/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.bcel.generic;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Hashtable;
import java.util.List;
import java.util.Objects;
import java.util.Stack;
import java.util.stream.Collectors;

import org.apache.bcel.Const;
import org.apache.bcel.classfile.AnnotationEntry;
import org.apache.bcel.classfile.Annotations;
import org.apache.bcel.classfile.Attribute;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.CodeException;
import org.apache.bcel.classfile.ExceptionTable;
import org.apache.bcel.classfile.LineNumber;
import org.apache.bcel.classfile.LineNumberTable;
import org.apache.bcel.classfile.LocalVariable;
import org.apache.bcel.classfile.LocalVariableTable;
import org.apache.bcel.classfile.LocalVariableTypeTable;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.classfile.ParameterAnnotationEntry;
import org.apache.bcel.classfile.ParameterAnnotations;
import org.apache.bcel.classfile.RuntimeVisibleParameterAnnotations;
import org.apache.bcel.classfile.Utility;
import org.apache.bcel.util.Args;
import org.apache.bcel.util.BCELComparator;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.stream.Streams;

/**
 * Template class for building up a method. This is done by defining exception handlers, adding thrown exceptions, local
 * variables and attributes, whereas the 'LocalVariableTable' and 'LineNumberTable' attributes will be set automatically
 * for the code. Use stripAttributes() if you don't like this.
 *
 * While generating code it may be necessary to insert NOP operations. You can use the 'removeNOPs' method to get rid
 * off them. The resulting method object can be obtained via the 'getMethod()' method.
 *
 * @see InstructionList
 * @see Method
 */
public class MethodGen extends FieldGenOrMethodGen {

    static final class BranchStack {

        private final Stack<BranchTarget> branchTargets = new Stack<>();
        private final Hashtable<InstructionHandle, BranchTarget> visitedTargets = new Hashtable<>();

        public BranchTarget pop() {
            if (!branchTargets.empty()) {
                return branchTargets.pop();
            }
            return null;
        }

        public void push(final InstructionHandle target, final int stackDepth) {
            if (visited(target)) {
                return;
            }
            branchTargets.push(visit(target, stackDepth));
        }

        private BranchTarget visit(final InstructionHandle target, final int stackDepth) {
            final BranchTarget bt = new BranchTarget(target, stackDepth);
            visitedTargets.put(target, bt);
            return bt;
        }

        private boolean visited(final InstructionHandle target) {
            return visitedTargets.get(target) != null;
        }
    }

    static final class BranchTarget {

        final InstructionHandle target;
        final int stackDepth;

        BranchTarget(final InstructionHandle target, final int stackDepth) {
            this.target = target;
            this.stackDepth = stackDepth;
        }
    }

    private static BCELComparator<FieldGenOrMethodGen> bcelComparator = new BCELComparator<FieldGenOrMethodGen>() {

        @Override
        public boolean equals(final FieldGenOrMethodGen a, final FieldGenOrMethodGen b) {
            return a == b || a != null && b != null && Objects.equals(a.getName(), b.getName()) && Objects.equals(a.getSignature(), b.getSignature());
        }

        @Override
        public int hashCode(final FieldGenOrMethodGen o) {
            return o != null ? Objects.hash(o.getSignature(), o.getName()) : 0;
        }
    };

    private static byte[] getByteCodes(final Method method) {
        final Code code = method.getCode();
        if (code == null) {
            throw new IllegalStateException(String.format("The method '%s' has no code.", method));
        }
        return code.getCode();
    }

    /**
     * Gets the comparison strategy object.
     *
     * @return Comparison strategy object.
     */
    public static BCELComparator<FieldGenOrMethodGen> getComparator() {
        return bcelComparator;
    }

    /**
     * Gets the maximum stack depth of an instruction list by performing control flow analysis.
     *
     * @param cp The constant pool generator.
     * @param il The instruction list.
     * @param et The exception handlers.
     * @return maximum stack depth used by method.
     */
    public static int getMaxStack(final ConstantPoolGen cp, final InstructionList il, final CodeExceptionGen[] et) {
        final BranchStack branchTargets = new BranchStack();
        /*
         * Initially, populate the branch stack with the exception handlers, because these aren't (necessarily) branched to
         * explicitly. in each case, the stack will have depth 1, containing the exception object.
         */
        for (final CodeExceptionGen element : et) {
            final InstructionHandle handlerPc = element.getHandlerPC();
            if (handlerPc != null) {
                branchTargets.push(handlerPc, 1);
            }
        }
        int stackDepth = 0;
        int maxStackDepth = 0;
        InstructionHandle ih = il.getStart();
        while (ih != null) {
            final Instruction instruction = ih.getInstruction();
            final short opcode = instruction.getOpcode();
            final int delta = instruction.produceStack(cp) - instruction.consumeStack(cp);
            stackDepth += delta;
            if (stackDepth > maxStackDepth) {
                maxStackDepth = stackDepth;
            }
            // choose the next instruction based on whether current is a branch.
            if (instruction instanceof BranchInstruction) {
                final BranchInstruction branch = (BranchInstruction) instruction;
                if (instruction instanceof Select) {
                    // explore all of the select's targets. the default target is handled below.
                    final Select select = (Select) branch;
                    final InstructionHandle[] targets = select.getTargets();
                    for (final InstructionHandle target : targets) {
                        branchTargets.push(target, stackDepth);
                    }
                    // nothing to fall through to.
                    ih = null;
                } else if (!(branch instanceof IfInstruction)) {
                    // if an instruction that comes back to following PC,
                    // push next instruction, with stack depth reduced by 1.
                    if (opcode == Const.JSR || opcode == Const.JSR_W) {
                        branchTargets.push(ih.getNext(), stackDepth - 1);
                    }
                    ih = null;
                }
                // for all branches, the target of the branch is pushed on the branch stack.
                // conditional branches have a fall through case, selects don't, and
                // jsr/jsr_w return to the next instruction.
                branchTargets.push(branch.getTarget(), stackDepth);
            } else // check for instructions that terminate the method.
            if (opcode == Const.ATHROW || opcode == Const.RET || opcode >= Const.IRETURN && opcode <= Const.RETURN) {
                ih = null;
            }
            // normal case, go to the next instruction.
            if (ih != null) {
                ih = ih.getNext();
            }
            // if we have no more instructions, see if there are any deferred branches to explore.
            if (ih == null) {
                final BranchTarget bt = branchTargets.pop();
                if (bt != null) {
                    ih = bt.target;
                    stackDepth = bt.stackDepth;
                }
            }
        }
        return maxStackDepth;
    }

    /**
     * Sets the comparison strategy object.
     *
     * @param comparator Comparison strategy object.
     */
    public static void setComparator(final BCELComparator<FieldGenOrMethodGen> comparator) {
        bcelComparator = comparator;
    }

    private String className;
    private Type[] argTypes;
    private String[] argNames;
    private int maxLocals;
    private int maxStack;
    private InstructionList il;

    private boolean stripAttributes;
    private boolean compactCodeHeader;
    private LocalVariableTypeTable localVariableTypeTable;
    private final List<LocalVariableGen> variableList = new ArrayList<>();

    private final List<LineNumberGen> lineNumberList = new ArrayList<>();

    private final List<CodeExceptionGen> exceptionList = new ArrayList<>();

    private final List<String> throwsList = new ArrayList<>();

    private final List<Attribute> codeAttrsList = new ArrayList<>();

    private List<AnnotationEntryGen>[] paramAnnotations; // Array of lists containing AnnotationGen objects

    private boolean hasParameterAnnotations;

    private boolean haveUnpackedParameterAnnotations;

    private List<MethodObserver> observers;

    /**
     * Declare method. If the method is non-static the constructor automatically declares a local variable '$this' in slot
     * 0. The actual code is contained in the 'il' parameter, which may further manipulated by the user. But they must take
     * care not to remove any instruction (handles) that are still referenced from this object.
     *
     * For example one may not add a local variable and later remove the instructions it refers to without causing havoc. It
     * is safe however if you remove that local variable, too.
     *
     * @param accessFlags access qualifiers.
     * @param returnType method type.
     * @param argTypes argument types.
     * @param argNames argument names (if this is null, default names will be provided for them).
     * @param methodName name of method.
     * @param className class name containing this method (may be null, if you don't care).
     * @param il instruction list associated with this method, may be null only for abstract or native methods.
     * @param cp constant pool.
     */
    public MethodGen(final int accessFlags, final Type returnType, final Type[] argTypes, String[] argNames, final String methodName, final String className,
        final InstructionList il, final ConstantPoolGen cp) {
        super(accessFlags);
        setType(returnType);
        setArgumentTypes(argTypes);
        setArgumentNames(argNames);
        setName(methodName);
        setClassName(className);
        setInstructionList(il);
        setConstantPool(cp);
        final boolean abstract_ = isAbstract() || isNative();
        InstructionHandle start = null;
        final InstructionHandle end = null;
        if (!abstract_) {
            start = il.getStart();
            // end == null => live to end of method
            /*
             * Add local variables, namely the implicit 'this' and the arguments
             */
            if (!isStatic() && className != null) { // Instance method -> 'this' is local var 0
                addLocalVariable("this", ObjectType.getInstance(className), start, end);
            }
        }
        if (argTypes != null) {
            final int size = argTypes.length;
            for (final Type argType : argTypes) {
                if (Type.VOID == argType) {
                    throw new ClassGenException("'void' is an illegal argument type for a method");
                }
            }
            if (argNames != null) { // Names for variables provided?
                if (size != argNames.length) {
                    throw new ClassGenException("Mismatch in argument array lengths: " + size + " versus " + argNames.length);
                }
            } else { // Give them dummy names
                argNames = new String[size];
                for (int i = 0; i < size; i++) {
                    argNames[i] = "arg" + i;
                }
                setArgumentNames(argNames);
            }
            if (!abstract_) {
                for (int i = 0; i < size; i++) {
                    addLocalVariable(argNames[i], argTypes[i], start, end);
                }
            }
        }
    }

    /**
     * Instantiate from existing method.
     *
     * @param method method.
     * @param className class name containing this method.
     * @param cp constant pool.
     */
    public MethodGen(final Method method, final String className, final ConstantPoolGen cp) {
        this(method.getAccessFlags(), Type.getReturnType(method.getSignature()), Type.getArgumentTypes(method.getSignature()),
            null /* may be overridden anyway */
            , method.getName(), className,
            (method.getAccessFlags() & (Const.ACC_ABSTRACT | Const.ACC_NATIVE)) == 0 ? new InstructionList(getByteCodes(method)) : null, cp);
        final Attribute[] attributes = method.getAttributes();
        for (final Attribute attribute : attributes) {
            Attribute a = attribute;
            if (a instanceof Code) {
                final Code c = (Code) a;
                compactCodeHeader = c.isCompactCodeHeader();
                setMaxStack(c.getMaxStack());
                setMaxLocals(c.getMaxLocals());
                final CodeException[] ces = c.getExceptionTable();
                if (ces != null) {
                    for (final CodeException ce : ces) {
                        final int type = ce.getCatchType();
                        ObjectType cType = null;
                        if (type > 0) {
                            final String cen = method.getConstantPool().getConstantString(type, Const.CONSTANT_Class);
                            cType = ObjectType.getInstance(cen);
                        }
                        final int endPc = ce.getEndPC();
                        final int length = getByteCodes(method).length;
                        InstructionHandle end;
                        if (length == endPc) { // May happen, because end_pc is exclusive
                            end = il.getEnd();
                        } else {
                            end = il.findHandle(endPc);
                            end = end.getPrev(); // Make it inclusive
                        }
                        addExceptionHandler(il.findHandle(ce.getStartPC()), end, il.findHandle(ce.getHandlerPC()), cType);
                    }
                }
                final Attribute[] cAttributes = c.getAttributes();
                for (final Attribute cAttribute : cAttributes) {
                    a = cAttribute;
                    if (a instanceof LineNumberTable) {
                        ((LineNumberTable) a).forEach(l -> {
                            final InstructionHandle ih = il.findHandle(l.getStartPC());
                            if (ih != null) {
                                addLineNumber(ih, l.getLineNumber());
                            }
                        });
                    } else if (a instanceof LocalVariableTable) {
                        updateLocalVariableTable((LocalVariableTable) a);
                    } else if (a instanceof LocalVariableTypeTable) {
                        this.localVariableTypeTable = (LocalVariableTypeTable) a.copy(cp.getConstantPool());
                    } else {
                        addCodeAttribute(a);
                    }
                }
            } else if (a instanceof ExceptionTable) {
                Collections.addAll(throwsList, ((ExceptionTable) a).getExceptionNames());
            } else if (a instanceof Annotations) {
                final Annotations runtimeAnnotations = (Annotations) a;
                runtimeAnnotations.forEach(element -> addAnnotationEntry(new AnnotationEntryGen(element, cp, false)));
            } else {
                addAttribute(a);
            }
        }
    }

    /**
     * Adds annotations as an attribute.
     *
     * @param cp The constant pool generator.
     * @since 6.0
     */
    public void addAnnotationsAsAttribute(final ConstantPoolGen cp) {
        addAll(AnnotationEntryGen.getAnnotationAttributes(cp, super.getAnnotationEntries()));
    }

    /**
     * Add an attribute to the code. Currently, the JVM knows about the LineNumberTable, LocalVariableTable and StackMap
     * attributes, where the former two will be generated automatically and the latter is used for the MIDP only. Other
     * attributes will be ignored by the JVM but do no harm.
     *
     * @param a attribute to be added.
     */
    public void addCodeAttribute(final Attribute a) {
        codeAttrsList.add(a);
    }

    /**
     * Add an exception possibly thrown by this method.
     *
     * @param className (fully qualified) name of exception.
     */
    public void addException(final String className) {
        throwsList.add(className);
    }

    /**
     * Add an exception handler, that is, specify region where a handler is active and an instruction where the actual handling
     * is done.
     *
     * @param startPc Start of region (inclusive).
     * @param endPc End of region (inclusive).
     * @param handlerPc Where handling is done.
     * @param catchType class type of handled exception or null if any exception is handled.
     * @return new exception handler object.
     */
    public CodeExceptionGen addExceptionHandler(final InstructionHandle startPc, final InstructionHandle endPc, final InstructionHandle handlerPc,
        final ObjectType catchType) {
        if (startPc == null || endPc == null || handlerPc == null) {
            throw new ClassGenException("Exception handler target is a null instruction");
        }
        final CodeExceptionGen c = new CodeExceptionGen(startPc, endPc, handlerPc, catchType);
        exceptionList.add(c);
        return c;
    }

    /**
     * Give an instruction a line number corresponding to the source code line.
     *
     * @param ih instruction to tag.
     * @param srcLine The source line number.
     * @return new line number object.
     * @see LineNumber
     */
    public LineNumberGen addLineNumber(final InstructionHandle ih, final int srcLine) {
        final LineNumberGen l = new LineNumberGen(ih, srcLine);
        lineNumberList.add(l);
        return l;
    }

    /**
     * Adds a local variable to this method and assigns an index automatically.
     *
     * @param name variable name.
     * @param type variable type.
     * @param start from where the variable is valid, if this is null, it is valid from the start.
     * @param end until where the variable is valid, if this is null, it is valid to the end.
     * @return new local variable object.
     * @see LocalVariable
     */
    public LocalVariableGen addLocalVariable(final String name, final Type type, final InstructionHandle start, final InstructionHandle end) {
        return addLocalVariable(name, type, maxLocals, start, end);
    }

    /**
     * Adds a local variable to this method.
     *
     * @param name variable name.
     * @param type variable type.
     * @param slot The index of the local variable, if type is long or double, the next available index is slot+2.
     * @param start from where the variable is valid.
     * @param end until where the variable is valid.
     * @return new local variable object.
     * @see LocalVariable
     */
    public LocalVariableGen addLocalVariable(final String name, final Type type, final int slot, final InstructionHandle start, final InstructionHandle end) {
        return addLocalVariable(name, type, slot, start, end, slot);
    }

    /**
     * Adds a local variable to this method.
     *
     * @param name variable name.
     * @param type variable type.
     * @param slot The index of the local variable, if type is long or double, the next available index is slot+2.
     * @param start from where the variable is valid.
     * @param end until where the variable is valid.
     * @param origIndex The index of the local variable prior to any modifications.
     * @return new local variable object.
     * @see LocalVariable
     */
    public LocalVariableGen addLocalVariable(final String name, final Type type, final int slot, final InstructionHandle start, final InstructionHandle end,
        final int origIndex) {
        final byte t = type.getType();
        if (t != Const.T_ADDRESS) {
            final int add = type.getSize();
            if (slot + add > maxLocals) {
                maxLocals = slot + add;
            }
            final LocalVariableGen l = new LocalVariableGen(slot, name, type, start, end, origIndex);
            final int i;
            if ((i = variableList.indexOf(l)) >= 0) {
                variableList.set(i, l);
            } else {
                variableList.add(l);
            }
            return l;
        }
        throw new IllegalArgumentException("Cannot use " + type + " as the type of a local variable");
    }

    /**
     * Add observer for this object.
     *
     * @param o The observer to add.
     */
    public void addObserver(final MethodObserver o) {
        if (observers == null) {
            observers = new ArrayList<>();
        }
        observers.add(o);
    }

    /**
     * Adds a parameter annotation.
     *
     * @param parameterIndex The parameter index.
     * @param annotation The annotation.
     */
    public void addParameterAnnotation(final int parameterIndex, final AnnotationEntryGen annotation) {
        ensureExistingParameterAnnotationsUnpacked();
        if (!hasParameterAnnotations) {
            @SuppressWarnings("unchecked") // OK
            final List<AnnotationEntryGen>[] parmList = new List[argTypes.length];
            paramAnnotations = parmList;
            hasParameterAnnotations = true;
        }
        final List<AnnotationEntryGen> existingAnnotations = paramAnnotations[parameterIndex];
        if (existingAnnotations != null) {
            existingAnnotations.add(annotation);
        } else {
            final List<AnnotationEntryGen> l = new ArrayList<>();
            l.add(annotation);
            paramAnnotations[parameterIndex] = l;
        }
    }

    /**
     * Adds parameter annotations as an attribute.
     *
     * @param cp The constant pool generator.
     * @since 6.0
     */
    public void addParameterAnnotationsAsAttribute(final ConstantPoolGen cp) {
        if (!hasParameterAnnotations) {
            return;
        }
        final Attribute[] attrs = AnnotationEntryGen.getParameterAnnotationAttributes(cp, paramAnnotations);
        if (attrs != null) {
            addAll(attrs);
        }
    }

    private Attribute[] addRuntimeAnnotationsAsAttribute(final ConstantPoolGen cp) {
        final Attribute[] attrs = AnnotationEntryGen.getAnnotationAttributes(cp, super.getAnnotationEntries());
        addAll(attrs);
        return attrs;
    }

    private Attribute[] addRuntimeParameterAnnotationsAsAttribute(final ConstantPoolGen cp) {
        if (!hasParameterAnnotations) {
            return Attribute.EMPTY_ARRAY;
        }
        final Attribute[] attrs = AnnotationEntryGen.getParameterAnnotationAttributes(cp, paramAnnotations);
        addAll(attrs);
        return attrs;
    }

    private void adjustLocalVariableTypeTable(final LocalVariableTable lvt) {
        final LocalVariable[] lv = lvt.getLocalVariableTable();
        for (final LocalVariable element : localVariableTypeTable.getLocalVariableTypeTable()) {
            for (final LocalVariable l : lv) {
                if (element.getName().equals(l.getName()) && element.getIndex() == l.getOrigIndex()) {
                    element.setLength(l.getLength());
                    element.setStartPC(l.getStartPC());
                    element.setIndex(l.getIndex());
                    break;
                }
            }
        }
    }

    /**
     * Creates a deep copy of this method.
     *
     * @param className The class name.
     * @param cp The constant pool generator.
     * @return deep copy of this method.
     */
    public MethodGen copy(final String className, final ConstantPoolGen cp) {
        final Method m = ((MethodGen) clone()).getMethod();
        final MethodGen mg = new MethodGen(m, className, super.getConstantPool());
        if (super.getConstantPool() != cp) {
            mg.setConstantPool(cp);
            mg.getInstructionList().replaceConstantPool(super.getConstantPool(), cp);
        }
        return mg;
    }

    /**
     * Goes through the attributes on the method and identifies any that are RuntimeParameterAnnotations, extracting their
     * contents and storing them as parameter annotations. There are two kinds of parameter annotation - visible and
     * invisible. Once they have been unpacked, these attributes are deleted. (The annotations will be rebuilt as attributes
     * when someone builds a Method object out of this MethodGen object).
     */
    private void ensureExistingParameterAnnotationsUnpacked() {
        if (haveUnpackedParameterAnnotations) {
            return;
        }
        // Find attributes that contain parameter annotation data
        final Attribute[] attrs = getAttributes();
        ParameterAnnotations paramAnnVisAttr = null;
        ParameterAnnotations paramAnnInvisAttr = null;
        for (final Attribute attribute : attrs) {
            if (attribute instanceof ParameterAnnotations) {
                // Initialize paramAnnotations
                if (!hasParameterAnnotations) {
                    @SuppressWarnings("unchecked") // OK
                    final List<AnnotationEntryGen>[] parmList = new List[argTypes.length];
                    paramAnnotations = parmList;
                    Arrays.setAll(paramAnnotations, i -> new ArrayList<>());
                }
                hasParameterAnnotations = true;
                final ParameterAnnotations rpa = (ParameterAnnotations) attribute;
                if (rpa instanceof RuntimeVisibleParameterAnnotations) {
                    paramAnnVisAttr = rpa;
                } else {
                    paramAnnInvisAttr = rpa;
                }
                final ParameterAnnotationEntry[] parameterAnnotationEntries = rpa.getParameterAnnotationEntries();
                for (int j = 0; j < parameterAnnotationEntries.length; j++) {
                    // This returns Annotation[] ...
                    final ParameterAnnotationEntry immutableArray = rpa.getParameterAnnotationEntries()[j];
                    // ... which needs transforming into an AnnotationGen[] ...
                    final List<AnnotationEntryGen> mutable = makeMutableVersion(immutableArray.getAnnotationEntries());
                    // ... then add these to any we already know about
                    paramAnnotations[j].addAll(mutable);
                }
            }
        }
        if (paramAnnVisAttr != null) {
            removeAttribute(paramAnnVisAttr);
        }
        if (paramAnnInvisAttr != null) {
            removeAttribute(paramAnnInvisAttr);
        }
        haveUnpackedParameterAnnotations = true;
    }

    /**
     * Return value as defined by given BCELComparator strategy. By default two MethodGen objects are said to be equal when
     * their names and signatures are equal.
     *
     * @see Object#equals(Object)
     */
    @Override
    public boolean equals(final Object obj) {
        return obj instanceof FieldGenOrMethodGen && bcelComparator.equals(this, (FieldGenOrMethodGen) obj);
    }

    // J5TODO: Should paramAnnotations be an array of arrays? Rather than an array of lists, this
    // is more likely to suggest to the caller it is readonly (which a List does not).

    /**
     * Gets a list of AnnotationGen objects representing parameter annotations.
     *
     * @param i The parameter index.
     * @return list of AnnotationGen objects.
     * @since 6.0
     */
    public List<AnnotationEntryGen> getAnnotationsOnParameter(final int i) {
        ensureExistingParameterAnnotationsUnpacked();
        if (!hasParameterAnnotations || i > argTypes.length) {
            return null;
        }
        return paramAnnotations[i];
    }

    /**
     * Gets the argument name at the specified index.
     *
     * @param i The argument index.
     * @return The argument name.
     */
    public String getArgumentName(final int i) {
        return argNames[i];
    }

    /**
     * Gets all argument names.
     *
     * @return array of argument names.
     */
    public String[] getArgumentNames() {
        return argNames.clone();
    }

    /**
     * Gets the argument type at the specified index.
     *
     * @param i The argument index.
     * @return The argument type.
     */
    public Type getArgumentType(final int i) {
        return argTypes[i];
    }

    /**
     * Gets all argument types.
     *
     * @return array of argument types.
     */
    public Type[] getArgumentTypes() {
        return argTypes.clone();
    }

    /**
     * Gets the class that contains this method.
     *
     * @return class that contains this method.
     */
    public String getClassName() {
        return className;
    }

    /**
     * Gets all attributes of this method.
     *
     * @return all attributes of this method.
     */
    public Attribute[] getCodeAttributes() {
        return codeAttrsList.toArray(Attribute.EMPTY_ARRAY);
    }

    /**
     * Gets the exception handlers for the 'Code' attribute.
     *
     * @return code exceptions for 'Code' attribute.
     */
    private CodeException[] getCodeExceptions() {
        final int size = exceptionList.size();
        final CodeException[] cExc = new CodeException[size];
        Arrays.setAll(cExc, i -> exceptionList.get(i).getCodeException(super.getConstantPool()));
        return cExc;
    }

    /**
     * Gets an array of declared exception handlers.
     *
     * @return array of declared exception handlers.
     */
    public CodeExceptionGen[] getExceptionHandlers() {
        return exceptionList.toArray(CodeExceptionGen.EMPTY_ARRAY);
    }

    /**
     * Gets an array of thrown exceptions.
     *
     * @return array of thrown exceptions.
     */
    public String[] getExceptions() {
        return throwsList.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

    /**
     * Gets the 'Exceptions' attribute of all the exceptions thrown by this method.
     *
     * @return 'Exceptions' attribute of all the exceptions thrown by this method.
     */
    private ExceptionTable getExceptionTable(final ConstantPoolGen cp) {
        final int size = throwsList.size();
        final int[] ex = new int[size];
        Arrays.setAll(ex, i -> cp.addClass(throwsList.get(i)));
        return new ExceptionTable(cp.addUtf8("Exceptions"), 2 + 2 * size, ex, cp.getConstantPool());
    }

    /**
     * Gets the instruction list.
     *
     * @return The instruction list.
     */
    public InstructionList getInstructionList() {
        return il;
    }

    /**
     * Gets an array of line numbers.
     *
     * @return array of line numbers.
     */
    public LineNumberGen[] getLineNumbers() {
        return lineNumberList.toArray(LineNumberGen.EMPTY_ARRAY);
    }

    /**
     * Gets the 'LineNumberTable' attribute of all the local variables of this method.
     *
     * @param cp The constant pool generator.
     * @return 'LineNumberTable' attribute of all the local variables of this method.
     */
    public LineNumberTable getLineNumberTable(final ConstantPoolGen cp) {
        final int size = lineNumberList.size();
        final LineNumber[] ln = new LineNumber[size];
        Arrays.setAll(ln, i -> lineNumberList.get(i).getLineNumber());
        return new LineNumberTable(cp.addUtf8("LineNumberTable"), 2 + ln.length * 4, ln, cp.getConstantPool());
    }

    /**
     * Gets an array of declared local variables sorted by index.
     *
     * If the range of the variable has not been set yet, it will be set to be valid from the start to the end of the
     * instruction list.
     *
     * @return array of declared local variables sorted by index.
     */
    public LocalVariableGen[] getLocalVariables() {
        final int size = variableList.size();
        final LocalVariableGen[] lg = new LocalVariableGen[size];
        variableList.toArray(lg);
        for (int i = 0; i < size; i++) {
            if (lg[i].getStart() == null && il != null) {
                lg[i].setStart(il.getStart());
            }
            if (lg[i].getEnd() == null && il != null) {
                lg[i].setEnd(il.getEnd());
            }
        }
        if (size > 1) {
            Arrays.sort(lg, Comparator.comparingInt(LocalVariableGen::getIndex));
        }
        return lg;
    }

    /**
     * Gets the 'LocalVariableTable' attribute of all the local variables of this method.
     *
     * @param cp The constant pool generator.
     * @return 'LocalVariableTable' attribute of all the local variables of this method.
     */
    public LocalVariableTable getLocalVariableTable(final ConstantPoolGen cp) {
        final LocalVariableGen[] lg = getLocalVariables();
        final int size = lg.length;
        final LocalVariable[] lv = new LocalVariable[size];
        Arrays.setAll(lv, i -> lg[i].getLocalVariable(cp));
        return new LocalVariableTable(cp.addUtf8("LocalVariableTable"), 2 + lv.length * 10, lv, cp.getConstantPool());
    }

    /**
     * Gets the 'LocalVariableTypeTable' attribute of this method.
     *
     * @return 'LocalVariableTypeTable' attribute of this method.
     */
    public LocalVariableTypeTable getLocalVariableTypeTable() {
        return localVariableTypeTable;
    }

    /**
     * Gets the maximum number of local variables.
     *
     * @return The maximum number of local variables.
     */
    public int getMaxLocals() {
        return maxLocals;
    }

    /**
     * Gets the maximum stack size.
     *
     * @return The maximum stack size.
     */
    public int getMaxStack() {
        return maxStack;
    }

    /**
     * Gets method object. Never forget to call setMaxStack() or setMaxStack(max), respectively, before calling this method
     * (the same applies for max locals).
     *
     * <p>
     * When initialized from an existing method, the Code header layout is preserved. Use {@link #setCompactCodeHeader(boolean)} to change it.
     * </p>
     *
     * @return method object.
     * @throws org.apache.bcel.classfile.ClassFormatException Thrown if Code values do not fit the selected header layout.
     */
    public Method getMethod() {
        final String signature = getSignature();
        final ConstantPoolGen cp = super.getConstantPool();
        final int nameIndex = cp.addUtf8(super.getName());
        final int signatureIndex = cp.addUtf8(signature);
        /*
         * Also updates positions of instructions, that is, their indices
         */
        final byte[] byteCode = il != null ? il.getByteCode() : null;
        LineNumberTable lnt = null;
        LocalVariableTable lvt = null;
        /*
         * Create LocalVariableTable and LineNumberTable attributes (for debuggers, for example)
         */
        if (!variableList.isEmpty() && !stripAttributes) {
            updateLocalVariableTable(getLocalVariableTable(cp));
            lvt = getLocalVariableTable(cp);
        }
        // Updating the local variable table can increase maxLocals. Validate before adding temporary attributes.
        if (compactCodeHeader && byteCode != null && !isAbstract() && !isNative()) {
            Args.requireU1(maxStack, "maxStack");
            Args.requireU1(maxLocals, "maxLocals");
            Args.requireU2(byteCode.length, "Code length attribute");
        }
        if (lvt != null) {
            addCodeAttribute(lvt);
        }
        if (localVariableTypeTable != null) {
            // LocalVariable length in LocalVariableTypeTable is not updated automatically. It's a difference with
            // LocalVariableTable.
            if (lvt != null) {
                adjustLocalVariableTypeTable(lvt);
            }
            addCodeAttribute(localVariableTypeTable);
        }
        if (!lineNumberList.isEmpty() && !stripAttributes) {
            addCodeAttribute(lnt = getLineNumberTable(cp));
        }
        final Attribute[] codeAttrs = getCodeAttributes();
        /*
         * Each attribute causes 6 additional header bytes
         */
        int attrsLen = 0;
        for (final Attribute codeAttr : codeAttrs) {
            attrsLen += codeAttr.getLength() + 6;
        }
        final CodeException[] cExc = getCodeExceptions();
        final int excLen = cExc.length * 8; // Every entry takes 8 bytes
        Code code = null;
        if (byteCode != null && !isAbstract() && !isNative()) {
            // Remove any stale code attribute
            final Attribute[] attributes = getAttributes();
            for (final Attribute a : attributes) {
                if (a instanceof Code) {
                    removeAttribute(a);
                }
            }
            code = new Code(cp.addUtf8("Code"), 8 + byteCode.length + // prologue byte code
                2 + excLen + // exceptions
                2 + attrsLen, // attributes
                maxStack, maxLocals, byteCode, cExc, codeAttrs, cp.getConstantPool());
            code.setCompactCodeHeader(compactCodeHeader);
            addAttribute(code);
        }
        final Attribute[] annotations = addRuntimeAnnotationsAsAttribute(cp);
        final Attribute[] parameterAnnotations = addRuntimeParameterAnnotationsAsAttribute(cp);
        ExceptionTable et = null;
        if (!throwsList.isEmpty()) {
            addAttribute(et = getExceptionTable(cp));
            // Add 'Exceptions' if there are "throws" clauses
        }
        final Method m = new Method(super.getAccessFlags(), nameIndex, signatureIndex, getAttributes(), cp.getConstantPool());
        // Undo effects of adding attributes
        if (lvt != null) {
            removeCodeAttribute(lvt);
        }
        if (localVariableTypeTable != null) {
            removeCodeAttribute(localVariableTypeTable);
        }
        if (lnt != null) {
            removeCodeAttribute(lnt);
        }
        if (code != null) {
            removeAttribute(code);
        }
        if (et != null) {
            removeAttribute(et);
        }
        removeRuntimeAttributes(annotations);
        removeRuntimeAttributes(parameterAnnotations);
        return m;
    }

    /**
     * Gets the return type.
     *
     * @return The return type.
     */
    public Type getReturnType() {
        return getType();
    }

    @Override
    public String getSignature() {
        return Type.getMethodSignature(super.getType(), argTypes);
    }

    /**
     * Return value as defined by given BCELComparator strategy. By default return the hash code of the method's name XOR
     * signature.
     *
     * @see Object#hashCode()
     */
    @Override
    public int hashCode() {
        return bcelComparator.hashCode(this);
    }

    /**
     * Gets whether generated Code attributes use compact four-byte headers.
     *
     * @return Whether generated Code attributes use compact headers.
     * @since 6.14.0
     * @see Code#isCompactCodeHeader()
     */
    public boolean isCompactCodeHeader() {
        return compactCodeHeader;
    }

    private List<AnnotationEntryGen> makeMutableVersion(final AnnotationEntry[] mutableArray) {
        return Streams.of(mutableArray).map(ae -> new AnnotationEntryGen(ae, getConstantPool(), false)).collect(Collectors.toList());
    }

    /**
     * Remove a code attribute.
     *
     * @param a The attribute to remove.
     */
    public void removeCodeAttribute(final Attribute a) {
        codeAttrsList.remove(a);
    }

    /**
     * Remove all code attributes.
     */
    public void removeCodeAttributes() {
        localVariableTypeTable = null;
        codeAttrsList.clear();
    }

    /**
     * Remove an exception.
     *
     * @param c The exception to remove.
     */
    public void removeException(final String c) {
        throwsList.remove(c);
    }

    /**
     * Remove an exception handler.
     *
     * @param c The exception handler to remove.
     */
    public void removeExceptionHandler(final CodeExceptionGen c) {
        exceptionList.remove(c);
    }

    /**
     * Remove all line numbers.
     */
    public void removeExceptionHandlers() {
        exceptionList.clear();
    }

    /**
     * Remove all exceptions.
     */
    public void removeExceptions() {
        throwsList.clear();
    }

    /**
     * Remove a line number.
     *
     * @param l The line number to remove.
     */
    public void removeLineNumber(final LineNumberGen l) {
        lineNumberList.remove(l);
    }

    /**
     * Remove all line numbers.
     */
    public void removeLineNumbers() {
        lineNumberList.clear();
    }

    /**
     * Remove a local variable, its slot will not be reused, if you do not use addLocalVariable with an explicit index
     * argument.
     *
     * @param l The local variable to remove.
     */
    public void removeLocalVariable(final LocalVariableGen l) {
        l.dispose();
        variableList.remove(l);
    }

    /**
     * Remove all local variables.
     */
    public void removeLocalVariables() {
        variableList.forEach(LocalVariableGen::dispose);
        variableList.clear();
    }

    /**
     * Remove the LocalVariableTypeTable
     */
    public void removeLocalVariableTypeTable() {
        localVariableTypeTable = null;
    }

    /**
     * Remove all NOPs from the instruction list (if possible) and update every object referring to them, that is, branch
     * instructions, local variables and exception handlers.
     */
    public void removeNOPs() {
        if (il != null) {
            InstructionHandle next;
            /*
             * Check branch instructions.
             */
            for (InstructionHandle ih = il.getStart(); ih != null; ih = next) {
                next = ih.getNext();
                if (next != null && ih.getInstruction() instanceof NOP) {
                    try {
                        il.delete(ih);
                    } catch (final TargetLostException e) {
                        for (final InstructionHandle target : e.getTargets()) {
                            for (final InstructionTargeter targeter : target.getTargeters()) {
                                targeter.updateTarget(target, next);
                            }
                        }
                    }
                }
            }
        }
    }

    /**
     * Remove observer for this object.
     *
     * @param o The observer to remove.
     */
    public void removeObserver(final MethodObserver o) {
        if (observers != null) {
            observers.remove(o);
        }
    }

    /**
     * Would prefer to make this private, but need a way to test if client is using BCEL version 6.5.0 or later that
     * contains fix for BCEL-329.
     *
     * @param attributes The attributes to remove.
     * @since 6.5.0
     */
    public void removeRuntimeAttributes(final Attribute[] attributes) {
        Streams.of(attributes).forEach(this::removeAttribute);
    }

    /**
     * Sets the argument name at the specified index.
     *
     * @param i The argument index.
     * @param name The argument name.
     */
    public void setArgumentName(final int i, final String name) {
        argNames[i] = name;
    }

    /**
     * Sets all argument names.
     *
     * @param argNames The argument names.
     */
    public void setArgumentNames(final String[] argNames) {
        this.argNames = ArrayUtils.nullToEmpty(argNames);
    }

    /**
     * Sets the argument type at the specified index.
     *
     * @param i The argument index.
     * @param type The argument type.
     */
    public void setArgumentType(final int i, final Type type) {
        argTypes[i] = type;
    }

    /**
     * Sets all argument types.
     *
     * @param argTypes The argument types.
     */
    public void setArgumentTypes(final Type[] argTypes) {
        this.argTypes = argTypes != null ? argTypes : Type.NO_ARGS;
    }

    /**
     * Sets the class name.
     *
     * @param className The class name.
     */
    public void setClassName(final String className) { // TODO could be package-protected?
        this.className = className;
    }

    /**
     * Sets the header layout of generated Code attributes.
     *
     * <p>
     * Compact headers encode {@code max_stack}, {@code max_locals}, and {@code code_length} as unsigned one-, one-, and two-byte fields, respectively,
     * totaling 4 bytes instead of the standard 8. This changes only these field widths, not the bytecode or the remaining attribute layout.
     * Compact headers are intended for historical class file versions 45.0 through 45.2.
     * </p>
     *
     * <p>
     * Newly created methods use standard headers by default. Methods initialized from an existing method preserve its header layout.
     * {@link #getMethod()} checks that compact headers have {@code max_stack} and {@code max_locals} from 0 through 255 and a code length
     * of at most 65535 bytes.
     * </p>
     *
     * <p>
     * When dumping the enclosing class, {@link org.apache.bcel.classfile.JavaClass#dump(java.io.DataOutputStream)} may select a different layout
     * for consistency with the class version and its other methods. This does not change the generated Code attribute's header setting.
     * </p>
     *
     * @param compactCodeHeader Whether to generate compact four-byte Code headers ({@code true}) or standard eight-byte headers ({@code false}).
     * @since 6.14.0
     * @see Code#setCompactCodeHeader(boolean)
     */
    public void setCompactCodeHeader(final boolean compactCodeHeader) {
        this.compactCodeHeader = compactCodeHeader;
    }

    /**
     * Sets the instruction list.
     *
     * @param il The instruction list.
     */
    public void setInstructionList(final InstructionList il) { // TODO could be package-protected?
        this.il = il;
    }

    /**
     * Sets the maximum number of local variables by examining the method signature, the instructions and the local
     * variable table entries added via {@link #addLocalVariable}.
     */
    public void setMaxLocals() { // TODO could be package-protected? (some tests would need repackaging)
        if (il != null) {
            int max = isStatic() ? 0 : 1;
            for (final Type argType : argTypes) {
                max += argType.getSize();
            }
            for (InstructionHandle ih = il.getStart(); ih != null; ih = ih.getNext()) {
                final Instruction ins = ih.getInstruction();
                if (ins instanceof LocalVariableInstruction || ins instanceof RET || ins instanceof IINC) {
                    final int index = ((IndexedInstruction) ins).getIndex() + ((TypedInstruction) ins).getType(super.getConstantPool()).getSize();
                    if (index > max) {
                        max = index;
                    }
                }
            }
            // Local variables may be registered (for example, copied from an existing LocalVariableTable) without
            // being referenced by any instruction, for example unused variables emitted by some compilers. Account for
            // those too, so a later call does not shrink maxLocals below what those entries require.
            for (final LocalVariableGen lv : variableList) {
                final int index = lv.getIndex() + lv.getType().getSize();
                if (index > max) {
                    max = index;
                }
            }
            maxLocals = max;
        } else {
            maxLocals = 0;
        }
    }

    /**
     * Sets maximum number of local variables.
     *
     * @param m The maximum number of local variables.
     */
    public void setMaxLocals(final int m) {
        maxLocals = m;
    }

    /**
     * Sets the maximum stack size by performing control flow analysis.
     */
    public void setMaxStack() { // TODO could be package-protected? (some tests would need repackaging)
        if (il != null) {
            maxStack = getMaxStack(super.getConstantPool(), il, getExceptionHandlers());
        } else {
            maxStack = 0;
        }
    }

    /**
     * Sets maximum stack size for this method.
     *
     * @param m The maximum stack size.
     */
    public void setMaxStack(final int m) { // TODO could be package-protected?
        maxStack = m;
    }

    /**
     * Sets the return type.
     *
     * @param returnType The return type.
     */
    public void setReturnType(final Type returnType) {
        setType(returnType);
    }

    /**
     * Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O.
     *
     * @param flag whether to strip attributes.
     */
    public void stripAttributes(final boolean flag) {
        stripAttributes = flag;
    }

    /**
     * Return string representation close to declaration format, 'public static void main(String[]) throws IOException',
     * for example.
     *
     * @return String representation of the method.
     */
    @Override
    public final String toString() {
        final String access = Utility.accessToString(super.getAccessFlags());
        String signature = Type.getMethodSignature(super.getType(), argTypes);
        signature = Utility.methodSignatureToString(signature, super.getName(), access, true, getLocalVariableTable(super.getConstantPool()));
        final StringBuilder buf = new StringBuilder(signature);
        for (final Attribute a : getAttributes()) {
            if (!(a instanceof Code || a instanceof ExceptionTable)) {
                buf.append(" [").append(a).append("]");
            }
        }

        if (!throwsList.isEmpty()) {
            for (final String throwsDescriptor : throwsList) {
                buf.append("\n\t\tthrows ").append(throwsDescriptor);
            }
        }
        return buf.toString();
    }

    /**
     * Call notify() method on all observers. This method is not called automatically whenever the state has changed, but
     * has to be called by the user after they have finished editing the object.
     */
    public void update() {
        if (observers != null) {
            for (final MethodObserver observer : observers) {
                observer.notify(this);
            }
        }
    }

    private void updateLocalVariableTable(final LocalVariableTable a) {
        removeLocalVariables();
        for (final LocalVariable l : a.getLocalVariableTable()) {
            InstructionHandle start = il.findHandle(l.getStartPC());
            final InstructionHandle end = il.findHandle(l.getStartPC() + l.getLength());
            // Repair malformed handles
            if (start == null) {
                start = il.getStart();
            }
            // end == null => live to end of method
            // Since we are recreating the LocalVaraible, we must
            // propagate the orig_index to new copy.
            addLocalVariable(l.getName(), Type.getType(l.getSignature()), l.getIndex(), start, end, l.getOrigIndex());
        }
    }
}