/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2007 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package alterrs.asm.commons;

import alterrs.asm.Label;
import alterrs.asm.MethodAdapter;
import alterrs.asm.MethodVisitor;
import alterrs.asm.Opcodes;
import alterrs.asm.Type;

/**
 * A {@link alterrs.asm.MethodAdapter} that renumbers local variables in their
 * order of appearance. This adapter allows one to easily add new local
 * variables to a method. It may be used by inheriting from this class, but the
 * preferred way of using it is via delegation: the next visitor in the chain
 * can indeed add new locals when needed by calling {@link #newLocal} on this
 * adapter (this requires a reference back to this {@link LocalVariablesSorter}
 * ).
 * 
 * @author Chris Nokleberg
 * @author Eugene Kuleshov
 * @author Eric Bruneton
 */
public class LocalVariablesSorter extends MethodAdapter {

	private static final Type OBJECT_TYPE = Type
			.getObjectType("java/lang/Object");

	/**
	 * Mapping from old to new local variable indexes. A local variable at index
	 * i of size 1 is remapped to 'mapping[2*i]', while a local variable at
	 * index i of size 2 is remapped to 'mapping[2*i+1]'.
	 */
	private int[] mapping = new int[40];

	/**
	 * Array used to store stack map local variable types after remapping.
	 */
	private Object[] newLocals = new Object[20];

	/**
	 * Index of the first local variable, after formal parameters.
	 */
	protected final int firstLocal;

	/**
	 * Index of the next local variable to be created by {@link #newLocal}.
	 */
	protected int nextLocal;

	/**
	 * Indicates if at least one local variable has moved due to remapping.
	 */
	private boolean changed;

	/**
	 * Creates a new {@link LocalVariablesSorter}.
	 * 
	 * @param access
	 *            access flags of the adapted method.
	 * @param desc
	 *            the method's descriptor (see {@link Type Type}).
	 * @param mv
	 *            the method visitor to which this adapter delegates calls.
	 */
	public LocalVariablesSorter(final int access, final String desc,
			final MethodVisitor mv) {
		super(mv);
		Type[] args = Type.getArgumentTypes(desc);
		nextLocal = (Opcodes.ACC_STATIC & access) == 0 ? 1 : 0;
		for (int i = 0; i < args.length; i++) {
			nextLocal += args[i].getSize();
		}
		firstLocal = nextLocal;
	}

	public void visitVarInsn(final int opcode, final int var) {
		Type type;
		switch (opcode) {
		case Opcodes.LLOAD:
		case Opcodes.LSTORE:
			type = Type.LONG_TYPE;
			break;

		case Opcodes.DLOAD:
		case Opcodes.DSTORE:
			type = Type.DOUBLE_TYPE;
			break;

		case Opcodes.FLOAD:
		case Opcodes.FSTORE:
			type = Type.FLOAT_TYPE;
			break;

		case Opcodes.ILOAD:
		case Opcodes.ISTORE:
			type = Type.INT_TYPE;
			break;

		default:
			// case Opcodes.ALOAD:
			// case Opcodes.ASTORE:
			// case RET:
			type = OBJECT_TYPE;
			break;
		}
		mv.visitVarInsn(opcode, remap(var, type));
	}

	public void visitIincInsn(final int var, final int increment) {
		mv.visitIincInsn(remap(var, Type.INT_TYPE), increment);
	}

	public void visitMaxs(final int maxStack, final int maxLocals) {
		mv.visitMaxs(maxStack, nextLocal);
	}

	public void visitLocalVariable(final String name, final String desc,
			final String signature, final Label start, final Label end,
			final int index) {
		int newIndex = remap(index, Type.getType(desc));
		mv.visitLocalVariable(name, desc, signature, start, end, newIndex);
	}

	public void visitFrame(final int type, final int nLocal,
			final Object[] local, final int nStack, final Object[] stack) {
		if (type != Opcodes.F_NEW) { // uncompressed frame
			throw new IllegalStateException(
					"ClassReader.accept() should be called with EXPAND_FRAMES flag");
		}

		if (!changed) { // optimization for the case where mapping = identity
			mv.visitFrame(type, nLocal, local, nStack, stack);
			return;
		}

		// creates a copy of newLocals
		Object[] oldLocals = new Object[newLocals.length];
		System.arraycopy(newLocals, 0, oldLocals, 0, oldLocals.length);

		// copies types from 'local' to 'newLocals'
		// 'newLocals' already contains the variables added with 'newLocal'

		int index = 0; // old local variable index
		int number = 0; // old local variable number
		for (; number < nLocal; ++number) {
			Object t = local[number];
			int size = t == Opcodes.LONG || t == Opcodes.DOUBLE ? 2 : 1;
			if (t != Opcodes.TOP) {
				Type typ = OBJECT_TYPE;
				if (t == Opcodes.INTEGER) {
					typ = Type.INT_TYPE;
				} else if (t == Opcodes.FLOAT) {
					typ = Type.FLOAT_TYPE;
				} else if (t == Opcodes.LONG) {
					typ = Type.LONG_TYPE;
				} else if (t == Opcodes.DOUBLE) {
					typ = Type.DOUBLE_TYPE;
				} else if (t instanceof String) {
					typ = Type.getObjectType((String) t);
				}
				setFrameLocal(remap(index, typ), t);
			}
			index += size;
		}

		// removes TOP after long and double types as well as trailing TOPs

		index = 0;
		number = 0;
		for (int i = 0; index < newLocals.length; ++i) {
			Object t = newLocals[index++];
			if (t != null && t != Opcodes.TOP) {
				newLocals[i] = t;
				number = i + 1;
				if (t == Opcodes.LONG || t == Opcodes.DOUBLE) {
					index += 1;
				}
			} else {
				newLocals[i] = Opcodes.TOP;
			}
		}

		// visits remapped frame
		mv.visitFrame(type, number, newLocals, nStack, stack);

		// restores original value of 'newLocals'
		newLocals = oldLocals;
	}

	// -------------

	/**
	 * Creates a new local variable of the given type.
	 * 
	 * @param type
	 *            the type of the local variable to be created.
	 * @return the identifier of the newly created local variable.
	 */
	public int newLocal(final Type type) {
		Object t;
		switch (type.getSort()) {
		case Type.BOOLEAN:
		case Type.CHAR:
		case Type.BYTE:
		case Type.SHORT:
		case Type.INT:
			t = Opcodes.INTEGER;
			break;
		case Type.FLOAT:
			t = Opcodes.FLOAT;
			break;
		case Type.LONG:
			t = Opcodes.LONG;
			break;
		case Type.DOUBLE:
			t = Opcodes.DOUBLE;
			break;
		case Type.ARRAY:
			t = type.getDescriptor();
			break;
		// case Type.OBJECT:
		default:
			t = type.getInternalName();
			break;
		}
		int local = nextLocal;
		nextLocal += type.getSize();
		setLocalType(local, type);
		setFrameLocal(local, t);
		return local;
	}

	/**
	 * Sets the current type of the given local variable. The default
	 * implementation of this method does nothing.
	 * 
	 * @param local
	 *            a local variable identifier, as returned by {@link #newLocal
	 *            newLocal()}.
	 * @param type
	 *            the type of the value being stored in the local variable
	 */
	protected void setLocalType(final int local, final Type type) {
	}

	private void setFrameLocal(final int local, final Object type) {
		int l = newLocals.length;
		if (local >= l) {
			Object[] a = new Object[Math.max(2 * l, local + 1)];
			System.arraycopy(newLocals, 0, a, 0, l);
			newLocals = a;
		}
		newLocals[local] = type;
	}

	private int remap(final int var, final Type type) {
		if (var + type.getSize() <= firstLocal) {
			return var;
		}
		int key = 2 * var + type.getSize() - 1;
		int size = mapping.length;
		if (key >= size) {
			int[] newMapping = new int[Math.max(2 * size, key + 1)];
			System.arraycopy(mapping, 0, newMapping, 0, size);
			mapping = newMapping;
		}
		int value = mapping[key];
		if (value == 0) {
			value = newLocalMapping(type);
			setLocalType(value, type);
			mapping[key] = value + 1;
		} else {
			value--;
		}
		if (value != var) {
			changed = true;
		}
		return value;
	}

	protected int newLocalMapping(final Type type) {
		int local = nextLocal;
		nextLocal += type.getSize();
		return local;
	}
}
