A R function to read an Excalidraw Markdown file created with Obsidian to a list

read_excalidraw.R

#' Read an Excalidraw Markdown file created using the Obsidian Excalidraw
#' plugin.
#'
#' Plugin: https://github.com/zsviczian/obsidian-excalidraw-plugin
#'
#' This function uses the experimental yyjsonr package
#' <https://github.com/coolbutuseless/yyjsonr>. jsonlite would also work here.
#'
#' @param file A Markdown file created with the Obsidian Excalidraw plugin.
#' @param ... Additional parameters passed to [readr::read_lines()]
#' @noRd
read_excalidraw <- function(file, ...) {

  file_txt <- readr::read_lines(file, ...)

  # Read text elements from Markdown
  txt_elements <- file_txt[index_txt(file_txt, c("# Text Elements", "%%"))]
  txt_elements <- data.frame("elements" = text_elements[txt_elements != ""])
  txt_elements <- tidyr::separate_wider_delim(
    txt_elements,
    cols = all_of("elements"),
    " ^",
    names = c("text", "id")
    )

  # Read and parse JSON (which also includes text elements)
  drawing <- file_txt[index_txt(file_txt, c("```json",  "```"))]
  # pak::pkg_install("coolbutuseless/yyjsonr")
  drawing <- yyjsonr::from_json_str(paste0(drawing, collapse = ""))

  # Return list
  list(
    "text" = txt_elements,
    "drawing" = drawing
  )
}

#' Helper function to index a text file based on limit strings
#'
#' @param txt A text file read with [readr::read_lines()] or a path to a text
#'   file.
#' @param lims A length 2 character vector with unique values where the first
#'   appearance of the first value and first appearance of the second value
#'   define the start and end of the indexed range
#' @noRd
index_txt <- function(txt = NULL, lims = c("```json",  "```"), ...) {
  if (rlang::is_string(txt) && fs::is_file(txt)) {
    txt <- readr::read_lines(txt, ...)
  }

  stopifnot(
    all(lims %in% txt),
    length(unique(lims)) == 2
  )

  c((which(txt == lims[[1]])[[1]] + 1):(which(txt == lims[[2]])[[1]] - 1))
}