Use lorenz library for proper Mapping model

6 files changed, 326 insertions, 133 deletions

diff --git a/src/main/java/com/replaymod/gradle/remap/PsiMapper.java b/src/main/java/com/replaymod/gradle/remap/PsiMapper.java
index 17d0783..c1b2d41 100644
--- a/src/main/java/com/replaymod/gradle/remap/PsiMapper.java
+++ b/src/main/java/com/replaymod/gradle/remap/PsiMapper.java
@@ -18,7 +18,11 @@ import com.intellij.psi.PsiPackage;
 import com.intellij.psi.PsiQualifiedNamedElement;
 import com.intellij.psi.PsiSwitchLabelStatement;
 import com.intellij.psi.PsiTypeElement;
-import com.replaymod.gradle.remap.Transformer.Mapping;
+import org.cadixdev.bombe.type.signature.MethodSignature;
+import org.cadixdev.lorenz.MappingSet;
+import org.cadixdev.lorenz.model.ClassMapping;
+import org.cadixdev.lorenz.model.Mapping;
+import org.cadixdev.lorenz.model.MethodMapping;
 
 import java.util.ArrayDeque;
 import java.util.Arrays;
@@ -27,6 +31,8 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.TreeMap;
 
+import static com.replaymod.gradle.remap.PsiUtils.getSignature;
+
 class PsiMapper {
     private static final String CLASS_MIXIN = "org.spongepowered.asm.mixin.Mixin";
     private static final String CLASS_ACCESSOR = "org.spongepowered.asm.mixin.gen.Accessor";
@@ -34,17 +40,23 @@ class PsiMapper {
     private static final String CLASS_INJECT = "org.spongepowered.asm.mixin.injection.Inject";
     private static final String CLASS_REDIRECT = "org.spongepowered.asm.mixin.injection.Redirect";
 
-    private final Map<String, Mapping> map;
-    private final Map<String, Mapping> mixinMappings = new HashMap<>();
+    private final MappingSet map;
+    private final Map<String, ClassMapping<?, ?>> mixinMappings = new HashMap<>();
     private final PsiFile file;
     private boolean error;
     private TreeMap<TextRange, String> changes = new TreeMap<>(Comparator.comparing(TextRange::getStartOffset));
 
-    PsiMapper(Map<String, Mapping> map, PsiFile file) {
+    PsiMapper(MappingSet map, PsiFile file) {
         this.map = map;
         this.file = file;
     }
 
+    private void error(PsiElement at, String message) {
+        int line = StringUtil.offsetToLineNumber(file.getText(), at.getTextOffset());
+        System.err.println(file.getName() + ":" + line + ": " + message);
+        error = true;
+    }
+
     private void replace(PsiElement e, String with) {
         changes.put(e.getTextRange(), with);
     }
@@ -87,12 +99,12 @@ class PsiMapper {
         if (declaringClass == null) return;
         String name = declaringClass.getQualifiedName();
         if (name == null) return;
-        Mapping mapping = this.mixinMappings.get(name);
+        ClassMapping<?, ?> mapping = this.mixinMappings.get(name);
         if (mapping == null) {
-            mapping = map.get(name);
+            mapping = map.getClassMapping(name).orElse(null);
         }
         if (mapping == null) return;
-        String mapped = mapping.fields.get(field.getName());
+        String mapped = mapping.getFieldMapping(field.getName()).map(Mapping::getDeobfuscatedName).orElse(null);
         if (mapped == null || mapped.equals(field.getName())) return;
         replaceIdentifier(expr, mapped);
 
@@ -100,20 +112,20 @@ class PsiMapper {
                 && !((PsiJavaCodeReferenceElement) expr).isQualified() // qualified access is fine
                 && !isSwitchCase(expr) // referencing constants in case statements is fine
         ) {
-            int line = StringUtil.offsetToLineNumber(file.getText(), expr.getTextOffset());
-            System.err.println(file.getName() + ":" + line + ": Implicit member reference to remapped field \"" + field.getName() + "\". " +
+            error(expr, "Implicit member reference to remapped field \"" + field.getName() + "\". " +
                     "This can cause issues if the remapped reference becomes shadowed by a local variable and is therefore forbidden. " +
                     "Use \"this." + field.getName() + "\" instead.");
-            error = true;
         }
     }
 
     private void map(PsiElement expr, PsiMethod method) {
+        if (method.isConstructor()) return;
+
         PsiClass declaringClass = method.getContainingClass();
         if (declaringClass == null) return;
         ArrayDeque<PsiClass> parentQueue = new ArrayDeque<>();
         parentQueue.offer(declaringClass);
-        Mapping mapping = null;
+        ClassMapping<?, ?> mapping = null;
 
         String name = declaringClass.getQualifiedName();
         if (name != null) {
@@ -121,7 +133,7 @@ class PsiMapper {
         }
         while (true) {
             if (mapping != null) {
-                String mapped = mapping.methods.get(method.getName());
+                String mapped = mapping.getMethodMapping(getSignature(method)).map(Mapping::getDeobfuscatedName).orElse(null);
                 if (mapped != null) {
                     if (!mapped.equals(method.getName())) {
                         replaceIdentifier(expr, mapped);
@@ -144,7 +156,7 @@ class PsiMapper {
 
                 name = declaringClass.getQualifiedName();
                 if (name == null) continue;
-                mapping = map.get(name);
+                mapping = map.getClassMapping(name).orElse(null);
             }
         }
     }
@@ -152,10 +164,11 @@ class PsiMapper {
     private void map(PsiElement expr, PsiQualifiedNamedElement resolved) {
         String name = resolved.getQualifiedName();
         if (name == null) return;
-        Mapping mapping = map.get(name);
+        ClassMapping<?, ?> mapping = map.getClassMapping(name).orElse(null);
         if (mapping == null) return;
-        String mapped = mapping.newName;
+        String mapped = mapping.getDeobfuscatedName();
         if (mapped.equals(name)) return;
+        mapped = mapped.replace('/', '.');
 
         if (expr.getText().equals(name)) {
             replace(expr, mapped);
@@ -189,7 +202,7 @@ class PsiMapper {
         return null;
     }
 
-    private void remapAccessors(Mapping mapping) {
+    private void remapAccessors(ClassMapping<?, ?> mapping) {
         file.accept(new JavaRecursiveElementVisitor() {
             @Override
             public void visitMethod(PsiMethod method) {
@@ -218,7 +231,7 @@ class PsiMapper {
                     throw new IllegalArgumentException("Cannot determine accessor target for " + method);
                 }
 
-                String mapped = mapping.fields.get(target);
+                String mapped = mapping.getFieldMapping(target).map(Mapping::getDeobfuscatedName).orElse(null);
                 if (mapped != null && !mapped.equals(target)) {
                     // Update accessor target
                     String parameterList;
@@ -235,7 +248,7 @@ class PsiMapper {
         });
     }
 
-    private void remapInjectsAndRedirects(Mapping mapping) {
+    private void remapInjectsAndRedirects(ClassMapping<?, ?> mapping) {
         file.accept(new JavaRecursiveElementVisitor() {
             @Override
             public void visitMethod(PsiMethod method) {
@@ -250,7 +263,21 @@ class PsiMapper {
                     // Note: mixin supports multiple targets, we do not (yet)
                     String literalValue = attribute.getLiteralValue();
                     if (literalValue == null) continue;
-                    String mapped = mapping.methods.get(literalValue);
+                    String mapped;
+                    if (literalValue.contains("(")) {
+                        mapped = mapping.getMethodMapping(MethodSignature.of(literalValue)).map(Mapping::getDeobfuscatedName).orElse(null);
+                    } else {
+                        mapped = null;
+                        for (MethodMapping methodMapping : mapping.getMethodMappings()) {
+                            if (methodMapping.getObfuscatedName().equals(literalValue)) {
+                                String name = methodMapping.getDeobfuscatedName();
+                                if (mapped != null && !mapped.equals(name)) {
+                                    error(attribute, "Ambiguous mixin method \"" + literalValue + "\" maps to \"" + mapped + "\" and \"" + name + "\"");
+                                }
+                                mapped = name;
+                            }
+                        }
+                    }
                     if (mapped != null && !mapped.equals(literalValue)) {
                         PsiAnnotationMemberValue value = attribute.getValue();
                         assert value != null;
@@ -261,12 +288,12 @@ class PsiMapper {
         });
     }
 
-    private Mapping remapInternalType(String internalType, StringBuilder result) {
+    private ClassMapping<?, ?> remapInternalType(String internalType, StringBuilder result) {
         if (internalType.charAt(0) == 'L') {
             String type = internalType.substring(1, internalType.length() - 1).replace('/', '.');
-            Mapping mapping = map.get(type);
+            ClassMapping<?, ?> mapping = map.getClassMapping(type).orElse(null);
             if (mapping != null) {
-                result.append('L').append(mapping.newName.replace('.', '/')).append(';');
+                result.append('L').append(mapping.getFullDeobfuscatedName()).append(';');
                 return mapping;
             }
         }
@@ -287,10 +314,14 @@ class PsiMapper {
         String returnType = signature.substring(argsEnd + 1);
 
         StringBuilder builder = new StringBuilder(signature.length() + 32);
-        Mapping mapping = remapInternalType(owner, builder);
+        ClassMapping<?, ?> mapping = remapInternalType(owner, builder);
         String mapped = null;
         if (mapping != null) {
-            mapped = (method ? mapping.methods : mapping.fields).get(name);
+            mapped = (method
+                    ? mapping.getMethodMapping(MethodSignature.of(signature.substring(ownerEnd + 1)))
+                    : mapping.getFieldMapping(name))
+                    .map(Mapping::getDeobfuscatedName)
+                    .orElse(null);
         }
         builder.append(mapped != null ? mapped : name);
         if (method) {
@@ -350,16 +381,18 @@ class PsiMapper {
 
                 PsiClass target = getMixinTarget(annotation);
                 if (target == null) return;
+                String qualifiedName = target.getQualifiedName();
+                if (qualifiedName == null) return;
 
-                Mapping mapping = map.get(target.getQualifiedName());
+                ClassMapping<?, ?> mapping = map.getClassMapping(qualifiedName).orElse(null);
                 if (mapping == null) return;
 
                 mixinMappings.put(psiClass.getQualifiedName(), mapping);
 
-                if (!mapping.fields.isEmpty()) {
+                if (!mapping.getFieldMappings().isEmpty()) {
                     remapAccessors(mapping);
                 }
-                if (!mapping.methods.isEmpty()) {
+                if (!mapping.getMethodMappings().isEmpty()) {
                     remapInjectsAndRedirects(mapping);
                 }
             }
diff --git a/src/main/java/com/replaymod/gradle/remap/PsiUtils.java b/src/main/java/com/replaymod/gradle/remap/PsiUtils.java
new file mode 100644
index 0000000..ec4d1c8
--- /dev/null
+++ b/src/main/java/com/replaymod/gradle/remap/PsiUtils.java
@@ -0,0 +1,61 @@
+package com.replaymod.gradle.remap;
+
+import com.intellij.psi.PsiArrayType;
+import com.intellij.psi.PsiClass;
+import com.intellij.psi.PsiClassType;
+import com.intellij.psi.PsiMethod;
+import com.intellij.psi.PsiPrimitiveType;
+import com.intellij.psi.PsiType;
+import com.intellij.psi.util.TypeConversionUtil;
+import org.cadixdev.bombe.type.ArrayType;
+import org.cadixdev.bombe.type.FieldType;
+import org.cadixdev.bombe.type.MethodDescriptor;
+import org.cadixdev.bombe.type.ObjectType;
+import org.cadixdev.bombe.type.Type;
+import org.cadixdev.bombe.type.VoidType;
+import org.cadixdev.bombe.type.signature.MethodSignature;
+
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+class PsiUtils {
+    static MethodSignature getSignature(PsiMethod method) {
+        return new MethodSignature(method.getName(), getDescriptor(method));
+    }
+
+    private static MethodDescriptor getDescriptor(PsiMethod method) {
+        return new MethodDescriptor(
+                Arrays.stream(method.getParameterList().getParameters())
+                        .map(it -> getFieldType(it.getType()))
+                        .collect(Collectors.toList()),
+                getType(method.getReturnType())
+        );
+    }
+
+    private static FieldType getFieldType(PsiType type) {
+        type = TypeConversionUtil.erasure(type);
+        if (type instanceof PsiPrimitiveType) {
+            return FieldType.of(((PsiPrimitiveType) type).getKind().getBinaryName());
+        } else if (type instanceof PsiArrayType) {
+            PsiArrayType array = (PsiArrayType) type;
+            return new ArrayType(array.getArrayDimensions(), getFieldType(array.getDeepComponentType()));
+        } else if (type instanceof PsiClassType) {
+            PsiClass resolved = ((PsiClassType) type).resolve();
+            if (resolved == null) throw new NullPointerException("Failed to resolve type " + type);
+            String qualifiedName = resolved.getQualifiedName();
+            if (qualifiedName == null) throw new NullPointerException("Type " + type + " has no qualified name.");
+            return new ObjectType(qualifiedName);
+        } else {
+            throw new IllegalArgumentException("Cannot translate type " + type);
+        }
+    }
+
+    private static Type getType(PsiType type) {
+        if (TypeConversionUtil.isVoidType(type)) {
+            return VoidType.INSTANCE;
+        } else {
+            return getFieldType(type);
+        }
+    }
+
+}
diff --git a/src/main/java/com/replaymod/gradle/remap/Transformer.java b/src/main/java/com/replaymod/gradle/remap/Transformer.java
index 1cbd425..8a9ec9c 100644
--- a/src/main/java/com/replaymod/gradle/remap/Transformer.java
+++ b/src/main/java/com/replaymod/gradle/remap/Transformer.java
@@ -11,6 +11,8 @@ import com.intellij.openapi.vfs.VirtualFileManager;
 import com.intellij.openapi.vfs.local.CoreLocalFileSystem;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.PsiManager;
+import com.replaymod.gradle.remap.legacy.LegacyMapping;
+import org.cadixdev.lorenz.MappingSet;
 import org.jetbrains.kotlin.cli.common.CLIConfigurationKeys;
 import org.jetbrains.kotlin.cli.common.config.KotlinSourceRoot;
 import org.jetbrains.kotlin.cli.common.messages.MessageRenderer;
@@ -37,21 +39,20 @@ import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 class Transformer {
-    private Map<String, Mapping> map;
+    private MappingSet map;
     private String[] classpath;
     private boolean fail;
 
     public static void main(String[] args) throws IOException {
-        Map<String, Mapping> mappings;
+        MappingSet mappings;
         if (args[0].isEmpty()) {
-            mappings = new HashMap<>();
+            mappings = MappingSet.create();
         } else {
-            mappings = readMappings(new File(args[0]), args[1].equals("true"));
+            mappings = LegacyMapping.readMappingSet(new File(args[0]).toPath(), args[1].equals("true"));
         }
         Transformer transformer = new Transformer(mappings);
 
@@ -95,7 +96,7 @@ class Transformer {
         }
     }
 
-    public Transformer(Map<String, Mapping> mappings) {
+    public Transformer(MappingSet mappings) {
         this.map = mappings;
     }
 
@@ -165,104 +166,4 @@ class Transformer {
         }
     }
 
-    public static class Mapping {
-        public String oldName;
-        public String newName;
-        public Map<String, String> fields = new HashMap<>();
-        public Map<String, String> methods = new HashMap<>();
-    }
-
-    public static Map<String, Mapping> readMappings(File mappingFile, boolean invert) throws IOException {
-        Map<String, Mapping> mappings = new HashMap<>();
-        Map<String, Mapping> revMappings = new HashMap<>();
-        int lineNumber = 0;
-        for (String line : Files.readAllLines(mappingFile.toPath(), StandardCharsets.UTF_8)) {
-            lineNumber++;
-            if (line.trim().startsWith("#") || line.trim().isEmpty()) continue;
-
-            String[] parts = line.split(" ");
-            if (parts.length < 2 || line.contains(";")) {
-                throw new IllegalArgumentException("Failed to parse line " + lineNumber + " in " + mappingFile.getPath() + ".");
-            }
-
-            Mapping mapping = mappings.get(parts[0]);
-            if (mapping == null) {
-                mapping = new Mapping();
-                mapping.oldName = mapping.newName = parts[0];
-                mappings.put(mapping.oldName, mapping);
-            }
-
-            if (parts.length == 2) {
-                // Class mapping
-                mapping.newName = parts[1];
-                // Possibly merge with reverse mapping
-                Mapping revMapping = revMappings.remove(mapping.newName);
-                if (revMapping != null) {
-                    mapping.fields.putAll(revMapping.fields);
-                    mapping.methods.putAll(revMapping.methods);
-                }
-                revMappings.put(mapping.newName, mapping);
-            } else if (parts.length == 3 || parts.length == 4) {
-                String fromName = parts[1];
-                String toName;
-                Mapping revMapping;
-                if (parts.length == 4) {
-                    toName = parts[3];
-                    revMapping = revMappings.get(parts[2]);
-                    if (revMapping == null) {
-                        revMapping = new Mapping();
-                        revMapping.oldName = revMapping.newName = parts[2];
-                        revMappings.put(revMapping.newName, revMapping);
-                    }
-                } else {
-                    toName = parts[2];
-                    revMapping = mapping;
-                }
-                if (fromName.endsWith("()")) {
-                    // Method mapping
-                    fromName = fromName.substring(0, fromName.length() - 2);
-                    toName = toName.substring(0, toName.length() - 2);
-                    mapping.methods.put(fromName, toName);
-                    revMapping.methods.put(fromName, toName);
-                } else {
-                    // Field mapping
-                    mapping.fields.put(fromName, toName);
-                    revMapping.fields.put(fromName, toName);
-                }
-            } else {
-                throw new IllegalArgumentException("Failed to parse line " + lineNumber + " in " + mappingFile.getPath() + ".");
-            }
-        }
-        if (invert) {
-            Stream.concat(
-                    mappings.values().stream(),
-                    revMappings.values().stream()
-            ).distinct().forEach(it -> {
-                String oldName = it.oldName;
-                it.oldName = it.newName;
-                it.newName = oldName;
-                it.fields = it.fields.entrySet().stream().collect(Collectors.toMap(Entry::getValue, Entry::getKey));
-                it.methods = it.methods.entrySet().stream().collect(Collectors.toMap(Entry::getValue, Entry::getKey));
-            });
-        }
-        return Stream.concat(
-                mappings.values().stream(),
-                revMappings.values().stream()
-        ).collect(Collectors.toMap(mapping -> mapping.oldName, Function.identity(), (mapping, other) -> {
-            if (!other.oldName.equals(other.newName)) {
-                if (!mapping.oldName.equals(mapping.newName)
-                        && !other.oldName.equals(mapping.oldName)
-                        && !other.newName.equals(mapping.newName)) {
-                    throw new IllegalArgumentException("Conflicting mappings: "
-                            + mapping.oldName + " -> " + mapping.newName
-                            + " and " + other.oldName + " -> " + other.newName);
-                }
-                mapping.oldName = other.oldName;
-                mapping.newName = other.newName;
-            }
-            mapping.fields.putAll(other.fields);
-            mapping.methods.putAll(other.methods);
-            return mapping;
-        }));
-    }
 }
diff --git a/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMapping.java b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMapping.java
new file mode 100644
index 0000000..05a85d9
--- /dev/null
+++ b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMapping.java
@@ -0,0 +1,118 @@
+package com.replaymod.gradle.remap.legacy;
+
+import org.cadixdev.lorenz.MappingSet;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class LegacyMapping {
+    public static MappingSet readMappingSet(Path mappingFile, boolean invert) throws IOException {
+        return new LegacyMappingsReader(readMappings(mappingFile, invert)).read();
+    }
+
+    public static Map<String, LegacyMapping> readMappings(Path mappingFile, boolean invert) throws IOException {
+        Map<String, LegacyMapping> mappings = new HashMap<>();
+        Map<String, LegacyMapping> revMappings = new HashMap<>();
+        int lineNumber = 0;
+        for (String line : Files.readAllLines(mappingFile, StandardCharsets.UTF_8)) {
+            lineNumber++;
+            if (line.trim().startsWith("#") || line.trim().isEmpty()) continue;
+
+            String[] parts = line.split(" ");
+            if (parts.length < 2 || line.contains(";")) {
+                throw new IllegalArgumentException("Failed to parse line " + lineNumber + " in " + mappingFile + ".");
+            }
+
+            LegacyMapping mapping = mappings.get(parts[0]);
+            if (mapping == null) {
+                mapping = new LegacyMapping();
+                mapping.oldName = mapping.newName = parts[0];
+                mappings.put(mapping.oldName, mapping);
+            }
+
+            if (parts.length == 2) {
+                // Class mapping
+                mapping.newName = parts[1];
+                // Possibly merge with reverse mapping
+                LegacyMapping revMapping = revMappings.remove(mapping.newName);
+                if (revMapping != null) {
+                    mapping.fields.putAll(revMapping.fields);
+                    mapping.methods.putAll(revMapping.methods);
+                }
+                revMappings.put(mapping.newName, mapping);
+            } else if (parts.length == 3 || parts.length == 4) {
+                String fromName = parts[1];
+                String toName;
+                LegacyMapping revMapping;
+                if (parts.length == 4) {
+                    toName = parts[3];
+                    revMapping = revMappings.get(parts[2]);
+                    if (revMapping == null) {
+                        revMapping = new LegacyMapping();
+                        revMapping.oldName = revMapping.newName = parts[2];
+                        revMappings.put(revMapping.newName, revMapping);
+                    }
+                } else {
+                    toName = parts[2];
+                    revMapping = mapping;
+                }
+                if (fromName.endsWith("()")) {
+                    // Method mapping
+                    fromName = fromName.substring(0, fromName.length() - 2);
+                    toName = toName.substring(0, toName.length() - 2);
+                    mapping.methods.put(fromName, toName);
+                    revMapping.methods.put(fromName, toName);
+                } else {
+                    // Field mapping
+                    mapping.fields.put(fromName, toName);
+                    revMapping.fields.put(fromName, toName);
+                }
+            } else {
+                throw new IllegalArgumentException("Failed to parse line " + lineNumber + " in " + mappingFile + ".");
+            }
+        }
+        if (invert) {
+            Stream.concat(
+                    mappings.values().stream(),
+                    revMappings.values().stream()
+            ).distinct().forEach(it -> {
+                String oldName = it.oldName;
+                it.oldName = it.newName;
+                it.newName = oldName;
+                it.fields = it.fields.entrySet().stream().collect(Collectors.toMap(Map.Entry::getValue, Map.Entry::getKey));
+                it.methods = it.methods.entrySet().stream().collect(Collectors.toMap(Map.Entry::getValue, Map.Entry::getKey));
+            });
+        }
+        return Stream.concat(
+                mappings.values().stream(),
+                revMappings.values().stream()
+        ).collect(Collectors.toMap(mapping -> mapping.oldName, Function.identity(), (mapping, other) -> {
+            if (!other.oldName.equals(other.newName)) {
+                if (!mapping.oldName.equals(mapping.newName)
+                        && !other.oldName.equals(mapping.oldName)
+                        && !other.newName.equals(mapping.newName)) {
+                    throw new IllegalArgumentException("Conflicting mappings: "
+                            + mapping.oldName + " -> " + mapping.newName
+                            + " and " + other.oldName + " -> " + other.newName);
+                }
+                mapping.oldName = other.oldName;
+                mapping.newName = other.newName;
+            }
+            mapping.fields.putAll(other.fields);
+            mapping.methods.putAll(other.methods);
+            return mapping;
+        }));
+    }
+
+    public String oldName;
+    public String newName;
+    public Map<String, String> fields = new HashMap<>();
+    public Map<String, String> methods = new HashMap<>();
+}
diff --git a/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingSetModelFactory.java b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingSetModelFactory.java
new file mode 100644
index 0000000..eb72788
--- /dev/null
+++ b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingSetModelFactory.java
@@ -0,0 +1,36 @@
+package com.replaymod.gradle.remap.legacy;
+
+import org.cadixdev.bombe.type.signature.MethodSignature;
+import org.cadixdev.lorenz.MappingSet;
+import org.cadixdev.lorenz.impl.MappingSetModelFactoryImpl;
+import org.cadixdev.lorenz.impl.model.TopLevelClassMappingImpl;
+import org.cadixdev.lorenz.model.MethodMapping;
+import org.cadixdev.lorenz.model.TopLevelClassMapping;
+
+import java.util.Optional;
+
+public class LegacyMappingSetModelFactory extends MappingSetModelFactoryImpl {
+    @Override
+    public TopLevelClassMapping createTopLevelClassMapping(MappingSet parent, String obfuscatedName, String deobfuscatedName) {
+        return new TopLevelClassMappingImpl(parent, obfuscatedName, deobfuscatedName) {
+            private MethodSignature stripDesc(MethodSignature signature) {
+                // actual descriptor isn't included in legacy format
+                return MethodSignature.of(signature.getName(), "()V");
+            }
+
+            @Override
+            public boolean hasMethodMapping(MethodSignature signature) {
+                return super.hasMethodMapping(signature) || super.hasMethodMapping(stripDesc(signature));
+            }
+
+            @Override
+            public Optional<MethodMapping> getMethodMapping(MethodSignature signature) {
+                Optional<MethodMapping> maybeMapping = super.getMethodMapping(signature);
+                if (!maybeMapping.isPresent() || !maybeMapping.get().hasMappings()) {
+                    maybeMapping = super.getMethodMapping(stripDesc(signature));
+                }
+                return maybeMapping;
+            }
+        };
+    }
+}
diff --git a/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingsReader.java b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingsReader.java
new file mode 100644
index 0000000..502f7ba
--- /dev/null
+++ b/src/main/java/com/replaymod/gradle/remap/legacy/LegacyMappingsReader.java
@@ -0,0 +1,44 @@
+package com.replaymod.gradle.remap.legacy;
+
+import org.cadixdev.lorenz.MappingSet;
+import org.cadixdev.lorenz.io.MappingsReader;
+import org.cadixdev.lorenz.model.ClassMapping;
+
+import java.util.Map;
+
+public class LegacyMappingsReader extends MappingsReader {
+    private final Map<String, LegacyMapping> map;
+
+    public LegacyMappingsReader(Map<String, LegacyMapping> map) {
+        this.map = map;
+    }
+
+    @Override
+    public MappingSet read() {
+        return read(MappingSet.create(new LegacyMappingSetModelFactory()));
+    }
+
+    @Override
+    public MappingSet read(MappingSet mappings) {
+        if (!(mappings.getModelFactory() instanceof LegacyMappingSetModelFactory)) {
+            throw new IllegalArgumentException("legacy mappings must use legacy model factory, use read() instead");
+        }
+        for (LegacyMapping legacyMapping : map.values()) {
+            ClassMapping classMapping = mappings.getOrCreateClassMapping(legacyMapping.oldName)
+                    .setDeobfuscatedName(legacyMapping.newName);
+            for (Map.Entry<String, String> entry : legacyMapping.fields.entrySet()) {
+                classMapping.getOrCreateFieldMapping(entry.getKey())
+                        .setDeobfuscatedName(entry.getValue());
+            }
+            for (Map.Entry<String, String> entry : legacyMapping.methods.entrySet()) {
+                classMapping.getOrCreateMethodMapping(entry.getKey(), "()V")
+                        .setDeobfuscatedName(entry.getValue());
+            }
+        }
+        return mappings;
+    }
+
+    @Override
+    public void close() {
+    }
+}