package foundation.data.rule;

import foundation.dao.bizlogic.ICodeProvider;
import foundation.data.entity.Entity;
import foundation.data.object.IParamProvider;
import foundation.util.MapList;
import foundation.variant.provider.DataEvent;

public abstract class FieldDefaultValueCreator {
	
	private static MapList<String, Class<? extends FieldDefaultValueCreator>> items;
	protected String fieldName;
	protected String category;
	protected String rule;
	protected FieldDefaultValueType type;
	
	static {
		items = new MapList<String, Class<? extends FieldDefaultValueCreator>>();
	}

	public static FieldDefaultValueCreator getInstance(String fieldName, String expression) throws Exception {
		String rule = expression;
		int pos = expression.indexOf(".");
		
		FieldDefaultValueCreator result = null;
		
		//1. 形如@{user.id}、@{newDate}这样的规则
		if (expression.startsWith("@{")) {
			result = new VariantDefaultValueCreator();
		}
		
		//2. 形如Code.OrderCode这样的规则
		else if (pos > 0) {
			String category = expression.substring(0, pos);
			rule = expression.substring(pos + 1);
			
			Class<? extends FieldDefaultValueCreator> clazz = items.get(category);
			if (clazz != null) {
				result = clazz.newInstance();
			}
		}
		else {
			result = new SimpleDefaultValueCreator();
		}
		
		if (result == null) {
			result = new SimpleDefaultValueCreator();
		}
		
		result.setFieldName(fieldName);
		result.setRule(rule);
		
		return result;
	}
	
	public abstract Object exec(DataEvent saveEvent, Entity entity, IParamProvider paramProvider);

	public static void registerOne(String category, Class<? extends FieldDefaultValueCreator> clazz) {
		if (category == null) {
			return;
		}
		
		items.add(category, clazz);		
	}

	protected void setRule(String rule) {
		this.rule = rule;
	}

	public String getFieldName() {
		return fieldName;
	}

	public void setFieldName(String fieldName) {
		this.fieldName = fieldName;
	}

	public FieldDefaultValueType getType() {
		return type;
	}

	public ICodeProvider getCodeProvider() {
		return null;
	}

}