package alterrs.asm.commons;

import java.util.Collections;
import java.util.Comparator;

import alterrs.asm.MethodVisitor;
import alterrs.asm.tree.MethodNode;
import alterrs.asm.tree.TryCatchBlockNode;

/**
 * Sorts the exception handlers in a method innermost-to-outermost. This allows
 * the programmer to add handlers without worrying about ordering them correctly
 * with respect to existing, in-code handlers.
 * <p/>
 * Behavior is only defined for properly-nested handlers. If any "try" blocks
 * overlap (something that isn't possible in Java code) then this may not do
 * what you want. In fact, this adapter just sorts by the length of the "try"
 * block, taking advantage of the fact that a given try block must be larger
 * than any block it contains).
 * 
 * @author Adrian Sampson
 */
public class TryCatchBlockSorter extends MethodNode {

	private final MethodVisitor mv;

	public TryCatchBlockSorter(final MethodVisitor mv, final int access,
			final String name, final String desc, final String signature,
			final String[] exceptions) {
		super(access, name, desc, signature, exceptions);
		this.mv = mv;
	}

	public void visitEnd() {
		// Compares TryCatchBlockNodes by the length of their "try" block.
		Comparator comp = new Comparator() {

			public int compare(Object o1, Object o2) {
				int len1 = blockLength((TryCatchBlockNode) o1);
				int len2 = blockLength((TryCatchBlockNode) o2);
				return len1 - len2;
			}

			private int blockLength(TryCatchBlockNode block) {
				int startidx = instructions.indexOf(block.start);
				int endidx = instructions.indexOf(block.end);
				return endidx - startidx;
			}
		};
		Collections.sort(tryCatchBlocks, comp);
		if (mv != null) {
			accept(mv);
		}
	}
}
