#' @title Plotting pseudo-time ordering or gene expression in Model-based
#' clustering in PCA
#' @description The PCA representation can either be used to show pseudo-time
#' ordering or the gene expression of a particular gene.
#' @param object \code{DISCBIO} class object.
#' @param type either `order` to plot pseudo-time ordering or `exp` to plot gene
#' expression
#' @param g  Individual gene name or vector with a group of gene names
#'   corresponding to a subset of valid row names of the \code{ndata} slot of
#'   the \code{DISCBIO} object. Ignored if `type="order"`.
#' @param n String of characters representing the title of the plot. Default is
#'   NULL and the first element of \code{g} is chosen. Ignored if
#'   `type="order"`.
#' @importFrom RColorBrewer brewer.pal
#' @importFrom grDevices colorRampPalette
#' @importFrom graphics layout par image
#' @return A plot of the PCA.
#' @export

PlotMBpca <- function(object, type = "order", g = NULL, n = NULL) {
  # ==========================================================================
  # Validation
  # ==========================================================================
  data <- object@MBclusters
  if (type == "exp") {
    if (is.null(g)) {
      stop('g must be provided if type="exp"')
    }
    if (length(intersect(g, rownames(object@ndata))) < length(unique(g))) {
      stop(
        "second argument does not correspond to set of rownames slot",
        "ndata of SCseq object"
      )
    }
    if (is.null(n)) {
      n <- g[1]
    }
    logObj <- log(object@ndata)
    l <- apply(logObj[g, ] - .1, 2, sum) + .1
    x <- data$pcareduceres
  } else if (type == "order") {
    MBordertable <- cbind(data$pcareduceres, object@MBordering)
    l <- MBordertable[, 3]
    x <- MBordertable
  } else {
    stop("Invalid type. Valid alternatives as 'order' and 'exp'.")
  }
  # ==========================================================================
  # Plotting
  # ==========================================================================
  mi <- min(l, na.rm = TRUE)
  ma <- max(l, na.rm = TRUE)
  ColorRamp <- colorRampPalette(rev(brewer.pal(n = 11, name = "RdYlBu")))(100)
  ColorLevels <- seq(mi, ma, length = length(ColorRamp))
  v <- round((l - mi) / (ma - mi) * 99 + 1, 0)
  layout(
    matrix(
      data = c(1, 3, 2, 4),
      nrow = 2,
      ncol = 2
    ),
    widths = c(5, 1, 5, 1),
    heights = c(5, 1, 1, 1)
  )
  opar <- withr::local_par(mar = c(5, 5, 2.5, 2))
  on.exit(withr::local_par(opar))
  plot(
    x[, 1],
    x[, 2],
    xlab = "PC1",
    ylab = "PC2",
    pch = 20,
    cex = 0,
    col = "grey",
    las = 1,
    main = n
  )
  for (k in seq_len(length(v))) {
    points(
      x[k, 1],
      x[k, 2],
      col = ColorRamp[v[k]],
      pch = 20,
      cex = 2
    )
  }
  opar <- withr::local_par(mar = c(3, 2.5, 2.5, 2))
  on.exit(withr::local_par(opar))
  image(
    1,
    ColorLevels,
    matrix(
      data = ColorLevels,
      ncol = length(ColorLevels),
      nrow = 1
    ),
    col = ColorRamp,
    xlab = "",
    ylab = "",
    las = 2,
    xaxt = "n"
  )
  layout(1)
}