result.kt

package com.qwert2603.myapplication

import androidx.annotation.CheckResult
import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking

class Storage {

    suspend fun get(): Result<String> = runCatching {
        delay(1)
        "smth"
    }

    @CheckResult
    suspend fun save(s: String): Result<Unit> = runCatching {
        delay(2)
    }
}

class Service {

    suspend fun get(): Result<String> = runCatching {
        delay(3)
        "anth"
    }
}

inline fun <T> Result<T>.recoverCatching(
    onError: (Throwable) -> Result<T>,
): Result<T> = if (isSuccess) this else onError(exceptionOrNull()!!)

inline fun <T> Result<T>.onSuccessCatching(
    onSuccess: (T) -> Result<Unit>,
): Result<T> {
    val value = getOrNull()
    return if (value != null) {
        onSuccess(value).map { value }
    } else {
        this
    }
}

class Interactor(
    private val storage: Storage,
    private val service: Service,
) {
    suspend fun go(): Result<String> =
        service.get()
            .onSuccessCatching { storage.save(it) }
//            .onSuccess { storage.save(it) }
            .recoverCatching { storage.get() }
}

fun main() {
    runBlocking {
        val interactor = Interactor(Storage(), Service())
        interactor.go()
    }
}