get_OSD: TXT and HTML formats and unified interface

R/get_OSD.R

@@ -0,0 +1,157 @@
+#' Fetch Official Series Description Data from JSON, HTML or TXT sources
+#'
+#' @param series A character vector of Official Series names e.g. `"Chewacla"`
+#' @param result Select `"json"`, `"html"`, or `"txt"` output
+#' 
+#' @param base_url Optional: alternate JSON/HTML/TXT repository path. Default: `NULL` uses `"https://github.com/ncss-tech/SoilKnowledgeBase"` for `result="json"` 
+#' 
+#' @param verbose Print errors and warning messages related to HTTP requests? Default: `FALSE`
+#' 
+#' @details The default `base_url` for `result="json"` is to JSON files stored in a GitHub repository  that is regularly updated from the official source of Series Descriptions. Using format: `https://raw.githubusercontent.com/ncss-tech/SoilKnowledgeBase/main/inst/extdata/OSD/{LETTER}/{SERIES}.json` for JSON. And `"https://soilseriesdesc.sc.egov.usda.gov/OSD_Docs/{LETTER}/{SERIES}.html` is for `result="html"` (official source).
+#'
+#' @return For JSON result: A `data.frame` with 1 row per series, and 1 column per "section" in the OSD as defined in National Soil Survey Handbook. For TXT or HTML result a list of character vectors containing OSD text with 1 element per series and one value per line.
+#' @export
+#' @aliases get_OSD_JSON
+#' @examples
+#'
+#' \donttest{
+#' if(requireNamespace("curl") &
+#'    curl::has_internet()) {
+#'    
+#' series <- c("Musick", "Hector", "Chewacla")
+#' get_OSD(series)
+#' }
+#' }
+get_OSD <- function(series, base_url = NULL, result = c("json","html","txt"), verbose = FALSE) {
+  result <- match.arg(tolower(result), c("json","html","txt"))
+
+  a_url <- NULL
+  if (!is.null(base_url)) {
+    a_url <- base_url
+  }
+
+  switch(result, 
+         "json" = { .get_OSD_JSON(series, base_url = a_url, verbose = verbose) },
+         "html" = { .get_OSD_HTML(series, base_url = a_url, verbose = verbose) },
+         "txt" =  { .get_OSD_TXT(series, verbose = verbose)  })
+}
+
+.get_OSD_HTML <- function(series, base_url = NULL, verbose = FALSE) {
+  if(!requireNamespace('rvest', quietly=TRUE))
+    stop('please install the `rvest` package', call.=FALSE)
+
+  if (missing(base_url) || is.null(base_url))
+    base_url <- 'https://soilseriesdesc.sc.egov.usda.gov/OSD_Docs/'
+
+  # get HTML content and strip blank / NA lines
+  res <- sapply(.seriesNameToURL(series, base_url = base_url), function(x) {
+    htmlres <- try(rvest::html_text(rvest::read_html(x)), silent = !verbose)
+
+    if (inherits(htmlres, 'try-error'))
+      return(NULL)
+
+    .stripOSDContents(readLines(textConnection(htmlres)))
+  })
+  names(res) <- toupper(series)
+  res
+}
+
+.get_OSD_TXT <- function(series, base_url = "", verbose = FALSE) {
+  sapply(series, function(x) {
+    fp <- .seriesNameToURL(x, base_url = base_url, extension = "txt")
+
+    if (!file.exists(fp))
+      return(NULL)
+
+    # remove empty lines and fix other markup
+    try(.stripOSDContents(readLines(fp)), silent = !verbose)
+  })
+}
+
+get_OSD_JSON <- function(series, base_url = NULL) {
+  # .Deprecated("get_OSD")
+  .get_OSD_JSON(series, base_url)
+}
+
+.get_OSD_JSON <- function(series, base_url = NULL, verbose = FALSE) {
+
+  # http://github.com/ncss-tech/SoilKnowledgeBase is default JSON repository path
+  if (missing(base_url) || is.null(base_url))
+    base_url <- "https://raw.githubusercontent.com/ncss-tech/SoilKnowledgeBase/main/inst/extdata/OSD"
+
+  if (!requireNamespace("jsonlite"))
+    stop("package `jsonlite` is required", call. = FALSE)
+
+  # convert series name to upper case and remove NA
+  series <- toupper(na.omit(series))
+
+  # get first letter of each taxon (if any)
+  if (length(series) > 0 && all(nchar(series) > 1)) {
+    firstLetter <- substr(series, 0, 1)
+  } else stop("argument `series` should be character vector of existing official series names", call. = FALSE)
+
+  # construct URL
+  path <- file.path(base_url, firstLetter, paste0(series, ".json"))
+
+  # query, handle errors, return 'tidy' data.frame result
+  data.frame(data.table::rbindlist(lapply(seq_along(path), function(i) {
+
+    p <- path[i]
+    jsp <- try(jsonlite::read_json(p), silent = TRUE)
+
+    # warning will be generated for non-existent URL
+    if (inherits(jsp, 'try-error'))
+      return(NULL)
+
+    jspn <- names(jsp)[!names(jsp) %in% c('SITE','HORIZONS')]
+    res <- try({
+      data.table::as.data.table(lapply(jspn, function(m) {
+        x <- jsp[[m]]
+        res2 <- x[[length(x)]]
+        if (is.null(res2))
+          res2 <- NA
+        res2
+      }))
+    }, silent = FALSE)
+    colnames(res) <- jspn
+
+    jsp$SITE[[1]][[1]]$id <- i
+    res$SITE <- list(data.frame(data.table::rbindlist(lapply(jsp$SITE[[1]], data.frame), fill = TRUE)))
+    res$HORIZONS <- list(data.frame(data.table::rbindlist(lapply(jsp$HORIZONS[[1]], data.frame), fill = TRUE)))
+
+    # handles weird cases
+    if (inherits(res, 'try-error'))
+      return(NULL)
+
+    return(res)
+  })))
+
+}
+
+## Migrated / adapted from parseOSD repo
+## 2021-06-21
+## D.E. Beaudette
+
+# generate a link to the OSD for a vector of series names
+.seriesNameToURL <- function(s, base_url = 'http://soilseriesdesc.sc.egov.usda.gov/OSD_Docs/',
+                             extension = 'html') {
+  paste0(base_url, .seriesNameToFileName(s, extension = extension))
+}
+
+# prepare a file name and capitalized-first-letter folder based on a series name
+.seriesNameToFileName <- function(s, extension = 'txt') {
+
+  # convert space to _
+  s <- gsub(pattern = ' ', replacement = '_', toupper(s))
+
+  # TODO: convert apostrophe
+
+  sprintf('%s/%s.%s', substr(s, 1, 1), s, extension)
+}
+
+  # remove empty lines and NA strip double quotes by converting to " inches"
+.stripOSDContents <- function(x) {
+  x <- x[which(x != '')]
+  x <- x[which(!is.na(x))]
+  gsub('"', ' inches', x)
+}