package org.drools.template.objects;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import org.drools.template.DataProvider;
import org.drools.template.parser.Column;
import org.drools.template.parser.TemplateContainer;

/**
 * An object of this class acts as a DataProvider for rule templates.
 * It may be created with a collection of maps or objects. The template's
 * column names are used as keys or Bean-stype accessors to obtain the
 * actual parameters for the substitution.
 * 
 * @author Wolfgang Laun
 */
public class ObjectDataProvider implements DataProvider {

	private Column[] columns;
    private Iterator<?> iter;
	
     /**
     * Constructor from a template container
     * @param tcont a template container
     * @param objs a collection of maps or objects  
     */
	public ObjectDataProvider( TemplateContainer tcont, Collection<?> objs ) {
	    columns = tcont.getColumns();
        iter = objs.iterator();
	}


	public boolean hasNext() {
		return iter.hasNext();
	}

	private Method getMethod( Class<?> clazz, String field ){
		String Field = Character.toUpperCase( field.charAt( 0 ) ) + field.substring( 1 );
		String getter = "get" + Field;
		try {
			return clazz.getMethod( getter );
		} catch (SecurityException e) {
			return null;
		} catch (NoSuchMethodException e) {
		}
		getter = "is" + Field;
		try {
			return clazz.getMethod( getter );
		} catch (SecurityException e) {
			return null;
		} catch (NoSuchMethodException e) {
		}
		getter = field;
		try {
			return clazz.getMethod( getter );
		} catch (Exception e) {
			return null;
		}
	}
	
	private Field getField( Class<?> clazz, String field ){
		try {
			return clazz.getField( field );
		} catch (Exception e) {
			return null;
		}
	}
	
	private String[] nextFromMap( Object obj ) {
		@SuppressWarnings( "unchecked" )
		Map<String,Object> map = (Map)obj;
		String[] values = new String[columns.length];
		for( int iCol = 0; iCol < columns.length; iCol++ ){
			Object target = map.get( columns[iCol].getName() );
			values[iCol] = target == null ? null : target.toString();
		}
		return values;
	}

	private String[] nextFromObject( Object obj ) {
		Class<?> clazz = obj.getClass();
		String[] values = new String[columns.length];
		for( int iCol = 0; iCol < columns.length; iCol++ ){
			String fieldName = columns[iCol].getName();
			Object val = null;
			try {
				Method method = getMethod( clazz, fieldName );
				if( method != null ){
					val = method.invoke( obj );
				} else {
					Field field = getField( clazz, fieldName );
					if( field != null ){
						val = field.get( obj );
					}
				}
			} catch (Exception e) {
				// leave it null
			}
			values[iCol] = val == null ? null : val.toString();
		}
		return values;
	}
	
	public String[] next() {
		Object obj = iter.next();
		if( obj instanceof Map ){
			return nextFromMap( obj );
		} else {
			return nextFromObject( obj );
		}
	}
}