/**

 * 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.bck2brwsr.vmtest;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStream;

import java.lang.reflect.Method;

import java.net.URL;

import java.util.Enumeration;

import java.util.Map;

import java.util.WeakHashMap;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import org.apidesign.vm4brwsr.Bck2Brwsr;

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 VMTest}.{@link #create(YourClass.class);

 * }</pre>

 *

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

 */

public final class VMTest implements ITest {

    private final Run first, second;

    private final Method m;

    private VMTest(Method m, Run first, Run second) {

        this.first = first;

        this.second = second;

        this.m = m;

    }

    /** Inspects <code>clazz</code> and for each {@lik Compare} method creates

     * instances of tests. Each insteance runs the test in different virtual

     * machine and at the end they compare the results.

     * 

     * @param clazz the class to inspect

     * @return the set of created tests

     */

    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 Run real = new Run(m, false);

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

            ret[cnt++] = real;

            ret[cnt++] = js;

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

        }

        Object[] r = new Object[cnt];

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

            r[i] = ret[i];

        }

        return r;

    }

    /** Test that compares the previous results.

     * @throws Throwable 

     */

    @Test(dependsOnGroups = "run") public void compareResults() throws Throwable {

        Object v1 = first.value;

        Object v2 = second.value;

        if (v1 instanceof Number) {

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

        }

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

    }

    /** Test name.

     * @return name of the tested method followed by a suffix

     */

    @Override

    public String getTestName() {

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

    }

    /** Helper method that inspects the classpath and loads given resource

     * (usually a class file). Used while running tests in Rhino.

     * 

     * @param name resource name to find

     * @return the array of bytes in the given resource

     * @throws IOException I/O in case something goes wrong

     */

    public static byte[] read(String name) throws IOException {

        URL u = null;

        Enumeration<URL> en = VMTest.class.getClassLoader().getResources(name);

        while (en.hasMoreElements()) {

            u = en.nextElement();

        }

        if (u == null) {

            throw new IOException("Can't find " + name);

        }

        try (InputStream is = u.openStream()) {

            byte[] arr;

            arr = new byte[is.available()];

            int offset = 0;

            while (offset < arr.length) {

                int len = is.read(arr, offset, arr.length - offset);

                if (len == -1) {

                    throw new IOException("Can't read " + name);

                }

                offset += len;

            }

            return arr;

        }

    }

    public static final class Run implements ITest {

        private final Method m;

        private final boolean js;

        Object value;

        private Invocable code;

        private CharSequence codeSeq;

        private static final Map<Class,Object[]> compiled = new WeakHashMap<Class,Object[]>();

        private Run(Method m, boolean js) {

            this.m = m;

            this.js = js;

        }

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

            final Object[] data = compiled.get(clazz);

            if (data != null) {

                code = (Invocable) data[0];

                codeSeq = (CharSequence) data[1];

                return;

            }

            StringBuilder sb = new StringBuilder();

            Bck2Brwsr.generate(sb, VMTest.class.getClassLoader());

            ScriptEngineManager sem = new ScriptEngineManager();

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

            sb.append("\nfunction initVM() {"

                + "\n  return bck2brwsr("

                + "\n    function(name) { return org.apidesign.bck2brwsr.vmtest.VMTest.read(name);}"

                + "\n  );"

                + "\n};");

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

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

            code = (Invocable) js;

            codeSeq = sb;

            compiled.put(clazz, new Object[] { code, codeSeq });

        }

        @Test(groups = "run") public void executeCode() throws Throwable {

            if (js) {

                try {

                    compileTheCode(m.getDeclaringClass());

                    Object vm = code.invokeFunction("initVM");

                    Object inst = code.invokeMethod(vm, "loadClass", m.getDeclaringClass().getName());

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

                } catch (Exception ex) {

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

                }

            } else {

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

            }

        }

        @Override

        public String getTestName() {

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

        }

        private static String computeSignature(Method m) {

            StringBuilder sb = new StringBuilder();

            appendType(sb, m.getReturnType());

            for (Class<?> c : m.getParameterTypes()) {

                appendType(sb, c);

            }

            return sb.toString();

        }

        private static void appendType(StringBuilder sb, Class<?> t) {

            if (t == null) {

                sb.append('V');

                return;

            }

            if (t.isPrimitive()) {

                int ch = -1;

                if (t == int.class) {

                    ch = 'I';

                }

                if (t == short.class) {

                    ch = 'S';

                }

                if (t == byte.class) {

                    ch = 'B';

                }

                if (t == boolean.class) {

                    ch = 'Z';

                }

                if (t == long.class) {

                    ch = 'J';

                }

                if (t == float.class) {

                    ch = 'F';

                }

                if (t == double.class) {

                    ch = 'D';

                }

                assert ch != -1 : "Unknown primitive type " + t;

                sb.append((char)ch);

                return;

            }

            if (t.isArray()) {

                sb.append("_3");

                appendType(sb, t.getComponentType());

                return;

            }

            sb.append('L');

            sb.append(t.getName().replace('.', '_'));

            sb.append("_2");

        }

    }

    static StringBuilder dumpJS(CharSequence sb) throws IOException {

        File f = File.createTempFile("execution", ".js");

        FileWriter w = new FileWriter(f);

        w.append(sb);

        w.close();

        return new StringBuilder(f.getPath());

    }

}