:multi_noise", null)));
+        Path file = folder.getRoot().toPath().resolve("nested").resolve(WorldgenCatalogStore.FILE_NAME);
+
+        WorldgenCatalogStore.write(file, catalog);
+        WorldgenCatalog read = WorldgenCatalogStore.read(file);
+
+        assertEquals(catalog, read);
+        assertTrue(Files.list(file.getParent()).allMatch(path -> path.equals(file)));
+    }
+
+    @Test
+    public void indexResolvesNamespacesAndFeatureOwners() {
+        WorldgenCatalog catalog = new WorldgenCatalog(WorldgenCatalog.FORMAT, "26.3", "fabric", 0L, "",
+                List.of(),
+                List.of(new CatalogBiome("examplemod:glade", 0.7F, 0.8F, true, List.of(), List.of(List.of("examplemod:flowers")), List.of(), null),
+                        new CatalogBiome("minecraft:forest", 0.7F, 0.8F, true, List.of(), List.of(List.of("examplemod:flowers")), List.of(), null),
+                        new CatalogBiome("minecraft:desert", 2.0F, 0.0F, false, List.of(), List.of(), List.of(), null)),
+                List.of(), List.of(), List.of(), List.of());
+        WorldgenCatalogIndex index = WorldgenCatalogIndex.of(catalog);
+
+        assertEquals(1, index.biomesIn("examplemod").size());
+        assertEquals(2, index.biomesDeclaring("examplemod:flowers").size());
+        assertEquals("minecraft", WorldgenCatalogIndex.namespaceOf("plains"));
+        assertTrue(index.biome("minecraft:desert").isPresent());
+    }
+}