#' Bulma Document Renderer
#'
#' @section YAML options:
#' You can pass additional options to the underlying template via the `bulma`
#' YAML item. The following options can be specified there.
#' \itemize{
#'   \item{`hero`: Classes applied to the hero containing the title.}
#'   \item{`hero_body`: Classes applied to the hero body container.}
#'   \item{`hero_button`: Classes applied to the `header_links` buttons}
#'   \item{`hero_links`: Links that will be displayed under title as buttons.
#'         Formatted as a list, each element having entries for `name`, `url`,
#'         and `icon`. Icons use [Font Awesome](https://fontawesome.com/icons);
#'         see [fa_icon()] for help constructing the Font Awesome class. The
#'         full Font Awesome class name is required.}
#' }
#'
#' ```
#' ---
#' bulma:
#'   hero: ["info"]
#'   hero_button: ["is-secondary", "is-outlined"]
#'   hero_links:
#'     - name: Github
#'       url: https://github.com/
#'       icon: '`r bulma::fa_icon("github")`'
#'     - name: Twitter
#'       url: https://twitter.com
#'       icon: "fab fa-twitter"
#' ---
#' ```
#'
#' @inheritParams rmarkdown::html_document_base
#' @inheritDotParams rmarkdown::html_document_base
#' @export
bulma_document <- function(
  ...,
  css = NULL,
  fig_width = 10,
  fig_height = 7,
  fig_retina = 2,
  keep_md = FALSE,
  dev = "png",
  toc = FALSE,
  toc_depth = 3,
  mathjax = "default",
  pandoc_args = NULL,
  extra_dependencies = NULL
) {
  css_files <- c(
    "--css", bulma_file("bulma", "bulma.min.css"))

  if (!is.null(css)) {
    for (css_file in css) {
      css_files <- c(css_files, "--css", css_file)
    }
  }
  deps <- list(
    htmltools::htmlDependency(
      name = "bulma",
      version = "0.7.2",
      src = bulma_file("bulma"),
      stylesheet = "bulma.min.css"
    ),
    rmarkdown::html_dependency_font_awesome(),
    if (toc) htmltools::htmlDependency(
      name = "gumshoe",
      version = "3.5.1",
      src = bulma_file("bulma"),
      script = "gumshoe.min.js"
    ),
    if (toc) htmltools::htmlDependency(
      name = "vanillajs-scrollspy",
      version = "2.0.3",
      src = bulma_file("bulma"),
      script = "vanillajs-scrollspy.min.js"
    )
  )

  deps <- deps[!vapply(deps, is.null, logical(1))]
  extra_dependencies <- append(extra_dependencies, deps)

  # preprocessor ----
  pre_processor <- function(metadata, input_file, runtime, knit_meta, files_dir, output_dir) {
    # browser()
  }

  pandoc_args <- c(pandoc_args,
                   "--section-divs",
                   rmarkdown::pandoc_toc_args(toc, toc_depth))

  mathjax_url <- if (mathjax %in% c("default", "local")) {
    mathjax_local <- Sys.getenv("RMARKDOWN_MATHJAX_PATH", unset = NA)
    if (mathjax == "local" && is.na(mathjax_local)) {
        rlang::warn(
          glue("Please use `Sys.setenv('RMARKDOWN_MATHJAX_PATH')` to set local mathjax location.",
               "Falling back to online mathjax from https://mathjax.rstudio.com")
        )
      }
    mathjax_path <- ifelse(mathjax == "default" || is.na(mathjax_local),
                           "https://mathjax.rstudio.com/latest",
                           mathjax_local)
    file.path(mathjax_path, "MathJax.js?config=TeX-AMS-MML_HTMLorMML")
  } else mathjax

  if (!is.null(mathjax_url)) {
    pandoc_args <- c(pandoc_args, "--mathjax", "--variable",
                     paste0("mathjax-url:", mathjax_url))
  }

  rmarkdown::output_format(
    knitr = rmarkdown::knitr_options_html(
      fig_width, fig_height, fig_retina, keep_md, dev
    ),
    pandoc = rmarkdown::pandoc_options(
      to = "html5",
      from = "markdown+ascii_identifiers+tex_math_single_backslash",
      args = c(
        css_files,
        pandoc_args,
        "--variable", "rmarkdown-will-handle-deps",
        "--template",
        bulma_file("bulma", "bulma.html")
      ),
    ),
    pre_processor = pre_processor,
    clean_supporting = TRUE,
    base_format = rmarkdown::html_document_base(
      self_contained = TRUE, template = NULL,
      # pandoc_args = pandoc_args,
      mathjax = mathjax,
      extra_dependencies = extra_dependencies
    )
  )
}


bulma_file <- function(...) {
  system.file(..., package = "bulma")
}