R/get_moves.R

In dryguy/rbitr: Arbiter: One who ensures adherence to the rules and laws of chess

#' Get the chess moves from a character vector containing movetext
#'
#' Given a character vector of movetext, return a list of character vectors
#'   each containing moves in long algebraic notation (LAN).
#'
#' @details The movetext field of a PGN file contains chess moves in standard
#'   algebraic notation (SAN), along with optional annotations and comments. The
#'   `get_moves()` function extracts the individual moves and converts them to
#'   long algebraic notation (LAN). The movetext vectors are typically obtained
#'   from a PGN file using the `get_pgn()` function.
#'
#' @param movetext A character vector of movetext in SAN format.
#'
#' @return A list of character vectors, where each vector contains the LAN
#'   format moves of the corresponding movetext.
#' @export
#'
#' @seealso
#'   * [rbitr::get_pgn()] to get the movetext and other data from a PGN file.
#'   * [rbitr::clean_movetext()] to remove comments and annotations from
#'     movetext.
#'
#' @examples
#' movetext <- c('1. e4 {Best by test.} e5', '1. h3?! h6')
#' get_moves(movetext)

get_moves <- function(movetext) {
  assertthat::assert_that(is.character(movetext))
  movetext <- clean_movetext(movetext)
  moves <- lapply(movetext, convert_to_lan)
  moves <- unlist(lapply(moves, tolower), use.names = FALSE)
  strsplit(moves, ' ', fixed = TRUE)
}

#' convert_to_lan
#'
#' Internal helper function for `get_moves()`. This is a wrapper around
#'   `bigchess::san2lan()` to deal with empty movetext. When movetext == '', it
#'   returns ' ', which in `get_moves()` gets passed to `strsplit()` that will
#'   convert it to ''.
#'
#' @param movetext A character vector of movetext in SAN format.
#'
#' @return A character vector of movetext in LAN format.
#'
#' @export
convert_to_lan <- function(movetext) {
  if(movetext == '') {
    return(' ')
  } else {
    return(bigchess::san2lan(movetext))
  }
}