deeperunderstanding

fun main() {

    val lines = Try {
        File("./my-pets.csv").readLines().map { it.split(',') }
    }

    val pets : Try<ResultSet<Pet>> = lines.map {
        it.map(::toPet).asResultSet().map { pet -> pet.copy(name = pet.name.toUpperCase()) }
    }
    

deeperunderstanding

typealias ResultSet<T> = Pair<List<Success<T>>, List<Failure<T>>>

fun <T> List<Try<T>>.asResultSet(): ResultSet<T> = this.partition { it is Success } as ResultSet<T>

fun <T, R> ResultSet<T>.map(transform: (T) -> R): ResultSet<R> =
    this.first.map { it.map(transform) }.asResultSet().let { result ->
        Pair(result.first, this.second as List<Failure<R>> + result.second)
    }

deeperunderstanding

fun main() {
    val resultA : Try<String> = Try { "Hello, World" }
    val resultB : Try<String> = Try { throw Exception("Not Today!") }

    println(resultA)
    println(resultB)
}

deeperunderstanding

fun toPet(values: List<String>): Try<Pet> {
    val name = values[0]
    val ageTry = Try { values[1].toInt() }.recoverWith { Failure<Int>(Exception("Cannot extract age!")) }
    val typeTry = PetType.lookup(values[2]).recover { PetType.Invalid }

    return ageTry.flatMap { age -> typeTry.map { type -> Pet(name, age, type) } }
}


enum class PetType(val type: String) {

deeperunderstanding

fun toPet(values: List<String>): Try<Pet> {
    val name = values[0]
    val ageTry = Try { values[1].toInt() }
    val typeTry = PetType.lookup(values[2])

    return ageTry.flatMap { age -> typeTry.map { type -> Pet(name, age, type) } }
}

enum class PetType(val type: String) {

deeperunderstanding

sealed class Try<T> {

    companion object {
        operator fun <T> invoke(func: () -> T): Try<T> =
            try {
                Success(func())
            } catch (error: Exception) {
                Failure(error)
            }
    }

deeperunderstanding

object TrySequence {
    operator fun <T> Try<T>.component1(): T = when (this) {
        is Success -> this.value
        is Failure -> throw this.error
    }
}

fun <T> Try.Companion.sequential(func: TrySequence.() -> T): Try<T> {
    return Try { func(TrySequence) }
}

deeperunderstanding

fun toPet(values: List<String>) = Try.sequential {
    val name = values[0]
    val (age) = Try { values[1].trim().toInt() }
    val (type) = PetType.lookup(values[2].trim())

    Pet(name, age, type)
}

deeperunderstanding

fun main() {

    val lines = Try {
        File("./my-pets.csv").readLines().map { it.split(',') }
    }

    val pets : Try<List<Pet>> = lines.flatMap { Try.traverse(it, ::toPet) }

    when (pets) {
        is Success -> println(pets.value)

deeperunderstanding

fun <T, R> Try.Companion.traverse(list: List<T>, transform: (T) -> Try<R>): Try<List<R>> = Try {
    val newList = mutableListOf<R>()
    for (value in list) {
        when(val result = transform(value)) {
            is Success -> newList.add(result.value)
            is Failure -> throw result.error
        }
    }
    newList
}