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package com.fasterxml.jackson.databind;

import java.lang.reflect.Type;

import com.fasterxml.jackson.annotation.ObjectIdGenerator;
import com.fasterxml.jackson.annotation.ObjectIdResolver;
import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
import com.fasterxml.jackson.databind.cfg.MapperConfig;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.ObjectIdInfo;
import com.fasterxml.jackson.databind.type.TypeFactory;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.Converter;

/**
 * Shared base class for {@link DeserializationContext} and
 * {@link SerializerProvider}, context objects passed through data-binding
 * process. Designed so that some of implementations can rely on shared
 * aspects like access to secondary contextual objects like type factories
 * or handler instantiators.
 * 
 * @since 2.2
 */
public abstract class DatabindContext
{
    /*
    /**********************************************************
    /* Generic config access
    /**********************************************************
     */

    /**
     * Accessor to currently active configuration (both per-request configs
     * and per-mapper config).
     */
    public abstract MapperConfig getConfig();

    /**
     * Convenience method for accessing serialization view in use (if any); equivalent to:
     *     *   getConfig().getAnnotationIntrospector();
     *
     */
    public abstract AnnotationIntrospector getAnnotationIntrospector();
    
    /*
    /**********************************************************
    /* Access to specific config settings
    /**********************************************************
     */
    
    /**
     * Convenience method for checking whether specified serialization
     * feature is enabled or not.
     * Shortcut for:
     *     *  getConfig().isEnabled(feature);
     *
     */
    public final boolean isEnabled(MapperFeature feature) {
        return getConfig().isEnabled(feature);
    }

    /**
     * Convenience method for accessing serialization view in use (if any); equivalent to:
     *     *   getConfig().canOverrideAccessModifiers();
     *
     */
    public final boolean canOverrideAccessModifiers() {
        return getConfig().canOverrideAccessModifiers();
    }

    /**
     * Accessor for locating currently active view, if any;
     * returns null if no view has been set.
     */
    public abstract Class getActiveView();
    
    /*
    /**********************************************************
    /* Generic attributes (2.3+)
    /**********************************************************
     */

    /**
     * Method for accessing attributes available in this context.
     * Per-call attributes have highest precedence; attributes set
     * via {@link ObjectReader} or {@link ObjectWriter} have lower
     * precedence.
     * 
     * @param key Key of the attribute to get
     * @return Value of the attribute, if any; null otherwise
     * 
     * @since 2.3
     */
    public abstract Object getAttribute(Object key);

    /**
     * Method for setting per-call value of given attribute.
     * This will override any previously defined value for the
     * attribute within this context.
     * 
     * @param key Key of the attribute to set
     * @param value Value to set attribute to
     * 
     * @return This context object, to allow chaining
     * 
     * @since 2.3
     */
    public abstract DatabindContext setAttribute(Object key, Object value);

    /*
    /**********************************************************
    /* Type instantiation/resolution
    /**********************************************************
     */

    /**
     * Convenience method for constructing {@link JavaType} for given JDK
     * type (usually {@link java.lang.Class})
     */
    public JavaType constructType(Type type) {
         return getTypeFactory().constructType(type);
    }

    /**
     * Convenience method for constructing subtypes, retaining generic
     * type parameter (if any)
     */
    public JavaType constructSpecializedType(JavaType baseType, Class subclass) {
        // simple optimization to avoid costly introspection if type-erased type does NOT differ
        if (baseType.getRawClass() == subclass) {
            return baseType;
        }
        return getConfig().constructSpecializedType(baseType, subclass);
    }

    public abstract TypeFactory getTypeFactory();

    /*
    /**********************************************************
    /* Helper object construction
    /**********************************************************
     */

    public ObjectIdGenerator objectIdGeneratorInstance(Annotated annotated,
            ObjectIdInfo objectIdInfo)
        throws JsonMappingException
    {
        Class implClass = objectIdInfo.getGeneratorType();
        final MapperConfig config = getConfig();
        HandlerInstantiator hi = config.getHandlerInstantiator();
        ObjectIdGenerator gen = (hi == null) ? null : hi.objectIdGeneratorInstance(config, annotated, implClass);
        if (gen == null) {
            gen = (ObjectIdGenerator) ClassUtil.createInstance(implClass,
                    config.canOverrideAccessModifiers());
        }
        return gen.forScope(objectIdInfo.getScope());
    }

    public ObjectIdResolver objectIdResolverInstance(Annotated annotated, ObjectIdInfo objectIdInfo)
    {
        Class implClass = objectIdInfo.getResolverType();
        final MapperConfig config = getConfig();
        HandlerInstantiator hi = config.getHandlerInstantiator();
        ObjectIdResolver resolver = (hi == null) ? null : hi.resolverIdGeneratorInstance(config, annotated, implClass);
        if (resolver == null) {
            resolver = ClassUtil.createInstance(implClass, config.canOverrideAccessModifiers());
        }

        return resolver;
    }

    /**
     * Helper method to use to construct a {@link Converter}, given a definition
     * that may be either actual converter instance, or Class for instantiating one.
     * 
     * @since 2.2
     */
    @SuppressWarnings("unchecked")
    public Converter converterInstance(Annotated annotated,
            Object converterDef)
        throws JsonMappingException
    {
        if (converterDef == null) {
            return null;
        }
        if (converterDef instanceof Converter) {
            return (Converter) converterDef;
        }
        if (!(converterDef instanceof Class)) {
            throw new IllegalStateException("AnnotationIntrospector returned Converter definition of type "
                    +converterDef.getClass().getName()+"; expected type Converter or Class instead");
        }
        Class converterClass = (Class)converterDef;
        // there are some known "no class" markers to consider too:
        if (converterClass == Converter.None.class || ClassUtil.isBogusClass(converterClass)) {
            return null;
        }
        if (!Converter.class.isAssignableFrom(converterClass)) {
            throw new IllegalStateException("AnnotationIntrospector returned Class "
                    +converterClass.getName()+"; expected Class");
        }
        final MapperConfig config = getConfig();
        HandlerInstantiator hi = config.getHandlerInstantiator();
        Converter conv = (hi == null) ? null : hi.converterInstance(config, annotated, converterClass);
        if (conv == null) {
            conv = (Converter) ClassUtil.createInstance(converterClass,
                    config.canOverrideAccessModifiers());
        }
        return (Converter) conv;
    }
}