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This project is a Scala library to facilitate functional logging.
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/*
 * Copyright (c) 2021. Phasmid Software
 */

package com.phasmidsoftware.flog

import scala.annotation.implicitNotFound

/**
 * A type class to enable objects to be rendered laconically as Strings for the purpose of logging.
 *
 * @tparam T the underlying type of the Loggable.
 */
@implicitNotFound(msg = "Cannot find an implicit instance of Loggable[${T}]. Typically, you should invoke a suitable method from Loggables.")
trait Loggable[T] {

  /**
   * Generate a compact String without any newlines for t.
   *
   * @param t the given value to log.
   * @return a String without newlines.
   */
  def toLog(t: T): String
}

/**
 * Companion object to Loggable.
 * This is where the compiler can find the various implicit values of Loggable[T].
 */
object Loggable {

  trait LoggableUnit extends Loggable[Unit] {
    def toLog(t: Unit): String = ""
  }

  implicit object LoggableUnit extends LoggableUnit

  trait LoggableBoolean extends Loggable[Boolean] {
    def toLog(t: Boolean): String = t.toString
  }

  implicit object LoggableBoolean extends LoggableBoolean

  trait LoggableByte extends Loggable[Byte] {
    def toLog(t: Byte): String = t.toString
  }

  implicit object LoggableByte extends LoggableByte

  trait LoggableShort extends Loggable[Short] {
    def toLog(t: Short): String = t.toString
  }

  implicit object LoggableShort extends LoggableShort

  trait LoggableInt extends Loggable[Int] {
    def toLog(t: Int): String = t.toString
  }

  implicit object LoggableInt extends LoggableInt

  trait LoggableLong extends Loggable[Long] {
    def toLog(t: Long): String = t.toString
  }

  implicit object LoggableLong extends LoggableLong

  trait LoggableBigInt extends Loggable[BigInt] {
    def toLog(t: BigInt): String = t.toString
  }

  implicit object LoggableBigInt extends LoggableBigInt

  trait LoggableString extends Loggable[String] {
    def toLog(t: String): String = t
  }

  implicit object LoggableString extends LoggableString

  trait LoggableDouble extends Loggable[Double] {
    def toLog(t: Double): String = t.toString
  }

  implicit object LoggableDouble extends LoggableDouble

  trait LoggableBigDecimal extends Loggable[BigDecimal] {
    def toLog(t: BigDecimal): String = t.toString
  }

  implicit object LoggableBigDecimal extends LoggableBigDecimal

  abstract class LoggableOption[T](implicit evidence: Loggable[T]) extends Loggable[Option[T]] {
    implicit val z: Loggable[Option[T]] = new Loggables {}.optionLoggable

    def toLog(t: Option[T]): String = z.toLog(t)
  }

  implicit object LoggableOptionInt extends LoggableOption[Int]

  implicit object LoggableOptionString extends LoggableOption[String]
}