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package com.google.inject.internal;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

import com.google.common.base.Function;
import com.google.common.base.Joiner;
import com.google.common.base.Joiner.MapJoiner;
import com.google.common.base.Preconditions;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.inject.BindingAnnotation;
import com.google.inject.Key;
import com.google.inject.ScopeAnnotation;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.util.Classes;
import com.google.inject.name.Named;
import com.google.inject.name.Names;

import javax.inject.Qualifier;
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Collection;
import java.util.Map;

/**
 * Annotation utilities.
 *
 */
public class Annotations {

    private static final MapJoiner JOINER = Joiner.on(", ").withKeyValueSeparator("=");
    private static final Function DEEP_TO_STRING_FN = new Function() {
        @Override
        public String apply(Object arg) {
            String s = Arrays.deepToString(new Object[]{arg});
            return s.substring(1, s.length() - 1); // cut off brackets
        }
    };

    private static final LoadingCache, Annotation> cache =
            CacheBuilder.newBuilder()
                    .weakKeys()
                    .build(new CacheLoader<>() {
                        @Override
                        public Annotation load(Class input) {
                            return generateAnnotationImpl(input);
                        }
                    });

    private static final AnnotationChecker scopeChecker = new AnnotationChecker(
            Arrays.asList(ScopeAnnotation.class, javax.inject.Scope.class));
    private static final AnnotationChecker bindingAnnotationChecker = new AnnotationChecker(
            Arrays.asList(BindingAnnotation.class, Qualifier.class));

    /**
     * Returns {@code true} if the given annotation type has no attributes.
     */
    public static boolean isMarker(Class annotationType) {
        return annotationType.getDeclaredMethods().length == 0;
    }

    public static boolean isAllDefaultMethods(Class annotationType) {
        boolean hasMethods = false;
        for (Method m : annotationType.getDeclaredMethods()) {
            hasMethods = true;
            if (m.getDefaultValue() == null) {
                return false;
            }
        }
        return hasMethods;
    }

    /**
     * Generates an Annotation for the annotation class. Requires that the annotation is all
     * optionals.
     */
    @SuppressWarnings("unchecked")
    public static  T generateAnnotation(Class annotationType) {
        Preconditions.checkState(
                isAllDefaultMethods(annotationType), "%s is not all default methods", annotationType);
        return (T) cache.getUnchecked(annotationType);
    }

    private static  T generateAnnotationImpl(final Class annotationType) {
        final Map members = resolveMembers(annotationType);
        return annotationType.cast(Proxy.newProxyInstance(
                annotationType.getClassLoader(),
                new Class[]{annotationType},
                (proxy, method, args) -> {
                    String name = method.getName();
                    switch (name) {
                        case "annotationType":
                            return annotationType;
                        case "toString":
                            return annotationToString(annotationType, members);
                        case "hashCode":
                            return annotationHashCode(annotationType, members);
                        case "equals":
                            return annotationEquals(annotationType, members, args[0]);
                        default:
                            return members.get(name);
                    }
                }));
    }

    private static ImmutableMap resolveMembers(
            Class annotationType) {
        ImmutableMap.Builder result = ImmutableMap.builder();
        for (Method method : annotationType.getDeclaredMethods()) {
            result.put(method.getName(), method.getDefaultValue());
        }
        return result.build();
    }

    /**
     * Implements {@link Annotation#equals}.
     */
    private static boolean annotationEquals(Class type,
                                            Map members, Object other) throws Exception {
        if (!type.isInstance(other)) {
            return false;
        }
        for (Method method : type.getDeclaredMethods()) {
            String name = method.getName();
            if (!Arrays.deepEquals(
                    new Object[]{method.invoke(other)}, new Object[]{members.get(name)})) {
                return false;
            }
        }
        return true;
    }

    /**
     * Implements {@link Annotation#hashCode}.
     */
    private static int annotationHashCode(Class type,
                                          Map members) throws Exception {
        int result = 0;
        for (Method method : type.getDeclaredMethods()) {
            String name = method.getName();
            Object value = members.get(name);
            result += (127 * name.hashCode()) ^ (Arrays.deepHashCode(new Object[]{value}) - 31);
        }
        return result;
    }

    /**
     * Implements {@link Annotation#toString}.
     */
    private static String annotationToString(Class type,
                                             Map members) throws Exception {
        StringBuilder sb = new StringBuilder().append("@").append(type.getName()).append("(");
        JOINER.appendTo(sb, Maps.transformValues(members, DEEP_TO_STRING_FN));
        return sb.append(")").toString();
    }

    /**
     * Returns true if the given annotation is retained at runtime.
     */
    public static boolean isRetainedAtRuntime(Class annotationType) {
        Retention retention = annotationType.getAnnotation(Retention.class);
        return retention != null && retention.value() == RetentionPolicy.RUNTIME;
    }

    /**
     * Returns the scope annotation on {@code type}, or null if none is specified.
     */
    public static Class findScopeAnnotation(
            Errors errors, Class implementation) {
        return findScopeAnnotation(errors, implementation.getAnnotations());
    }

    /**
     * Returns the scoping annotation, or null if there isn't one.
     */
    public static Class findScopeAnnotation(Errors errors, Annotation[] annotations) {
        Class found = null;

        for (Annotation annotation : annotations) {
            Class annotationType = annotation.annotationType();
            if (isScopeAnnotation(annotationType)) {
                if (found != null) {
                    errors.duplicateScopeAnnotations(found, annotationType);
                } else {
                    found = annotationType;
                }
            }
        }

        return found;
    }

    static boolean containsComponentAnnotation(Annotation[] annotations) {
        for (Annotation annotation : annotations) {
            // TODO(user): Should we scope this down to dagger.Component?
            if (annotation.annotationType().getSimpleName().equals("Component")) {
                return true;
            }
        }

        return false;
    }

    private static final boolean QUOTE_MEMBER_VALUES = determineWhetherToQuote();

    public static String memberValueString(String value) {
        return QUOTE_MEMBER_VALUES ? "\"" + value + "\"" : value;
    }

    @Retention(RUNTIME)
    private @interface TestAnnotation {
        String value();
    }

    @TestAnnotation("determineWhetherToQuote")
    private static boolean determineWhetherToQuote() {
        try {
            String annotation = Annotations.class
                            .getDeclaredMethod("determineWhetherToQuote")
                            .getAnnotation(TestAnnotation.class)
                            .toString();
            return annotation.contains("\"determineWhetherToQuote\"");
        } catch (NoSuchMethodException e) {
            throw new AssertionError(e);
        }
    }

    public static boolean isScopeAnnotation(Class annotationType) {
        return scopeChecker.hasAnnotations(annotationType);
    }

    /**
     * Adds an error if there is a misplaced annotations on {@code type}. Scoping
     * annotations are not allowed on abstract classes or interfaces.
     */
    public static void checkForMisplacedScopeAnnotations(
            Class type, Object source, Errors errors) {
        if (Classes.isConcrete(type)) {
            return;
        }

        Class scopeAnnotation = findScopeAnnotation(errors, type);
        if (scopeAnnotation != null
                // We let Dagger Components through to aid migrations.
                && !containsComponentAnnotation(type.getAnnotations())) {
            errors.withSource(type).scopeAnnotationOnAbstractType(scopeAnnotation, type, source);
        }
    }

    /**
     * Gets a key for the given type, member and annotations.
     */
    public static Key getKey(TypeLiteral type, Member member, Annotation[] annotations,
                                Errors errors) throws ErrorsException {
        int numErrorsBefore = errors.size();
        Annotation found = findBindingAnnotation(errors, member, annotations);
        errors.throwIfNewErrors(numErrorsBefore);
        return found == null ? Key.get(type) : Key.get(type, found);
    }

    /**
     * Returns the binding annotation on {@code member}, or null if there isn't one.
     */
    public static Annotation findBindingAnnotation(Errors errors, Member member, Annotation[] annotations) {
        Annotation found = null;

        for (Annotation annotation : annotations) {
            Class annotationType = annotation.annotationType();
            if (isBindingAnnotation(annotationType)) {
                if (found != null) {
                    errors.duplicateBindingAnnotations(member, found.annotationType(), annotationType);
                } else {
                    found = annotation;
                }
            }
        }

        return found;
    }

    /**
     * Returns true if annotations of the specified type are binding annotations.
     */
    public static boolean isBindingAnnotation(Class annotationType) {
        return bindingAnnotationChecker.hasAnnotations(annotationType);
    }

    /**
     * If the annotation is an instance of {@code javax.inject.Named}, canonicalizes to
     * com.google.guice.name.Named.  Returns the given annotation otherwise.
     */
    public static Annotation canonicalizeIfNamed(Annotation annotation) {
        if (annotation instanceof javax.inject.Named) {
            return Names.named(((javax.inject.Named) annotation).value());
        } else {
            return annotation;
        }
    }

    /**
     * If the annotation is the class {@code javax.inject.Named}, canonicalizes to
     * com.google.guice.name.Named. Returns the given annotation class otherwise.
     */
    public static Class canonicalizeIfNamed(
            Class annotationType) {
        if (annotationType == javax.inject.Named.class) {
            return Named.class;
        } else {
            return annotationType;
        }
    }

    /**
     * Returns the name the binding should use. This is based on the annotation. If the annotation has
     * an instance and is not a marker annotation, we ask the annotation for its toString. If it was a
     * marker annotation or just an annotation type, we use the annotation's name. Otherwise, the name
     * is the empty string.
     */
    public static String nameOf(Key key) {
        Annotation annotation = key.getAnnotation();
        Class annotationType = key.getAnnotationType();
        if (annotation != null && !isMarker(annotationType)) {
            return key.getAnnotation().toString();
        } else if (key.getAnnotationType() != null) {
            return "@" + key.getAnnotationType().getName();
        } else {
            return "";
        }
    }

    /**
     * Checks for the presence of annotations. Caches results because Android doesn't.
     */
    static class AnnotationChecker {
        private final Collection> annotationTypes;

        /**
         * Returns true if the given class has one of the desired annotations.
         */
        private CacheLoader, Boolean> hasAnnotations =
                new CacheLoader<>() {
                    @Override
                    public Boolean load(Class annotationType) {
                        for (Annotation annotation : annotationType.getAnnotations()) {
                            if (annotationTypes.contains(annotation.annotationType())) {
                                return true;
                            }
                        }
                        return false;
                    }
                };

        final LoadingCache, Boolean> cache =
                CacheBuilder.newBuilder().weakKeys().build(hasAnnotations);

        /**
         * Constructs a new checker that looks for annotations of the given types.
         */
        AnnotationChecker(Collection> annotationTypes) {
            this.annotationTypes = annotationTypes;
        }

        /**
         * Returns true if the given type has one of the desired annotations.
         */
        boolean hasAnnotations(Class annotated) {
            return cache.getUnchecked(annotated);
        }
    }
}




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