+ randomColor <- function() {
+   paste0("#", paste0(sample(c(0:9, letters[1:6]), size = 6, replace = TRUE), collapse = ""))
+ }

# make color mapping
if (is.numeric(metadata[[metadata_col]])){
    #check if divergent or sequential?
    row_annot <- HeatmapAnnotation(df=metadata[,metadata_col, drop=FALSE], which="row")
    
}else{
    n_cat <- length(unique(metadata[[metadata_col]]))
    qual_col_pals = brewer.pal.info[brewer.pal.info$category == 'qual',]
    all_brewer_colors <- unique(unlist(mapply(brewer.pal, qual_col_pals$maxcolors, rownames(qual_col_pals))))
+    if (n_cat <= length(all_brewer_colors)){
+        # get nice colors
        colors <- sample(all_brewer_colors,n_cat)
+    }else{
+        # too many groups, get random colors
+        colors <- replicate(n_cat, randomColor())
+    }
    names(colors) <- unique(metadata[[metadata_col]])
    colors_list <- list()
    colors_list[[metadata_col]] <- colors# put here the mapped colors
    
    row_annot <- HeatmapAnnotation(df=metadata[,metadata_col, drop=FALSE], which="row", col=colors_list)
}