#' Magic mirror that returns kable's attributes
#'
#' @param input The output of kable
#' @importFrom knitr kable
#' @import stringr
#' @export

magic_mirror <- function(input){
  if(!"knitr_kable" %in% attr(input, "class")){
    warning("magic_mirror may not be able to produce correct result if the",
            " input table is not rendered by knitr::kable. ")
  }
  kable_format <- attr(input, "format")
  if (kable_format == "latex"){
    kable_info <- magic_mirror_latex(input)
  }
  if (kable_format == "html"){
    kable_info <- magic_mirror_html(input)
  }
  return(kable_info)
}

#' Magic mirror for latex tables --------------
#' @param input The output of kable
magic_mirror_latex <- function(input){
  kable_info <- list(tabular = NULL, booktabs = NULL, align = NULL,
                     ncol=NULL, nrow=NULL, colnames = NULL, rownames = NULL,
                     caption = NULL, contents = NULL)
  # Tabular
  kable_info$tabular <- ifelse(
    grepl("\\\\begin\\{tabular\\}", input),
    "tabular", "longtable"
  )
  # Booktabs
  kable_info$booktabs <- ifelse(grepl("\\\\toprule", input), TRUE, FALSE)
  # Align
  kable_info$align <- gsub("\\|", "", str_match(
    input, paste0("\\\\begin\\{", kable_info$tabular,"\\}.*\\{(.*?)\\}"))[2])
  # N of columns
  kable_info$ncol <- nchar(kable_info$align)
  # Caption
  kable_info$caption <- str_match(input, "caption\\{(.*?)\\}")[2]
  # N of rows
  kable_info$nrow <- str_count(input, "\\\\\n") -
    # in the dev version (currently as of 11.2015) of knitr, when longtable is
    # enabled, caption is moved inside the tabular environment. As a result,
    # the number of rows should be adjusted.
    ifelse(
      kable_info$tabular == "longtable" & !is.na(kable_info$caption) &
        !str_detect(input, "\\\\begin\\{table\\}\\n\\n\\\\caption"),
      1,0
    )
  # Contents
  kable_info$contents <- str_match_all(input, "\n(.*)\\\\\\\\")[[1]][,2]
  # Column names
  kable_info$colnames <- str_split(kable_info$contents[1], " \\& ")[[1]]
  # Row names
  kable_info$rownames <- str_extract(kable_info$contents, "^[^ &]*")
  return(kable_info)
}

#' Magic Mirror for html table --------
#'
#' @param input The output of kable
#'
#' @importFrom XML readHTMLTable
magic_mirror_html <- function(input){
  kable_info <- list(table.attr = NULL, align = NULL,
                     ncol=NULL, nrow=NULL, colnames = NULL, rownames = NULL,
                     caption = NULL, contents = NULL)
  kable_data <- readHTMLTable(input[1])
  # Caption
  kable_info$caption <- names(kable_data)
  # Contents
  kable_info$contents <- kable_data[[1]]
  # colnames
  kable_info$colnames <- str_replace_all(
    str_trim(names(kable_data[[1]])), "V[0-9]{1,2}", ""
  )
  # rownames
  kable_info$rownames <- as.character(kable_data[[1]][,1])
  if(str_trim(names(kable_data[[1]])[1]) != "V1"){
    kable_info$rownames <- c(str_trim(names(kable_data[[1]])[1]),
                             kable_info$rownames)}
  # ncol
  kable_info$ncol <- length(kable_info$colnames)
  # nrow
  kable_info$nrow <- length(kable_info$rownames)
  # table.attr
  kable_info$table.attr <- str_match(input, "<table class = '(.*)'>")[2]
  # align
  kable_info$align <- str_match_all(
    input, 'style=\\"text-align:([^;]*);'
    )[[1]][,2]
  kable_info$align <- paste0(
    str_extract(tail(kable_info$align, kable_info$ncol), "."), collapse = ""
  )
  return(kable_info)
}

#' @export
magrittr::`%>%`