add functionality to read sample data from github release

R/gt3x_sample_data.R

@@ -1,19 +1,53 @@
 #' Path to read.gt3x package sample data
 #'
-#' @param index The index of a sample file to retrieve
+#' @param index Integer. The index of a sample file to retrieve. If NULL (default) the path to the directory
+#' including the sample files will be returned.
 #'
 #' @examples
 #' dir <- gt3x_datapath()
+#' gt3x_filename <- gt3x_datapath(1)
 #'
 #' @export
 gt3x_datapath <- function(index = NULL) {
-  datadir <- file.path(path.package("read.gt3x"), "extdata")
-  if(!dir.exists(datadir)) stop("Data directory not found")
-  # TODO: download data the first time this is called.
+  homedir <-  path.expand('~')
+  datadir <- file.path(homedir, ".read.gt3x-data")
+  if(!dir.exists(datadir))
+    dir.create(datadir)
+  filenames <- gt3x_filename(index)
+  for(filename in filenames) {
+    if(!file.exists(file.path(datadir, filename)))
+      gt3x_download(url = gt3x_url(filename=filename), destfile = file.path(datadir, filename))
+  }
   if(!is.null(index)) {
     files <- list_gt3x(datadir)
-    if(index > length(files)) stop("Index is larger than the number of sample files, which there are ", length(files))
     return(files[index])
   }
   datadir
 }
+
+#' Download a gt3xfile
+gt3x_download <- function(url, destfile) {
+  download.file(url = url, destfile = destfile, method = "auto", mode = "wb")
+}
+
+#' Get url of gt3x sample files
+gt3x_url <- function(index = NULL, filename = NULL, version = "v0.1-alpha", baseurl = "https://github.com/THLfi/read.gt3x/releases/download") {
+  dataurl <- gt3x_dataurl(version, baseurl)
+  if(is.null(filename))
+    filename <- gt3x_filename(index)
+  file.path(dataurl, filename)
+}
+
+#' Get url of github release
+gt3x_dataurl <- function(version = "v0.1-alpha", baseurl = "https://github.com/THLfi/read.gt3x/releases/download") {
+  url <- file.path(baseurl, version)
+}
+
+#' Get sample gt3x filenames
+gt3x_filename <- function(index = NULL) {
+  files <- c("EE_left_29.5.2017-05-30.gt3x", "SS_left_19.5.2017-05-22.gt3x")
+  if(is.null(index)) return(files)
+  if(index > length(files)) stop("Index is larger than the number of available files")
+  if(index < 1) stop("Index can't be less than 1")
+  files[index]
+}