#' @importFrom rlang eval_tidy
get_facets <- function(data, vars) {
  byvars <- lapply(X = vars, FUN = eval_tidy, data = data)
  facets <- split(x = data, f = byvars, sep = "|__|")
  lapply(
    X = seq_along(facets),
    FUN = function(i) {
      facet <- facets[[i]]
      attr(facet, "keys") <- strsplit(
        x = names(facets)[i], 
        split = "|__|", fixed = TRUE
      )[[1]]
      facet
    }
  )
}

set_scale <- function(ax, values, scales = c("fixed", "free", "free_y", "free_x"), axis = c("x", "y")) {
  scales <- match.arg(scales)
  axis <- match.arg(axis)
  if (is.null(values))
    return(ax)
  if (inherits(values, c("numeric", "integer", "Date", "POSIXt"))) {
    range_vals <- range(pretty(values), na.rm = TRUE)
  } else {
    range_vals <- NULL
  }
  
  fmt <- function(x, time = inherits(values, c("Date", "POSIXt"))) {
    if (is.null(x))
      return(NULL)
    if (time)
      x <- format_date(x)
    x
  }
  
  fun_axis <- switch(
    axis,
    "x" = ax_xaxis,
    "y" = ax_yaxis
  )
  
  if (scales == "fixed") {
    ax <- fun_axis(
      ax = ax,
      min = fmt(range_vals[1]), 
      max = fmt(range_vals[2])
    )
  } else if (scales == "free") {
    ax <- fun_axis(
      ax = ax,
      min = character(0), 
      max = character(0)
    )
  } else {
    ax <- fun_axis(
      ax = ax,
      min = fmt(range_vals[1]), 
      max = fmt(range_vals[2])
    )
    if (scales == "free_x" & axis == "x") {
      ax <- fun_axis(
        ax = ax,
        min = character(0), 
        max = character(0)
      )
    }
    if (scales == "free_y" & axis == "y") {
      ax <- fun_axis(
        ax = ax,
        min = character(0), 
        max = character(0)
      )
    }
  }
  
  return(ax)
}

#' @importFrom rlang eval_tidy is_null is_function
build_facets <- function(chart) {
  data <- chart$x$data
  mapall <- lapply(chart$x$mapping, eval_tidy, data = data)
  labeller <- chart$x$facet$labeller
  facets_data <- get_facets(data, chart$x$facet$vars)
  lapply(
    X = seq_along(facets_data),
    FUN = function(i) {
      new <- chart
      facet <- facets_data[[i]]
      if (!is_null(labeller) && is_function(labeller)) {
        keys <- attr(facet, "keys")
        # browser()
        new <- ax_title(new, text = labeller(keys))
      }
      mapdata <- lapply(chart$x$mapping, eval_tidy, data = facet)
      new$x$ax_opts$series <- make_series(mapdata, chart$x$mapping, chart$x$type, chart$x$serie_name)
      new <- set_scale(new, mapall$x, scales = chart$x$facet$scales, axis = "x")
      new <- set_scale(new, mapall$y, scales = chart$x$facet$scales, axis = "y")
      new$height <- chart$x$facet$chart_height
      new$x$facet <- NULL
      class(new) <- setdiff(class(new), "apex_facet")
      return(new)
    }
  )
}

build_grid <- function(content, nrow = NULL, ncol = NULL, col_gap = "0px", row_gap = "0px") {
  n <- length(content)
  if (is.null(nrow) & !is.null(ncol))
    nrow <- ceiling(n / ncol)
  if (!is.null(nrow) & is.null(ncol))
    ncol <- ceiling(n / nrow)
  if (is.null(nrow) & is.null(ncol)) {
    if (n %% 3 < 1) {
      ncol <- 3
      nrow <- ceiling(n / ncol)
    } else {
      ncol <- 2
      nrow <- ceiling(n / ncol)
    } 
  }
  htmltools::tags$div(
    class = "apexcharter-facet-container",
    style = "display: grid;",
    style = sprintf("grid-template-columns: repeat(%s, 1fr);", ncol),
    style = sprintf("grid-template-rows: repeat(%s, 1fr);", nrow),
    style = sprintf("grid-column-gap: %s;", col_gap),
    style = sprintf("grid-row-gap: %s;", row_gap),
    content
  )
}



#' Facet wrap for ApexCharts
#'
#' @param ax An \code{apexcharts} \code{htmlwidget} object.
#' @param vars Variable(s) to use for facetting, wrapped in \code{vars(...)}.
#' @param nrow,ncol Number of row and column in output matrix.
#' @param chart_height Individual chart height.
#'
#' @return An \code{apexcharts} \code{htmlwidget} object.
#' @export
#'
#' @examples
ax_facet_wrap <- function(ax, 
                          vars, 
                          nrow = NULL,
                          ncol = NULL,
                          scales = c("fixed", "free", "free_y", "free_x"),
                          labeller = label_value,
                          chart_height = "300px") {
  if (!inherits(ax, "apex"))
    stop("ax_facet_wrap only works with charts generated with apex()", call. = FALSE)
  scales <- match.arg(scales)
  ax$x$facet <- list(
    vars = vars,
    nrow = nrow,
    ncol = ncol,
    scales = scales,
    labeller = labeller,
    chart_height = chart_height
  )
  class(ax) <- c("apex_facet", class(ax))
  return(ax)
}









# Print methods -----------------------------------------------------------

#' @export
print.apex_facet <- function(x, ...) {
  facets_charts <- build_facets(x)
  TAG <- build_grid(facets_charts, nrow = x$x$facet$nrow, ncol = x$x$facet$ncol)
  print(htmltools::browsable(TAG))
}

knit_print.apex_facet <- function(x, ..., options = NULL) {
  facets_charts <- build_facets(x)
  TAG <- build_grid(facets_charts, nrow = x$x$facet$nrow, ncol = x$x$facet$ncol)
  knitr::knit_print(htmltools::browsable(TAG), options = options, ...)
}