feat: implemented abstraction logic

12 files changed, 566 insertions, 184 deletions

diff --git a/src/main/java/ftbsc/lll/exceptions/InvalidResourceException.java b/src/main/java/ftbsc/lll/exceptions/InvalidResourceException.java
new file mode 100644
index 0000000..060d57c
--- /dev/null
+++ b/src/main/java/ftbsc/lll/exceptions/InvalidResourceException.java
@@ -0,0 +1,23 @@
+package ftbsc.lll.exceptions;
+
+/**
+ * Thrown when a resource passed as an argument is not found.
+ */
+public class InvalidResourceException extends RuntimeException {
+
+	/**
+	 * Empty constructor, used when the provided resource exists but no
+	 * mapper was able to read it.
+	 */
+	public InvalidResourceException() {
+		super("The given resource was not claimed by any mapper!");
+	}
+
+	/**
+	 * Named constructor, used when the specified resource doesn't exist.
+	 * @param name the resource name
+	 */
+	public InvalidResourceException(String name) {
+		super(String.format("Specified resource %s was not found!", name));
+	}
+}
diff --git a/src/main/java/ftbsc/lll/exceptions/MalformedMappingsException.java b/src/main/java/ftbsc/lll/exceptions/MalformedMappingsException.java
new file mode 100644
index 0000000..1352855
--- /dev/null
+++ b/src/main/java/ftbsc/lll/exceptions/MalformedMappingsException.java
@@ -0,0 +1,7 @@
+package ftbsc.lll.exceptions;
+
+public class MalformedMappingsException extends Exception {
+	public MalformedMappingsException(String mapping, String type) {
+		super(String.format("Unexpected token at line %s for mapper type %s!", mapping, type));
+	}
+}
diff --git a/src/main/java/ftbsc/lll/exceptions/MappingNotFoundException.java b/src/main/java/ftbsc/lll/exceptions/MappingNotFoundException.java
index 6c286fc..85ac08f 100644
--- a/src/main/java/ftbsc/lll/exceptions/MappingNotFoundException.java
+++ b/src/main/java/ftbsc/lll/exceptions/MappingNotFoundException.java
@@ -9,19 +9,10 @@ public class MappingNotFoundException extends RuntimeException {
 
 	/**
 	 * Constructs a new mapping not found exception for the specified mapping.
+	 * @param type the type of mapping
 	 * @param mapping the relevant mapping
 	 */
-	public MappingNotFoundException(String mapping) {
-		super(String.format("Could not find mapping for %s!", mapping));
-	}
-
-	/**
-	 * Constructs a new mapping not found exception for the specified mapping
-	 * with the specified reason.
-	 * @param mapping the relevant mapping
-	 * @param reason the reason message
-	 */
-	public MappingNotFoundException(String mapping, String reason) {
-		this(mapping + ": " + reason);
+	public MappingNotFoundException(String type, String mapping) {
+		super(String.format("Could not find mapping for %s %s!", type, mapping));
 	}
 }
diff --git a/src/main/java/ftbsc/lll/mapper/AbstractMapper.java b/src/main/java/ftbsc/lll/mapper/AbstractMapper.java
new file mode 100644
index 0000000..037e7c9
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/AbstractMapper.java
@@ -0,0 +1,142 @@
+package ftbsc.lll.mapper;
+
+import ftbsc.lll.exceptions.MalformedMappingsException;
+import ftbsc.lll.exceptions.MappingNotFoundException;
+import ftbsc.lll.mapper.tools.data.ClassData;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A default implementation of {@link IMapper} meant to
+ * recycle as much code as possible.
+ */
+public abstract class AbstractMapper implements IMapper {
+
+	/**
+	 * A {@link Map} tying each plain class name to its class data.
+	 */
+	protected final Map<String, ClassData> mappings = new HashMap<>();
+
+	/**
+	 * A {@link Map} tying each obfuscated name to its class data.
+	 */
+	protected final Map<String, ClassData> mappingsInverted = new HashMap<>();
+
+	/**
+	 * Populates the {@link IMapper} given the lines, ignoring errors depending on the
+	 * given ignoreErrors flag.
+	 * @param lines the lines to read
+	 * @param ignoreErrors try to ignore errors and keep going
+	 * @throws MalformedMappingsException if an error is encountered and ignoreErrors is false
+	 */
+	@Override
+	public void populate(List<String> lines, boolean ignoreErrors) throws MalformedMappingsException {
+		this.processLines(lines, ignoreErrors);
+		this.mappings.forEach((name, data) -> {
+			ClassData reverse = data.generateReverseMappings(this);
+			this.mappingsInverted.put(data.nameMapped, reverse);
+		});
+	}
+
+	/**
+	 * Reads the given lines of text and attempts to interpret them as
+	 * mappings of the given type.
+	 * @param lines the lines to read
+	 * @param ignoreErrors try to ignore errors and keep going
+	 * @throws MalformedMappingsException if an error is encountered and ignoreErrors is false
+	 */
+	protected abstract void processLines(List<String> lines, boolean ignoreErrors) throws MalformedMappingsException;
+
+	/**
+	 * Completely resets the mapper, clearing it of all existing mappings.
+	 */
+	@Override
+	public void reset() {
+		this.mappings.clear();
+		this.mappingsInverted.clear();
+	}
+
+	/**
+	 * Gets a name of a class from the given {@link Map}.
+	 * @param name the name
+	 * @param mappings the {@link Map} to pull data from
+	 * @return the mapped name
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	private static String mapClass(String name, Map<String, ClassData> mappings) {
+		ClassData data = mappings.get(name.replace('.', '/'));
+		if(data == null)
+			throw new MappingNotFoundException("class", name);
+		else return data.nameMapped;
+	}
+
+	/**
+	 * Gets the obfuscated name of the class.
+	 * @param name the plain internal name of the desired class
+	 * @return the obfuscated name of the class
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	@Override
+	public String obfuscateClass(String name)  {
+		return mapClass(name, this.mappings);
+	}
+
+	/**
+	 * Gets the plain name of the class.
+	 * @param nameObf the obfuscated internal name of the desired class
+	 * @return the plain name of the class
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	@Override
+	public String deobfuscateClass(String nameObf) throws MappingNotFoundException {
+		return mapClass(nameObf, this.mappingsInverted);
+	}
+
+	/**
+	 * Gets the name of a member from the given {@link Map}.
+	 * @param parentName the parent class
+	 * @param mappings the {@link Map} to pull data from
+	 * @param memberName the field or method name
+	 * @param methodDescriptor the method descriptor, may be null or partial
+	 * @return the mapped member name
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	private static String mapMember(String parentName, Map<String, ClassData> mappings,
+																	String memberName, String methodDescriptor) {
+		ClassData data = mappings.get(parentName.replace('.', '/'));
+		if(data == null)
+			throw new MappingNotFoundException("class", parentName);
+
+		if(methodDescriptor == null)
+			return data.mapField(memberName).name;
+		else return data.mapMethod(memberName, methodDescriptor).signature.name;
+	}
+
+	/**
+	 * Gets the obfuscated name of a class member (field or method).
+	 * @param parentName the unobfuscated internal name of the parent class
+	 * @param memberName the field or method name
+	 * @param methodDescriptor the optional descriptor of the member, may be null or partial
+	 * @return the obfuscated name of the given member
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	@Override
+	public String obfuscateMember(String parentName, String memberName, String methodDescriptor) {
+		return mapMember(parentName, this.mappings, memberName, methodDescriptor);
+	}
+
+	/**
+	 * Gets the plain name of a class member (field or method).
+	 * @param parentName       the obfuscated internal name of the parent class
+	 * @param memberName       the obfuscated field name or method signature
+	 * @param methodDescriptor the obfuscated descriptor of the member (only for methods)
+	 * @return the plain name of the given member
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	@Override
+	public String deobfuscateMember(String parentName, String memberName, String methodDescriptor) throws MappingNotFoundException {
+		return mapMember(parentName, this.mappingsInverted, memberName, methodDescriptor);
+	}
+}
diff --git a/src/main/java/ftbsc/lll/mapper/IMapper.java b/src/main/java/ftbsc/lll/mapper/IMapper.java
index 8adf860..96b5d6f 100644
--- a/src/main/java/ftbsc/lll/mapper/IMapper.java
+++ b/src/main/java/ftbsc/lll/mapper/IMapper.java
@@ -1,56 +1,80 @@
 package ftbsc.lll.mapper;
 
+import ftbsc.lll.exceptions.MalformedMappingsException;
 import ftbsc.lll.exceptions.MappingNotFoundException;
 
-import java.util.HashSet;
-import java.util.ServiceLoader;
-import java.util.Set;
+import java.util.*;
 
 /**
  * A generic obfuscation mapper.
  */
 public interface IMapper {
+	/**
+	 * Checks whether this mapper can process the given lines.
+	 * @param lines the lines to read
+	 * @return whether this type of mapper can process these lines
+	 */
+	boolean claim(List<String> lines);
 
 	/**
-	 * Reads the given lines of text and attempts to interpret them as
-	 * mappings of the given type.
+	 * Defines a priority for this implementation: the higher the number,
+	 * the higher the priority.
+	 * This is used to resolve conflicts when multiple mappers attempt to
+	 * {@link #claim(List) claim} a given mapping file.
+	 * @return the priority
+	 */
+	default int priority() {
+		return 0;
+	}
+
+	/**
+	 * Populates the {@link IMapper} given the lines, ignoring errors depending on the
+	 * given ignoreErrors flag.
 	 * @param lines the lines to read
+	 * @param ignoreErrors try to ignore errors and keep going
+	 * @throws MalformedMappingsException if an error is encountered and ignoreErrors is false
 	 */
-	void populate(Iterable<String> lines);
+	void populate(List<String> lines, boolean ignoreErrors) throws MalformedMappingsException;
+
+	/**
+	 * Completely resets the mapper, clearing it of all existing mappings.
+	 */
+	void reset();
 
 	/**
 	 * Gets the obfuscated name of the class.
-	 * @param name the unobfuscated internal name of the desired class
+	 * @param name the plain internal name of the desired class
 	 * @return the obfuscated name of the class
 	 * @throws MappingNotFoundException if no mapping is found
 	 */
-	String obfuscateClass(String name);
+	String obfuscateClass(String name) throws MappingNotFoundException;
+
+	/**
+	 * Gets the plain name of the class.
+	 * @param nameObf the obfuscated internal name of the desired class
+	 * @return the plain name of the class
+	 * @throws MappingNotFoundException if no mapping is found
+	 */
+	String deobfuscateClass(String nameObf) throws MappingNotFoundException;
 
 	/**
 	 * Gets the obfuscated name of a class member (field or method).
-	 * @param parentName the unobfuscated internal name of the parent class
+	 * @param parentName the plain internal name of the parent class
 	 * @param memberName the field name or method signature
-	 * @param methodDescriptor the descriptor of the member
+	 * @param methodDescriptor the descriptor of the member (only for methods)
 	 * @return the obfuscated name of the given member
 	 * @throws MappingNotFoundException if no mapping is found
 	 */
-	String obfuscateMember(String parentName, String memberName, String methodDescriptor);
+	String obfuscateMember(String parentName, String memberName, String methodDescriptor) throws MappingNotFoundException;
 
 	/**
-	 * Loads all valid parsers available in the classpath (via the Java Service API),
-	 * attempts to parse the given lines into mappings, and returns all built mappers
-	 * that succeeded without throwing errors or ftbsc.lll.exceptions.
-	 * @param lines the lines of the mapping file
-	 * @return a {@link Set} of mappers that could interpret the given input
+	 * Gets the plain name of a class member (field or method).
+	 * @param parentName the obfuscated internal name of the parent class
+	 * @param memberName the obfuscated field name or method signature
+	 * @param methodDescriptor the obfuscated descriptor of the member (only for methods)
+	 * @return the plain name of the given member
+	 * @throws MappingNotFoundException if no mapping is found
 	 */
-	static Set<IMapper> getMappers(Iterable<String> lines) {
-		Set<IMapper> parsed = new HashSet<>();
-		for(IMapper mapper: ServiceLoader.load(IMapper.class)) {
-			try {
-				mapper.populate(lines);
-				parsed.add(mapper);
-			} catch(Throwable ignored) {}
-		}
-		return parsed;
-	}
+	String deobfuscateMember(String parentName, String memberName, String methodDescriptor) throws MappingNotFoundException;
+
 }
diff --git a/src/main/java/ftbsc/lll/mapper/MapperProvider.java b/src/main/java/ftbsc/lll/mapper/MapperProvider.java
new file mode 100644
index 0000000..819e792
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/MapperProvider.java
@@ -0,0 +1,73 @@
+package ftbsc.lll.mapper;
+
+import ftbsc.lll.exceptions.InvalidResourceException;
+
+import java.io.*;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * The main class of the mapper library. It loads all the
+ * valid {@link IMapper}s and gets information from them.
+ */
+public class MapperProvider {
+	private static MapperProvider INSTANCE = null;
+
+	private static MapperProvider getInstance() {
+		return INSTANCE == null ? (INSTANCE = new MapperProvider()) : INSTANCE;
+	}
+
+	private Set<IMapper> loadedMappers = null;
+
+	private void loadMappers() {
+		this.loadedMappers = new HashSet<>();
+		for(IMapper mapper: ServiceLoader.load(IMapper.class))
+			this.loadedMappers.add(mapper);
+		if(this.loadedMappers.isEmpty())
+			throw new RuntimeException("Something went wrong: no mapper types were loaded successfully!");
+	}
+
+	/**
+	 * Loads all valid parsers available in the classpath (via the Java Service API),
+	 * attempts to load the resource at given location and to populate a mapper with
+	 * its data.
+	 * @param data the file as a list of strings
+	 * @return a {@link IMapper} (populating it is left to the user)
+	 */
+	public static IMapper getMapper(List<String> data) {
+		if(getInstance().loadedMappers == null)
+			getInstance().loadMappers();
+		return getInstance().loadedMappers.stream()
+			.filter(m -> m.claim(data))
+			.max(Comparator.comparingInt(IMapper::priority))
+			.orElseThrow(InvalidResourceException::new);
+	}
+
+	/**
+	 * Gets a resource and parses it into a {@link List} of {@link String}s.
+	 * @param location either a URL or a local path
+	 * @return a {@link List} containing the lines of the resource
+	 * @throws InvalidResourceException if provided an invalid resource
+	 */
+	public static List<String> fetchFromLocalOrRemote(String location) {
+		InputStream targetStream;
+		try {
+			URI target = new URI(location);
+			targetStream = target.toURL().openStream();
+		} catch(URISyntaxException | IOException e) {
+			//may be a local file path
+			File f = new File(location);
+			try {
+				targetStream = new FileInputStream(f);
+			} catch(FileNotFoundException ex) {
+				throw new InvalidResourceException(location);
+			}
+		}
+
+		return new BufferedReader(new InputStreamReader(targetStream,
+			StandardCharsets.UTF_8)).lines().collect(Collectors.toList());
+	}
+}
diff --git a/src/main/java/ftbsc/lll/mapper/impl/TSRGMapper.java b/src/main/java/ftbsc/lll/mapper/impl/TSRGMapper.java
index 041fb2f..2bd4d28 100644
--- a/src/main/java/ftbsc/lll/mapper/impl/TSRGMapper.java
+++ b/src/main/java/ftbsc/lll/mapper/impl/TSRGMapper.java
@@ -1,75 +1,60 @@
 package ftbsc.lll.mapper.impl;
 
 import com.google.auto.service.AutoService;
-import ftbsc.lll.exceptions.MappingNotFoundException;
+import ftbsc.lll.exceptions.MalformedMappingsException;
+import ftbsc.lll.mapper.AbstractMapper;
 import ftbsc.lll.mapper.IMapper;
-import ftbsc.lll.mapper.tools.ClassData;
+import ftbsc.lll.mapper.tools.data.ClassData;
 
-import java.util.HashMap;
-import java.util.Map;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
- * Parses a .tsrg file into a mapper capable of converting from
- * plain names to obfuscated ones and vice versa.
+ * A {@link IMapper} capable of parsing TSRG (an intermediary
+ * format used by Forge) files.
  */
 
 @AutoService(IMapper.class)
-public class TSRGMapper implements IMapper {
+public class TSRGMapper extends AbstractMapper {
 
 	/**
-	 * A Map containing the deobfuscated names as keys and information about
-	 * each class as values.
+	 * Checks whether this mapper can process the given lines.
+	 * @param lines the lines to read
+	 * @return whether this type of mapper can process these lines
 	 */
-	private final Map<String, ClassData> mappings = new HashMap<>();
+	@Override
+	public boolean claim(List<String> lines) {
+		return lines.get(0).startsWith("tsrg2 left right");
+	}
 
 	/**
 	 * Reads the given lines of text and attempts to interpret them as
 	 * mappings of the given type.
 	 * @param lines the lines to read
+	 * @param ignoreErrors try to ignore errors and keep going
+	 * @throws MalformedMappingsException if an error is encountered and ignoreErrors is false
 	 */
 	@Override
-	public void populate(Iterable<String> lines) {
+	protected void processLines(List<String> lines, boolean ignoreErrors) throws MalformedMappingsException {
+		//skip the first line ("tsrg2 left right")
+		lines = new ArrayList<>(lines);
+		lines.remove(0);
+
 		String currentClass = "";
 		for(String l : lines) {
 			if(l == null) continue;
-			if(l.startsWith("\t"))
-				mappings.get(currentClass).addMember(l);
-			else {
+			if(l.startsWith("\t") || l.startsWith(" ")) {
+				String[] split = l.trim().split(" ");
+				if(split.length == 2) //field
+					this.mappings.get(currentClass).addField(split[0], split[1]);
+				else if (split.length == 3)//method
+					this.mappings.get(currentClass).addMethod(split[0], split[2], split[1]); //add child
+			} else {
 				String[] sp = l.split(" ");
 				ClassData s = new ClassData(sp[0], sp[1]);
-				currentClass = s.unobf;
-				mappings.put(s.unobf, s);
+				currentClass = s.name;
+				this.mappings.put(s.name, s);
 			}
 		}
 	}
-
-	/**
-	 * Gets the obfuscated name of the class.
-	 * @param name the unobfuscated internal name of the desired class
-	 * @return the obfuscated name of the class
-	 * @throws MappingNotFoundException if no mapping is found
-	 */
-	@Override
-	public String obfuscateClass(String name)  {
-		ClassData data = mappings.get(name.replace('.', '/'));
-		if(data == null)
-			throw new MappingNotFoundException(name);
-		else return data.obf;
-	}
-
-	/**
-	 * Gets the obfuscated name of a class member (field or method).
-	 * @param parentName the unobfuscated internal name of the parent class
-	 * @param memberName the field name or method signature
-	 * @param methodDescriptor the optional descriptor of the member, may be null or partial
-	 * @return the obfuscated name of the given member
-	 * @throws MappingNotFoundException if no mapping is found
-	 */
-	@Override
-	public String obfuscateMember(String parentName, String memberName, String methodDescriptor) {
-		ClassData data = mappings.get(parentName.replace('.', '/'));
-		if(data == null)
-			throw new MappingNotFoundException(parentName + "::" + memberName);
-		return data.get(memberName, methodDescriptor);
-	}
 }
diff --git a/src/main/java/ftbsc/lll/mapper/tools/ClassData.java b/src/main/java/ftbsc/lll/mapper/tools/ClassData.java
deleted file mode 100644
index a9fbcec..0000000
--- a/src/main/java/ftbsc/lll/mapper/tools/ClassData.java
+++ /dev/null
@@ -1,100 +0,0 @@
-package ftbsc.lll.mapper.tools;
-
-import ftbsc.lll.exceptions.AmbiguousMappingException;
-import ftbsc.lll.exceptions.MappingNotFoundException;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.stream.Collectors;
-
-/**
- * Container class used to store information about classes.
- */
-public class ClassData {
-	/**
-	 * The unobfuscated name (FQN with '/' instad of '.') of the class.
-	 */
-	public final String unobf;
-
-	/**
-	 * The obfuscated internal name (FQN with '/' instad of '.') of the class.
-	 */
-	public final String obf;
-
-	/**
-	 * A {@link Map} tying each member's name or signature to its
-	 * obfuscated counterpart.
-	 */
-	public final Map<String, String> members;
-
-	/**
-	 * The constructor. It takes in the names (obfuscated and non-obfuscated)
-	 * of a class.
-	 * @param unobf the unobfuscated name
-	 * @param obf the obfuscated name
-	 */
-	public ClassData(String unobf, String obf) {
-		this.unobf = unobf;
-		this.obf = obf;
-		this.members = new HashMap<>();
-	}
-
-	/**
-	 * Adds a member to the target class.
-	 * For fields only the names are required; for methods,
-	 * this takes in the full signature ({@code name + " " + space}).
-	 * @param s the String representing the declaration line
-	 */
-	public void addMember(String s) {
-		String[] split = s.trim().split(" ");
-		if(split.length == 2) //field
-			members.put(split[0], split[1]);
-		else if (split.length == 3) //method
-			members.put(split[0] + " " + split[1], split[2]);
-	}
-
-	/**
-	 * Gets an obfuscated member given the method name and a method descriptor,
-	 * which may be partial (i.e. not include return type) or null if the member
-	 * is not a method.
-	 * @param memberName member name
-	 * @param methodDescriptor the method descriptor, or null if it's not a method
-	 * @return the requested obfuscated name, or null if nothing was found
-	 * @throws AmbiguousMappingException if not enough data was given to uniquely identify a mapping
-	 */
-	public String get(String memberName, String methodDescriptor) {
-
-		//find all keys that start with the name
-		List<String> candidates = members.keySet().stream().filter(
-			m -> m.split(" ")[0].equals(memberName)
-		).collect(Collectors.toList());
-
-		if(methodDescriptor != null) {
-			String signature = String.format("%s %s", memberName, methodDescriptor);
-			candidates = candidates.stream().filter(
-				m -> m.equals(signature)
-			).collect(Collectors.toList());
-		}
-
-		switch(candidates.size()) {
-			case 0:
-				throw new MappingNotFoundException(String.format(
-					"%s.%s%s",
-					this.unobf,
-					memberName,
-					methodDescriptor == null ? "" : "()"
-				));
-			case 1:
-				return members.get(candidates.get(0));
-			default:
-				throw new AmbiguousMappingException(String.format(
-					"Mapper could not uniquely identify member %s.%s%s, found %d!",
-					this.unobf,
-					memberName,
-					methodDescriptor == null ? "" : "()",
-					candidates.size()
-				));
-		}
-	}
-}
\ No newline at end of file
diff --git a/src/main/java/ftbsc/lll/mapper/tools/data/ClassData.java b/src/main/java/ftbsc/lll/mapper/tools/data/ClassData.java
new file mode 100644
index 0000000..5ae4124
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/tools/data/ClassData.java
@@ -0,0 +1,117 @@
+package ftbsc.lll.mapper.tools.data;
+
+import ftbsc.lll.exceptions.MappingNotFoundException;
+import ftbsc.lll.mapper.IMapper;
+import ftbsc.lll.mapper.tools.MappingUtils;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/**
+ * Container class used to store information about classes.
+ */
+public class ClassData {
+
+	/**
+	 * The internal (like the fully-qualified name, but with '/' instead
+	 * of '.') of the class.
+	 */
+	public final String name;
+
+	/**
+	 * The mapped internal (like the fully-qualified name, but with '/'
+	 * instead of '.') of the class.
+	 */
+	public final String nameMapped;
+
+	/**
+	 * A {@link Map} tying each method's signature to its data class.
+	 */
+	private final Map<MethodSignature, MethodData> methods;
+
+	/**
+	 * A {@link Map} tying each field's name to its data class.
+	 */
+	private final Map<String, FieldData> fields;
+
+	/**
+	 * The constructor. It takes in the names (plain and mapped) of a class.
+	 * @param name the plain name
+	 * @param nameMapped the mapped name
+	 */
+	public ClassData(String name, String nameMapped) {
+		this.name = name;
+		this.nameMapped = nameMapped;
+		this.methods = new HashMap<>();
+		this.fields = new HashMap<>();
+	}
+
+	/**
+	 * Adds a method to the target class.
+	 * @param name the method name
+	 * @param nameMapped the mapped method name
+	 * @param descriptor the descriptor of the method
+	 */
+	public void addMethod(String name, String nameMapped, String descriptor) {
+		MethodData data = new MethodData(this, name, nameMapped, descriptor);
+		this.methods.put(data.signature, data);
+	}
+
+	/**
+	 * Adds a field to the target class.
+	 * @param plain the name of the field
+	 * @param mapped the mapped name of the field
+	 */
+	public void addField(String plain, String mapped) {
+		this.fields.put(plain, new FieldData(this, plain, mapped));
+	}
+
+	/**
+	 * Generates the reverse mappings for this class.
+	 * Should always be called only after the given mapper has finished
+	 * processing all classes.
+	 * @param mapper the mapper that generated this data
+	 */
+	public ClassData generateReverseMappings(IMapper mapper) {
+		ClassData reverse = new ClassData(this.nameMapped, this.name);
+		this.methods.forEach((signature, data) -> reverse.addMethod(nameMapped, signature.name,
+			MappingUtils.obfuscateMethodDescriptor(signature.descriptor, mapper)));
+		this.fields.forEach((name, data) -> reverse.addField(data.nameMapped, name));
+		return reverse;
+	}
+
+	/**
+	 * Gets the {@link MethodData} from its name and descriptor, which may be partial
+	 * (i.e. not include the return type).
+	 * @param methodName the method name
+	 * @param methodDescriptor the method descriptor, which may be partial
+	 * @return the requested {@link MethodData}
+	 * @throws MappingNotFoundException if the mapping wasn't found
+	 */
+	public MethodData mapMethod(String methodName, String methodDescriptor) {
+		List<MethodSignature> signatures = this.methods.keySet().stream().filter(
+			s -> s.name.equals(methodName) && s.descriptor.startsWith(methodDescriptor)
+		).collect(Collectors.toList());
+		if(signatures.size() > 1)
+			throw new RuntimeException(); //should never happen unless something goes horribly wrong
+		else if(signatures.isEmpty())
+			throw new MappingNotFoundException("method",
+				String.format("%s::%s%s", this.name, methodName, methodDescriptor));
+		return this.methods.get(signatures.get(0));
+	}
+
+	/**
+	 * Gets the {@link FieldData} its name.
+	 * @param fieldName the field name
+	 * @return the requested {@link FieldData}
+	 * @throws MappingNotFoundException if the mapping wasn't found
+	 */
+	public FieldData mapField(String fieldName) {
+		FieldData data = this.fields.get(fieldName);
+		if(data == null)
+			throw new MappingNotFoundException("field", String.format("%s.%s", this.name, fieldName));
+		else return data;
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/ftbsc/lll/mapper/tools/data/FieldData.java b/src/main/java/ftbsc/lll/mapper/tools/data/FieldData.java
new file mode 100644
index 0000000..bcc3985
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/tools/data/FieldData.java
@@ -0,0 +1,34 @@
+
+package ftbsc.lll.mapper.tools.data;
+
+/**
+ * Container class for method data.
+ */
+public class FieldData {
+	/**
+	 * The internal name of the parent class.
+	 */
+	public final ClassData parentClass;
+
+	/**
+	 * The name of the method.
+	 */
+	public final String name;
+
+	/**
+	 * The name mapped.
+	 */
+	public final String nameMapped;
+
+	/**
+	 * Constructs a new {@link FieldData}.
+	 * @param parentClass the {@link ClassData} representation of the parent class
+	 * @param name the field name
+	 * @param nameMapped the mapped field name
+	 */
+	public FieldData(ClassData parentClass, String name, String nameMapped) {
+		this.parentClass = parentClass;
+		this.name = name;
+		this.nameMapped = nameMapped;
+	}
+}
diff --git a/src/main/java/ftbsc/lll/mapper/tools/data/MethodData.java b/src/main/java/ftbsc/lll/mapper/tools/data/MethodData.java
new file mode 100644
index 0000000..27c418c
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/tools/data/MethodData.java
@@ -0,0 +1,35 @@
+package ftbsc.lll.mapper.tools.data;
+
+/**
+ * Container class for method data.
+ */
+public class MethodData {
+
+	/**
+	 * The internal name of the parent class.
+	 */
+	public final ClassData parentClass;
+
+	/**
+	 * The signature of the method.
+	 */
+	public final MethodSignature signature;
+
+	/**
+	 * The mapped name of the method.
+	 */
+	final String nameMapped;
+
+	/**
+	 * Constructs a new {@link MethodData}.
+	 * @param parentClass the {@link ClassData} representation of the parent class
+	 * @param name the method name
+	 * @param nameMapped the mapped method name
+	 * @param descriptor the method's descriptor
+	 */
+	public MethodData(ClassData parentClass, String name, String nameMapped, String descriptor) {
+		this.parentClass = parentClass;
+		this.signature = new MethodSignature(name, descriptor);
+		this.nameMapped = nameMapped;
+	}
+}
diff --git a/src/main/java/ftbsc/lll/mapper/tools/data/MethodSignature.java b/src/main/java/ftbsc/lll/mapper/tools/data/MethodSignature.java
new file mode 100644
index 0000000..08770be
--- /dev/null
+++ b/src/main/java/ftbsc/lll/mapper/tools/data/MethodSignature.java
@@ -0,0 +1,51 @@
+package ftbsc.lll.mapper.tools.data;
+
+import java.util.Objects;
+
+/**
+ * Container class for method signature data.
+ */
+public class MethodSignature {
+	/**
+	 * The name of the method.
+	 */
+	public final String name;
+
+	/**
+	 * The descriptor of the method.
+	 */
+	public final String descriptor;
+
+	/**
+	 * Constructs a new {@link MethodSignature}. The parameters should be
+	 * either plain or obfuscated in the same way;
+	 * @param name       the method name
+	 * @param descriptor the method descriptor
+	 */
+	public MethodSignature(String name, String descriptor) {
+		this.name = name;
+		this.descriptor = descriptor;
+	}
+
+	/**
+	 * Checks if two {@link MethodSignature}s represent the same method.
+	 * @param o the other signature
+	 * @return whether they represent the same method
+	 */
+	@Override
+	public boolean equals(Object o) {
+		if(this == o) return true;
+		if(o == null || getClass() != o.getClass()) return false;
+		MethodSignature signature = (MethodSignature) o;
+		return Objects.equals(name, signature.name) && Objects.equals(descriptor, signature.descriptor);
+	}
+
+	/**
+	 * Calculates a hash based on name and descriptor.
+	 * @return the hash code
+	 */
+	@Override
+	public int hashCode() {
+		return Objects.hash(name, descriptor);
+	}
+}