package cuchaz.enigma.bytecode;

import javassist.CtBehavior;
import javassist.CtClass;
import javassist.bytecode.ByteArray;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.ConstPool;
import javassist.bytecode.LocalVariableAttribute;
import javassist.bytecode.LocalVariableTypeAttribute;
import cuchaz.enigma.mapping.ArgumentEntry;
import cuchaz.enigma.mapping.BehaviorEntry;
import cuchaz.enigma.mapping.EntryFactory;
import cuchaz.enigma.mapping.Translator;


public class LocalVariableRenamer {
	
	private Translator m_translator;
	
	public LocalVariableRenamer(Translator translator) {
		m_translator = translator;
	}

	public void rename(CtClass c) {
		for (CtBehavior behavior : c.getDeclaredBehaviors()) {
			
			// if there's a local variable table, just rename everything to v1, v2, v3, ... for now
			CodeAttribute codeAttribute = behavior.getMethodInfo().getCodeAttribute();
			if (codeAttribute == null) {
				continue;
			}
			
			BehaviorEntry behaviorEntry = EntryFactory.getBehaviorEntry(behavior);
			ConstPool constants = c.getClassFile().getConstPool();
			
			LocalVariableAttribute table = (LocalVariableAttribute)codeAttribute.getAttribute(LocalVariableAttribute.tag);
			if (table != null) {
				renameTable(behaviorEntry, constants, table);
			}
			
			LocalVariableTypeAttribute typeTable = (LocalVariableTypeAttribute)codeAttribute.getAttribute(LocalVariableAttribute.typeTag);
			if (typeTable != null) {
				renameTable(behaviorEntry, constants, typeTable);
			}
		}
	}

	// DEBUG
	@SuppressWarnings("unused")
	private void dumpTable(LocalVariableAttribute table) {
		for (int i=0; i<table.tableLength(); i++) {
			System.out.println(String.format("\t%d (%d): %s %s",
				i, table.index(i), table.variableName(i), table.descriptor(i)
			));
		}
	}

	private void renameTable(BehaviorEntry behaviorEntry, ConstPool constants, LocalVariableAttribute table) {
		
		// skip empty tables
		if (table.tableLength() <= 0) {
			return;
		}
		
		// where do we start counting variables?
		int starti = 0;
		if (table.variableName(0).equals("this")) {
			// skip the "this" variable
			starti = 1;
		}
		
		// rename method arguments first
		int numArgs = 0;
		if (behaviorEntry.getSignature() != null) {
			numArgs = behaviorEntry.getSignature().getArgumentTypes().size();
			for (int i=starti; i<starti + numArgs && i<table.tableLength(); i++) {
				int argi = i - starti;
				String argName = m_translator.translate(new ArgumentEntry(behaviorEntry, argi, ""));
				if (argName == null) {
					argName = "a" + (argi + 1);
				}
				renameVariable(table, i, constants.addUtf8Info(argName));
			}
		}
		
		// then rename the rest of the args, if any
		for (int i=starti + numArgs; i<table.tableLength(); i++) {
			int firstIndex = table.index(starti + numArgs);
			renameVariable(table, i, constants.addUtf8Info("v" + (table.index(i) - firstIndex + 1)));
		}
	}
	
	private void renameVariable(LocalVariableAttribute table, int i, int stringId) {
		// based off of LocalVariableAttribute.nameIndex()
		ByteArray.write16bit(stringId, table.get(), i*10 + 6);
	}
}