package com.fasterxml.jackson.databind.ser;

import java.util.*;
import java.util.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.ser.impl.ReadOnlyClassToSerializerMap;
import com.fasterxml.jackson.databind.util.TypeKey;

Simple cache object that allows for doing 2-level lookups: first level is
by "local" read-only lookup Map (used without locking)
and second backup level is by a shared modifiable HashMap.
The idea is that after a while, most serializers are found from the
local Map (to optimize performance, reduce lock contention),
but that during buildup we can use a shared map to reduce both
number of distinct read-only maps constructed, and number of
serializers constructed.

Cache contains three kinds of entries,
based on combination of class pair key. First class in key is for the
type to serialize, and second one is type used for determining how
to resolve value type. One (but not both) of entries can be null.
/**
 * Simple cache object that allows for doing 2-level lookups: first level is
 * by "local" read-only lookup Map (used without locking)
 * and second backup level is by a shared modifiable HashMap.
 * The idea is that after a while, most serializers are found from the
 * local Map (to optimize performance, reduce lock contention),
 * but that during buildup we can use a shared map to reduce both
 * number of distinct read-only maps constructed, and number of
 * serializers constructed.
 *<p>
 * Cache contains three kinds of entries,
 * based on combination of class pair key. First class in key is for the
 * type to serialize, and second one is type used for determining how
 * to resolve value type. One (but not both) of entries can be null.
 */
public final class SerializerCache
{
    
Shared, modifiable map; all access needs to be through synchronized blocks.
 NOTE: keys are of various types (see below for key types), in addition to basic JavaType used for "untyped" serializers. /**
     * Shared, modifiable map; all access needs to be through synchronized blocks.
     *<p>
     * NOTE: keys are of various types (see below for key types), in addition to
     * basic {@link JavaType} used for "untyped" serializers.
     */
    private final HashMap<TypeKey, JsonSerializer<Object>> _sharedMap
        = new HashMap<TypeKey, JsonSerializer<Object>>(64);

    
Most recent read-only instance, created from _sharedMap, if any.
/**
     * Most recent read-only instance, created from _sharedMap, if any.
     */
    private final AtomicReference<ReadOnlyClassToSerializerMap> _readOnlyMap
        = new AtomicReference<ReadOnlyClassToSerializerMap>();

    public SerializerCache() { }

    
Method that can be called to get a read-only instance populated from the
most recent version of the shared lookup Map.
/**
     * Method that can be called to get a read-only instance populated from the
     * most recent version of the shared lookup Map.
     */
    public ReadOnlyClassToSerializerMap getReadOnlyLookupMap()
    {
        ReadOnlyClassToSerializerMap m = _readOnlyMap.get();
        if (m != null) {
            return m;
        }
        return _makeReadOnlyLookupMap();
    }

    private final synchronized ReadOnlyClassToSerializerMap _makeReadOnlyLookupMap() {
        // double-locking; safe, but is it really needed? Not doing that is only a perf problem,
        // not correctness
        ReadOnlyClassToSerializerMap m = _readOnlyMap.get();
        if (m == null) {
            m = ReadOnlyClassToSerializerMap.from(_sharedMap);
            _readOnlyMap.set(m);
        }
        return m;
    }

    /*
    /**********************************************************
    /* Lookup methods for accessing shared (slow) cache
    /**********************************************************
     */

    public synchronized int size() {
        return _sharedMap.size();
    }

    
Method that checks if the shared (and hence, synchronized) lookup Map might have
untyped serializer for given type.
/**
     * Method that checks if the shared (and hence, synchronized) lookup Map might have
     * untyped serializer for given type.
     */
    public JsonSerializer<Object> untypedValueSerializer(Class<?> type)
    {
        synchronized (this) {
            return _sharedMap.get(new TypeKey(type, false));
        }
    }

    public JsonSerializer<Object> untypedValueSerializer(JavaType type)
    {
        synchronized (this) {
            return _sharedMap.get(new TypeKey(type, false));
        }
    }

    public JsonSerializer<Object> typedValueSerializer(JavaType type)
    {
        synchronized (this) {
            return _sharedMap.get(new TypeKey(type, true));
        }
    }

    public JsonSerializer<Object> typedValueSerializer(Class<?> cls)
    {
        synchronized (this) {
            return _sharedMap.get(new TypeKey(cls, true));
        }
    }

    /*
    /**********************************************************
    /* Methods for adding shared serializer instances
    /**********************************************************
     */
    
    
Method called if none of lookups succeeded, and caller had to construct
a serializer. If so, we will update the shared lookup map so that it
can be resolved via it next time.
/**
     * Method called if none of lookups succeeded, and caller had to construct
     * a serializer. If so, we will update the shared lookup map so that it
     * can be resolved via it next time.
     */
    public void addTypedSerializer(JavaType type, JsonSerializer<Object> ser)
    {
        synchronized (this) {
            if (_sharedMap.put(new TypeKey(type, true), ser) == null) {
                // let's invalidate the read-only copy, too, to get it updated
                _readOnlyMap.set(null);
            }
        }
    }

    public void addTypedSerializer(Class<?> cls, JsonSerializer<Object> ser)
    {
        synchronized (this) {
            if (_sharedMap.put(new TypeKey(cls, true), ser) == null) {
                // let's invalidate the read-only copy, too, to get it updated
                _readOnlyMap.set(null);
            }
        }
    }
    
    public void addAndResolveNonTypedSerializer(Class<?> type, JsonSerializer<Object> ser,
            SerializerProvider provider)
        throws JsonMappingException
    {
        synchronized (this) {
            if (_sharedMap.put(new TypeKey(type, false), ser) == null) {
                _readOnlyMap.set(null);
            }
            // Need resolution to handle cyclic POJO type dependencies
            /* 14-May-2011, tatu: Resolving needs to be done in synchronized manner;
             *   this because while we do need to register instance first, we also must
             *   keep lock until resolution is complete.
             */
            if (ser instanceof ResolvableSerializer) {
                ((ResolvableSerializer) ser).resolve(provider);
            }
        }
    }

    public void addAndResolveNonTypedSerializer(JavaType type, JsonSerializer<Object> ser,
            SerializerProvider provider)
        throws JsonMappingException
    {
        synchronized (this) {
            if (_sharedMap.put(new TypeKey(type, false), ser) == null) {
                _readOnlyMap.set(null);
            }
            // Need resolution to handle cyclic POJO type dependencies
            /* 14-May-2011, tatu: Resolving needs to be done in synchronized manner;
             *   this because while we do need to register instance first, we also must
             *   keep lock until resolution is complete.
             */
            if (ser instanceof ResolvableSerializer) {
                ((ResolvableSerializer) ser).resolve(provider);
            }
        }
    }

    
Another alternative that will cover both access via raw type and matching
fully resolved type, in one fell swoop.
Since:
2.7/**
     * Another alternative that will cover both access via raw type and matching
     * fully resolved type, in one fell swoop.
     *
     * @since 2.7
     */
    public void addAndResolveNonTypedSerializer(Class<?> rawType, JavaType fullType,
            JsonSerializer<Object> ser,
            SerializerProvider provider)
        throws JsonMappingException
    {
        synchronized (this) {
            Object ob1 = _sharedMap.put(new TypeKey(rawType, false), ser);
            Object ob2 = _sharedMap.put(new TypeKey(fullType, false), ser);
            if ((ob1 == null) || (ob2 == null)) {
                _readOnlyMap.set(null);
            }
            if (ser instanceof ResolvableSerializer) {
                ((ResolvableSerializer) ser).resolve(provider);
            }
        }
    }

    
Method called by StdSerializerProvider#flushCachedSerializers() to
clear all cached serializers
/**
     * Method called by StdSerializerProvider#flushCachedSerializers() to
     * clear all cached serializers
     */
    public synchronized void flush() {
        _sharedMap.clear();
    }
}