moving to a workflow subclass

* add some required packages/versions
* draft workflow class
* add truthy testing
* begin predict method

Author: dajmcdon

DESCRIPTION

@@ -23,7 +23,8 @@ Imports:
     tibble,
     tidyr,
     tidyselect,
-    tensr
+    tensr,
+    hardhat (>= 1.0.0.9000)
 Suggests: 
     covidcast,
     data.table,
@@ -37,7 +38,9 @@ Suggests:
 VignetteBuilder: 
     knitr
 Remotes:
-    dajmcdon/epiprocess
+    dajmcdon/epiprocess,
+    tidymodels/hardhat,
+    tidymodels/recipes
 Config/testthat/edition: 3
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)

R/epi_recipe.R

@@ -137,7 +137,7 @@ epi_recipe.epi_df <-
       levels = NULL,
       retained = NA
     )
-    class(out) <- "recipe"
+    class(out) <- c("epi_recipe", "recipe")
     out
   }
 
@@ -210,3 +210,19 @@ epi_form2args <- function(formula, data, ...) {
   list(x = data, vars = vars, roles = roles)
 }
 
+is_epi_recipe <- function(x) {
+  inherits(x, "epi_recipe")
+}
+
+add_epi_recipe <- function(
+    x, recipe, ..., blueprint = default_epi_recipe_blueprint()) {
+  add_recipe(x, recipe, ..., blueprint = blueprint)
+}
+
+default_epi_recipe_blueprint <-
+  function(intercept = FALSE, allow_novel_levels = FALSE, fresh = TRUE,
+           bake_dependent_roles = c("time_value", "geo_value", "key", "raw"),
+           composition = "tibble") {
+    hardhat::default_recipe_blueprint(
+      intercept, allow_novel_levels, fresh, bake_dependent_roles, composition)
+  }

R/epi_workflow.R

@@ -0,0 +1,18 @@
+#' @export
+epi_workflow <- function(preprocessor = NULL, spec = NULL) {
+  out <- workflow(preprocessor, spec)
+  class(out) <- c("epi_workflow", class(out))
+}
+
+predict.epi_workflow <-
+  function(object, new_data, type = NULL, opts = list(), forecast_date, ...) {
+    out <- predict(object, new_data, type = type, opts = opts, ...)
+    if (is_epi_df(new_data)) {
+      ek <- epi_keys(new_data)
+
+    }
+  }
+
+is_epi_workflow <- function(x) {
+  inherits(x, "epi_workflow")
+}