# v0.0.0
#' Split REDCap repeating instruments table into multiple tables
#'
#' This will take a raw data frame from REDCap and split it into a base table
#' and give individual tables for each repeating instrument. Metadata
#' is used to determine which fields should be included in each resultant table.
#'
#' @param records data.frame containing the records
#' @param metadata data.frame containing the metadata
#' @author Paul W. Egeler, M.S., GStat
#' @examples
#' \dontrun{
#' library(jsonlite)
#' library(RCurl)
#' 
#' # Get the metadata
#' result.meta <- postForm(
#'     api_url,
#'     token = api_token,
#'     content = 'metadata',
#'     format = 'json'
#' )
#' 
#' # Get the records
#' result.record <- postForm(
#'     uri = api_url,
#'     token = api_token,
#'     content = 'record',
#'     format = 'json',
#'     type = 'flat',
#'     rawOrLabel = 'raw',
#'     rawOrLabelHeaders = 'raw',
#'     exportCheckboxLabel = 'false',
#'     exportSurveyFields = 'false',
#'     exportDataAccessGroups = 'false',
#'     returnFormat = 'json'
#' )
#' 
#' records <- fromJSON(result.record)
#' metadata <- fromJSON(result.meta)
#'
#' REDCap_split(records, metadata)
#' }
#' @return a list of data.frames
#' @export
REDCap_split <- function(records, metadata) {

	# Check to see if there were any repeating instruments

	if (!any(names(records) == "redcap_repeat_instrument")) {

		warning("There are no repeating instruments.\n")

		return(list(records))

	}

	# Clean the metadata
	metadata <- metadata[metadata["field_type"] != "descriptive", 1:4]

	# Identify the subtables in the data
	subtables <- unique(records["redcap_repeat_instrument"])
	subtables <- subtables[subtables != ""]

	# Split the table based on instrument
	out <- split.data.frame(records, records["redcap_repeat_instrument"])

	# Delete the variables that are not relevant
	for (i in names(out)) {

		if (i == "") {

			out[[which(names(out) == "")]] <-
				out[[which(names(out) == "")]][metadata[`!`(metadata[,2] %in% subtables), 1]]

		} else {

			out[[i]] <-
				out[[i]][c(names(records[1:3]),metadata[metadata[,2] == i, 1])]

		}

	}

	return(out)

}