/**

 * Back 2 Browser Bytecode Translator

 * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, version 2 of the License.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. Look for COPYING file in the top folder.

 * If not, see http://opensource.org/licenses/GPL-2.0.

 */

package org.apidesign.vm4brwsr;

import java.lang.reflect.Method;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import org.testng.Assert;

import org.testng.ITest;

import org.testng.annotations.Factory;

import org.testng.annotations.Test;

/** A TestNG {@link Factory} that seeks for {@link Compare} annotations

 * in provided class and builds set of tests that compare the computations

 * in real as well as JavaScript virtual machines. Use as:<pre>

 * {@code @}{@link Factory} public static create() {

 *   return @{link CompareVMs}.{@link #create(YourClass.class);

 * }</pre>

 *

 * @author Jaroslav Tulach <jtulach@netbeans.org>

 */

public final class CompareVMs implements ITest {

    private final Method m;

    private final boolean js;

    private final CompareVMs first, second;

    private Object value;

    private static Invocable code;

    private static CharSequence codeSeq;

    private CompareVMs(Method m, boolean js) {

        this.m = m;

        this.js = js;

        this.first = null;

        this.second = null;

    }

    private CompareVMs(Method m, CompareVMs first, CompareVMs second) {

        this.first = first;

        this.second = second;

        this.m = m;

        this.js = false;

    }

    private static void compileTheCode(Class<?> clazz) throws Exception {

        if (code != null) {

            return;

        }

        StringBuilder sb = new StringBuilder();

        class SkipMe extends GenJS {

            public SkipMe(Appendable out) {

                super(out);

            }

            @Override

            protected boolean requireReference(String cn) {

                if (cn.contains("CompareVMs")) {

                    return true;

                }

                return super.requireReference(cn);

            }

        }

        SkipMe sm = new SkipMe(sb);

        sm.doCompile(CompareVMs.class.getClassLoader(), StringArray.asList(

            clazz.getName().replace('.', '/')

        ));

        ScriptEngineManager sem = new ScriptEngineManager();

        ScriptEngine js = sem.getEngineByExtension("js");

        Object res = js.eval(sb.toString());

        Assert.assertTrue(js instanceof Invocable, "It is invocable object: " + res);

        code = (Invocable)js;

        codeSeq = sb;

    }

    public static Object[] create(Class<?> clazz) {

        Method[] arr = clazz.getMethods();

        Object[] ret = new Object[3 * arr.length];

        int cnt = 0;

        for (Method m : arr) {

            Compare c = m.getAnnotation(Compare.class);

            if (c == null) {

                continue;

            }

            final CompareVMs real = new CompareVMs(m, false);

            final CompareVMs js = new CompareVMs(m, true);

            ret[cnt++] = real;

            ret[cnt++] = js;

            ret[cnt++] = new CompareVMs(m, real, js);

        }

        Object[] r = new Object[cnt];

        for (int i = 0; i < cnt; i++) {

            r[i] = ret[i];

        }

        return r;

    }

    @Test public void runTest() throws Throwable {

        if (first != null) {

            Object v1 = first.value;

            Object v2 = second.value;

            if (v1 instanceof Number) {

                v1 = ((Number)v1).doubleValue();

            }

            Assert.assertEquals(v1, v2, "Comparing results");

        } else {

            if (js) {

                try {

                    compileTheCode(m.getDeclaringClass());

                    Object inst = code.invokeFunction(m.getDeclaringClass().getName().replace('.', '_'), false);

                    value = code.invokeMethod(inst, m.getName() + "__I");

                } catch (Exception ex) {

                    throw new AssertionError(StaticMethodTest.dumpJS(codeSeq)).initCause(ex);

                }

            } else {

                value = m.invoke(m.getDeclaringClass().newInstance());

            }

        }

    }

    @Override

    public String getTestName() {

        if (first != null) {

            return m.getName() + "[Compare]";

        }

        return m.getName() + (js ? "[JavaScript]" : "[Java]");

    }

}