#' Pivot data from long to wide
#'
#' @description "Widens" data, increasing the number of columns and
#'   decreasing the number of rows.
#'
#' @param .df A data.frame or data.table
#' @param id_cols A set of columns that uniquely identifies each observation.
#'   Defaults to all columns in the data table except for the columns specified in `names_from` and `values_from`.
#'   Typically used when you have additional variables that is directly related.
#'   `tidyselect` compatible.
#' @param names_from A pair of arguments describing which column (or columns) to get the name of the output column `name_from`,
#'   and which column (or columns) to get the cell values from `values_from`).
#'   `tidyselect` compatible.
#' @param values_from A pair of arguments describing which column (or columns) to get the name of the output column `name_from`,
#'   and which column (or columns) to get the cell values from `values_from`.
#'   `tidyselect` compatible.
#' @param names_sep the separator between the names of the columns
#' @param names_prefix prefix to add to the names of the new columns
#' @param names_glue Instead of using `names_sep` and `names_prefix`, you can supply a
#'   glue specification that uses the `names_from` columns (and special `.value`) to create custom column names
#' @param names_sort Should the resulting new columns be sorted
#' @param names_repair Treatment of duplicate names. See `?vctrs::vec_as_names` for options/details.
#' @param values_fn Should the data be aggregated before casting? If the formula doesn't identify a single observation for each cell, then aggregation defaults to length with a message.
#' @param values_fill If values are missing, what value should be filled in
#'
#' @examples
#' test_df <- data.table(
#'   a = rep(c("a", "b", "c"), 2),
#'   b = c(rep("x", 3), rep("y", 3)),
#'   vals = 1:6
#' )
#'
#' test_df %>%
#'   pivot_wider.(names_from = b, values_from = vals)
#'
#' test_df %>%
#'   pivot_wider.(
#'     names_from = b, values_from = vals, names_prefix = "new_"
#'   )
#' @export
pivot_wider. <- function(.df,
                         names_from = name,
                         values_from = value,
                         id_cols = NULL,
                         names_sep = "_",
                         names_prefix = "",
                         names_glue = NULL,
                         names_sort = FALSE,
                         names_repair = "check_unique",
                         values_fill = NULL,
                         values_fn = NULL) {
  UseMethod("pivot_wider.")
}

#' @export
pivot_wider..tidytable <- function(.df,
                                  names_from = name,
                                  values_from = value,
                                  id_cols = NULL,
                                  names_sep = "_",
                                  names_prefix = "",
                                  names_glue = NULL,
                                  names_sort = FALSE,
                                  names_repair = "check_unique",
                                  values_fill = NULL,
                                  values_fn = NULL) {
  id_cols <- enquo(id_cols)
  values_fn <- enquo(values_fn)

  names_from <- tidyselect_names(.df, {{ names_from }})
  values_from <- tidyselect_names(.df, {{ values_from }})

  uses_dot_value <- FALSE
  if (!is.null(names_glue)) {
    if (str_detect.(names_glue, ".value")) {
      uses_dot_value <- TRUE
    }
  }

  if (quo_is_null(id_cols)) {
    data_names <- names(.df)
    id_cols <- data_names[!data_names %in% c(names_from, values_from)]
  } else {
    id_cols <- tidyselect_names(.df, !!id_cols)
  }

  if (names_sort) {
    .df <- arrange.(.df, !!!syms(names_from))
  }

  if (nchar(names_prefix) > 0 && is.null(names_glue)) {
    .first_name <- sym(names_from[[1]])

    .df <- mutate.(.df, !!.first_name := paste0(!!names_prefix, !!.first_name))
  } else if (uses_dot_value) {
    glue_df <- distinct.(.df, !!!syms(names_from))
    values_from_reps <- nrow(glue_df)
    glue_df <- vec_rep(glue_df, length(values_from))
    glue_df$.value <- vec_rep_each(values_from, values_from_reps)

    glue_vars <- as.character(glue_data(glue_df, names_glue))
  } else if (!is.null(names_glue)) {
    .df <- mutate.(.df, .names_from = glue(names_glue))
    .df <- relocate.(.df, .names_from, .before = !!sym(names_from[[1]]))
    .df <- .df[, -..names_from]

    names_from <- ".names_from"
  }

  no_id <- length(id_cols) == 0

  if (no_id) {
    lhs <- "..."
  } else {
    lhs <- paste(id_cols, collapse = " + ")
  }

  rhs <- paste(names_from, collapse = " + ")

  dcast_form <- paste(lhs, rhs, sep = " ~ ")

  dcast_call <- call2_dt(
    "dcast",
    .df,
    formula = dcast_form,
    value.var = values_from,
    fun.aggregate = expr(!!values_fn),
    sep = names_sep,
    fill = values_fill
  )

  .df <- eval_tidy(dcast_call)

  if (no_id) .df[, . := NULL]

  if (uses_dot_value) {
    new_vars <- setdiff(names(.df), id_cols)

    setnames(.df, new_vars, glue_vars)
  }

  .df <- df_name_repair(.df, .name_repair = names_repair)

  as_tidytable(.df)
}

#' @export
pivot_wider..data.frame <- function(.df,
                                    names_from = name,
                                    values_from = value,
                                    id_cols = NULL,
                                    names_sep = "_",
                                    names_prefix = "",
                                    names_glue = NULL,
                                    names_sort = FALSE,
                                    names_repair = "check_unique",
                                    values_fill = NULL,
                                    values_fn = NULL) {
  .df <- as_tidytable(.df)
  pivot_wider.(
    .df, names_from = {{ names_from }}, values_from = {{ values_from }},
    id_cols = {{ id_cols }}, names_sep = names_sep,
    names_prefix = names_prefix, names_glue = names_glue,
    names_sort = names_sort, names_repair = names_repair,
    values_fill = values_fill, values_fn = {{ values_fn }}
  )
}

globalVariables(c(".", ".names_from", "..names_from", "name", "value"))