add add_footnote_adv (temp name) for html table
diff --git a/R/footnote.R b/R/footnote.R
new file mode 100644
index 0000000..f502456
--- /dev/null
+++ b/R/footnote.R
@@ -0,0 +1,148 @@
+#' Add advanced footnote
+#'
+#' @export
+add_footnote_adv <- function(kable_input,
+                             general = NULL,
+                             number = NULL,
+                             alphabet = NULL,
+                             symbol = NULL,
+                             footnote_order = c("general", "number",
+                                                "alphabet", "symbol"),
+                             footnote_as_chunk = FALSE,
+                             general_title = "Note: ",
+                             number_title = "",
+                             alphabet_title = "",
+                             symbol_title = ""
+) {
+  kable_format <- attr(kable_input, "format")
+  if (!kable_format %in% c("html", "latex")) {
+    message("Currently generic markdown table using pandoc is not supported.")
+    return(kable_input)
+  }
+  footnote_titles <- list(
+    general = general_title, number = number_title,
+    alphabet = alphabet_title, symbol = symbol_title
+  )
+  footnote_contents <- list(
+    general = general, number = number, alphabet = alphabet, symbol = symbol
+  )
+  notnull <- names(footnote_contents)[!sapply(footnote_contents, is.null)]
+  if (length(notnull) == 0) {return(kable_input)}
+  if (length(alphabet) > 26) {
+    alphabet <- alphabet[1:26]
+    warning("Please don't use more than 26 footnotes in table_footnote ",
+            "alphabet. Use number instead.")
+  }
+  if (length(symbol) > 20) {
+    symbol <- symbol[1:20]
+    warning("Please don't use more than 20 footnotes in table_footnote ",
+            "symbol. Use number instead.")
+  }
+  footnote_order <- footnote_order[footnote_order %in% notnull]
+  footnote_titles <- footnote_titles[footnote_order]
+  footnote_contents <- footnote_contents[footnote_order]
+  footnote_table <- footnote_table_maker(
+    kable_format, footnote_titles, footnote_contents
+  )
+  if (kable_format == "html") {
+    return(add_footnote_adv_html(kable_input, footnote_table, footnote_as_chunk))
+  }
+  # if (kable_format == "latex") {
+  #   return(add_footnote_adv_latex(kable_input, footnote_table))
+  # }
+}
+
+footnote_table_maker <- function(format, footnote_titles, footnote_contents) {
+  number_index <- read.csv(system.file("symbol_index.csv",
+                                       package = "kableExtra"))
+  if (format == "latex") {
+    symbol_index <- number_index$symbol.latex
+  } else {
+    symbol_index <- number_index$symbol.html
+  }
+  contents_length <- sapply(footnote_contents, length)
+
+  if (!is.null(footnote_contents$general)) {
+    footnote_contents$general <- data.frame(
+      index = "",
+      footnote = paste(footnote_contents$general, collapse = " ")
+    )
+  }
+  if (!is.null(footnote_contents$number)) {
+    footnote_contents$number <- data.frame(
+      index = as.character(1:length(footnote_contents$number)),
+      footnote = footnote_contents$number
+    )
+  }
+  if (!is.null(footnote_contents$alphabet)) {
+    footnote_contents$alphabet <- data.frame(
+      index = letters[1:length(footnote_contents$alphabet)],
+      footnote = footnote_contents$alphabet
+    )
+  }
+  if (!is.null(footnote_contents$symbol)) {
+    footnote_contents$symbol <- data.frame(
+      index = symbol_index[1:length(footnote_contents$symbol)],
+      footnote = footnote_contents$symbol
+    )
+  }
+
+  out <- list()
+  out$contents <- footnote_contents
+  out$titles <- footnote_titles
+  return(out)
+}
+
+# HTML
+add_footnote_adv_html <- function(kable_input, footnote_table,
+                                  footnote_as_chunk) {
+  kable_attrs <- attributes(kable_input)
+  kable_xml <- read_kable_as_xml(kable_input)
+
+  new_html_footnote <- adv_html_tfoot_maker(footnote_table, footnote_as_chunk)
+  xml_add_child(kable_xml, new_html_footnote)
+
+  out <- as_kable_xml(kable_xml)
+  attributes(out) <- kable_attrs
+  return(out)
+}
+
+adv_html_tfoot_maker <- function(footnote_table, footnote_as_chunk) {
+  footnote_types <- names(footnote_table$contents)
+  footnote_text <- c()
+  for (i in footnote_types) {
+    footnote_text <- c(footnote_text, adv_html_tfoot_maker_(
+      footnote_table$contents[[i]], footnote_table$titles[[i]], i,
+      footnote_as_chunk))
+  }
+  footnote_text <- paste0(
+    "<tfoot>", paste0(footnote_text, collapse = ""), "</tfoot>"
+  )
+  footnote_node <- read_html(footnote_text, options = c("RECOVER", "NOERROR"))
+  return(xml_child(xml_child(footnote_node, 1), 1))
+}
+
+adv_html_tfoot_maker_ <- function(ft_contents, ft_title, ft_type, ft_chunk) {
+
+  footnote_text <- apply(ft_contents, 1, function(x) {
+    paste0('<sup>', x[1], '</sup> ', x[2])
+  })
+  if (ft_title != "") {
+    title_text <- paste0('<strong>', ft_title, '</strong>')
+    footnote_text <- c(title_text, footnote_text)
+  }
+  if (!ft_chunk) {
+    footnote_text <- paste0(
+      '<tr><td style="padding: 0; border: 0;" colspan="100%">',
+      footnote_text, '</td></tr>'
+    )
+  } else {
+    footnote_text <- paste0(
+      '<tr><td style="padding: 0; border: 0;" colspan="100%">',
+      paste0(footnote_text, collapse = ""),
+      '</td></tr>'
+    )
+  }
+  # }
+  return(footnote_text)
+}