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Query.scala
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Query.scala
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/*
* Copyright 2023 Lucas Satabin
*
* 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 fs2.data.mft.query
import cats.data.NonEmptyList
/* An abstract representation of query language that consists of
* nested for loops over some paths and tagged element construction.
*
* ''Note for implementers'': a path is always relative to the closes enclosing `for` clause.
*/
sealed trait Query[Tag, Path]
object Query {
case class Empty[Tag, Path]() extends Query[Tag, Path]
case class ForClause[Tag, Path](variable: String, source: Path, result: Query[Tag, Path]) extends Query[Tag, Path]
case class LetClause[Tag, Path](variable: String, query: Query[Tag, Path], result: Query[Tag, Path])
extends Query[Tag, Path]
case class Ordpath[Tag, Path](path: Path) extends Query[Tag, Path]
case class Variable[Tag, Path](name: String) extends Query[Tag, Path]
case class Node[Tag, Path](tag: Tag, child: Query[Tag, Path]) extends Query[Tag, Path]
case class Leaf[Tag, Path](tag: Tag) extends Query[Tag, Path]
case class Sequence[Tag, Path](elements: NonEmptyList[Query[Tag, Path]]) extends Query[Tag, Path]
case class LeafFunction[Tag, Path](f: Tag => Either[String, Tag]) extends Query[Tag, Path]
}