/**

 * 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.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

import java.util.Enumeration;

import javax.script.Invocable;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineManager;

import javax.script.ScriptException;

import static org.testng.Assert.*;

final class TestVM {

    private final Invocable code;

    private final CharSequence codeSeq;

    private final Object bck2brwsr;

    private TestVM(Invocable code, CharSequence codeSeq) throws ScriptException, NoSuchMethodException {

        this.code = code;

        this.codeSeq = codeSeq;

        this.bck2brwsr = code.invokeFunction("bck2brwsr");

    }

    public Object execCode(

        String msg, Class<?> clazz, String method, 

        Object expRes, Object... args

    ) throws Exception {

        Object ret = null;

        try {

            ret = code.invokeMethod(bck2brwsr, "loadClass", clazz.getName());

            ret = code.invokeMethod(ret, method, args);

        } catch (ScriptException ex) {

            fail("Execution failed in " + dumpJS(codeSeq), ex);

        } catch (NoSuchMethodException ex) {

            fail("Cannot find method in " + dumpJS(codeSeq), ex);

        }

        if (ret == null && expRes == null) {

            return null;

        }

        if (expRes.equals(ret)) {

            return null;

        }

        if (expRes instanceof Number) {

            // in case of Long it is necessary convert it to number

            // since the Long is represented by two numbers in JavaScript

            try {

                ret = code.invokeMethod(ret, "toFP");

                ret = code.invokeFunction("Number", ret);

            } catch (ScriptException ex) {

                fail("Conversion to number failed in " + dumpJS(codeSeq), ex);

            } catch (NoSuchMethodException ex) {

                fail("Cannot find global Number(x) function in " + dumpJS(codeSeq), ex);

            }

        }

        return ret;

    }

    void assertExec(

        String msg, Class clazz, String method, Object expRes, Object... args

    ) throws Exception {

        Object ret = execCode(msg, clazz, method, expRes, args);

        if (ret == null) {

            return;

        }

        if (expRes != null && expRes.equals(ret)) {

            return;

        }

        assertEquals(ret, expRes, msg + "was: " + ret + "\n" + dumpJS(codeSeq));

    }    

    static TestVM compileClass(String... names) throws ScriptException, IOException {

        return compileClass(null, names);

    }

    static TestVM compileClass(StringBuilder sb, String... names) throws ScriptException, IOException {

        return compileClass(sb, null, names);

    }

    static TestVM compileClass(StringBuilder sb, ScriptEngine[] eng, String... names) throws ScriptException, IOException {

        if (sb == null) {

            sb = new StringBuilder();

        }

        Bck2Brwsr.generate(sb, new EmulationResources(), names);

        ScriptEngineManager sem = new ScriptEngineManager();

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

        if (eng != null) {

            eng[0] = js;

        }

        try {

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

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

            return new TestVM((Invocable) js, sb);

        } catch (Exception ex) {

            if (sb.length() > 2000) {

                sb = dumpJS(sb);

            }

            fail("Could not evaluate:\n" + sb, ex);

            return null;

        }

    }

    Object loadClass(String loadClass, String name) throws ScriptException, NoSuchMethodException {

        return code.invokeMethod(bck2brwsr, "loadClass", Exceptions.class.getName());

    }

    Object invokeMethod(Object obj, String method, Object... params) throws ScriptException, NoSuchMethodException {

        return code.invokeMethod(obj, method, params);

    }

    Object invokeFunction(String methodName, Object... args) throws ScriptException, NoSuchMethodException {

        return code.invokeFunction(methodName, args);

    }

    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());

    }

    @Override

    public String toString() {

        try {

            return dumpJS(codeSeq).toString();

        } catch (IOException ex) {

            return ex.toString();

        }

    }

    private static class EmulationResources implements Bck2Brwsr.Resources {

        @Override

        public InputStream get(String name) throws IOException {

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

            URL u = null;

            while (en.hasMoreElements()) {

                u = en.nextElement();

            }

            if (u == null) {

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

            }

            if (u.toExternalForm().contains("rt.jar!")) {

                throw new IOException("No emulation for " + u);

            }

            return u.openStream();

        }

    }

}