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Cursor.scala
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Cursor.scala
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/*
* Copyright 2023 Valdemar Grange
*
* 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 gql
import cats.data._
import cats.implicits._
import cats._
/** One arc in a GraphQL path.
*/
sealed trait GraphArc {
def asString: String
}
object GraphArc {
final case class Field(name: String) extends GraphArc {
def asString = name
}
final case class Index(index: Int) extends GraphArc {
def asString = index.toString
}
}
/** A collection of GraphQL arcs wraped up with an associated algebra. Usually used for reporting where an error occured.
*/
final case class Cursor(path: Chain[GraphArc]) {
def add(next: GraphArc): Cursor = Cursor(path :+ next)
def index(idx: Int) = add(GraphArc.Index(idx))
def field(name: String) = add(GraphArc.Field(name))
def headOption = path.headOption
def head = headOption.get
def lastOption = path.lastOption
def last = lastOption.get
def tail = Cursor(Chain.fromOption(path.uncons).flatMap { case (_, tl) => tl })
def uncons = path.uncons.map { case (p, tl) => (p, Cursor(tl)) }
def dropInit = Cursor(Chain.fromOption(path.initLast).flatMap { case (c, _) => c })
lazy val formatted = {
val tl = path.map {
case GraphArc.Field(name) => s".$name"
case GraphArc.Index(i) => s"[$i]"
}
s"root${tl.mkString_("")}"
}
}
object Cursor {
val empty = Cursor(Chain.empty)
implicit val monoidForCursor: Monoid[Cursor] = new Monoid[Cursor] {
def empty = Cursor.empty
def combine(x: Cursor, y: Cursor) = Cursor(x.path ++ y.path)
}
implicit val showForCursor: Show[Cursor] = Show.show[Cursor](_.formatted)
}