/***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * 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 http://www.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2002 Anders Bengtsson <ndrsbngtssn@yahoo.se>
 * Copyright (C) 2002-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2004-2005 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
 * 
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package org.jruby.internal.runtime.methods;

import org.jruby.RubyModule;
import org.jruby.internal.runtime.AbstractIRMethod;
import org.jruby.ir.IRFlags;
import org.jruby.ir.IRMethod;
import org.jruby.ir.IRScope;
import org.jruby.runtime.Arity;
import org.jruby.runtime.Block;
import org.jruby.runtime.Helpers;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.runtime.callsite.CacheEntry;

/**
 * Represents a method which has been aliased.
 *
 * Aliased methods pass as frame class the implementationClass they were created with, which should reflect
 * the level in the related class hierarchy where the alias appears. This allows aliased methods that super to do
 * so from the appropriate starting level.
 */
public class AliasMethod extends DynamicMethod {
    private final CacheEntry entry;
    private final boolean findImplementer;

    /**
     * For some java native methods it is convenient to pass in a String instead
     * of a ByteList.
     */ 
    public AliasMethod(RubyModule implementationClass, CacheEntry entry, String oldName) {
        super(implementationClass, entry.method.getVisibility(), oldName);

        this.entry = entry;

        boolean findImplementer = true;

        // This logic is an attempt to reduce the number of cases that must do an implementer search,
        // since it is only needed for super calls (and possibly other features that require the caller's
        // frame class to be available).
        // TODO: general support for DynamicMethod.needsClass etc, so we can easily make this determination.
        if (entry.method instanceof AbstractIRMethod) {
            AbstractIRMethod irMethod = (AbstractIRMethod) entry.method;

            // Ensure scope is ready for flags
            irMethod.ensureInstrsReady();

            IRScope irScope = irMethod.getIRScope();
            if (irScope instanceof IRMethod
                    && !irScope.getFlags().contains(IRFlags.REQUIRES_CLASS)) {
                findImplementer = false;
            }
        }

        this.findImplementer = findImplementer;
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg1, IRubyObject arg2) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg1, arg2);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg1, IRubyObject arg2, IRubyObject arg3) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg1, arg2, arg3);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject[] args) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, args);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, Block block) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, block);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg1, Block block) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg1, block);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg1, IRubyObject arg2, Block block) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg1, arg2, block);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject arg1, IRubyObject arg2, IRubyObject arg3, Block block) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, arg1, arg2, arg3, block);
    }

    @Override
    public IRubyObject call(ThreadContext context, IRubyObject self, RubyModule klazz, String unused, IRubyObject[] args, Block block) {
        return entry.method.call(context, self, calculateSourceModule(self, klazz), name, args, block);
    }

    public DynamicMethod dup() {
        return new AliasMethod(implementationClass, entry, name);
    }

    @Override
    public Arity getArity(){
        return entry.method.getArity();
    }

    public String getOldName() {
        return entry.method.getName();
    }
    
    @Override
    public DynamicMethod getRealMethod() {
        return entry.method.getRealMethod();
    }

    @Override
    public long getSerialNumber() {
        return entry.method.getSerialNumber();
    }

    // MRI: vm_call0_body and aliased_callable_method_entry
    /* FIXME: This is not quite right. It appears that MRI does this logic at call time, but I believe
              the calculated class is cached somewhere along with the "callable" method entry. The code
              below means all aliases in modules will do the implementer search, unless we can detect
              that the related method does not need "super". We can improve this at cache time in either
              CacheEntry logic or CallSite logic.
     */
    private RubyModule calculateSourceModule(IRubyObject self, RubyModule incomingSourceModule) {
        if (entry.method.definedClass != null) return definedClass;

        if (findImplementer) {
            return Helpers.findImplementerIfNecessary(self.getMetaClass(), entry.method.getImplementationClass());
        } else {
            return incomingSourceModule;
        }
    }

}
