/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.ignite.spark.impl.optimization.accumulator

import org.apache.ignite.spark.impl.optimization.{IgniteQueryContext, exprToString, toAttributeReference}
import org.apache.spark.sql.catalyst.expressions.{Attribute, NamedExpression, SortOrder}

/**
  * Accumulator to store info about UNION query.
  */
private[apache] case class UnionSQLAccumulator(
    igniteQueryContext: IgniteQueryContext,
    children: Seq[QueryAccumulator],
    outputExpressions: Seq[NamedExpression],
    orderBy: Option[Seq[SortOrder]] = None
) extends QueryAccumulator {
    /** @inheritdoc */
    override def compileQuery(prettyPrint: Boolean = false): String = {
        val delim = if (prettyPrint) "\n" else " "
        val tab = if (prettyPrint) "  " else ""

        val query = children.map(_.compileQuery(prettyPrint)).mkString(s"${delim}UNION$delim")

        orderBy match {
            case Some(sortOrders) ⇒
                query + s"${delim}ORDER BY ${sortOrders.map(exprToString(_)).mkString(s",$delim$tab")}"

            case None ⇒ query
        }
    }

    /** @inheritdoc */
    override def simpleString: String =
        s"UnionSQLAccumulator(orderBy: ${orderBy.map(_.map(exprToString(_)).mkString(", ")).getOrElse("[]")})"

    /** @inheritdoc */
    override def withOutputExpressions(outputExpressions: Seq[NamedExpression]): QueryAccumulator =
        copy(outputExpressions= outputExpressions)

    /** @inheritdoc */
    override def withOrderBy(orderBy: Seq[SortOrder]): QueryAccumulator = copy(orderBy = Some(orderBy))

    /** @inheritdoc */
    override def output: Seq[Attribute] = outputExpressions.map(toAttributeReference(_, Seq.empty))

    /** @inheritdoc */
    override lazy val qualifier: String = igniteQueryContext.uniqueTableAlias
}
