/***** BEGIN LICENSE BLOCK *****
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 * The contents of this file are subject to the Common Public
 * License Version 1.0 (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/cpl-v10.html
 *
 * Software distributed under the License is distributed on an "AS
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 * Copyright (C) 2008 JRuby project
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package org.jruby.ext.ffi;

import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import org.jruby.Ruby;
import org.jruby.RubyClass;
import org.jruby.RubyModule;
import org.jruby.anno.JRubyClass;
import org.jruby.anno.JRubyMethod;
import org.jruby.internal.runtime.methods.DynamicMethod;
import org.jruby.runtime.Arity;
import org.jruby.runtime.ObjectAllocator;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.builtin.IRubyObject;

/**
 * A native function invoker
 */
@JRubyClass(name = "FFI::" + AbstractInvoker.CLASS_NAME, parent = "Object")
public abstract class AbstractInvoker extends Pointer {
    static final String CLASS_NAME = "AbstractInvoker";

    /**
     * Reference map to keep libraries open for as long as there is a method mapped
     * to that library.
     */
    private static final Map<DynamicMethod, AbstractInvoker> refmap
            = Collections.synchronizedMap(new WeakHashMap<DynamicMethod, AbstractInvoker>());
    
    /**
     * The arity of this function.
     */
    protected final Arity arity;
    
    public static RubyClass createAbstractInvokerClass(Ruby runtime, RubyModule module) {
        RubyClass result = module.defineClassUnder(CLASS_NAME,
                module.getClass("Pointer"),
                ObjectAllocator.NOT_ALLOCATABLE_ALLOCATOR);
        result.defineAnnotatedMethods(AbstractInvoker.class);
        result.defineAnnotatedConstants(AbstractInvoker.class);

        return result;
    }
    
    /**
     * Creates a new <tt>AbstractInvoker</tt> instance.
     * @param arity
     */
    protected AbstractInvoker(Ruby runtime, RubyClass klass, int arity, DirectMemoryIO io) {
        super(runtime, klass, io, 0);
        this.arity = Arity.fixed(arity);
    }

    /**
     * Attaches this function to a ruby module or class.
     * 
     * @param module The module or class to attach the function to.
     * @param methodName The ruby name to attach the function as.
     */
    @JRubyMethod(name="attach")
    public IRubyObject attach(ThreadContext context, IRubyObject obj, IRubyObject methodName) {
        
        DynamicMethod m = createDynamicMethod(obj.getSingletonClass());
        obj.getSingletonClass().addMethod(methodName.asJavaString(), m);
        if (obj instanceof RubyModule) {
            ((RubyModule) obj).addMethod(methodName.asJavaString(), m);
        }
        refmap.put(m, this);
        
        return this;
    }
    protected abstract DynamicMethod createDynamicMethod(RubyModule module);

    /**
     * Returns the {@link org.jruby.runtime.Arity} of this function.
     * 
     * @return The <tt>Arity</tt> of the native function.
     */
    public final Arity getArity() {
        return arity;
    }
}
