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package caliban.client

import scala.util.Try
import java.util.UUID

import caliban.client.CalibanClientError.DecodingError
import caliban.client.__Value._

import scala.annotation.implicitNotFound

/**
 * Typeclass that defines how to decode a scalar from a GraphQL response into a proper value of type `A`.
 */
@implicitNotFound(
  """Cannot find a ScalarDecoder for type ${A}.

Caliban needs it to know how to decode a scalar of type ${A}.
"""
)
trait ScalarDecoder[+A] {
  def decode(value: __Value): Either[DecodingError, A]
}

object ScalarDecoder {
  implicit val short: ScalarDecoder[Short]           = {
    case __NumberValue(value) => Right(value.toShort)
    case other                => Left(DecodingError(s"Can't build a Short from input $other"))
  }
  implicit val int: ScalarDecoder[Int]               = {
    case __NumberValue(value) =>
      Try(value.toIntExact).toEither.left.map(ex => DecodingError(s"Can't build an Int from input $value", Some(ex)))
    case other                => Left(DecodingError(s"Can't build an Int from input $other"))
  }
  implicit val long: ScalarDecoder[Long]             = {
    case __NumberValue(value) =>
      Try(value.toLongExact).toEither.left.map(ex => DecodingError(s"Can't build a Long from input $value", Some(ex)))
    case other                => Left(DecodingError(s"Can't build a Long from input $other"))
  }
  implicit val bigInt: ScalarDecoder[BigInt]         = {
    case __NumberValue(value) =>
      Try(value.toBigIntExact).toEither.left
        .map(ex => DecodingError(s"Can't build a BigInt from input $value", Some(ex)))
        .flatMap {
          case None    => Left(DecodingError(s"Can't build a BigInt from input $value"))
          case Some(v) => Right(v)
        }
    case __StringValue(value) =>
      Try(BigInt(value)).toEither.left
        .map(ex => DecodingError(s"Can't build a BigInt from input $value", Some(ex)))
    case other                => Left(DecodingError(s"Can't build a BigInt from input $other"))
  }
  implicit val float: ScalarDecoder[Float]           = {
    case __NumberValue(value) => Right(value.toFloat)
    case other                => Left(DecodingError(s"Can't build a Float from input $other"))
  }
  implicit val double: ScalarDecoder[Double]         = {
    case __NumberValue(value) => Right(value.toDouble)
    case other                => Left(DecodingError(s"Can't build a Double from input $other"))
  }
  implicit val bigDecimal: ScalarDecoder[BigDecimal] = {
    case __NumberValue(value) => Right(value)
    case __StringValue(value) =>
      Try(BigDecimal(value)).toEither.left
        .map(ex => DecodingError(s"Can't build a BigDecimal from input $value", Some(ex)))
    case other                => Left(DecodingError(s"Can't build a BigDecimal from input $other"))
  }
  implicit val boolean: ScalarDecoder[Boolean]       = {
    case __BooleanValue(value) => Right(value)
    case other                 => Left(DecodingError(s"Can't build a Boolean from input $other"))
  }
  implicit val string: ScalarDecoder[String]         = {
    case __StringValue(value) => Right(value)
    case other                => Left(DecodingError(s"Can't build a String from input $other"))
  }
  implicit val uuid: ScalarDecoder[UUID]             = {
    case __StringValue(value) =>
      Try(UUID.fromString(value)).toEither.left
        .map(ex => DecodingError(s"Can't build a UUID from input $value", Some(ex)))
    case other                => Left(DecodingError(s"Can't build a UUID from input $other"))
  }
  implicit val unit: ScalarDecoder[Unit]             = {
    case __ObjectValue(Nil) => Right(())
    case other              => Left(DecodingError(s"Can't build Unit from input $other"))
  }
  implicit val json: ScalarDecoder[__Value]          = value => Right(value)
}