Add support for the natives/classifier concepts in Minecraft version …

…manifests (#45)

These were used in 1.18 and below to reference natives instead of rules.

src/main/java/net/neoforged/neoform/runtime/artifacts/ArtifactManager.java

@@ -66,7 +66,7 @@ public Artifact get(MinecraftLibrary library) throws IOException {
             throw new IllegalArgumentException("Cannot download a library that has no artifact defined: " + library);
         }
 
-        var artifactCoordinate = MavenCoordinate.parse(library.artifactId());
+        var artifactCoordinate = library.getMavenCoordinate();
         var externalArtifact = getFromExternalManifest(artifactCoordinate);
         if (externalArtifact != null) {
             return externalArtifact;

src/main/java/net/neoforged/neoform/runtime/manifests/MinecraftLibrary.java

@@ -1,12 +1,17 @@
 package net.neoforged.neoform.runtime.manifests;
 
 import com.google.gson.annotations.SerializedName;
+import net.fabricmc.loom.nativeplatform.OperatingSystem;
+import net.neoforged.neoform.runtime.utils.MavenCoordinate;
+import net.neoforged.neoform.runtime.utils.OsType;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 
-public record MinecraftLibrary(@SerializedName("name") String artifactId, Downloads downloads, List<Rule> rules) {
+public record MinecraftLibrary(@SerializedName("name") String artifactId, Downloads downloads, List<Rule> rules,
+                               @Nullable Map<OsType, String> natives) {
     public MinecraftLibrary {
         Objects.requireNonNull(artifactId, "name");
         rules = Objects.requireNonNullElseGet(rules, List::of);
@@ -31,10 +36,44 @@ public boolean rulesMatch() {
 
     @Nullable
     public MinecraftDownload getArtifactDownload() {
-        return downloads != null ? downloads.artifact : null;
+        if (downloads == null) {
+            return null;
+        }
+
+        if (natives != null) {
+            var classifier = natives.get(OsType.current());
+            if (classifier != null) {
+                var download = downloads.classifiers.get(classifier);
+                if (download == null) {
+                    throw new IllegalStateException("Download for " + artifactId + " references classifier " + classifier
+                                                    + " for natives for OS " + OperatingSystem.CURRENT + " but it doesn't exist.");
+                }
+                return download;
+            }
+        }
+
+        return downloads.artifact;
     }
 
-    public record Downloads(MinecraftDownload artifact) {
+    public MavenCoordinate getMavenCoordinate() {
+        var coordinate = MavenCoordinate.parse(artifactId);
+
+        if (natives != null) {
+            String classifier = natives.get(OsType.current());
+            if (classifier != null) {
+                coordinate = coordinate.withClassifier(classifier);
+            }
+        }
+
+        return coordinate;
+    }
+
+    public record Downloads(MinecraftDownload artifact, Map<String, MinecraftDownload> classifiers) {
+        public Downloads {
+            if (classifiers == null) {
+                classifiers = Map.of();
+            }
+        }
     }
 
     @Override

src/main/java/net/neoforged/neoform/runtime/utils/MavenCoordinate.java

@@ -118,4 +118,14 @@ public URI toRepositoryUri(URI baseUri) {
             return URI.create(originalBaseUri + "/" + relativePath);
         }
     }
+
+    public MavenCoordinate withClassifier(String classifier) {
+        return new MavenCoordinate(
+                groupId,
+                artifactId,
+                extension,
+                classifier,
+                version
+        );
+    }
 }

src/main/java/net/neoforged/neoform/runtime/utils/OsType.java

@@ -0,0 +1,33 @@
+package net.neoforged.neoform.runtime.utils;
+
+import com.google.gson.annotations.SerializedName;
+
+public enum OsType {
+    @SerializedName("windows")
+    WINDOWS,
+    @SerializedName("linux")
+    LINUX,
+    @SerializedName("osx")
+    MAC,
+    UNKNOWN;
+
+    private static final OsType CURRENT;
+
+    static {
+        var osName = System.getProperty("os.name");
+        // The following matches the logic in Apache Commons Lang 3 SystemUtils
+        if (osName.startsWith("Linux") || osName.startsWith("LINUX")) {
+            CURRENT = OsType.LINUX;
+        } else if (osName.startsWith("Mac OS X")) {
+            CURRENT = OsType.MAC;
+        } else if (osName.startsWith("Windows")) {
+            CURRENT = OsType.WINDOWS;
+        } else {
+            CURRENT = OsType.UNKNOWN;
+        }
+    }
+
+    public static OsType current() {
+        return CURRENT;
+    }
+}

src/main/java/net/neoforged/neoform/runtime/utils/OsUtil.java

@@ -1,41 +1,18 @@
 package net.neoforged.neoform.runtime.utils;
 
 public final class OsUtil {
-    private static OsType TYPE;
-
-    static {
-        var osName = System.getProperty("os.name");
-        // The following matches the logic in Apache Commons Lang 3 SystemUtils
-        if (osName.startsWith("Linux") || osName.startsWith("LINUX")) {
-            TYPE = OsType.LINUX;
-        } else if (osName.startsWith("Mac OS X")) {
-            TYPE = OsType.MAC;
-        } else if (osName.startsWith("Windows")) {
-            TYPE = OsType.WINDOWS;
-        } else {
-            TYPE = OsType.UNKNOWN;
-        }
-    }
-
     private OsUtil() {
     }
 
     public static boolean isWindows() {
-        return TYPE == OsType.WINDOWS;
+        return OsType.current() == OsType.WINDOWS;
     }
 
     public static boolean isLinux() {
-        return TYPE == OsType.LINUX;
+        return OsType.current() == OsType.LINUX;
     }
 
     public static boolean isMac() {
-        return TYPE == OsType.MAC;
-    }
-
-    enum OsType {
-        WINDOWS,
-        LINUX,
-        MAC,
-        UNKNOWN
+        return OsType.current() == OsType.MAC;
     }
 }