package com.fasterxml.jackson.databind;

import java.io.IOException;
import java.util.Iterator;

import com.fasterxml.jackson.core.*;

import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitable;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.ser.PropertyWriter;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.NameTransformer;

Abstract class that defines API used by ObjectMapper (and other chained JsonSerializers too) to serialize Objects of arbitrary types into JSON, using provided JsonGenerator. StdSerializer instead of this class, since it will implement many of optional methods of this class. 

NOTE: various serialize methods are never (to be) called
with null values -- caller must handle null values, usually by calling SerializerProvider.findNullValueSerializer to obtain serializer to use. This also means that custom serializers cannot be directly used to change the output to produce when serializing null values. 
 If serializer is an aggregate one -- meaning it delegates handling of some of its contents by using other serializer(s) -- it typically also needs to implement ResolvableSerializer, which can locate secondary serializers needed. This is important to allow dynamic overrides of serializers; separate call interface is needed to separate resolution of secondary serializers (which may have cyclic link back to serializer itself, directly or indirectly). 
 In addition, to support per-property annotations (to configure aspects of serialization on per-property basis), serializers may want to implement ContextualSerializer, which allows specialization of serializers: call to ContextualSerializer.createContextual is passed information on property, and can create a newly configured serializer for handling that particular property. 
 If both ResolvableSerializer and ContextualSerializer are implemented, resolution of serializers occurs before contextualization. /**
 * Abstract class that defines API used by {@link ObjectMapper} (and
 * other chained {@link JsonSerializer}s too) to serialize Objects of
 * arbitrary types into JSON, using provided {@link JsonGenerator}.
 * {@link com.fasterxml.jackson.databind.ser.std.StdSerializer} instead
 * of this class, since it will implement many of optional
 * methods of this class.
 *<p>
 * NOTE: various <code>serialize</code> methods are never (to be) called
 * with null values -- caller <b>must</b> handle null values, usually
 * by calling {@link SerializerProvider#findNullValueSerializer} to obtain
 * serializer to use.
 * This also means that custom serializers cannot be directly used to change
 * the output to produce when serializing null values.
 *<p>
 * If serializer is an aggregate one -- meaning it delegates handling of some
 * of its contents by using other serializer(s) -- it typically also needs
 * to implement {@link com.fasterxml.jackson.databind.ser.ResolvableSerializer},
 * which can locate secondary serializers needed. This is important to allow dynamic
 * overrides of serializers; separate call interface is needed to separate
 * resolution of secondary serializers (which may have cyclic link back
 * to serializer itself, directly or indirectly).
 *<p>
 * In addition, to support per-property annotations (to configure aspects
 * of serialization on per-property basis), serializers may want
 * to implement 
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer},
 * which allows specialization of serializers: call to
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer#createContextual}
 * is passed information on property, and can create a newly configured
 * serializer for handling that particular property.
 *<p>
 * If both
 * {@link com.fasterxml.jackson.databind.ser.ResolvableSerializer} and
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer}
 * are implemented, resolution of serializers occurs before
 * contextualization.
 */
public abstract class JsonSerializer<T>
    implements JsonFormatVisitable // since 2.1
{
    /*
    /**********************************************************
    /* Fluent factory methods for constructing decorated versions
    /**********************************************************
     */

    
Method that will return serializer instance that produces
"unwrapped" serialization, if applicable for type being
serialized (which is the case for some serializers
that produce JSON Objects as output).
If no unwrapped serializer can be constructed, will simply
return serializer as-is.

Default implementation just returns serializer as-is,
indicating that no unwrapped variant exists
Params:
unwrapper – Name transformation to use to convert between names
  of unwrapper properties/**
     * Method that will return serializer instance that produces
     * "unwrapped" serialization, if applicable for type being
     * serialized (which is the case for some serializers
     * that produce JSON Objects as output).
     * If no unwrapped serializer can be constructed, will simply
     * return serializer as-is.
     *<p>
     * Default implementation just returns serializer as-is,
     * indicating that no unwrapped variant exists
     * 
     * @param unwrapper Name transformation to use to convert between names
     *   of unwrapper properties
     */
    public JsonSerializer<T> unwrappingSerializer(NameTransformer unwrapper) {
        return this;
    }

    
Method that can be called to try to replace serializer this serializer delegates calls to. If not supported (either this serializer does not delegate anything; or it does not want any changes), should either throw UnsupportedOperationException (if operation does not make sense or is not allowed); or return this serializer as is. 
Since:
2.1/**
     * Method that can be called to try to replace serializer this serializer
     * delegates calls to. If not supported (either this serializer does not
     * delegate anything; or it does not want any changes), should either
     * throw {@link UnsupportedOperationException} (if operation does not
     * make sense or is not allowed); or return this serializer as is.
     * 
     * @since 2.1
     */
    public JsonSerializer<T> replaceDelegatee(JsonSerializer<?> delegatee) {
        throw new UnsupportedOperationException();
    }

    
Mutant factory method that is called if contextual configuration indicates that
a specific filter (as specified by filterId) is to be used for
serialization.

Default implementation simply returns this; sub-classes that do support
filtering will need to create and return new instance if filter changes.
Since:
2.6/**
     * Mutant factory method that is called if contextual configuration indicates that
     * a specific filter (as specified by <code>filterId</code>) is to be used for
     * serialization.
     *<p>
     * Default implementation simply returns <code>this</code>; sub-classes that do support
     * filtering will need to create and return new instance if filter changes.
     *
     * @since 2.6
     */
    public JsonSerializer<?> withFilterId(Object filterId) {
        return this;
    }

    /*
    /**********************************************************
    /* Serialization methods
    /**********************************************************
     */

    
Method that can be called to ask implementation to serialize
values of type this serializer handles.
Params:
value – Value to serialize; can not be null.
gen – Generator used to output resulting Json content
serializers – Provider that can be used to get serializers for
  serializing Objects value contains, if any./**
     * Method that can be called to ask implementation to serialize
     * values of type this serializer handles.
     *
     * @param value Value to serialize; can <b>not</b> be null.
     * @param gen Generator used to output resulting Json content
     * @param serializers Provider that can be used to get serializers for
     *   serializing Objects value contains, if any.
     */
    public abstract void serialize(T value, JsonGenerator gen, SerializerProvider serializers)
        throws IOException;

    
Method that can be called to ask implementation to serialize
values of type this serializer handles, using specified type serializer
for embedding necessary type information.
 Default implementation will throw UnsupportedOperationException to indicate that proper type handling needs to be implemented. 

For simple datatypes written as a single scalar value (JSON String, Number, Boolean),
implementation would look like:
 // note: method to call depends on whether this type is serialized as JSON scalar, object or Array!
 typeSer.writeTypePrefixForScalar(value, gen);
 serialize(value, gen, provider);
 typeSer.writeTypeSuffixForScalar(value, gen);

and implementations for type serialized as JSON Arrays or Objects would differ slightly,
as START-ARRAY/END-ARRAY and
START-OBJECT/END-OBJECT pairs
need to be properly handled with respect to serializing of contents.
Params:
value – Value to serialize; can not be null.
gen – Generator used to output resulting Json content
serializers – Provider that can be used to get serializers for
  serializing Objects value contains, if any.
typeSer – Type serializer to use for including type information/**
     * Method that can be called to ask implementation to serialize
     * values of type this serializer handles, using specified type serializer
     * for embedding necessary type information.
     *<p>
     * Default implementation will throw {@link UnsupportedOperationException}
     * to indicate that proper type handling needs to be implemented.
     *<p>
     * For simple datatypes written as a single scalar value (JSON String, Number, Boolean),
     * implementation would look like:
     *<pre>
     *  // note: method to call depends on whether this type is serialized as JSON scalar, object or Array!
     *  typeSer.writeTypePrefixForScalar(value, gen);
     *  serialize(value, gen, provider);
     *  typeSer.writeTypeSuffixForScalar(value, gen);
     *</pre>
     * and implementations for type serialized as JSON Arrays or Objects would differ slightly,
     * as <code>START-ARRAY</code>/<code>END-ARRAY</code> and
     * <code>START-OBJECT</code>/<code>END-OBJECT</code> pairs
     * need to be properly handled with respect to serializing of contents.
     *
     * @param value Value to serialize; can <b>not</b> be null.
     * @param gen Generator used to output resulting Json content
     * @param serializers Provider that can be used to get serializers for
     *   serializing Objects value contains, if any.
     * @param typeSer Type serializer to use for including type information
     */
    public void serializeWithType(T value, JsonGenerator gen, SerializerProvider serializers,
            TypeSerializer typeSer)
        throws IOException
    {
        Class<?> clz = handledType();
        if (clz == null) {
            clz = value.getClass();
        }
        serializers.reportBadDefinition(clz, String.format(
                "Type id handling not implemented for type %s (by serializer of type %s)",
                clz.getName(), getClass().getName()));
    }

    /*
    /**********************************************************
    /* Other accessors
    /**********************************************************
     */

    
Method for accessing type of Objects this serializer can handle.
Note that this information is not guaranteed to be exact -- it
may be a more generic (super-type) -- but it should not be
incorrect (return a non-related type).

Default implementation will return null, which essentially means
same as returning Object.class would; that is, that
nothing is known about handled type.

/**
     * Method for accessing type of Objects this serializer can handle.
     * Note that this information is not guaranteed to be exact -- it
     * may be a more generic (super-type) -- but it should not be
     * incorrect (return a non-related type).
     *<p>
     * Default implementation will return null, which essentially means
     * same as returning <code>Object.class</code> would; that is, that
     * nothing is known about handled type.
     *<p>
     */
    public Class<T> handledType() { return null; }

    
Method called to check whether given serializable value is
considered "empty" value (for purposes of suppressing serialization
of empty values).

Default implementation will consider only null values to be empty.
Deprecated:
Since 2.5 Use isEmpty(SerializerProvider, Object) instead; will be removed from 3.0/**
     * Method called to check whether given serializable value is
     * considered "empty" value (for purposes of suppressing serialization
     * of empty values).
     *<p>
     * Default implementation will consider only null values to be empty.
     * 
     * @deprecated Since 2.5 Use {@link #isEmpty(SerializerProvider, Object)} instead;
     *   will be removed from 3.0
     */
    @Deprecated
    public boolean isEmpty(T value) {
        return isEmpty(null, value);
    }

    
Method called to check whether given serializable value is
considered "empty" value (for purposes of suppressing serialization
of empty values).

Default implementation will consider only null values to be empty.
 NOTE: replaces isEmpty(Object), which was deprecated in 2.5 
Since:
2.5/**
     * Method called to check whether given serializable value is
     * considered "empty" value (for purposes of suppressing serialization
     * of empty values).
     *<p>
     * Default implementation will consider only null values to be empty.
     *<p>
     * NOTE: replaces {@link #isEmpty(Object)}, which was deprecated in 2.5
     * 
     * @since 2.5
     */
    public boolean isEmpty(SerializerProvider provider, T value) {
        return (value == null);
    }
    
    
Method that can be called to see whether this serializer instance
will use Object Id to handle cyclic references.
/**
     * Method that can be called to see whether this serializer instance
     * will use Object Id to handle cyclic references.
     */
    public boolean usesObjectId() {
        return false;
    }

    
Accessor for checking whether this serializer is an
"unwrapping" serializer; this is necessary to know since
it may also require caller to suppress writing of the
leading property name.
/**
     * Accessor for checking whether this serializer is an
     * "unwrapping" serializer; this is necessary to know since
     * it may also require caller to suppress writing of the
     * leading property name.
     */
    public boolean isUnwrappingSerializer() {
        return false;
    }
    
    
Accessor that can be used to determine if this serializer uses
another serializer for actual serialization, by delegating
calls. If so, will return immediate delegate (which itself may
delegate to further serializers); otherwise will return null.
Returns:
Serializer this serializer delegates calls to, if null;
  null otherwise.
Since:
2.1/**
     * Accessor that can be used to determine if this serializer uses
     * another serializer for actual serialization, by delegating
     * calls. If so, will return immediate delegate (which itself may
     * delegate to further serializers); otherwise will return null.
     * 
     * @return Serializer this serializer delegates calls to, if null;
     *   null otherwise.
     * 
     * @since 2.1
     */
    public JsonSerializer<?> getDelegatee() {
        return null;
    }

    
Accessor for iterating over logical properties that the type handled by this serializer has, from serialization perspective. Actual type of properties, if any, will be BeanPropertyWriter. Of standard Jackson serializers, only BeanSerializer exposes properties. 
Since:
2.6/**
     * Accessor for iterating over logical properties that the type
     * handled by this serializer has, from serialization perspective.
     * Actual type of properties, if any, will be
     * {@link com.fasterxml.jackson.databind.ser.BeanPropertyWriter}.
     * Of standard Jackson serializers, only {@link com.fasterxml.jackson.databind.ser.BeanSerializer}
     * exposes properties.
     *
     * @since 2.6
     */
    public Iterator<PropertyWriter> properties() {
        return ClassUtil.emptyIterator();
    }

    /*
    /**********************************************************
    /* Default JsonFormatVisitable implementation
    /**********************************************************
     */

    
Default implementation simply calls JsonFormatVisitorWrapper.expectAnyFormat(JavaType). 
Since:
2.1/**
     * Default implementation simply calls {@link JsonFormatVisitorWrapper#expectAnyFormat(JavaType)}.
     * 
     * @since 2.1
     */
    @Override
    public void acceptJsonFormatVisitor(JsonFormatVisitorWrapper visitor, JavaType type)
        throws JsonMappingException
    {
        visitor.expectAnyFormat(type);
    }

    /*
    /**********************************************************
    /* Helper class(es)
    /**********************************************************
     */

    
This marker class is only to be used with annotations, to
indicate that no serializer is configured.
 Specifically, this class is to be used as the marker for annotation JsonSerialize. /**
     * This marker class is only to be used with annotations, to
     * indicate that <b>no serializer is configured</b>.
     *<p>
     * Specifically, this class is to be used as the marker for
     * annotation {@link com.fasterxml.jackson.databind.annotation.JsonSerialize}.
     */
    public abstract static class None
        extends JsonSerializer<Object> { }
}