ApolloResult.kt

/**
 * Result of an operation using Apollo. It matches the possible states of a GraphQL response:
 * - https://www.apollographql.com/docs/kotlin/essentials/errors#truth-table
 * - https://github.com/HedvigInsurance/android/blob/0eb8c4a862644be4dd5beb717c8142666e6ff846/app/apollo/apollo-core/src/commonMain/kotlin/com/hedvig/android/apollo/ApolloCallExt.kt#L106-L127
 */
sealed interface ApolloResult<out T> {
    /**
     * Response with a valid result.
     */
    sealed interface Valid<out T : Any> : ApolloResult<T> {
        val result: T
    }

    /**
     * Response without a valid result.
     */
    sealed interface Invalid : ApolloResult<Nothing>

    /**
     * Response with errors.
     */
    sealed interface Flawed<out T> : ApolloResult<T> {
        val errors: List<Error>
    }

    /**
     * Complete data was received.
     */
    @JvmInline
    value class Full<T : Any>(override val result: T) : Valid<T>

    /**
     * Partial data was received alongside field error(s).
     */
    data class Partial<T : Any>(
        override val result: T,
        override val errors: List<Error>,
    ) : Valid<T>, Flawed<T>

    /**
     * A GraphQL request error happened or a Graph field error bubbled up.
     */
    @JvmInline
    value class Empty(override val errors: List<Error>) : Invalid, Flawed<Nothing>

    /**
     * A fetch error happened.
     */
    @JvmInline
    value class FetchError(val exception: ApolloException) : Invalid
}

/**
 * Transform an `ApolloResponse` into a `ApolloResult`.
 *
 * @return `ApolloResult` with the result of the operation.
 */
internal fun <D : Operation.Data> ApolloResponse<D>.toResult(): ApolloResult<D> {
    val data = data
    val errors = errors
    val exception = exception
    if (data != null) {
        return if (errors.isNullOrEmpty()) {
            ApolloResult.Full(data)
        } else {
            ApolloResult.Partial(data, errors)
        }
    }
    if (exception != null) {
        return ApolloResult.FetchError(exception)
    }
    if (!errors.isNullOrEmpty()) {
        return ApolloResult.Empty(errors)
    }
    return ApolloResult.FetchError(
        DefaultApolloException("Server returned no data, no errors, and no exception")
    )
}