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Arg.scala
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Arg.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._
import cats.data._
import cats.implicits._
import gql.ast._
import gql.parser.Const
import gql.parser.{Value => V}
import gql.std.FreeApply
import gql.resolver.Resolver
/** A GraphQL argument declaration with an optional default value. The argument references an input type, which is suspended in Eval for
* recursion.
*/
final case class ArgValue[A](
name: String,
input: Eval[In[A]],
defaultValue: Option[V[Const, Unit]],
description: Option[String]
) {
def document(description: String) = copy(description = Some(description))
def default(value: V[Const, Unit]) = copy(defaultValue = Some(value))
}
/** A GraphQL argument value suppled in respect to a declared [[ArgValue]], usually provided by a calling client.
*/
final case class ArgParam[A](
defaulted: Boolean,
value: A
)
/** A combination of an argument declaration [[ArgParam]] and a decoder function for [[ArgParam]]. This structure is more specialized than
* just decoding with [[Arg]], since you will have access to field specific information such as if the argument was provided explicitly or
* the default was used.
*
* The trivial implementation of an [[ArgDecoder]] given an [[ArgValue]]:
* {{{
* val av: ArgValue[A] = ???
* ArgDecoder[A, A](av, _.value.asRight)
* }}}
*/
final case class ArgDecoder[A, B](
av: ArgValue[A],
decode: ArgParam[A] => Either[String, B]
)
/** A small free algebra for combining arguments and decoding them. [[ArgDecoder]] can trivially be lifted into [[Arg]] with loss of
* field-level information.
*
* Note that [[Arg]] must be non-empty, and therefore it does not form an [[cats.Applicative]], but instead it forms [[cats.Apply]].
*/
final case class Arg[+A](impl: FreeApply[Arg.Impl, ValidatedNec[String, A]]) {
def emap[B](f: A => Either[String, B]): Arg[B] =
Arg(impl.map(_.andThen(f(_).toValidatedNec)))
def entries: NonEmptyChain[ArgValue[?]] = impl.enumerate.map(_.av)
}
object Arg {
// We don't care where we came from, only that we can decode it.
type Impl[A] = ArgDecoder[?, A]
def makeFrom[A, B](av: ArgValue[A])(f: ArgParam[A] => Either[String, B]): Arg[B] = {
val fa: Impl[B] = ArgDecoder[A, B](av, f)
val lifted: FreeApply[Impl, B] = FreeApply.lift(fa)
val mapped: FreeApply[Impl, ValidatedNec[String, B]] = lifted.map(_.validNec[String])
Arg(mapped)
}
def make[A](av: ArgValue[A]): Arg[A] =
makeFrom(av)(_.value.asRight)
implicit val applyForArg: Apply[Arg] = new Apply[Arg] {
override def map[A, B](fa: Arg[A])(f: A => B): Arg[B] =
Arg(fa.impl.map(_.map(f)))
override def ap[A, B](ff: Arg[A => B])(fa: Arg[A]): Arg[B] =
Arg((fa.impl, ff.impl).mapN(_ ap _))
}
}
sealed trait EmptyableArg[A] {
def addArg[F[_], B]: Resolver[F, B, (A, B)]
}
object EmptyableArg {
case object Empty extends EmptyableArg[Unit] {
override def addArg[F[_], B]: Resolver[F, B, (Unit, B)] = Resolver.id[F, B].map(((), _))
}
final case class Lift[A](a: Arg[A]) extends EmptyableArg[A] {
override def addArg[F[_], B]: Resolver[F, B, (A, B)] = Resolver.id[F, B].arg(a)
}
}