package pt.ist.renderers.validators;

public class ISSNValidator extends RegexpValidator {

    private boolean required;

    public ISSNValidator() {
	super("[0-9]{4}-[0-9]{3}[0-9X]");
	setMessage("renderers.validator.issn");
	setKey(true);
	setRequired(false);
    }
    
    public ISSNValidator(HtmlChainValidator htmlChainValidator) {
	super(htmlChainValidator, "[0-9]{4}-[0-9]{3}[0-9X]");
	setMessage("renderers.validator.issn");
	setKey(true);
	setRequired(false);
    }

    @Override
    public void performValidation() {
	if (hasValue()) {
	    super.performValidation();
	    if (isValid()) {
		setValid(isCheckSumValid(getComponent().getValue()));
	    }
	} else {
	    setValid(!isRequired());
	}
    }

    private boolean isCheckSumValid(String value) {
	value = value.replaceAll("-", "");
	int res = 0;
	for (int i = 0; i < 7; i++) {
	    res += (8 - i) * (value.charAt(i) - '0');
	}

	int remainder = res % 11;
	int checkDigit = 11 - remainder;

	char result;
	if (remainder == 0) {
	    result = '0';
	} else {
	    if (checkDigit == 10) {
		result = 'X';
	    } else {
		result = (char) (checkDigit + '0');
	    }
	}
	return value.charAt(7) == result;
    }

    private boolean hasValue() {
	return (getComponent().getValue() != null && getComponent().getValue().length() > 0);
    }

    public boolean isRequired() {
	return required;
    }

    public void setRequired(boolean required) {
	this.required = required;
    }

}