/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.querydsl.core.types;

import java.util.List;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Maps;

/**
 * {@code QMap} represents a projection of type Map
 *
 * <p>Usage example</p>
 * <pre>
 * {@code
 * List<Map<Expression<?>,?> result = query.from(employee).select(Projections.map(employee.firstName, employee.lastName)).fetch();
 * for (Tuple row : result) {
 *     System.out.println("firstName " + row.get(employee.firstName));
 *     System.out.println("lastName " + row.get(employee.lastName));
 * }
 * }
 * </pre>
 *
 * @author tiwe
 *
 */
public class QMap extends FactoryExpressionBase<Map<Expression<?>,?>> {

    private static final long serialVersionUID = -7545994090073480810L;

    private final ImmutableList<Expression<?>> args;

    /**
     * Create a new QMap instance
     *
     * @param args
     */
    @SuppressWarnings("unchecked")
    protected QMap(Expression<?>... args) {
        super((Class) Map.class);
        this.args = ImmutableList.copyOf(args);
    }

    /**
     * Create a new QMap instance
     *
     * @param args
     */
    @SuppressWarnings("unchecked")
    protected QMap(ImmutableList<Expression<?>> args) {
        super((Class) Map.class);
        this.args = args;
    }

    /**
     * Create a new QMap instance
     *
     * @param args
     */
    @SuppressWarnings("unchecked")
    protected QMap(Expression<?>[]... args) {
        super((Class) Map.class);
        ImmutableList.Builder<Expression<?>> builder = ImmutableList.builder();
        for (Expression<?>[] exprs: args) {
            builder.add(exprs);
        }
        this.args = builder.build();
    }

    @Override
    @Nullable
    public <R, C> R accept(Visitor<R, C> v, C context) {
        return v.visit(this, context);
    }

    @Override
    public List<Expression<?>> getArgs() {
        return args;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        } else if (obj instanceof FactoryExpression) {
            FactoryExpression<?> c = (FactoryExpression<?>) obj;
            return args.equals(c.getArgs()) && getType().equals(c.getType());
        } else {
            return false;
        }
    }

    @Override
    @Nullable
    public Map<Expression<?>, ?> newInstance(Object... args) {
        Map<Expression<?>, Object> map = Maps.newHashMap();
        for (int i = 0; i < args.length; i++) {
            map.put(this.args.get(i), args[i]);
        }
        return map;
    }

}