package won.protocol.message;

import org.apache.jena.graph.Node;
import org.apache.jena.query.*;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.engine.binding.Binding;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * User: ypanchenko
 * Date: 02.06.2015
 */
public class WonSparqlValidator {
    private final Logger logger = LoggerFactory.getLogger(getClass());
    public static final Var SELECT_VALIDATION_VARIABLE = Var.alloc("check");
    public static final String SELECT_VALIDATION_PASSED_VALUE = "OK";

    private Query constraint;
    private String name = "unknown";

    public WonSparqlValidator(Query constraint) {
        if (!constraint.isAskType() && !constraint.isSelectType()) {
            throw new IllegalArgumentException("Wrong constriant type!");
        }
        this.constraint = constraint;
    }

    public WonSparqlValidator(Query constraint, String name) {
        if (!constraint.isAskType() && !constraint.isSelectType()) {
            throw new IllegalArgumentException("Wrong constriant type!");
        }
        this.constraint = constraint;
        this.name = name;
    }

    public ValidationResult validate(Dataset input) {
        if (logger.isDebugEnabled()) {
            logger.debug("validating constraint of WonSparqlValidator '{}'", name);
        }
        if (constraint.isAskType()) {
            return validateAsk(input);
        } else if (constraint.isSelectType()) {
            return validateSelect(input);
        }
        return new ValidationResult(false, "Invalid constraint: " + constraint.toString());
    }

    private ValidationResult validateSelect(final Dataset input) {
        try (QueryExecution qe = QueryExecutionFactory.create(constraint, input)) {
            ResultSet result = qe.execSelect();
            while (result.hasNext()) {
                Binding binding = result.nextBinding();
                Node node = binding.get(SELECT_VALIDATION_VARIABLE);
                if (node != null) {
                    if (node.isLiteral()) {
                        String resultString = node.getLiteralValue().toString();
                        if (SELECT_VALIDATION_PASSED_VALUE.equals(resultString)) {
                            return new ValidationResult();
                        } else {
                            return new ValidationResult(false, "SELECT query produced this binding: " + binding
                                    .toString());
                        }
                    }
                }
            }
            return new ValidationResult(false, "SELECT query did not produce a binding for required variable 'check'");
        }
    }

    private void printResult(final ResultSet result) {
        System.out.println(ResultSetFormatter.asText(result));
    }

    private ValidationResult validateAsk(final Dataset input) {
        try (QueryExecution qe = QueryExecutionFactory.create(constraint, input)) {
            if (qe.execAsk()) {
                return new ValidationResult(false, "ASK query returned true");
            }
            return new ValidationResult();
        }
    }

    public String getName() {
        return name;
    }

    public static class ValidationResult {
        private boolean valid = true;
        private String errorMessage = null;

        public ValidationResult() {
        }

        public ValidationResult(final boolean valid, final String errorMessage) {
            this.valid = valid;
            this.errorMessage = errorMessage;
        }

        public boolean isValid() {
            return valid;
        }

        public String getErrorMessage() {
            return errorMessage;
        }
    }
}