/*
 * Copyright (c) 2012, 2019 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql;

import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import org.eclipse.persistence.jpa.jpql.parser.AbsExpression;
import org.eclipse.persistence.jpa.jpql.parser.AbstractDoubleEncapsulatedExpression;
import org.eclipse.persistence.jpa.jpql.parser.AbstractSchemaName;
import org.eclipse.persistence.jpa.jpql.parser.AbstractTraverseParentVisitor;
import org.eclipse.persistence.jpa.jpql.parser.AdditionExpression;
import org.eclipse.persistence.jpa.jpql.parser.AllOrAnyExpression;
import org.eclipse.persistence.jpa.jpql.parser.AndExpression;
import org.eclipse.persistence.jpa.jpql.parser.ArithmeticFactor;
import org.eclipse.persistence.jpa.jpql.parser.AvgFunction;
import org.eclipse.persistence.jpa.jpql.parser.BetweenExpression;
import org.eclipse.persistence.jpa.jpql.parser.CaseExpression;
import org.eclipse.persistence.jpa.jpql.parser.CoalesceExpression;
import org.eclipse.persistence.jpa.jpql.parser.CollectionMemberExpression;
import org.eclipse.persistence.jpa.jpql.parser.CollectionValuedPathExpression;
import org.eclipse.persistence.jpa.jpql.parser.ComparisonExpression;
import org.eclipse.persistence.jpa.jpql.parser.CompoundExpression;
import org.eclipse.persistence.jpa.jpql.parser.ConcatExpression;
import org.eclipse.persistence.jpa.jpql.parser.ConstructorExpression;
import org.eclipse.persistence.jpa.jpql.parser.CountFunction;
import org.eclipse.persistence.jpa.jpql.parser.DateTime;
import org.eclipse.persistence.jpa.jpql.parser.DivisionExpression;
import org.eclipse.persistence.jpa.jpql.parser.EmptyCollectionComparisonExpression;
import org.eclipse.persistence.jpa.jpql.parser.EntityTypeLiteral;
import org.eclipse.persistence.jpa.jpql.parser.EntryExpression;
import org.eclipse.persistence.jpa.jpql.parser.ExistsExpression;
import org.eclipse.persistence.jpa.jpql.parser.Expression;
import org.eclipse.persistence.jpa.jpql.parser.FunctionExpression;
import org.eclipse.persistence.jpa.jpql.parser.IdentificationVariable;
import org.eclipse.persistence.jpa.jpql.parser.InExpression;
import org.eclipse.persistence.jpa.jpql.parser.IndexExpression;
import org.eclipse.persistence.jpa.jpql.parser.InputParameter;
import org.eclipse.persistence.jpa.jpql.parser.KeyExpression;
import org.eclipse.persistence.jpa.jpql.parser.KeywordExpression;
import org.eclipse.persistence.jpa.jpql.parser.LengthExpression;
import org.eclipse.persistence.jpa.jpql.parser.LikeExpression;
import org.eclipse.persistence.jpa.jpql.parser.LocateExpression;
import org.eclipse.persistence.jpa.jpql.parser.LowerExpression;
import org.eclipse.persistence.jpa.jpql.parser.MaxFunction;
import org.eclipse.persistence.jpa.jpql.parser.MinFunction;
import org.eclipse.persistence.jpa.jpql.parser.ModExpression;
import org.eclipse.persistence.jpa.jpql.parser.MultiplicationExpression;
import org.eclipse.persistence.jpa.jpql.parser.NotExpression;
import org.eclipse.persistence.jpa.jpql.parser.NullComparisonExpression;
import org.eclipse.persistence.jpa.jpql.parser.NullIfExpression;
import org.eclipse.persistence.jpa.jpql.parser.NumericLiteral;
import org.eclipse.persistence.jpa.jpql.parser.ObjectExpression;
import org.eclipse.persistence.jpa.jpql.parser.OrExpression;
import org.eclipse.persistence.jpa.jpql.parser.SizeExpression;
import org.eclipse.persistence.jpa.jpql.parser.SqrtExpression;
import org.eclipse.persistence.jpa.jpql.parser.StateFieldPathExpression;
import org.eclipse.persistence.jpa.jpql.parser.StringLiteral;
import org.eclipse.persistence.jpa.jpql.parser.SubstringExpression;
import org.eclipse.persistence.jpa.jpql.parser.SubtractionExpression;
import org.eclipse.persistence.jpa.jpql.parser.SumFunction;
import org.eclipse.persistence.jpa.jpql.parser.TrimExpression;
import org.eclipse.persistence.jpa.jpql.parser.TypeExpression;
import org.eclipse.persistence.jpa.jpql.parser.UpdateItem;
import org.eclipse.persistence.jpa.jpql.parser.UpperExpression;
import org.eclipse.persistence.jpa.jpql.parser.ValueExpression;
import org.eclipse.persistence.jpa.jpql.parser.WhenClause;

/**
 * This visitor calculates the type of an input parameter.
 * <p>
 * Provisional API: This interface is part of an interim API that is still under development and
 * expected to change significantly before reaching stability. It is available at this early stage
 * to solicit feedback from pioneering adopters on the understanding that any code that uses this
 * API will almost certainly be broken (repeatedly) as the API evolves.
 *
 * @version 2.5
 * @since 2.5
 * @author Pascal Filion
 */
public abstract class ParameterTypeVisitor extends AbstractTraverseParentVisitor {

    /**
     * The {@link Expression} that will help to determine the type of the input parameter.
     */
    protected Expression expression;

    /**
     * Used to ignore the type when calculating it. If <b>Object.class</b> was used, then it could
     * incorrectly calculate the type. Example: ":arg = 'JPQL' AND :arg IS NULL", the second :arg
     * should be ignored.
     */
    protected boolean ignoreType;

    /**
     * The {@link InputParameter} for which its type will be searched by visiting the query.
     */
    protected InputParameter inputParameter;

    /**
     * The well defined type, which does not have to be calculated.
     */
    protected Class<?> type;

    /**
     * The fully qualified name of the type.
     */
    protected String typeName;

    /**
     * This is used to prevent an infinite loop.
     */
    protected final Set<Expression> visitedExpressions;

    /**
     * Creates a new <code>ParameterTypeVisitor</code>.
     */
    protected ParameterTypeVisitor() {
        super();
        this.visitedExpressions = new HashSet<Expression>();
    }

    /**
     * Disposes this visitor.
     */
    public void dispose() {
        type           = null;
        typeName       = null;
        expression     = null;
        ignoreType     = false;
        inputParameter = null;
        visitedExpressions.clear();
    }

    /**
     * Returns the type, if it can be determined, of the input parameter.
     *
     * @return Either the closed type or {@link Object} if it can't be determined
     */
    public abstract Object getType();

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AbsExpression expression) {
        // The absolute function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AbstractSchemaName expression) {
        // An abstract schema type always have a type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AdditionExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AllOrAnyExpression expression) {
        super.visit(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AndExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ArithmeticFactor expression) {
        super.visit(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(AvgFunction expression) {
        // The average function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(BetweenExpression expression) {

        Expression betweenExpression = expression.getExpression();
        Expression lowerBound        = expression.getLowerBoundExpression();
        Expression upperBound        = expression.getUpperBoundExpression();

        // The input parameter is the expression to be tested within the range of values
        if (betweenExpression.isAncestor(inputParameter)) {

            if (visitedExpressions.add(expression)) {
                lowerBound.accept(this);
                visitedExpressions.remove(expression);
            }
            else {
                type = null;
                ignoreType = true;
                expression = null;
            }
        }
        // The input parameter is on the lower bound side, traverse the upper bound
        else if (lowerBound.isAncestor(inputParameter)) {

            if (visitedExpressions.add(expression)) {
                upperBound.accept(this);
                visitedExpressions.remove(expression);

                // The upper bound might also be an input parameter
                if ((type == null) && visitedExpressions.add(expression)) {
                    betweenExpression.accept(this);
                    visitedExpressions.remove(expression);
                }
            }
            else {
                type = null;
                ignoreType = true;
                expression = null;
            }
        }
        // The input parameter is on the upper bound side, traverse the lower bound
        else if (upperBound.isAncestor(inputParameter)) {

            if (visitedExpressions.add(expression)) {
                lowerBound.accept(this);
                visitedExpressions.remove(expression);

                // The lower bound might also be an input parameter
                if ((type == null) && visitedExpressions.add(expression)) {
                    betweenExpression.accept(this);
                    visitedExpressions.remove(expression);
                }
            }
            else {
                type = null;
                ignoreType = true;
                expression = null;
            }
        }
        else {
            type = Boolean.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(CaseExpression expression) {
        type = Object.class;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(CoalesceExpression expression) {
        type = Object.class;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(CollectionMemberExpression expression) {

        Expression pathExpression = expression.getCollectionValuedPathExpression();

        if (pathExpression.isAncestor(inputParameter)) {
            type = Collection.class;
        }
        else {
            type = Object.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(CollectionValuedPathExpression expression) {
        // A collection-valued path expression always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ComparisonExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ConcatExpression expression) {
        if (expression.getExpression().isAncestor(inputParameter)) {
            this.expression = expression;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ConstructorExpression expression) {
        typeName = expression.getClassName();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(CountFunction expression) {
        // The count function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(DateTime expression) {
        // A date/time always have a type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(DivisionExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(EmptyCollectionComparisonExpression expression) {

        // Can't determine the type
        if (expression.getExpression().isAncestor(inputParameter)) {
            ignoreType = true;
        }
        else {
            super.visit(expression);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(EntityTypeLiteral expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(EntryExpression expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ExistsExpression expression) {
        // The exist function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(FunctionExpression expression) {
        type = Object.class;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(IdentificationVariable expression) {
        // The identification variable always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(IndexExpression expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(InExpression expression) {

        if (expression.getInItems().isAncestor(inputParameter)) {

            // BNF: ... IN collection_valued_input_parameter
            if (expression.isSingleInputParameter()) {
                type = Collection.class;
            }
            else if (visitedExpressions.add(expression)) {
                expression.getExpression().accept(this);
                visitedExpressions.remove(expression);
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(InputParameter expression) {
        if (inputParameter == null) {
            this.inputParameter = expression;
            expression.getParent().accept(this);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(KeyExpression expression) {
        // KEY() always have a type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(KeywordExpression expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(LengthExpression expression) {

        // LENGTH takes a string as argument
        if (expression.isAncestor(inputParameter)) {
            type = String.class;
        }
        // LENGTH returns an integer value
        else {
            type = Integer.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(LikeExpression expression) {

        Expression stringExpression = expression.getStringExpression();
        Expression patternValue     = expression.getPatternValue();
        Expression escapeCharacter  = expression.getEscapeCharacter();

        if (stringExpression.isAncestor(inputParameter)) {
            this.type = String.class;
        } else if (patternValue.isAncestor(inputParameter)) {
            this.type = String.class;
        } else if (escapeCharacter.isAncestor(inputParameter)) {
            this.type = Character.class;
        } else {
            //Shouldnt go in here?
            this.type = boolean.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(LocateExpression expression) {

        Expression firstExpression  = expression.getFirstExpression();
        Expression secondExpression = expression.getSecondExpression();

        // The first two expressions should be a string
        if (firstExpression .isAncestor(inputParameter) ||
            secondExpression.isAncestor(inputParameter)) {

            this.type = String.class;
        }
        // It either returns an integer or the third argument is an integer
        else {
            this.type = Integer.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(LowerExpression expression) {
        // The lower function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(MaxFunction expression) {
        // The maximum function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(MinFunction expression) {
        // The minimum function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ModExpression expression) {
        visitDoubleEncapsulatedExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(MultiplicationExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(NotExpression expression) {
        super.visit(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(NullComparisonExpression expression) {

        // Can't determine the type
        if (expression.getExpression().isAncestor(inputParameter)) {
            ignoreType = true;
        }
        // A singled valued path expression always have a return type
        else {
            type = Object.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(NullIfExpression expression) {
        visitDoubleEncapsulatedExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(NumericLiteral expression) {
        // A numerical expression always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ObjectExpression expression) {
        super.visit(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(OrExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(SizeExpression expression) {
        // The modulo function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(SqrtExpression expression) {
        if (expression.isAncestor(inputParameter)) {
            super.visit(expression);
        }
        else {
            this.expression = expression;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(StateFieldPathExpression expression) {
        // A state field path expression always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(StringLiteral expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(SubstringExpression expression) {

        // The string primary is always a string
        if (expression.getFirstExpression().isAncestor(inputParameter)) {
            type = String.class;
        }
        // The first or second arithmetic expression is always an integer
        else if (expression.getSecondExpression().isAncestor(inputParameter) ||
                 expression.getThirdExpression() .isAncestor(inputParameter)) {

            type = Integer.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(SubtractionExpression expression) {
        visitCompoundExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(SumFunction expression) {
        // The sum function always have a return type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(TrimExpression expression) {

        if (expression.getTrimCharacter().isAncestor(inputParameter)) {
            type = Character.class;
        }
        else if (expression.getExpression().isAncestor(inputParameter)) {
            type = String.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(TypeExpression expression) {
        if (expression.getExpression() != inputParameter) {
            type = Class.class;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(UpdateItem expression) {
        expression.getStateFieldPathExpression().accept(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(UpperExpression expression) {
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(ValueExpression expression) {
        // VALUE() always have a type
        this.expression = expression;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visit(WhenClause expression) {
        super.visit(expression);
    }

    protected void visitCompoundExpression(CompoundExpression expression) {
        visitDoubleExpressions(
            expression,
            expression.getLeftExpression(),
            expression.getRightExpression(),
            true
        );
    }

    protected void visitDoubleEncapsulatedExpression(AbstractDoubleEncapsulatedExpression expression) {
        visitDoubleExpressions(
            expression,
            expression.getFirstExpression(),
            expression.getSecondExpression(),
            false
        );
    }

    protected void visitDoubleExpressions(Expression expression,
                                          Expression firstExpression,
                                          Expression secondExpression,
                                          boolean traverseParent) {

        // Now traverse the other side to find its return type
        if (firstExpression.isAncestor(inputParameter)) {
            if (visitedExpressions.add(expression)) {
                secondExpression.accept(this);
                visitedExpressions.remove(expression);
            }
            else {
                type = null;
                ignoreType = true;
                expression = null;
            }
        }
        // Now traverse the other side to find its return type
        else if (secondExpression.isAncestor(inputParameter)) {
            if (visitedExpressions.add(expression)) {
                firstExpression.accept(this);
                visitedExpressions.remove(expression);
            }
            else {
                type = null;
                ignoreType = true;
                expression = null;
            }
        }
        // Continue to traverse the hierarchy
        else if (traverseParent) {
            super.visit(expression);
        }
        // Otherwise stop here, the expression has a type
        else {
            this.expression = expression;
        }
    }
}