// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.bo.change;

import java.util.*;

import org.litesoft.core.util.*;

public class OriginalValueChangeTrackerImpl implements OriginalValueChangeTracker
{
    private HashSet<String> mChangedAttributeNames = new HashSet<String>();

    private transient Map<String, ChangeEntry> mAttributeNameToOriginalValues; // null == sent across the wire!

    public OriginalValueChangeTrackerImpl( Map<String, ChangeEntry> pAttributeNameToOriginalValues )
    {
        mAttributeNameToOriginalValues = pAttributeNameToOriginalValues;
    }

    public OriginalValueChangeTrackerImpl()
    {
        this( null );
    }

    public OriginalValueChangeTracker clear()
    {
        mChangedAttributeNames.clear();
        if ( mAttributeNameToOriginalValues != null )
        {
            mAttributeNameToOriginalValues.clear();
        }
        return createNullTracker();
    }

    public OriginalValueChangeTracker recordChange( String pAttributeName, ChangeEntry pNewChangeEntry, Object pOldValue, Object pNewValue )
    {
        if ( mAttributeNameToOriginalValues == null )
        {
            throw new IllegalStateException( "Attempt to record a change on a re-constituted from Serialization immutable instance!" );
        }

        if ( !mChangedAttributeNames.contains( pAttributeName ) ) // Not currently in change set
        {
            // then add it AND its Original value
            mChangedAttributeNames.add( pAttributeName );
            mAttributeNameToOriginalValues.put( pAttributeName, pNewChangeEntry );
            return this;
        }

        ChangeEntry zOrigChangeEntry = mAttributeNameToOriginalValues.get( pAttributeName );
        if ( pNewChangeEntry.equals( zOrigChangeEntry ) ) // Original value == new Value
        {
            // then pretend we never saw it!
            if ( mChangedAttributeNames.size() == 1 )
            {
                return clear();
            }
            mChangedAttributeNames.remove( pAttributeName );
            mAttributeNameToOriginalValues.remove( pAttributeName );
        }
        return this;
    }

    public boolean hasChanges()
    {
        return !mChangedAttributeNames.isEmpty();
    }

    public boolean isAttributeChanged( String pAttributeName )
    {
        return mChangedAttributeNames.contains( pAttributeName );
    }

    public boolean isOriginalValueAvailableFor( String pAttributeName )
    {
        return (mAttributeNameToOriginalValues != null) && mAttributeNameToOriginalValues.containsKey( pAttributeName );
    }

    public Object getOriginalValueFor( String pAttributeName )
    {
        ChangeEntry zChangeEntry = getOriginalValueChangeEntryFor( pAttributeName );
        return (zChangeEntry != null) ? zChangeEntry.getOriginalValue() : null;
    }

    public ChangeEntry getOriginalValueChangeEntryFor( String pAttributeName )
    {
        return (mAttributeNameToOriginalValues != null) ? mAttributeNameToOriginalValues.get( pAttributeName ) : null;
    }

    public String[] getChangedAttributeNames()
    {
        return mChangedAttributeNames.isEmpty() ? //
               UtilsCommon.EMPTY_STRING_ARRAY : //
               mChangedAttributeNames.toArray( new String[mChangedAttributeNames.size()] );
    }

    protected OriginalValueChangeTracker createNullTracker()
    {
        return OriginalValueChangeTrackerNull.INSTANCE;
    }
}