#' Import/export from clipboard
#'
#' These are helper functions around \code{\link{read.table}} and \code{\link{write.table}} to import from and export to clipboard with support for Windows, Linux and macOS. The data will be read and written as tab-separated by default, which makes it possible to copy and paste from other software like Excel and SPSS without further transformation. See Details for an example.
#' @rdname clipboard
#' @name clipboard
#' @inheritParams utils::read.table
#' @inheritParams utils::write.table
#' @param startrow \emph{n}th row to start importing from. When \code{header = TRUE}, the import will start on row \code{startrow} \emph{below} the header.
#' @param as_vector a logical value indicating whether data consisting of only one column should be imported as vector using \code{\link[dplyr]{pull}}. This will strip off the header.
#' @param info print info about copying
#' @keywords clipboard clipboard_import clipboard_export import export
#' @importFrom dplyr %>% pull as_tibble
#' @importFrom utils read.delim write.table object.size
#' @details For \code{clipboard_export()}, the reserved clipboard size for exporting will be set to 125\% of the object size of \code{x}. This way, it is possible to export data with thousands of rows as the only limit will be your systems RAM.
#'
#'   Example for copying from Excel:
#'   \if{html}{
#'     \out{<div style="text-align: left">}\figure{Excel_copy.png}\out{</div>}
#'   }
#'   \if{latex}{
#'     \out{\begin{left}}\figure{Excel_copy.png}\out{\end{left}}
#'   }
#'   \cr
#'   And pasting in R: \cr \cr
#'   \code{> data <- clipboard_import()} \cr
#'   \code{> data} \cr
#'   \if{html}{
#'     \out{<div style="text-align: left">}\figure{Excel_paste.png}\out{</div>}
#'   }
#'   \if{latex}{
#'     \out{\begin{left}}\figure{Excel_paste.png}\out{\end{left}}
#'   }
#' @export
#' @return data.frame
clipboard_import <- function(sep = '\t',
                             header = TRUE,
                             dec = ".",
                             na = c("", "NA", "NULL"),
                             startrow = 1,
                             as_vector = TRUE) {

  if (is_Windows() == TRUE) {
    file <- 'clipboard'
  } else {
    # use xclip package
    check_xclip()
    file <- pipe("xclip -o", "r")
    on.exit(close(file))
  }

  import_tbl <- tryCatch(read.delim(file = file,
                                    sep = sep,
                                    header = header,
                                    strip.white = TRUE,
                                    dec = dec,
                                    na.strings = na,
                                    fileEncoding = 'UTF-8',
                                    encoding = 'UTF-8',
                                    stringsAsFactors = FALSE),
                         error = function(e) {
                           FALSE
                         })

  if (import_tbl == FALSE) {
    cat("No clipboard content found.")
    if (Sys.info()['sysname'] %like% "Linux") {
      cat(" These functions do not work without X11 installed.")
    }
    cat("\n")
    return(invisible())
  }

  # use tibble, so column types will be translated correctly
  import_tbl <- as_tibble(import_tbl)

  if (startrow > 1) {
    # would else lose column headers
    import_tbl <- import_tbl[startrow:nrow(import_tbl),]
  }

  colnames(import_tbl) <- gsub('[.]+', '_', colnames(import_tbl))

  if (NCOL(import_tbl) == 1 & as_vector == TRUE) {
    import_tbl %>% pull(1)
  } else {
    import_tbl
  }
}

#' @rdname clipboard
#' @importFrom dplyr %>% pull as_tibble
#' @export
clipboard_export <- function(x,
                             sep = '\t',
                             dec = ".",
                             na = "",
                             header = TRUE,
                             info = TRUE) {

  x <- deparse(substitute(x))
  size <- x %>%
    get() %>%
    object.size() %>%
    formatC(format = 'd') %>%
    as.integer()

  x <- get(x)

  if (is_Windows() == TRUE) {
    # set size of clipboard to 125% of the object size of x
    file <- paste0("clipboard-", size * 1.25)
  } else {
    # use xclip package
    check_xclip()
    file <- pipe("xclip -i", "w")
    on.exit(close(file))
  }

  tryCatch(write.table(x = x,
                       file = file,
                       sep = sep,
                       na = na,
                       row.names = FALSE,
                       col.names = header,
                       dec = dec,
                       quote = FALSE),
           error = function(e) {
             FALSE
           })

  if (info == TRUE) {
    cat("Successfully exported to clipboard:", NROW(x), "obs. of", NCOL(x), "variables.\n")
  }

}

is_Windows <- function() {
  Sys.info()['sysname'] %like% "Windows"
}
check_xclip <- function() {
  if (!isTRUE(file.exists(Sys.which("xclip")[1L]))) {
    if (Sys.info()['sysname'] %like% "Linux") {
      stop("Please install Linux package xclip first.")
    } else {
      stop("Please install package xclip first (use `brew install xclip on macOS`).")
    }
  }
}