fix: fixed an error when adding alternatives (#9)

* Fixed an error when adding alternatives whilst some empty condition
  blocks were present would cause an error message in the UI.
* Also refactored `or_filtering_transformator` a bunch. Should
  be now more readable.

Author: kpagacz

DESCRIPTION

@@ -25,6 +25,7 @@ RoxygenNote: 7.3.3
 Depends:
   R (>= 4.1.0)
 Imports:
+  R6,
   checkmate,
   cowplot,
   dplyr,

NAMESPACE

@@ -11,6 +11,7 @@ export(or_filtering_transformator)
 export(patchwork_plot_decorator)
 export(remove_by_label)
 export(title_footer_decorator)
+import(R6)
 import(checkmate)
 import(dplyr)
 import(ggplot2)

R/BlockConditions.R

@@ -0,0 +1,55 @@
+#' Class `BlockConditions`
+#'
+#' This class represents a collection of conditions used for filtering datasets.
+#'
+#' @section Slots:
+#' \describe{
+#'   \item{\code{conditions}}{A list of conditions,
+#'      where each condition is a list containing variable, operator, and value.}
+#' }
+#' @keywords internal
+setClass("BlockConditions", slots = list(conditions = "list"))
+
+#' Add a condition to a `BlockConditions` object
+#'
+#' @param object A `BlockConditions` object.
+#' @param variable A character string specifying the variable/column name.
+#' @param operator A character string specifying the operator (e.g., "==", "!=", "<", ">", "<=", ">=").
+#' @param value The value to compare against.
+#'
+#' @return An updated `BlockConditions` object with the new condition added.
+#' @method add_condition BlockConditions
+#' @keywords internal
+setGeneric("add_condition", function(object, variable, operator, value) standardGeneric("add_condition"))
+
+#' Add conditions
+#' @keywords internal
+setMethod("add_condition", "BlockConditions", function(object, variable, operator, value) {
+  object@conditions <- c(object@conditions, list(list(variable = variable, operator = operator, value = value)))
+  object
+})
+
+#' Get condition expression
+#'
+#' @param object A `BlockConditions` object.
+#' @param dataname `character(1)` The name of the dataset to filter.
+#' @param data The reactive `data` object from `teal`.
+#' @return `character(1)` The condition expression.
+#' @method get_str_expressions BlockConditions
+#' @keywords internal
+setGeneric("get_str_expression", function(object, dataname, data) standardGeneric("get_str_expression"))
+
+#' Get condition expression
+#' @keywords internal
+setMethod("get_str_expression", "BlockConditions", function(object, dataname, data) {
+  conds <- lapply(object@conditions, function(cond) {
+    var <- cond$variable
+    val <- if (is.numeric(data()[[dataname]][[cond$variable]])) {
+      cond$value
+    } else {
+      paste0("'", cond$value, "'")
+    }
+    paste0(var, " ", cond$operator, " ", val)
+  })
+  paste0("(", paste(conds, collapse = " & "), ")")
+})