/*
 * 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 Option. An 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 com.foo.Bar is com.foo.Bar_OptionDescriptors. /**
 * 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;
    }
}