ConstraintParser.java

package org.openrosa.client.xforms;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Vector;

import org.openrosa.client.model.Condition;
import org.openrosa.client.model.FormDef;
import org.openrosa.client.model.QuestionDef;
import org.openrosa.client.model.ValidationRule;
import org.openrosa.client.model.ModelConstants;
import org.openrosa.client.xforms.XformConstants;

import com.google.gwt.xml.client.Element;


/**
 * Parses constraint attributes of xforms documents and builds the validation
 *  rule objects of the model.
 * 
 * @author daniel
 *
 */
public class ConstraintParser {

	/**
	 * All methods in this class are static and hence we expect no external
	 * Instantiation of this class.
	 */
	private ConstraintParser(){

	}
	
	
	/**
	 * Builds validation rule object from a list of constraint attribute values.
	 * 
	 * @param formDef the form defintion object to which the validation rules belong.
	 * @param constraints the map of constraint attribute values keyed by their 
	 * 					  question definition objects.
	 */
	public static void addValidationRules(FormDef formDef, HashMap constraints){
		Vector rules = new Vector();

		Iterator keys = constraints.keySet().iterator();
		//int id = 0;
		while(keys.hasNext()){
			QuestionDef qtn = (QuestionDef)keys.next();
			String valRuleString = ((String)constraints.get(qtn)).replace(">", ">").replace("<", "<");
			boolean hasValidationRule = valRuleString != null && !valRuleString.isEmpty();
			
			ValidationRule validationRule = buildValidationRule(formDef, qtn.getId(),(String)constraints.get(qtn));
			if(validationRule != null)
				rules.add(validationRule);
			
			boolean similar = isConstraintEquivalent(valRuleString, validationRule, formDef);
			if(similar){
				qtn.setHasAdvancedConstraint(false);
			}else{
				qtn.setHasAdvancedConstraint(true);
				qtn.setAdvancedConstraint(valRuleString);
			}
		}

		formDef.setValidationRules(rules);
	}
	
	public static boolean isConstraintEquivalent(String valString, ValidationRule valRule, FormDef formDef){
		String oldString = valString.trim();
		oldString = XformUtil.ripOutWhitespace(oldString);
		String newString = ConstraintBuilder.fromValidationRule2String(valRule, formDef);
		newString = XformUtil.ripOutWhitespace(newString);
		if(newString.toLowerCase().equals(oldString.toLowerCase())){
			return true;
		}else{
			return false;
		}
	}
	
	/**
	 * Creates a validation rule object from a constraint attribute value.
	 * 
	 * @param formDef the form definition object to build the validation rule for.
	 * @param questionId the identifier of the question which is the target of the validation rule.
	 * @param constraint the constraint attribute value.
	 * @return the validation rule object.
	 */
	private static ValidationRule buildValidationRule(FormDef formDef, int questionId, String constraint){

		ValidationRule validationRule = new ValidationRule(questionId,formDef);
		validationRule.setConditions(getValidationRuleConditions(formDef,constraint,questionId));
		validationRule.setConditionsOperator(XformParserUtil.getConditionsOperator(constraint));

		QuestionDef questionDef = formDef.getQuestion(questionId);
		if(questionDef == null){
			return validationRule;
		}
		Element node = questionDef.getBindNode();
		if(node == null)
			validationRule.setErrorMessage("");
		else
			validationRule.setErrorMessage(node.getAttribute(XformConstants.ATTRIBUTE_NAME_CONSTRAINT_MESSAGE));

		// If the validation rule has no conditions, then its as good as no rule at all.
//		if(validationRule.getConditions() == null || validationRule.getConditions().size() == 0)
//			return null;
		return validationRule;
	}
	
	/**
	 * Creates a skip rule object from a relevent attribute value.
	 * 
	 * @param formDef the form definition object to build the skip rule for.
	 * @param questionId the identifier of the question which is the target of the skip rule.
	 * @param constraint the relevant attribute value.
	 * @param id the identifier for the skip rule.
	 * @param action the skip rule action to apply to the above target question.
	 * @return the skip rule object.
	 */
	public static ValidationRule buildValidationRule(FormDef formDef, int questionId, String constraint, int id, int action){

		ValidationRule validationRule = new ValidationRule(formDef);
		validationRule.setQuestionId(id);
		//TODO For now we are only dealing with enabling and disabling.
		validationRule.setConditionsOperator(action);
		validationRule.setConditions(getValidationRuleConditions(formDef,constraint,action));
		validationRule.setConditionsOperator(XformParserUtil.getConditionsOperator(constraint));


		// If skip rule has no conditions, then its as good as no skip rule at all.
		if(validationRule.getConditions() == null || validationRule.getConditions().size() == 0){
			return null;
		}

		return validationRule;
		
	}

	
	
	
	/**
	 * Gets a list of conditions for a validation rule as per the constraint attribute value.
	 * 
	 * @param formDef the form definition object to which the validation rule belongs.
	 * @param constraint the relevant attribute value.
	 * @param questionId the identifier of the question which is the target of the validation rule.
	 * @return the conditions list.
	 */
	private static Vector getValidationRuleConditions(FormDef formDef, String constraint, int questionId){
		Vector conditions = new Vector();
		Vector list = XpathParser.getConditionsOperatorTokens(constraint);

		Condition condition  = new Condition();
		for(int i=0; i<list.size(); i++){
			condition = getValidationRuleCondition(formDef,(String)list.elementAt(i),questionId);
			if(condition != null)
				conditions.add(condition);
		}

		return conditions;
	}
	
	
	/**
	 * Creates a validation rule condition object from a portion of the constraint attribute value.
	 * 
	 * @param formDef the form definition object to which the validation rule belongs.
	 * @param constraint the token or portion from the constraint attribute value.
	 * @param questionId the identifier of the question that has the validation rule.
	 * @return the new condition object.
	 */
	private static Condition getValidationRuleCondition(FormDef formDef, String constraint, int questionId){		
		Condition condition  = new Condition();
		condition.setId(questionId);
		condition.setOperator(XformParserUtil.getOperator(constraint,ModelConstants.ACTION_ENABLE));
		condition.setQuestionId(questionId);

		//eg . <= 40"
		int pos = XformParserUtil.getOperatorPos(constraint);
		if(pos < 0)
			return null;

		QuestionDef questionDef = formDef.getQuestion(questionId);
		if(questionDef == null)
			return null;

		String value;
		//first try a value delimited by '
		int pos2 = constraint.lastIndexOf('\'');
		if(pos2 > 0){
			//pos1++;
			int pos1 = constraint.substring(0, pos2).lastIndexOf('\'',pos2);
			if(pos1 < 0){
				System.out.println("constraint value not closed with ' characher");
				return null;
			}
			pos1++;
			value = constraint.substring(pos1,pos2);
		}
		else //else we take whole value after operator	
			value = constraint.substring(pos+XformParserUtil.getOperatorSize(condition.getOperator(),ModelConstants.ACTION_ENABLE),constraint.length());

		value = value.trim();
		if(!(value.equals("null") || value.equals(""))){
			condition.setValue(value);

			//This is just for the designer
			if(value.startsWith(formDef.getQuestionID() + "/")){
				condition.setValueQtnDef((QuestionDef)formDef.getElement(value.substring(value.indexOf('/')+1)));
			}

			if(condition.getOperator() == ModelConstants.OPERATOR_NULL){
				return null; //no operator set hence making the condition invalid
			}
		}
		else
			condition.setOperator(ModelConstants.OPERATOR_IS_NULL);

		if(constraint.contains("length(.)") || constraint.contains("count(.)"))
			condition.setFunction(ModelConstants.FUNCTION_LENGTH);

		return condition;
	}
}