Expose layered mappings as an API (#490)

* Expose layered mappings as an API

* Add FileSpec

* Cleanup and support DependencyFileSpec

33 files changed, 522 insertions, 110 deletions

diff --git a/src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java b/src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java
index 0acb6da0..1a84efc9 100644
--- a/src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java
+++ b/src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java
@@ -38,9 +38,9 @@ import org.gradle.api.publish.maven.MavenPublication;
 import org.jetbrains.annotations.ApiStatus;
 
 import net.fabricmc.loom.api.decompilers.LoomDecompiler;
+import net.fabricmc.loom.api.mappings.layered.spec.LayeredMappingSpecBuilder;
 import net.fabricmc.loom.configuration.ide.RunConfigSettings;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
-import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpecBuilder;
 import net.fabricmc.loom.util.DeprecationHelper;
 
 /**
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingContext.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingContext.java
index 3fbfb655..cbc7d3ab 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingContext.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingContext.java
@@ -22,16 +22,22 @@
  * SOFTWARE.
  */
 
-package net.fabricmc.loom.configuration.providers.mappings;
+package net.fabricmc.loom.api.mappings.layered;
 
-import java.io.File;
+import java.nio.file.Path;
 
+import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.logging.Logger;
+import org.jetbrains.annotations.ApiStatus;
 
 import net.fabricmc.loom.configuration.providers.MinecraftProvider;
+import net.fabricmc.loom.configuration.providers.mappings.MappingsProvider;
 
+@ApiStatus.Experimental /* Very Experimental and not cleanly separated from the impl atm */
 public interface MappingContext {
-	File mavenFile(String mavenNotation);
+	Path resolveDependency(Dependency dependency);
+
+	Path resolveMavenDependency(String mavenNotation);
 
 	MappingsProvider mappingsProvider();
 
@@ -44,7 +50,7 @@ public interface MappingContext {
 	/**
 	 * Creates a temporary working dir to be used to store working files.
 	 */
-	File workingDirectory(String name);
+	Path workingDirectory(String name);
 
 	Logger getLogger();
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingLayer.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingLayer.java
index f3717894..1f28d65a 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingLayer.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingLayer.java
@@ -22,21 +22,28 @@
  * SOFTWARE.
  */
 
-package net.fabricmc.loom.configuration.providers.mappings;
+package net.fabricmc.loom.api.mappings.layered;
 
 import java.io.IOException;
 import java.util.Collections;
 import java.util.List;
 
+import org.jetbrains.annotations.ApiStatus;
+
 import net.fabricmc.mappingio.MappingVisitor;
 
+@ApiStatus.Experimental
 public interface MappingLayer {
 	void visit(MappingVisitor mappingVisitor) throws IOException;
 
-	default MappingNamespace getSourceNamespace() {
-		return MappingNamespace.NAMED;
+	default MappingsNamespace getSourceNamespace() {
+		return MappingsNamespace.NAMED;
 	}
 
+	/**
+	 * Provides a list of layer classes that this mapping layer depends on. If such a layer is not present an Exception will be thrown when trying to resolve the layer.
+	 * @return A list of MappingLayer classes to depend on.
+	 */
 	default List<Class<? extends MappingLayer>> dependsOn() {
 		return Collections.emptyList();
 	}
diff --git a/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingsNamespace.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingsNamespace.java
new file mode 100644
index 00000000..ae32f7f9
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingsNamespace.java
@@ -0,0 +1,56 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2016-2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.api.mappings.layered;
+
+import java.util.Locale;
+
+/**
+ * The standard namespaces used by loom.
+ */
+public enum MappingsNamespace {
+	/**
+	 * Official mappings are the names that are used in the vanilla Minecraft game jars, these are usually obfuscated.
+	 */
+	OFFICIAL,
+
+	/**
+	 * Intermediary mappings have been generated to provide a stable set of names across minecraft versions.
+	 *
+	 * <p>Intermediary is used in a production runtime (outside a dev env) allowing mods to run across multiple versions of the game. Mods are remapped from "named" at build time.
+	 *
+	 * @see <a href="https://github.com/FabricMC/intermediary/">github.com/FabricMC/intermediary/</a>
+	 */
+	INTERMEDIARY,
+
+	/**
+	 * Named mappings are the developer friendly names used to develop mods against.
+	 */
+	NAMED;
+
+	@Override
+	public String toString() {
+		return name().toLowerCase(Locale.ROOT);
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/FileSpec.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/FileSpec.java
new file mode 100644
index 00000000..19129e5d
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/FileSpec.java
@@ -0,0 +1,79 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.api.mappings.layered.spec;
+
+import java.io.File;
+import java.nio.file.Path;
+import java.util.Objects;
+
+import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.file.RegularFileProperty;
+import org.jetbrains.annotations.ApiStatus;
+
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.configuration.providers.mappings.utils.DependencyFileSpec;
+import net.fabricmc.loom.configuration.providers.mappings.utils.LocalFileSpec;
+import net.fabricmc.loom.configuration.providers.mappings.utils.MavenFileSpec;
+
+/**
+ * FileSpec should be used in MappingsSpec's that take an input file. The input file can either be a local file or a gradle dep.
+ */
+@ApiStatus.Experimental
+public interface FileSpec {
+	static FileSpec create(Object o) {
+		Objects.requireNonNull(o, "Object cannot be null");
+
+		if (o instanceof String s) {
+			return createFromMavenDependency(s);
+		} else if (o instanceof Dependency d) {
+			return createFromDependency(d);
+		} else if (o instanceof File f) {
+			return createFromFile(f);
+		} else if (o instanceof RegularFileProperty rfp) {
+			return createFromFile(rfp);
+		}
+
+		throw new UnsupportedOperationException("Cannot create FileSpec from object of type:" + o.getClass().getCanonicalName());
+	}
+
+	static FileSpec createFromMavenDependency(String dependencyNotation) {
+		return new MavenFileSpec(dependencyNotation);
+	}
+
+	static FileSpec createFromDependency(Dependency dependency) {
+		return new DependencyFileSpec(dependency);
+	}
+
+	static FileSpec createFromFile(File file) {
+		return new LocalFileSpec(file);
+	}
+
+	// Note resolved instantly, this is not lazy
+	static FileSpec createFromFile(RegularFileProperty regularFileProperty) {
+		return createFromFile(regularFileProperty.getAsFile().get());
+	}
+
+	Path get(MappingContext context);
+}
diff --git a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
new file mode 100644
index 00000000..05180172
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
@@ -0,0 +1,50 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.api.mappings.layered.spec;
+
+import org.gradle.api.Action;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Used to configure a layered mapping spec.
+ */
+@ApiStatus.Experimental
+public interface LayeredMappingSpecBuilder {
+	/**
+	 * Add a MappingsSpec layer.
+	 */
+	LayeredMappingSpecBuilder addLayer(MappingsSpec<?> mappingSpec);
+
+	/**
+	 * Add a layer that uses the official mappings provided by Mojang.
+	 */
+	LayeredMappingSpecBuilder officialMojangMappings();
+
+	default LayeredMappingSpecBuilder parchment(Object object) {
+		return parchment(object, parchmentMappingsSpecBuilder -> parchmentMappingsSpecBuilder.setRemovePrefix(true));
+	}
+
+	LayeredMappingSpecBuilder parchment(Object object, Action<ParchmentMappingsSpecBuilder> action);
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsSpec.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/MappingsSpec.java
index 8b6adcea..8511614e 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsSpec.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/MappingsSpec.java
@@ -22,8 +22,21 @@
  * SOFTWARE.
  */
 
-package net.fabricmc.loom.configuration.providers.mappings;
+package net.fabricmc.loom.api.mappings.layered.spec;
 
+import org.jetbrains.annotations.ApiStatus;
+
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+
+/**
+ * A MappingsSpec is an immutable set of data used to create the MappingLayer.
+ *
+ * <p>The hashCode is used to generate a hash of the full layered mapping spec, used to cache.
+ *
+ * <p>Commonly implemented as a record
+ */
+@ApiStatus.Experimental
 public interface MappingsSpec<L extends MappingLayer> {
 	L createLayer(MappingContext context);
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingNamespace.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/ParchmentMappingsSpecBuilder.java
index 991cdc79..ee3e07a0 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingNamespace.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/ParchmentMappingsSpecBuilder.java
@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2016-2021 FabricMC
+ * Copyright (c) 2021 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,16 +22,14 @@
  * SOFTWARE.
  */
 
-package net.fabricmc.loom.configuration.providers.mappings;
+package net.fabricmc.loom.api.mappings.layered.spec;
 
-import java.util.Locale;
+import org.jetbrains.annotations.ApiStatus;
 
-public enum MappingNamespace {
-	OFFICIAL,
-	INTERMEDIARY,
-	NAMED;
-
-	public String stringValue() {
-		return name().toLowerCase(Locale.ROOT);
-	}
+@ApiStatus.Experimental
+public interface ParchmentMappingsSpecBuilder {
+	/**
+	 * When enabled the "p" prefix will be stripped from parameter names.
+	 */
+	ParchmentMappingsSpecBuilder setRemovePrefix(boolean removePrefix);
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/accesswidener/AccessWidenerJarProcessor.java b/src/main/java/net/fabricmc/loom/configuration/accesswidener/AccessWidenerJarProcessor.java
index bca3f352..6ac63ac1 100644
--- a/src/main/java/net/fabricmc/loom/configuration/accesswidener/AccessWidenerJarProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/accesswidener/AccessWidenerJarProcessor.java
@@ -54,6 +54,7 @@ import net.fabricmc.accesswidener.AccessWidenerRemapper;
 import net.fabricmc.accesswidener.AccessWidenerVisitor;
 import net.fabricmc.accesswidener.AccessWidenerWriter;
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
 import net.fabricmc.loom.util.Checksum;
 import net.fabricmc.loom.util.Constants;
@@ -92,7 +93,7 @@ public class AccessWidenerJarProcessor implements JarProcessor {
 		}
 
 		//Remap accessWidener if its not named, allows for AE's to be written in intermediary
-		if (!accessWidener.getNamespace().equals("named")) {
+		if (!accessWidener.getNamespace().equals(MappingsNamespace.NAMED.toString())) {
 			try {
 				List<String> validNamespaces = loomGradleExtension.getMappingsProvider().getMappings().getMetadata().getNamespaces();
 
@@ -100,10 +101,10 @@ public class AccessWidenerJarProcessor implements JarProcessor {
 					throw new UnsupportedOperationException(String.format("Access Widener namespace '%s' is not a valid namespace, it must be one of: '%s'", accessWidener.getNamespace(), String.join(", ", validNamespaces)));
 				}
 
-				TinyRemapper tinyRemapper = loomGradleExtension.getMinecraftMappedProvider().getTinyRemapper("official", "named");
+				TinyRemapper tinyRemapper = loomGradleExtension.getMinecraftMappedProvider().getTinyRemapper(MappingsNamespace.OFFICIAL.toString(), MappingsNamespace.NAMED.toString());
 				tinyRemapper.readClassPath(loomGradleExtension.getMinecraftMappedProvider().getRemapClasspath());
 
-				AccessWidenerRemapper remapper = new AccessWidenerRemapper(accessWidener, tinyRemapper.getRemapper(), "named");
+				AccessWidenerRemapper remapper = new AccessWidenerRemapper(accessWidener, tinyRemapper.getRemapper(), MappingsNamespace.NAMED.toString());
 				accessWidener = remapper.remap();
 
 				tinyRemapper.finish();
@@ -160,7 +161,7 @@ public class AccessWidenerJarProcessor implements JarProcessor {
 	}
 
 	public byte[] getRemappedAccessWidener(Remapper asmRemapper) throws IOException {
-		AccessWidenerRemapper remapper = new AccessWidenerRemapper(accessWidener, asmRemapper, "intermediary");
+		AccessWidenerRemapper remapper = new AccessWidenerRemapper(accessWidener, asmRemapper, MappingsNamespace.INTERMEDIARY.toString());
 		AccessWidener remapped = remapper.remap();
 		AccessWidenerWriter accessWidenerWriter = new AccessWidenerWriter(remapped);
 
diff --git a/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java b/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java
index 808c857c..7cdc6670 100644
--- a/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java
@@ -54,6 +54,7 @@ import net.fabricmc.accesswidener.AccessWidenerRemapper;
 import net.fabricmc.accesswidener.AccessWidenerWriter;
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.RemappedConfigurationEntry;
 import net.fabricmc.loom.configuration.processors.dependency.ModDependencyInfo;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
@@ -113,7 +114,7 @@ public class ModProcessor {
 			AccessWidenerReader accessWidenerReader = new AccessWidenerReader(accessWidener);
 			accessWidenerReader.read(bufferedReader);
 
-			AccessWidenerRemapper accessWidenerRemapper = new AccessWidenerRemapper(accessWidener, remapper, "named");
+			AccessWidenerRemapper accessWidenerRemapper = new AccessWidenerRemapper(accessWidener, remapper, MappingsNamespace.NAMED.toString());
 			AccessWidener remapped = accessWidenerRemapper.remap();
 			AccessWidenerWriter accessWidenerWriter = new AccessWidenerWriter(remapped);
 
@@ -128,8 +129,8 @@ public class ModProcessor {
 
 	private static void remapJars(Project project, List<ModDependencyInfo> processList) throws IOException {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
-		String fromM = "intermediary";
-		String toM = "named";
+		String fromM = MappingsNamespace.INTERMEDIARY.toString();
+		String toM = MappingsNamespace.NAMED.toString();
 
 		MinecraftMappedProvider mappedProvider = extension.getMinecraftMappedProvider();
 		MappingsProviderImpl mappingsProvider = extension.getMappingsProvider();
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/GradleMappingContext.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/GradleMappingContext.java
index e62e9e91..0d780f16 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/GradleMappingContext.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/GradleMappingContext.java
@@ -25,12 +25,15 @@
 package net.fabricmc.loom.configuration.providers.mappings;
 
 import java.io.File;
+import java.nio.file.Path;
 
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
+import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.logging.Logger;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
 import net.fabricmc.loom.configuration.providers.MinecraftProvider;
 
 public class GradleMappingContext implements MappingContext {
@@ -45,9 +48,14 @@ public class GradleMappingContext implements MappingContext {
 	}
 
 	@Override
-	public File mavenFile(String mavenNotation) {
-		Configuration configuration = project.getConfigurations().detachedConfiguration(project.getDependencies().create(mavenNotation));
-		return configuration.getSingleFile();
+	public Path resolveDependency(Dependency dependency) {
+		Configuration configuration = project.getConfigurations().detachedConfiguration(dependency);
+		return configuration.getSingleFile().toPath();
+	}
+
+	@Override
+	public Path resolveMavenDependency(String mavenNotation) {
+		return resolveDependency(project.getDependencies().create(mavenNotation));
 	}
 
 	@Override
@@ -61,8 +69,8 @@ public class GradleMappingContext implements MappingContext {
 	}
 
 	@Override
-	public File workingDirectory(String name) {
-		return new File(minecraftProvider().dir("layered/working_dir/" + workingDirName), name);
+	public Path workingDirectory(String name) {
+		return new File(minecraftProvider().dir("layered/working_dir/" + workingDirName), name).toPath();
 	}
 
 	@Override
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpec.java
index 2e47af39..cb09d71f 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpec.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpec.java
@@ -26,6 +26,8 @@ package net.fabricmc.loom.configuration.providers.mappings;
 
 import java.util.List;
 
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
+
 public record LayeredMappingSpec(List<MappingsSpec<?>> layers) {
 	public String getVersion() {
 		// TODO something better?
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilder.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
index f61b8823..4f47cfbf 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilder.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
@@ -30,28 +30,33 @@ import java.util.List;
 
 import org.gradle.api.Action;
 
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.LayeredMappingSpecBuilder;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.ParchmentMappingsSpecBuilder;
 import net.fabricmc.loom.configuration.providers.mappings.intermediary.IntermediaryMappingsSpec;
 import net.fabricmc.loom.configuration.providers.mappings.mojmap.MojangMappingsSpec;
-import net.fabricmc.loom.configuration.providers.mappings.parchment.ParchmentMappingsSpecBuilder;
+import net.fabricmc.loom.configuration.providers.mappings.parchment.ParchmentMappingsSpecBuilderImpl;
 
-public class LayeredMappingSpecBuilder {
+public class LayeredMappingSpecBuilderImpl implements LayeredMappingSpecBuilder {
 	private final List<MappingsSpec<?>> layers = new LinkedList<>();
 
-	public LayeredMappingSpecBuilder officialMojangMappings() {
-		layers.add(new MojangMappingsSpec());
+	@Override
+	public LayeredMappingSpecBuilder addLayer(MappingsSpec<?> mappingSpec) {
+		layers.add(mappingSpec);
 		return this;
 	}
 
-	public LayeredMappingSpecBuilder parchment(String mavenNotation) {
-		parchment(mavenNotation, parchmentMappingsSpecBuilder -> parchmentMappingsSpecBuilder.setRemovePrefix(true));
-		return this;
+	@Override
+	public LayeredMappingSpecBuilder officialMojangMappings() {
+		return addLayer(new MojangMappingsSpec());
 	}
 
-	public LayeredMappingSpecBuilder parchment(String mavenNotation, Action<ParchmentMappingsSpecBuilder> action) {
-		ParchmentMappingsSpecBuilder builder = ParchmentMappingsSpecBuilder.builder(mavenNotation);
+	@Override
+	public LayeredMappingSpecBuilder parchment(Object object, Action<ParchmentMappingsSpecBuilder> action) {
+		ParchmentMappingsSpecBuilderImpl builder = ParchmentMappingsSpecBuilderImpl.builder(FileSpec.create(object));
 		action.execute(builder);
-		layers.add(builder.build());
-		return this;
+		return addLayer(builder.build());
 	}
 
 	public LayeredMappingSpec build() {
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
index 878a37e4..e15f6239 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
@@ -43,6 +43,8 @@ import org.zeroturnaround.zip.ZipEntrySource;
 import org.zeroturnaround.zip.ZipUtil;
 
 import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.mappingio.adapter.MappingDstNsReorder;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
 import net.fabricmc.mappingio.format.Tiny2Writer;
@@ -75,8 +77,8 @@ public class LayeredMappingsDependency implements SelfResolvingDependency {
 				try (Writer writer = new StringWriter()) {
 					Tiny2Writer tiny2Writer = new Tiny2Writer(writer, false);
 
-					MappingDstNsReorder nsReorder = new MappingDstNsReorder(tiny2Writer, Collections.singletonList(MappingNamespace.NAMED.stringValue()));
-					MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(nsReorder, MappingNamespace.INTERMEDIARY.stringValue(), true);
+					MappingDstNsReorder nsReorder = new MappingDstNsReorder(tiny2Writer, Collections.singletonList(MappingsNamespace.NAMED.toString()));
+					MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(nsReorder, MappingsNamespace.INTERMEDIARY.toString(), true);
 					mappings.accept(nsSwitch);
 
 					Files.deleteIfExists(mappingsFile);
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
index a3fa5294..b14902c5 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
@@ -28,6 +28,10 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
 
@@ -55,7 +59,7 @@ public class LayeredMappingsProcessor {
 			visitedLayers.add(layer.getClass());
 
 			// We have to rebuild a new tree to work on when a layer doesnt merge into layered
-			boolean rebuild = layer.getSourceNamespace() != MappingNamespace.NAMED;
+			boolean rebuild = layer.getSourceNamespace() != MappingsNamespace.NAMED;
 			MemoryMappingTree workingTree;
 
 			if (rebuild) {
@@ -63,7 +67,7 @@ public class LayeredMappingsProcessor {
 
 				// This can be null on the first layer
 				if (mappingTree.getSrcNamespace() != null) {
-					var sourceNsSwitch = new MappingSourceNsSwitch(tempTree, layer.getSourceNamespace().stringValue());
+					var sourceNsSwitch = new MappingSourceNsSwitch(tempTree, layer.getSourceNamespace().toString());
 					mappingTree.accept(sourceNsSwitch);
 				}
 
@@ -80,7 +84,7 @@ public class LayeredMappingsProcessor {
 
 			if (rebuild) {
 				mappingTree = new MemoryMappingTree();
-				workingTree.accept(new MappingSourceNsSwitch(mappingTree, MappingNamespace.NAMED.stringValue()));
+				workingTree.accept(new MappingSourceNsSwitch(mappingTree, MappingsNamespace.NAMED.toString()));
 			}
 		}
 
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
index 4554b8d3..0456adaf 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
@@ -48,6 +48,7 @@ import org.zeroturnaround.zip.ZipUtil;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.DependencyProvider;
 import net.fabricmc.loom.configuration.accesswidener.AccessWidenerJarProcessor;
 import net.fabricmc.loom.configuration.processors.JarProcessorManager;
@@ -276,7 +277,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 		project.getLogger().info(":merging mappings");
 
 		MemoryMappingTree tree = new MemoryMappingTree();
-		MappingSourceNsSwitch sourceNsSwitch = new MappingSourceNsSwitch(tree, MappingNamespace.OFFICIAL.stringValue());
+		MappingSourceNsSwitch sourceNsSwitch = new MappingSourceNsSwitch(tree, MappingsNamespace.OFFICIAL.toString());
 		readIntermediaryTree().accept(sourceNsSwitch);
 
 		try (BufferedReader reader = Files.newBufferedReader(from, StandardCharsets.UTF_8)) {
@@ -292,7 +293,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 
 	private MemoryMappingTree readIntermediaryTree() throws IOException {
 		MemoryMappingTree tree = new MemoryMappingTree();
-		MappingNsCompleter nsCompleter = new MappingNsCompleter(tree, Collections.singletonMap(MappingNamespace.NAMED.stringValue(), MappingNamespace.INTERMEDIARY.stringValue()), true);
+		MappingNsCompleter nsCompleter = new MappingNsCompleter(tree, Collections.singletonMap(MappingsNamespace.NAMED.toString(), MappingsNamespace.INTERMEDIARY.toString()), true);
 
 		try (BufferedReader reader = Files.newBufferedReader(getIntermediaryTiny(), StandardCharsets.UTF_8)) {
 			Tiny2Reader.read(reader, nsCompleter);
@@ -316,7 +317,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			runCommand(command, intermediaryMappings.toAbsolutePath().toString(),
 							yarnMappings.toAbsolutePath().toString(),
 							newMergedMappings.toAbsolutePath().toString(),
-							"intermediary", "official");
+							MappingsNamespace.INTERMEDIARY.toString(), MappingsNamespace.OFFICIAL.toString());
 		} catch (Exception e) {
 			throw new RuntimeException("Could not merge mappings from " + intermediaryMappings.toString()
 							+ " with mappings from " + yarnMappings, e);
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingLayer.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingLayer.java
index 0ca6414f..a6c06ba9 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingLayer.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingLayer.java
@@ -31,22 +31,22 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.Collections;
 
-import net.fabricmc.loom.configuration.providers.mappings.MappingLayer;
-import net.fabricmc.loom.configuration.providers.mappings.MappingNamespace;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.mappingio.MappingVisitor;
 import net.fabricmc.mappingio.adapter.MappingNsCompleter;
 import net.fabricmc.mappingio.format.Tiny2Reader;
 
 public record IntermediaryMappingLayer(File tinyFile) implements MappingLayer {
 	@Override
-	public MappingNamespace getSourceNamespace() {
-		return MappingNamespace.OFFICIAL;
+	public MappingsNamespace getSourceNamespace() {
+		return MappingsNamespace.OFFICIAL;
 	}
 
 	@Override
 	public void visit(MappingVisitor mappingVisitor) throws IOException {
 		// Populate named with intermediary and add Add a "named" namespace
-		MappingNsCompleter nsCompleter = new MappingNsCompleter(mappingVisitor, Collections.singletonMap(MappingNamespace.NAMED.stringValue(), MappingNamespace.INTERMEDIARY.stringValue()), true);
+		MappingNsCompleter nsCompleter = new MappingNsCompleter(mappingVisitor, Collections.singletonMap(MappingsNamespace.NAMED.toString(), MappingsNamespace.INTERMEDIARY.toString()), true);
 
 		try (BufferedReader reader = Files.newBufferedReader(tinyFile().toPath(), StandardCharsets.UTF_8)) {
 			Tiny2Reader.read(reader, nsCompleter);
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingsSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingsSpec.java
index 866ad9d7..194b3038 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingsSpec.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/intermediary/IntermediaryMappingsSpec.java
@@ -24,8 +24,8 @@
 
 package net.fabricmc.loom.configuration.providers.mappings.intermediary;
 
-import net.fabricmc.loom.configuration.providers.mappings.MappingContext;
-import net.fabricmc.loom.configuration.providers.mappings.MappingsSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 
 public record IntermediaryMappingsSpec() implements MappingsSpec<IntermediaryMappingLayer> {
 	@Override
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingLayer.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingLayer.java
index 03d0c010..dacfbaf7 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingLayer.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingLayer.java
@@ -25,7 +25,6 @@
 package net.fabricmc.loom.configuration.providers.mappings.mojmap;
 
 import java.io.BufferedReader;
-import java.io.File;
 import java.io.IOException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
@@ -35,8 +34,8 @@ import java.util.List;
 
 import org.gradle.api.logging.Logger;
 
-import net.fabricmc.loom.configuration.providers.mappings.MappingLayer;
-import net.fabricmc.loom.configuration.providers.mappings.MappingNamespace;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftVersionMeta;
 import net.fabricmc.loom.configuration.providers.mappings.intermediary.IntermediaryMappingLayer;
 import net.fabricmc.loom.util.HashedDownloadUtil;
@@ -46,30 +45,30 @@ import net.fabricmc.mappingio.format.ProGuardReader;
 
 public record MojangMappingLayer(MinecraftVersionMeta.Download clientDownload,
 									MinecraftVersionMeta.Download serverDownload,
-									File workingDir,
+									Path workingDir,
 									Logger logger) implements MappingLayer {
 	@Override
 	public void visit(MappingVisitor mappingVisitor) throws IOException {
-		var clientMappings = new File(workingDir(), "client.txt");
-		var serverMappings = new File(workingDir(), "server.txt");
+		Path clientMappings = workingDir().resolve("client.txt");
+		Path serverMappings = workingDir().resolve("server.txt");
 
 		download(clientMappings, serverMappings);
 
-		printMappingsLicense(clientMappings.toPath());
+		printMappingsLicense(clientMappings);
 
 		// Make official the source namespace
-		MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(mappingVisitor, MappingNamespace.OFFICIAL.stringValue());
+		MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(mappingVisitor, MappingsNamespace.OFFICIAL.toString());
 
-		try (BufferedReader clientBufferedReader = Files.newBufferedReader(clientMappings.toPath(), StandardCharsets.UTF_8);
-				BufferedReader serverBufferedReader = Files.newBufferedReader(serverMappings.toPath(), StandardCharsets.UTF_8)) {
-			ProGuardReader.read(clientBufferedReader, MappingNamespace.NAMED.stringValue(), MappingNamespace.OFFICIAL.stringValue(), nsSwitch);
-			ProGuardReader.read(serverBufferedReader, MappingNamespace.NAMED.stringValue(), MappingNamespace.OFFICIAL.stringValue(), nsSwitch);
+		try (BufferedReader clientBufferedReader = Files.newBufferedReader(clientMappings, StandardCharsets.UTF_8);
+				BufferedReader serverBufferedReader = Files.newBufferedReader(serverMappings, StandardCharsets.UTF_8)) {
+			ProGuardReader.read(clientBufferedReader, MappingsNamespace.NAMED.toString(), MappingsNamespace.OFFICIAL.toString(), nsSwitch);
+			ProGuardReader.read(serverBufferedReader, MappingsNamespace.NAMED.toString(), MappingsNamespace.OFFICIAL.toString(), nsSwitch);
 		}
 	}
 
-	private void download(File clientMappings, File serverMappings) throws IOException {
-		HashedDownloadUtil.downloadIfInvalid(new URL(clientDownload().url()), clientMappings, clientDownload().sha1(), logger(), false);
-		HashedDownloadUtil.downloadIfInvalid(new URL(serverDownload().url()), serverMappings, serverDownload().sha1(), logger(), false);
+	private void download(Path clientMappings, Path serverMappings) throws IOException {
+		HashedDownloadUtil.downloadIfInvalid(new URL(clientDownload().url()), clientMappings.toFile(), clientDownload().sha1(), logger(), false);
+		HashedDownloadUtil.downloadIfInvalid(new URL(serverDownload().url()), serverMappings.toFile(), serverDownload().sha1(), logger(), false);
 	}
 
 	private void printMappingsLicense(Path clientMappings) {
@@ -91,8 +90,8 @@ public record MojangMappingLayer(MinecraftVersionMeta.Download clientDownload,
 	}
 
 	@Override
-	public MappingNamespace getSourceNamespace() {
-		return MappingNamespace.OFFICIAL;
+	public MappingsNamespace getSourceNamespace() {
+		return MappingsNamespace.OFFICIAL;
 	}
 
 	@Override
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingsSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingsSpec.java
index 61bec479..59d14f42 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingsSpec.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingsSpec.java
@@ -24,8 +24,8 @@
 
 package net.fabricmc.loom.configuration.providers.mappings.mojmap;
 
-import net.fabricmc.loom.configuration.providers.mappings.MappingContext;
-import net.fabricmc.loom.configuration.providers.mappings.MappingsSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftVersionMeta;
 
 public record MojangMappingsSpec() implements MappingsSpec<MojangMappingLayer> {
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingLayer.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingLayer.java
index 448a33a1..f6b602e8 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingLayer.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingLayer.java
@@ -24,19 +24,19 @@
 
 package net.fabricmc.loom.configuration.providers.mappings.parchment;
 
-import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.nio.file.Path;
 import java.util.Objects;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
 import net.fabricmc.loom.LoomGradlePlugin;
-import net.fabricmc.loom.configuration.providers.mappings.MappingLayer;
-import net.fabricmc.loom.configuration.providers.mappings.MappingNamespace;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.mappingio.MappingVisitor;
 
-public record ParchmentMappingLayer(File parchmentFile, boolean removePrefix) implements MappingLayer {
+public record ParchmentMappingLayer(Path parchmentFile, boolean removePrefix) implements MappingLayer {
 	private static final String PARCHMENT_DATA_FILE_NAME = "parchment.json";
 
 	@Override
@@ -47,11 +47,11 @@ public record ParchmentMappingLayer(File parchmentFile, boolean removePrefix) im
 			mappingVisitor = new ParchmentPrefixStripingMappingVisitor(mappingVisitor);
 		}
 
-		parchmentData.visit(mappingVisitor, MappingNamespace.NAMED.stringValue());
+		parchmentData.visit(mappingVisitor, MappingsNamespace.NAMED.toString());
 	}
 
 	private ParchmentTreeV1 getParchmentData() throws IOException {
-		try (var zipFile = new ZipFile(parchmentFile())) {
+		try (var zipFile = new ZipFile(parchmentFile().toFile())) {
 			ZipEntry zipFileEntry = zipFile.getEntry(PARCHMENT_DATA_FILE_NAME);
 			Objects.requireNonNull(zipFileEntry, "Could not find %s in parchment data file".formatted(PARCHMENT_DATA_FILE_NAME));
 
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpec.java
index 2b3f48b2..5af9503f 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpec.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpec.java
@@ -24,12 +24,13 @@
 
 package net.fabricmc.loom.configuration.providers.mappings.parchment;
 
-import net.fabricmc.loom.configuration.providers.mappings.MappingContext;
-import net.fabricmc.loom.configuration.providers.mappings.MappingsSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 
-public record ParchmentMappingsSpec(String mavenNotation, boolean removePrefix) implements MappingsSpec<ParchmentMappingLayer> {
+public record ParchmentMappingsSpec(FileSpec fileSpec, boolean removePrefix) implements MappingsSpec<ParchmentMappingLayer> {
 	@Override
 	public ParchmentMappingLayer createLayer(MappingContext context) {
-		return new ParchmentMappingLayer(context.mavenFile(mavenNotation()), removePrefix());
+		return new ParchmentMappingLayer(fileSpec.get(context), removePrefix());
 	}
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpecBuilder.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpecBuilderImpl.java
index 1fff3195..4830cad7 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpecBuilder.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/parchment/ParchmentMappingsSpecBuilderImpl.java
@@ -24,25 +24,29 @@
 
 package net.fabricmc.loom.configuration.providers.mappings.parchment;
 
-public class ParchmentMappingsSpecBuilder {
-	private final String mavenNotation;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.ParchmentMappingsSpecBuilder;
+
+public class ParchmentMappingsSpecBuilderImpl implements ParchmentMappingsSpecBuilder {
+	private final FileSpec fileSpec;
 
 	private boolean removePrefix;
 
-	private ParchmentMappingsSpecBuilder(String mavenNotation) {
-		this.mavenNotation = mavenNotation;
+	private ParchmentMappingsSpecBuilderImpl(FileSpec fileSpec) {
+		this.fileSpec = fileSpec;
 	}
 
-	public static ParchmentMappingsSpecBuilder builder(String depNotation) {
-		return new ParchmentMappingsSpecBuilder(depNotation);
+	public static ParchmentMappingsSpecBuilderImpl builder(FileSpec fileSpec) {
+		return new ParchmentMappingsSpecBuilderImpl(fileSpec);
 	}
 
+	@Override
 	public ParchmentMappingsSpecBuilder setRemovePrefix(boolean removePrefix) {
 		this.removePrefix = removePrefix;
 		return this;
 	}
 
 	public ParchmentMappingsSpec build() {
-		return new ParchmentMappingsSpec(mavenNotation, removePrefix);
+		return new ParchmentMappingsSpec(fileSpec, removePrefix);
 	}
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/DependencyFileSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/DependencyFileSpec.java
new file mode 100644
index 00000000..99c9d7d3
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/DependencyFileSpec.java
@@ -0,0 +1,69 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.utils;
+
+import java.io.File;
+import java.nio.file.Path;
+import java.util.Objects;
+import java.util.Set;
+
+import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.artifacts.SelfResolvingDependency;
+
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+
+public record DependencyFileSpec(Dependency dependency) implements FileSpec {
+	@Override
+	public Path get(MappingContext context) {
+		if (dependency instanceof SelfResolvingDependency selfResolvingDependency) {
+			Set<File> files = selfResolvingDependency.resolve();
+
+			if (files.size() == 0) {
+				throw new RuntimeException("SelfResolvingDependency (%s) resolved no files".formatted(selfResolvingDependency.toString()));
+			} else if (files.size() > 1) {
+				throw new RuntimeException("SelfResolvingDependency (%s) resolved too many files (%d) only 1 is expected".formatted(selfResolvingDependency.toString(), files.size()));
+			}
+
+			return files.iterator().next().toPath();
+		}
+
+		return context.resolveDependency(dependency);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(dependency.getGroup(), dependency.getName(), dependency.getVersion());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (obj instanceof DependencyFileSpec other) {
+			return other.dependency().contentEquals(this.dependency());
+		}
+
+		return false;
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/LocalFileSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/LocalFileSpec.java
new file mode 100644
index 00000000..d870d691
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/LocalFileSpec.java
@@ -0,0 +1,63 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.utils;
+
+import java.io.File;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Objects;
+
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.util.Checksum;
+
+public class LocalFileSpec implements FileSpec {
+	private final File file;
+	private final int hash;
+
+	public LocalFileSpec(File file) {
+		this.file = file;
+		this.hash = calculateHashCode();
+	}
+
+	private int calculateHashCode() {
+		if (!file.exists()) {
+			throw new RuntimeException("Could not find %s, it must be present at spec creation time to calculate mappings hash".formatted(file.getAbsolutePath()));
+		}
+
+		// Use the file hash as part of the spec, this means if the input file changes the mappings will be re-generated.
+		return Objects.hash(Arrays.hashCode(Checksum.sha256(file)), file.getAbsolutePath());
+	}
+
+	@Override
+	public Path get(MappingContext context) {
+		return file.toPath();
+	}
+
+	@Override
+	public int hashCode() {
+		return hash;
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/MavenFileSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/MavenFileSpec.java
new file mode 100644
index 00000000..f833fe15
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/MavenFileSpec.java
@@ -0,0 +1,37 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.utils;
+
+import java.nio.file.Path;
+
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+
+public record MavenFileSpec(String dependencyNotation) implements FileSpec {
+	@Override
+	public Path get(MappingContext context) {
+		return context.resolveMavenDependency(dependencyNotation);
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java b/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
index b95f8195..7535e1a9 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
@@ -35,6 +35,7 @@ import java.util.function.Consumer;
 import com.google.common.collect.ImmutableMap;
 import org.gradle.api.Project;
 
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.DependencyProvider;
 import net.fabricmc.loom.configuration.providers.MinecraftProviderImpl;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
@@ -99,7 +100,7 @@ public class MinecraftMappedProvider extends DependencyProvider {
 	}
 
 	private void mapMinecraftJar() throws IOException {
-		String fromM = "official";
+		String fromM = MappingsNamespace.OFFICIAL.toString();
 
 		MappingsProviderImpl mappingsProvider = getExtension().getMappingsProvider();
 
@@ -107,8 +108,8 @@ public class MinecraftMappedProvider extends DependencyProvider {
 		Path outputMapped = minecraftMappedJar.toPath();
 		Path outputIntermediary = minecraftIntermediaryJar.toPath();
 
-		for (String toM : Arrays.asList("named", "intermediary")) {
-			Path output = "named".equals(toM) ? outputMapped : outputIntermediary;
+		for (String toM : Arrays.asList(MappingsNamespace.NAMED.toString(), MappingsNamespace.INTERMEDIARY.toString())) {
+			Path output = MappingsNamespace.NAMED.toString().equals(toM) ? outputMapped : outputIntermediary;
 
 			getProject().getLogger().lifecycle(":remapping minecraft (TinyRemapper, " + fromM + " -> " + toM + ")");
 
diff --git a/src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java b/src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java
index b1c4b12c..93e88523 100644
--- a/src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java
+++ b/src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java
@@ -37,12 +37,13 @@ import org.gradle.api.publish.maven.MavenPublication;
 import net.fabricmc.loom.api.LoomGradleExtensionAPI;
 import net.fabricmc.loom.api.MixinExtensionAPI;
 import net.fabricmc.loom.api.decompilers.LoomDecompiler;
+import net.fabricmc.loom.api.mappings.layered.spec.LayeredMappingSpecBuilder;
 import net.fabricmc.loom.configuration.ide.RunConfigSettings;
 import net.fabricmc.loom.configuration.mods.ModVersionParser;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
 import net.fabricmc.loom.configuration.providers.mappings.GradleMappingContext;
 import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpec;
-import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpecBuilder;
+import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpecBuilderImpl;
 import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingsDependency;
 import net.fabricmc.loom.util.DeprecationHelper;
 
@@ -113,7 +114,7 @@ public abstract class LoomGradleExtensionApiImpl implements LoomGradleExtensionA
 
 	@Override
 	public Dependency layered(Action<LayeredMappingSpecBuilder> action) {
-		LayeredMappingSpecBuilder builder = new LayeredMappingSpecBuilder();
+		LayeredMappingSpecBuilderImpl builder = new LayeredMappingSpecBuilderImpl();
 		action.execute(builder);
 		LayeredMappingSpec builtSpec = builder.build();
 		return new LayeredMappingsDependency(new GradleMappingContext(getProject(), builtSpec.getVersion().replace("+", "_").replace(".", "_")), builtSpec, builtSpec.getVersion());
diff --git a/src/main/java/net/fabricmc/loom/extension/MinecraftGradleExtension.java b/src/main/java/net/fabricmc/loom/extension/MinecraftGradleExtension.java
index c4ea3d39..5b02a7dc 100644
--- a/src/main/java/net/fabricmc/loom/extension/MinecraftGradleExtension.java
+++ b/src/main/java/net/fabricmc/loom/extension/MinecraftGradleExtension.java
@@ -36,9 +36,9 @@ import org.gradle.api.publish.maven.MavenPublication;
 import net.fabricmc.loom.api.LoomGradleExtensionAPI;
 import net.fabricmc.loom.api.MixinExtensionAPI;
 import net.fabricmc.loom.api.decompilers.LoomDecompiler;
+import net.fabricmc.loom.api.mappings.layered.spec.LayeredMappingSpecBuilder;
 import net.fabricmc.loom.configuration.ide.RunConfigSettings;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
-import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpecBuilder;
 import net.fabricmc.loom.util.DeprecationHelper;
 
 public class MinecraftGradleExtension implements LoomGradleExtensionAPI {
diff --git a/src/main/java/net/fabricmc/loom/task/MigrateMappingsTask.java b/src/main/java/net/fabricmc/loom/task/MigrateMappingsTask.java
index 508dfee6..2afc276b 100644
--- a/src/main/java/net/fabricmc/loom/task/MigrateMappingsTask.java
+++ b/src/main/java/net/fabricmc/loom/task/MigrateMappingsTask.java
@@ -49,10 +49,11 @@ import org.gradle.api.tasks.TaskAction;
 import org.gradle.api.tasks.options.Option;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.spec.LayeredMappingSpecBuilder;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
+import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingsDependency;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftMappedProvider;
-import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingSpecBuilder;
-import net.fabricmc.loom.configuration.providers.mappings.LayeredMappingsDependency;
 import net.fabricmc.loom.util.SourceRemapper;
 import net.fabricmc.lorenztiny.TinyMappingsJoiner;
 import net.fabricmc.mapping.tree.TinyMappingFactory;
@@ -166,9 +167,9 @@ public class MigrateMappingsTask extends AbstractLoomTask {
 		project.getLogger().info(":joining mappings");
 
 		MappingSet mappingSet = new TinyMappingsJoiner(
-				currentMappings, "named",
-				targetMappings, "named",
-				"intermediary"
+				currentMappings, MappingsNamespace.NAMED.toString(),
+				targetMappings, MappingsNamespace.NAMED.toString(),
+				MappingsNamespace.INTERMEDIARY.toString()
 		).read();
 
 		project.getLogger().lifecycle(":remapping");
diff --git a/src/main/java/net/fabricmc/loom/task/RemapJarTask.java b/src/main/java/net/fabricmc/loom/task/RemapJarTask.java
index 2bab9f5a..bd83c794 100644
--- a/src/main/java/net/fabricmc/loom/task/RemapJarTask.java
+++ b/src/main/java/net/fabricmc/loom/task/RemapJarTask.java
@@ -57,6 +57,7 @@ import org.zeroturnaround.zip.transform.StreamZipEntryTransformer;
 import org.zeroturnaround.zip.transform.ZipEntryTransformerEntry;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.build.JarRemapper;
 import net.fabricmc.loom.build.MixinRefmapHelper;
 import net.fabricmc.loom.build.nesting.JarNester;
@@ -130,8 +131,8 @@ public class RemapJarTask extends Jar {
 
 		MappingsProviderImpl mappingsProvider = extension.getMappingsProvider();
 
-		String fromM = "named";
-		String toM = "intermediary";
+		String fromM = MappingsNamespace.NAMED.toString();
+		String toM = MappingsNamespace.INTERMEDIARY.toString();
 
 		if (isMainRemapTask) {
 			jarRemapper.addToClasspath(getRemapClasspath());
diff --git a/src/main/java/net/fabricmc/loom/task/RemapSourcesJarTask.java b/src/main/java/net/fabricmc/loom/task/RemapSourcesJarTask.java
index 858c7ec1..26fd6a37 100644
--- a/src/main/java/net/fabricmc/loom/task/RemapSourcesJarTask.java
+++ b/src/main/java/net/fabricmc/loom/task/RemapSourcesJarTask.java
@@ -32,12 +32,13 @@ import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.OutputFile;
 import org.gradle.api.tasks.TaskAction;
 
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.util.SourceRemapper;
 
 public class RemapSourcesJarTask extends AbstractLoomTask {
 	private final RegularFileProperty input = getProject().getObjects().fileProperty();
 	private final RegularFileProperty output = getProject().getObjects().fileProperty().convention(input);
-	private final Property<String> targetNamespace = getProject().getObjects().property(String.class).convention("intermediary");
+	private final Property<String> targetNamespace = getProject().getObjects().property(String.class).convention(MappingsNamespace.INTERMEDIARY.toString());
 	private SourceRemapper sourceRemapper = null;
 	private final Property<Boolean> preserveFileTimestamps = getProject().getObjects().property(Boolean.class).convention(true);
 	private final Property<Boolean> reproducibleFileOrder = getProject().getObjects().property(Boolean.class).convention(false);
@@ -49,7 +50,7 @@ public class RemapSourcesJarTask extends AbstractLoomTask {
 	public void remap() throws Exception {
 		if (sourceRemapper == null) {
 			String direction = targetNamespace.get();
-			SourceRemapper.remapSources(getProject(), input.get().getAsFile(), output.get().getAsFile(), direction.equals("named"), reproducibleFileOrder.get(), preserveFileTimestamps.get());
+			SourceRemapper.remapSources(getProject(), input.get().getAsFile(), output.get().getAsFile(), direction.equals(MappingsNamespace.NAMED.toString()), reproducibleFileOrder.get(), preserveFileTimestamps.get());
 		} else {
 			sourceRemapper.scheduleRemapSources(input.get().getAsFile(), output.get().getAsFile(), reproducibleFileOrder.get(), preserveFileTimestamps.get());
 		}
diff --git a/src/main/java/net/fabricmc/loom/util/SourceRemapper.java b/src/main/java/net/fabricmc/loom/util/SourceRemapper.java
index 66c74dc3..8f7bf89e 100644
--- a/src/main/java/net/fabricmc/loom/util/SourceRemapper.java
+++ b/src/main/java/net/fabricmc/loom/util/SourceRemapper.java
@@ -40,6 +40,7 @@ import org.gradle.api.Project;
 import org.zeroturnaround.zip.ZipUtil;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.RemappedConfigurationEntry;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.util.gradle.ProgressLogger;
@@ -166,7 +167,7 @@ public class SourceRemapper {
 			try {
 				TinyTree m = mappingsProvider.getMappings();
 				project.getLogger().info(":loading " + (toNamed ? "intermediary -> named" : "named -> intermediary") + " source mappings");
-				return new TinyMappingsReader(m, toNamed ? "intermediary" : "named", toNamed ? "named" : "intermediary").read();
+				return new TinyMappingsReader(m, toNamed ? MappingsNamespace.INTERMEDIARY.toString() : MappingsNamespace.NAMED.toString(), toNamed ? MappingsNamespace.NAMED.toString() : MappingsNamespace.INTERMEDIARY.toString()).read();
 			} catch (Exception e) {
 				throw new RuntimeException(e);
 			}