# FIXME: where does time exactly come from? only test preds?

#' Prediction from resampling.
#'
#' Contains predictions from resampling, returned (among other stuff) by function [resample].
#' Can basically be used in the same way as [Prediction], its super class.
#' The main differences are:
#' (a) The internal data.frame (member `data`) contains an additional column `iter`, specifying the iteration
#' of the resampling strategy, and and additional columns `set`, specifying whether the prediction
#' was from an observation in the \dQuote{train} or \dQuote{test} set. (b) The prediction `time` is
#' a numeric vector, its length equals the number of iterations.
#' @name ResamplePrediction
#' @rdname ResamplePrediction
#' @family resample
NULL


makeResamplePrediction = function(instance, preds.test, preds.train, task.desc) {

  tenull = sapply(preds.test, is.null)
  trnull = sapply(preds.train, is.null)
  if (any(tenull)) pr.te = preds.test[!tenull] else pr.te = preds.test
  if (any(trnull)) pr.tr = preds.train[!trnull] else pr.tr = preds.train

  data = setDF(rbindlist(c(
    lapply(seq_along(pr.te), function(X) cbind(pr.te[[X]]$data, iter = X, set = "test")),
    lapply(seq_along(pr.tr), function(X) cbind(pr.tr[[X]]$data, iter = X, set = "train"))
  ), use.names = TRUE))

  if (!any(tenull) && instance$desc$predict %in% c("test", "both")) {
    p1 = preds.test[[1L]]
    pall = preds.test
  } else if (!any(trnull) && instance$desc$predict == "train") {
    p1 = preds.train[[1L]]
    pall = preds.train
  }


  makeS3Obj(c("ResamplePrediction", class(p1)),
    instance = instance,
    predict.type = p1$predict.type,
    data = data,
    threshold = p1$threshold,
    task.desc = task.desc,
    time = extractSubList(pall, "time")
  )
}

#' @export
print.ResamplePrediction = function(x, ...) {
  cat("Resampled Prediction for:\n")
  print(x$instance$desc)
  catf("predict.type: %s", x$predict.type)
  catf("threshold: %s", collapse(sprintf("%s=%.2f", names(x$threshold), x$threshold)))
  catf("time (mean): %.2f", mean(x$time))
  printHead(as.data.frame(x), ...)
}