/*

 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

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

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package org.graalvm.compiler.options.processor;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;

import javax.annotation.processing.AbstractProcessor;

import javax.annotation.processing.Filer;

import javax.annotation.processing.RoundEnvironment;

import javax.annotation.processing.SupportedAnnotationTypes;

import javax.lang.model.SourceVersion;

import javax.lang.model.element.Element;

import javax.lang.model.element.ElementKind;

import javax.lang.model.element.Modifier;

import javax.lang.model.element.Name;

import javax.lang.model.element.PackageElement;

import javax.lang.model.element.TypeElement;

import javax.lang.model.element.VariableElement;

import javax.lang.model.type.DeclaredType;

import javax.lang.model.type.TypeKind;

import javax.lang.model.type.TypeMirror;

import javax.lang.model.util.Elements;

import javax.lang.model.util.Types;

import javax.tools.Diagnostic.Kind;

import javax.tools.JavaFileObject;

import org.graalvm.compiler.options.Option;

import org.graalvm.compiler.options.OptionDescriptor;

import org.graalvm.compiler.options.OptionDescriptors;

import org.graalvm.compiler.options.OptionValue;

/**

 * Processes static fields annotated with {@link Option}. An {@link OptionDescriptors}

 * implementation is generated for each top level class containing at least one such field. The name

 * of the generated class for top level class {@code com.foo.Bar} is

 * {@code com.foo.Bar_OptionDescriptors}.

 */

@SupportedAnnotationTypes({"org.graalvm.compiler.options.Option"})

public class OptionProcessor extends AbstractProcessor {

    @Override

    public SourceVersion getSupportedSourceVersion() {

        return SourceVersion.latest();

    }

    private final Set<Element> processed = new HashSet<>();

    private void processElement(Element element, OptionsInfo info) {

        if (!element.getModifiers().contains(Modifier.STATIC)) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option field must be static", element);

            return;

        }

        if (element.getModifiers().contains(Modifier.PRIVATE)) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option field cannot be private", element);

            return;

        }

        Option annotation = element.getAnnotation(Option.class);

        assert annotation != null;

        assert element instanceof VariableElement;

        assert element.getKind() == ElementKind.FIELD;

        VariableElement field = (VariableElement) element;

        String fieldName = field.getSimpleName().toString();

        Elements elements = processingEnv.getElementUtils();

        Types types = processingEnv.getTypeUtils();

        TypeMirror fieldType = field.asType();

        if (fieldType.getKind() != TypeKind.DECLARED) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option field must be of type " + OptionValue.class.getName(), element);

            return;

        }

        DeclaredType declaredFieldType = (DeclaredType) fieldType;

        TypeMirror optionValueType = elements.getTypeElement(OptionValue.class.getName()).asType();

        if (!types.isSubtype(fieldType, types.erasure(optionValueType))) {

            String msg = String.format("Option field type %s is not a subclass of %s", fieldType, optionValueType);

            processingEnv.getMessager().printMessage(Kind.ERROR, msg, element);

            return;

        }

        if (!field.getModifiers().contains(Modifier.STATIC)) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option field must be static", element);

            return;

        }

        if (field.getModifiers().contains(Modifier.PRIVATE)) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option field cannot be private", element);

            return;

        }

        String help = annotation.help();

        if (help.length() != 0) {

            char firstChar = help.charAt(0);

            if (!Character.isUpperCase(firstChar)) {

                processingEnv.getMessager().printMessage(Kind.ERROR, "Option help text must start with upper case letter", element);

                return;

            }

        }

        String optionName = annotation.name();

        if (optionName.equals("")) {

            optionName = fieldName;

        }

        if (!Character.isUpperCase(optionName.charAt(0))) {

            processingEnv.getMessager().printMessage(Kind.ERROR, "Option name must start with capital letter", element);

            return;

        }

        DeclaredType declaredOptionValueType = declaredFieldType;

        while (!types.isSameType(types.erasure(declaredOptionValueType), types.erasure(optionValueType))) {

            List<? extends TypeMirror> directSupertypes = types.directSupertypes(declaredFieldType);

            assert !directSupertypes.isEmpty();

            declaredOptionValueType = (DeclaredType) directSupertypes.get(0);

        }

        assert !declaredOptionValueType.getTypeArguments().isEmpty();

        String optionType = declaredOptionValueType.getTypeArguments().get(0).toString();

        if (optionType.startsWith("java.lang.")) {

            optionType = optionType.substring("java.lang.".length());

        }

        Element enclosing = element.getEnclosingElement();

        String declaringClass = "";

        String separator = "";

        Set<Element> originatingElementsList = info.originatingElements;

        originatingElementsList.add(field);

        while (enclosing != null) {

            if (enclosing.getKind() == ElementKind.CLASS || enclosing.getKind() == ElementKind.INTERFACE) {

                if (enclosing.getModifiers().contains(Modifier.PRIVATE)) {

                    String msg = String.format("Option field cannot be declared in a private %s %s", enclosing.getKind().name().toLowerCase(), enclosing);

                    processingEnv.getMessager().printMessage(Kind.ERROR, msg, element);

                    return;

                }

                originatingElementsList.add(enclosing);

                declaringClass = enclosing.getSimpleName() + separator + declaringClass;

                separator = ".";

            } else {

                assert enclosing.getKind() == ElementKind.PACKAGE;

            }

            enclosing = enclosing.getEnclosingElement();

        }

        info.options.add(new OptionInfo(optionName, help, optionType, declaringClass, field));

    }

    private void createFiles(OptionsInfo info) {

        String pkg = ((PackageElement) info.topDeclaringType.getEnclosingElement()).getQualifiedName().toString();

        Name topDeclaringClass = info.topDeclaringType.getSimpleName();

        Element[] originatingElements = info.originatingElements.toArray(new Element[info.originatingElements.size()]);

        createOptionsDescriptorsFile(info, pkg, topDeclaringClass, originatingElements);

    }

    private void createOptionsDescriptorsFile(OptionsInfo info, String pkg, Name topDeclaringClass, Element[] originatingElements) {

        String optionsClassName = topDeclaringClass + "_" + OptionDescriptors.class.getSimpleName();

        Filer filer = processingEnv.getFiler();

        try (PrintWriter out = createSourceFile(pkg, optionsClassName, filer, originatingElements)) {

            out.println("// CheckStyle: stop header check");

            out.println("// CheckStyle: stop line length check");

            out.println("// GENERATED CONTENT - DO NOT EDIT");

            out.println("// Source: " + topDeclaringClass + ".java");

            out.println("package " + pkg + ";");

            out.println("");

            out.println("import java.util.*;");

            out.println("import " + OptionDescriptors.class.getPackage().getName() + ".*;");

            out.println("");

            out.println("public class " + optionsClassName + " implements " + OptionDescriptors.class.getSimpleName() + " {");

            String desc = OptionDescriptor.class.getSimpleName();

            int i = 0;

            Collections.sort(info.options);

            out.println("    @Override");

            out.println("    public OptionDescriptor get(String value) {");

            out.println("        // CheckStyle: stop line length check");

            if (info.options.size() == 1) {

                out.println("        if (value.equals(\"" + info.options.get(0).name + "\")) {");

            } else {

                out.println("        switch (value) {");

            }

            for (OptionInfo option : info.options) {

                String name = option.name;

                String optionValue;

                if (option.field.getModifiers().contains(Modifier.PRIVATE)) {

                    throw new InternalError();

                } else {

                    optionValue = option.declaringClass + "." + option.field.getSimpleName();

                }

                String type = option.type;

                String help = option.help;

                String declaringClass = option.declaringClass;

                Name fieldName = option.field.getSimpleName();

                if (info.options.size() == 1) {

                    out.printf("            return %s.create(\"%s\", %s.class, \"%s\", %s.class, \"%s\", %s);\n", desc, name, type, help, declaringClass, fieldName, optionValue);

                } else {

                    out.printf("            case \"" + name + "\": return %s.create(\"%s\", %s.class, \"%s\", %s.class, \"%s\", %s);\n", desc, name, type, help, declaringClass, fieldName,

                                    optionValue);

                }

            }

            out.println("        }");

            out.println("        // CheckStyle: resume line length check");

            out.println("        return null;");

            out.println("    }");

            out.println();

            out.println("    @Override");

            out.println("    public Iterator<" + desc + "> iterator() {");

            out.println("        // CheckStyle: stop line length check");

            out.println("        List<" + desc + "> options = Arrays.asList(");

            for (OptionInfo option : info.options) {

                String optionValue;

                if (option.field.getModifiers().contains(Modifier.PRIVATE)) {

                    throw new InternalError();

                } else {

                    optionValue = option.declaringClass + "." + option.field.getSimpleName();

                }

                String name = option.name;

                String type = option.type;

                String help = option.help;

                String declaringClass = option.declaringClass;

                Name fieldName = option.field.getSimpleName();

                String comma = i == info.options.size() - 1 ? "" : ",";

                out.printf("            %s.create(\"%s\", %s.class, \"%s\", %s.class, \"%s\", %s)%s\n", desc, name, type, help, declaringClass, fieldName, optionValue, comma);

                i++;

            }

            out.println("        );");

            out.println("        // CheckStyle: resume line length check");

            out.println("        return options.iterator();");

            out.println("    }");

            out.println("}");

        }

    }

    protected PrintWriter createSourceFile(String pkg, String relativeName, Filer filer, Element... originatingElements) {

        try {

            // Ensure Unix line endings to comply with code style guide checked by Checkstyle

            JavaFileObject sourceFile = filer.createSourceFile(pkg + "." + relativeName, originatingElements);

            return new PrintWriter(sourceFile.openWriter()) {

                @Override

                public void println() {

                    print("\n");

                }

            };

        } catch (IOException e) {

            throw new RuntimeException(e);

        }

    }

    static class OptionInfo implements Comparable<OptionInfo> {

        final String name;

        final String help;

        final String type;

        final String declaringClass;

        final VariableElement field;

        OptionInfo(String name, String help, String type, String declaringClass, VariableElement field) {

            this.name = name;

            this.help = help;

            this.type = type;

            this.declaringClass = declaringClass;

            this.field = field;

        }

        @Override

        public int compareTo(OptionInfo other) {

            return name.compareTo(other.name);

        }

        @Override

        public String toString() {

            return declaringClass + "." + field;

        }

    }

    static class OptionsInfo {

        final Element topDeclaringType;

        final List<OptionInfo> options = new ArrayList<>();

        final Set<Element> originatingElements = new HashSet<>();

        OptionsInfo(Element topDeclaringType) {

            this.topDeclaringType = topDeclaringType;

        }

    }

    private static Element topDeclaringType(Element element) {

        Element enclosing = element.getEnclosingElement();

        if (enclosing == null || enclosing.getKind() == ElementKind.PACKAGE) {

            assert element.getKind() == ElementKind.CLASS || element.getKind() == ElementKind.INTERFACE;

            return element;

        }

        return topDeclaringType(enclosing);

    }

    @Override

    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {

        if (roundEnv.processingOver()) {

            return true;

        }

        Map<Element, OptionsInfo> map = new HashMap<>();

        for (Element element : roundEnv.getElementsAnnotatedWith(Option.class)) {

            if (!processed.contains(element)) {

                processed.add(element);

                Element topDeclaringType = topDeclaringType(element);

                OptionsInfo options = map.get(topDeclaringType);

                if (options == null) {

                    options = new OptionsInfo(topDeclaringType);

                    map.put(topDeclaringType, options);

                }

                processElement(element, options);

            }

        }

        boolean ok = true;

        Map<String, OptionInfo> uniqueness = new HashMap<>();

        for (OptionsInfo info : map.values()) {

            for (OptionInfo option : info.options) {

                OptionInfo conflict = uniqueness.put(option.name, option);

                if (conflict != null) {

                    processingEnv.getMessager().printMessage(Kind.ERROR, "Duplicate option names for " + option + " and " + conflict, option.field);

                    ok = false;

                }

            }

        }

        if (ok) {

            for (OptionsInfo info : map.values()) {

                createFiles(info);

            }

        }

        return true;

    }

}