StringCollectionLens.java

package net.zer0bandwidth.android.lib.database.sqlitehouse.refractor;

import android.content.ContentValues;
import android.database.Cursor;
import android.os.Bundle;
import android.text.TextUtils;

import net.zer0bandwidth.android.lib.database.SQLiteSyntax;

import java.util.Collection;
import java.util.Collections;

import static net.zer0bandwidth.android.lib.database.SQLiteSyntax.SQLITE_NULL;

/**
 * Provides a canonical implementation of a {@link Lens} which can marshal a
 * collection of strings to/from a single column in a database row.
 * @since zer0bandwidth-net/android 0.1.5 (#42)
 */
public abstract class StringCollectionLens<C extends Collection<String>>
extends Lens<C>
implements Refractor<C>
{
/**
 * Implementation classes must provide a concrete override of this method to
 * declare the delimiter that is used/sought between items in the serialized
 * list.
 * @return the delimiter in the serialized list
 */
protected abstract String getDelimiter() ;

/**
 * Implementation classes must provide a concrete override of this method to
 * generate instances of the collection class which contains the list items.
 * @return a collection capable of storing the list items
 */
protected abstract C getCollectionInstance() ;

/**
 * Serializes the list as a string, using the delimiter provided by
 * {@link #getDelimiter()}.
 * @param asValues a collection of string values
 * @return a serialization of the list
 */
public String toStringValue( C asValues )
{
return ( asValues == null ? null :
TextUtils.join( this.getDelimiter(), asValues ) ) ;
}

@Override
public String getSQLiteDataType()
{ return SQLiteSyntax.SQLITE_TYPE_TEXT ; }

@Override
public String toSQLiteString( C o )
{
return ( o == null ? SQLITE_NULL :
String.format( "'%s'", this.toStringValue(o) ) ) ;
}

@Override
public StringCollectionLens<C> addToContentValues(
ContentValues vals, String sKey, C val )
{
vals.put( sKey, this.toStringValue(val) ) ;
return this ;
}

/**
 * Adds the collection of strings to a {@link Bundle} as a string array.
 *
 * This will <i>always</i> be rendered in the bundle as a string array,
 * regardless of the algorithm that would marshal the collection to/from a
 * database as a string serialization.
 *
 * @since zer0bandwidth-net/android 0.1.7 (#50)
 */
@Override
public StringCollectionLens<C> addToBundle(
Bundle bndl, String sKey, C val )
{
bndl.putStringArray( sKey, val.toArray( new String[val.size()] ) ) ;
return this ;
}

@Override
public C fromCursor( Cursor crs, String sKey )
{
String sValues = crs.getString( crs.getColumnIndex( sKey ) ) ;
if( sValues == null ) return null ;
C asValues = this.getCollectionInstance() ;
Collections.addAll( asValues, sValues.split( this.getDelimiter() ) ) ;
return asValues ;
}

/**
 * Fetches a collection of strings from a {@link Bundle} as a string array.
 *
 * This will <i>always</i> be rendered in the bundle as a string array,
 * regardless of the algorithm that would marshal the collection to/from a
 * database as a string serialization.
 *
 * @since zer0bandwidth-net/android 0.1.7 (#50)
 */
@Override
public C fromBundle( Bundle bndl, String sKey )
{
String[] asBundled = bndl.getStringArray( sKey ) ;
if( asBundled == null || asBundled.length == 0 ) return null ;
C asValues = this.getCollectionInstance() ;
Collections.addAll( asValues, asBundled ) ;
return asValues ;
}
}