gm: Create Music with Ease

#' @description In Lines, Clefs, and Tempos, round up the offsets
#' that exceed the lengths of their target bars.
#'
#' @noRd
round_offsets <- function(music) {
  meters <- music$meters

  for (name in names(music)) {
    component <- music[[name]]
    if (!("offset" %in% names(component))) next

    for (k in seq_len(NROW(component))) {
      case <- component[k, ]
      . <- round_offset(case$bar, case$offset, meters)
      music[[name]][k, ]$bar <- .$bar
      music[[name]][k, ]$offset <- .$offset
    }
  }

  music
}


#' @param meters Already sorted by `bar` in descending order.
#'
#' @param up Whether to round up an offset to the next bar,
#' when it is equal to the length of the current bar.
#'
#' @noRd
round_offset <- function(bar, offset, meters, up = TRUE) {
  bars <- meters$bar

  repeat {
    # Find the Meter for the current bar
    k <- find_by_bar(bar, bars)
    meter <- meters[k, ]
    value <- to_value(meter)

    # For tuplets, there can be very small differences which prevent
    # offsets from being rounded up.
    # Try the example in test-3-utils-tuplet-indicate.R
    # See https://stackoverflow.com/questions/9508518/
    # why-are-these-numbers-not-equal
    if (isTRUE(all.equal(offset, value))) {
      if (up) {
        bar <- bar + 1L
        offset <- 0

      } else {
        offset <- value
      }

      break
    }

    if (offset < value) break

    bar <- bar + 1L
    offset <- offset - value
  }

  list(bar = bar, offset = offset)
}


find_by_bar <- function(bar, bars) {
  which(bars <= bar)[1]
}