class MultiErrorStateGenerator internal constructor(
    internal val generators: List<ErrorStateGenerator>
) : (Throwable) -> ViewState.Error {

    override fun invoke( throwable: Throwable ): ViewState.Error {
        val errorStateFactory = ErrorStateFactory( throwable )
        val defaultError = errorStateFactory.default
        val generatorsIterator = generators.iterator()

        while ( generatorsIterator.hasNext() ) {
            val generatedError = generatorsIterator.next().invoke( errorStateFactory, throwable )
            if ( generatedError != defaultError ) return generatedError
        }
        return defaultError
    }
}

/** @return [MultiErrorStateGenerator] from 2 [ErrorStateGenerator] */
operator fun ErrorStateGenerator.plus( other: ErrorStateGenerator ) = MultiErrorStateGenerator(
    listOf( this, other )
)

/** @return [MultiErrorStateGenerator] from a [MultiErrorStateGenerator] and an [ErrorStateGenerator] */
operator fun MultiErrorStateGenerator.plus( other: ErrorStateGenerator ) = MultiErrorStateGenerator(
    generators + other
)