R/download_chelsa_trace21k.R

In pastclim: Manipulate Time Series of Climate Reconstructions

#' Download the CHELSA trace21k
#'
#' This function downloads annual and monthly variables from the CHELSA trace
#' v1.0 dataset.
#'
#' As this dataset is huge, we should not download all files in most situations.
#' For this reason, time_bp has to be set for downloading (but it is allowed for
#' virtual datasets)
#'
#' @param dataset the name of the dataset
#' @param bio_var the variable name
#' @param filename the filename as stored in the `data_path` of `pastclim`
#'   (includes the full data path)
#' @param time_bp the time steps for which the dataset should be built (NULL for
#'   all time steps)
#' @returns TRUE if the requested CHELSA variable was downloaded successfully
#'
#' @keywords internal

# nolint start
# download_chelsa_trace21(dataset = "CHELSA_trace21k_1.0_0.5m_vsi", bio_var = "bio06",
# filename = file.path(get_data_path(), "CHELSA_trace21k_1.0_0.5m_bio06_vsi.vrt"),
# time_bp= c(-22000,-10000,0))
# nolint end

download_chelsa_trace21k <- function(dataset, bio_var, filename = NULL,
                                     time_bp = NULL) {
  if (substr(dataset, nchar(dataset) - 2, nchar(dataset)) == "vsi") {
    virtual <- TRUE
  } else {
    virtual <- FALSE
  }

  if (!virtual && is.null(time_bp)) {
    stop("the CHELSA Trace21k dataset is very large. You can either use
         a virtual dataset (leaving the files on the server), or, if you want
         to download specific time slices, use 'download_chelsa_trace21k' by
         setting the time slices of interest with the parameter 'time_bp'.
         See the dataset help page for more information
         (use ??CHELSA_Trace21k)")
  }

  # convert time to an index to select the correct file
  avail_time_bp <- seq(0, -22000, -100)
  if (is.null(time_bp)) {
    time_bp <- avail_time_bp
  }
  if (!all(time_bp %in% avail_time_bp)) {
    stop(
      "some values in time_bp are not valid; only steps from 0 to ",
      "-22000 in steps of -100 are valid"
    )
  }
  avail_yr_id <- seq(20, -200, by = -1)
  # convert time_bp to yr_id
  yr_id <- avail_yr_id[match(time_bp, avail_time_bp)]

  # create file names for a given variable
  download_url <- filenames_chelsa_trace21k(
    dataset = dataset,
    bio_var = bio_var
  )
  # subset to the years that we want
  file_yr_id <- as.numeric(gsub(".*_(\\-?\\d+)_.*", "\\1", download_url))
  download_url <- download_url[match(yr_id, file_yr_id)]

  if (virtual) {
    if (!all(unlist(lapply(download_url, url_is_valid)))) {
      stop(
        "invalid URL for variable ", bio_var,
        "; either the server can not be reached at the moment, or ",
        "the path has changed"
      )
    }
    # add prefix for vsi dataset
    chelsa_url <- paste0("/vsicurl/", download_url) # urls of target files
  } else { # download the files
    # if we do not have a directory, create one
    chelsa_dir <- file.path(get_data_path(), "chelsa_2.1")
    if (!dir.exists(chelsa_dir)) {
      dir.create(chelsa_dir)
    }
    # and now download the files (so the url is actually a local file)
    chelsa_url <- file.path(chelsa_dir, basename(download_url))
    download_res <- curl::multi_download(download_url,
      destfiles = chelsa_url, resume = TRUE
    )
    if (any(!download_res$success)) {
      stop("something went wrong downloading the data; try again")
    }
  }

  # nolint start
  # we capture warnings from the vrt to make sure that all is well
  # vrt_path <- terra::vrt(x = chelsa_url,
  #                                  filename = filename,
  #                                  options=c("-separate"), overwrite=TRUE, return_filename=TRUE)
  # nolint end
  vrt_path <- filename

  if (file.exists(filename)) {
    file.remove(filename)
  }
  sf::gdal_utils(
    util = "buildvrt",
    source = chelsa_url,
    destination = filename,
    options = c("-separate")
  )

  # edit the vrt metadata
  edit_res <- vrt_set_meta(
    vrt_path = vrt_path, description = bio_var,
    time_vector = time_bp, time_bp = TRUE
  )
  if (!edit_res) {
    file.remove(vrt_path)
    stop(
      "something went wrong setting up this dataset",
      "\n the dataset wil need downloading again"
    )
  }
  return()
}