/**

 * HTML via Java(tm) Language Bindings

 * Copyright (C) 2013 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. apidesign.org

 * designates this particular file as subject to the

 * "Classpath" exception as provided by apidesign.org

 * in the License file that accompanied this code.

 *

 * 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://wiki.apidesign.org/wiki/GPLwithClassPathException

 */

package org.apidesign.html.boot.impl;

import java.io.Closeable;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.Reader;

import java.net.URL;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Enumeration;

import java.util.List;

import java.util.Map;

import java.util.concurrent.Callable;

import org.apidesign.html.boot.spi.Fn;

import org.objectweb.asm.AnnotationVisitor;

import org.objectweb.asm.ClassReader;

import org.objectweb.asm.ClassVisitor;

import org.objectweb.asm.ClassWriter;

import org.objectweb.asm.Label;

import org.objectweb.asm.MethodVisitor;

import org.objectweb.asm.Opcodes;

import org.objectweb.asm.Type;

import org.objectweb.asm.signature.SignatureReader;

import org.objectweb.asm.signature.SignatureVisitor;

import org.objectweb.asm.signature.SignatureWriter;

/**

 *

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

 */

public final class FnUtils implements Fn.Presenter {

    private FnUtils() {

    }

    /** Seeks for {@link JavaScriptBody} and {@link JavaScriptResource} annotations

     * in the bytecode and converts them into real code. Used by Maven plugin

     * postprocessing classes.

     * 

     * @param bytecode the original bytecode with javascript specific annotations

     * @param resources the resources to load

     * @return the transformed bytecode

     * @since 0.7

     */

    public static byte[] transform(byte[] bytecode, Map<String,InputStream> resources) {

        return transform(null, bytecode);

    }

    public static boolean isJavaScriptCapable(ClassLoader l) {

        if (l instanceof JsClassLoader) {

            return true;

        }

        Class<?> clazz;

        try (Closeable c = Fn.activate(new FnUtils())) {

            clazz = Class.forName(Test.class.getName(), true, l);

            final Object is = ((Callable<?>)clazz.newInstance()).call();

            return Boolean.TRUE.equals(is);

        } catch (Exception ex) {

            return false;

        }

    }

    public static boolean isValid(Fn fn) {

        return fn != null && fn.isValid();

    }

    public static ClassLoader newLoader(final FindResources f, final Fn.Presenter d, ClassLoader parent) {

        return new JsClassLoader(parent) {

            @Override

            protected URL findResource(String name) {

                List<URL> l = res(name, true);

                return l.isEmpty() ? null : l.get(0);

            }

            @Override

            protected Enumeration<URL> findResources(String name) {

                return Collections.enumeration(res(name, false));

            }

            private List<URL> res(String name, boolean oneIsEnough) {

                List<URL> l = new ArrayList<URL>();

                f.findResources(name, l, oneIsEnough);

                return l;

            }

            @Override

            protected Fn defineFn(String code, String... names) {

                return d.defineFn(code, names);

            }

            @Override

            protected void loadScript(Reader code) throws Exception {

                d.loadScript(code);

            }

        };

    }

    static String callback(final String body) {

        return new JsCallback() {

            @Override

            protected CharSequence callMethod(

                String ident, String fqn, String method, String params

            ) {

                StringBuilder sb = new StringBuilder();

                sb.append("vm.").append(mangle(fqn, method, params));

                sb.append("(");

                if (ident != null) {

                    sb.append(ident);

                }

                return sb;

            }

        }.parse(body);

    }

    static void loadScript(ClassLoader jcl, String resource) {

        final InputStream script = jcl.getResourceAsStream(resource);

        if (script == null) {

            throw new NullPointerException("Can't find " + resource);

        }

        try {

            Reader isr = null;

            try {

                isr = new InputStreamReader(script, "UTF-8");

                FnContext.currentPresenter().loadScript(isr);

            } finally {

                if (isr != null) {

                    isr.close();

                }

            }

        } catch (Exception ex) {

            throw new IllegalStateException("Can't execute " + resource, ex);

        } 

    }

    @Override

    public Fn defineFn(String code, String... names) {

        return new TrueFn();

    }

    @Override

    public void displayPage(URL page, Runnable onPageLoad) {

    }

    @Override

    public void loadScript(Reader code) throws Exception {

    }

    private static final class FindInClass extends ClassVisitor {

        private String name;

        private int found;

        private ClassLoader loader;

        public FindInClass(ClassLoader l, ClassVisitor cv) {

            super(Opcodes.ASM4, cv);

            this.loader = l;

        }

        @Override

        public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {

            this.name = name;

            super.visit(version, access, name, signature, superName, interfaces);

        }

        @Override

        public AnnotationVisitor visitAnnotation(String desc, boolean visible) {

            if ("Lnet/java/html/js/JavaScriptResource;".equals(desc)) {

                return new LoadResource();

            }

            return super.visitAnnotation(desc, visible);

        }

        @Override

        public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {

            return new FindInMethod(access, name, desc,

                    super.visitMethod(access & (~Opcodes.ACC_NATIVE), name, desc, signature, exceptions)

            );

        }

        private final class FindInMethod extends MethodVisitor {

            private final String name;

            private final String desc;

            private final int access;

            private List<String> args;

            private String body;

            private boolean bodyGenerated;

            public FindInMethod(int access, String name, String desc, MethodVisitor mv) {

                super(Opcodes.ASM4, mv);

                this.access = access;

                this.name = name;

                this.desc = desc;

            }

            @Override

            public AnnotationVisitor visitAnnotation(String desc, boolean visible) {

                if ("Lnet/java/html/js/JavaScriptBody;".equals(desc) // NOI18N

                        || "Lorg/apidesign/bck2brwsr/core/JavaScriptBody;".equals(desc) // NOI18N

                        ) {

                    found++;

                    return new FindInAnno();

                }

                return super.visitAnnotation(desc, visible);

            }

            private void generateJSBody(List<String> args, String body) {

                this.args = args;

                this.body = body;

            }

            @Override

            public void visitCode() {

                if (body == null) {

                    return;

                }

                generateBody();

            }

            private boolean generateBody() {

                if (bodyGenerated) {

                    return false;

                }

                bodyGenerated = true;

                super.visitFieldInsn(

                        Opcodes.GETSTATIC, FindInClass.this.name,

                        "$$fn$$" + name + "_" + found,

                        "Lorg/apidesign/html/boot/spi/Fn;"

                );

                super.visitInsn(Opcodes.DUP);

                super.visitMethodInsn(

                        Opcodes.INVOKESTATIC,

                        "org/apidesign/html/boot/spi/Fn", "isValid",

                        "(Lorg/apidesign/html/boot/spi/Fn;)Z"

                );

                Label ifNotNull = new Label();

                super.visitJumpInsn(Opcodes.IFNE, ifNotNull);

                // init Fn

                super.visitInsn(Opcodes.POP);

                super.visitLdcInsn(Type.getObjectType(FindInClass.this.name));

                super.visitLdcInsn(body);

                super.visitIntInsn(Opcodes.SIPUSH, args.size());

                super.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/String");

                boolean needsVM = false;

                for (int i = 0; i < args.size(); i++) {

                    assert !needsVM;

                    String argName = args.get(i);

                    needsVM = "vm".equals(argName);

                    super.visitInsn(Opcodes.DUP);

                    super.visitIntInsn(Opcodes.BIPUSH, i);

                    super.visitLdcInsn(argName);

                    super.visitInsn(Opcodes.AASTORE);

                }

                super.visitMethodInsn(Opcodes.INVOKESTATIC,

                        "org/apidesign/html/boot/spi/Fn", "define",

                        "(Ljava/lang/Class;Ljava/lang/String;[Ljava/lang/String;)Lorg/apidesign/html/boot/spi/Fn;"

                );

                super.visitInsn(Opcodes.DUP);

                super.visitFieldInsn(

                        Opcodes.PUTSTATIC, FindInClass.this.name,

                        "$$fn$$" + name + "_" + found,

                        "Lorg/apidesign/html/boot/spi/Fn;"

                );

                // end of Fn init

                super.visitLabel(ifNotNull);

                final int offset;

                if ((access & Opcodes.ACC_STATIC) == 0) {

                    offset = 1;

                    super.visitIntInsn(Opcodes.ALOAD, 0);

                } else {

                    offset = 0;

                    super.visitInsn(Opcodes.ACONST_NULL);

                }

                super.visitIntInsn(Opcodes.SIPUSH, args.size());

                super.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");

                class SV extends SignatureVisitor {

                    private boolean nowReturn;

                    private Type returnType;

                    private int index;

                    private int loadIndex = offset;

                    public SV() {

                        super(Opcodes.ASM4);

                    }

                    @Override

                    public void visitBaseType(char descriptor) {

                        final Type t = Type.getType("" + descriptor);

                        if (nowReturn) {

                            returnType = t;

                            return;

                        }

                        FindInMethod.super.visitInsn(Opcodes.DUP);

                        FindInMethod.super.visitIntInsn(Opcodes.SIPUSH, index++);

                        FindInMethod.super.visitVarInsn(t.getOpcode(Opcodes.ILOAD), loadIndex++);

                        String factory;

                        switch (descriptor) {

                            case 'I':

                                factory = "java/lang/Integer";

                                break;

                            case 'J':

                                factory = "java/lang/Long";

                                loadIndex++;

                                break;

                            case 'S':

                                factory = "java/lang/Short";

                                break;

                            case 'F':

                                factory = "java/lang/Float";

                                break;

                            case 'D':

                                factory = "java/lang/Double";

                                loadIndex++;

                                break;

                            case 'Z':

                                factory = "java/lang/Boolean";

                                break;

                            case 'C':

                                factory = "java/lang/Character";

                                break;

                            case 'B':

                                factory = "java/lang/Byte";

                                break;

                            default:

                                throw new IllegalStateException(t.toString());

                        }

                        FindInMethod.super.visitMethodInsn(Opcodes.INVOKESTATIC,

                                factory, "valueOf", "(" + descriptor + ")L" + factory + ";"

                        );

                        FindInMethod.super.visitInsn(Opcodes.AASTORE);

                    }

                    @Override

                    public SignatureVisitor visitArrayType() {

                        if (nowReturn) {

                            throw new IllegalStateException("Not supported yet");

                        }

                        loadObject();

                        return new SignatureWriter();

                    }

                    @Override

                    public void visitClassType(String name) {

                        if (nowReturn) {

                            returnType = Type.getObjectType(name);

                            return;

                        }

                        loadObject();

                    }

                    @Override

                    public SignatureVisitor visitReturnType() {

                        nowReturn = true;

                        return this;

                    }

                    private void loadObject() {

                        FindInMethod.super.visitInsn(Opcodes.DUP);

                        FindInMethod.super.visitIntInsn(Opcodes.SIPUSH, index++);

                        FindInMethod.super.visitVarInsn(Opcodes.ALOAD, loadIndex++);

                        FindInMethod.super.visitInsn(Opcodes.AASTORE);

                    }

                }

                SV sv = new SV();

                SignatureReader sr = new SignatureReader(desc);

                sr.accept(sv);

                if (needsVM) {

                    FindInMethod.super.visitInsn(Opcodes.DUP);

                    FindInMethod.super.visitIntInsn(Opcodes.SIPUSH, sv.index);

                    int lastSlash = FindInClass.this.name.lastIndexOf('/');

                    String jsCallbacks = FindInClass.this.name.substring(0, lastSlash + 1) + "$JsCallbacks$";

                    FindInMethod.super.visitFieldInsn(Opcodes.GETSTATIC, jsCallbacks, "VM", "L" + jsCallbacks + ";");

                    FindInMethod.super.visitMethodInsn(Opcodes.INVOKEVIRTUAL, jsCallbacks, "current", "()L" + jsCallbacks + ";");

                    FindInMethod.super.visitInsn(Opcodes.AASTORE);

                }

                super.visitMethodInsn(Opcodes.INVOKEVIRTUAL,

                        "org/apidesign/html/boot/spi/Fn", "invoke", "(Ljava/lang/Object;[Ljava/lang/Object;)Ljava/lang/Object;"

                );

                switch (sv.returnType.getSort()) {

                    case Type.VOID:

                        super.visitInsn(Opcodes.RETURN);

                        break;

                    case Type.ARRAY:

                    case Type.OBJECT:

                        super.visitTypeInsn(Opcodes.CHECKCAST, sv.returnType.getInternalName());

                        super.visitInsn(Opcodes.ARETURN);

                        break;

                    case Type.BOOLEAN:

                        super.visitTypeInsn(Opcodes.CHECKCAST, "java/lang/Boolean");

                        super.visitMethodInsn(Opcodes.INVOKEVIRTUAL,

                                "java/lang/Boolean", "booleanValue", "()Z"

                        );

                        super.visitInsn(Opcodes.IRETURN);

                        break;

                    default:

                        super.visitTypeInsn(Opcodes.CHECKCAST, "java/lang/Number");

                        super.visitMethodInsn(Opcodes.INVOKEVIRTUAL,

                                "java/lang/Number", sv.returnType.getClassName() + "Value", "()" + sv.returnType.getDescriptor()

                        );

                        super.visitInsn(sv.returnType.getOpcode(Opcodes.IRETURN));

                }

                return true;

            }

            @Override

            public void visitEnd() {

                super.visitEnd();

                if (body != null) {

                    if (generateBody()) {

                        // native method

                        super.visitMaxs(1, 0);

                    }

                    FindInClass.this.visitField(

                            Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC,

                            "$$fn$$" + name + "_" + found,

                            "Lorg/apidesign/html/boot/spi/Fn;",

                            null, null

                    );

                }

            }

            private final class FindInAnno extends AnnotationVisitor {

                private List<String> args = new ArrayList<String>();

                private String body;

                private boolean javacall = false;

                public FindInAnno() {

                    super(Opcodes.ASM4);

                }

                @Override

                public void visit(String name, Object value) {

                    if (name == null) {

                        args.add((String) value);

                        return;

                    }

                    if (name.equals("javacall")) { // NOI18N

                        javacall = (Boolean) value;

                        return;

                    }

                    assert name.equals("body");

                    body = (String) value;

                }

                @Override

                public AnnotationVisitor visitArray(String name) {

                    return this;

                }

                @Override

                public void visitEnd() {

                    if (body != null) {

                        if (javacall) {

                            body = callback(body);

                            args.add("vm");

                        }

                        generateJSBody(args, body);

                    }

                }

            }

        }

        private final class LoadResource extends AnnotationVisitor {

            public LoadResource() {

                super(Opcodes.ASM4);

            }

            @Override

            public void visit(String attrName, Object value) {

                String relPath = (String) value;

                if (relPath.startsWith("/")) {

                    loadScript(loader, relPath);

                } else {

                    int last = name.lastIndexOf('/');

                    String fullPath = name.substring(0, last + 1) + relPath;

                    loadScript(loader, fullPath);

                }

            }

        }

    }

    private static class ClassWriterEx extends ClassWriter {

        private ClassLoader loader;

        public ClassWriterEx(ClassLoader l, ClassReader classReader, int flags) {

            super(classReader, flags);

            this.loader = l;

        }

        @Override

        protected String getCommonSuperClass(final String type1, final String type2) {

            Class<?> c, d;

            try {

                c = Class.forName(type1.replace('/', '.'), false, loader);

                d = Class.forName(type2.replace('/', '.'), false, loader);

            } catch (Exception e) {

                throw new RuntimeException(e.toString());

            }

            if (c.isAssignableFrom(d)) {

                return type1;

            }

            if (d.isAssignableFrom(c)) {

                return type2;

            }

            if (c.isInterface() || d.isInterface()) {

                return "java/lang/Object";

            } else {

                do {

                    c = c.getSuperclass();

                } while (!c.isAssignableFrom(d));

                return c.getName().replace('.', '/');

            }

        }

    }

    static byte[] transform(ClassLoader loader, byte[] arr) {

        ClassReader cr = new ClassReader(arr) {

            // to allow us to compile with -profile compact1 on 

            // JDK8 while processing the class as JDK7, the highest

            // class format asm 4.1 understands to

            @Override

            public short readShort(int index) {

                short s = super.readShort(index);

                if (index == 6 && s > Opcodes.V1_7) {

                    return Opcodes.V1_7;

                }

                return s;

            }

        };

        FindInClass tst = new FindInClass(loader, null);

        cr.accept(tst, 0);

        if (tst.found > 0) {

            ClassWriter w = new ClassWriterEx(loader, cr, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);

            FindInClass fic = new FindInClass(loader, w);

            cr.accept(fic, 0);

            arr = w.toByteArray();

        }

        return arr;

    }

    private static final class TrueFn extends Fn {

        @Override

        public Object invoke(Object thiz, Object... args) throws Exception {

            return Boolean.TRUE;

        }

    } // end of TrueFn

}