R/assets-utils.R

In rstac: Client Library for SpatioTemporal Asset Catalog

asset_context <- new.env(parent = emptyenv())

asset_install <- function(key, asset) {
  val <- as.list(asset_context)
  if ("key" %in% names(asset_context))
    rm(list = c("key", "asset"), envir = asset_context)
  if (is.character(key)) {
    assign("key", key, envir = asset_context)
    assign("asset", asset, envir = asset_context)
  }
  val
}

asset_get <- function(field) {
  if (!"key" %in% names(asset_context))
    .error("Must be used inside `assets_select()`")
  asset_context$asset[[field]]
}

select_check_eval <- function(val) {
  if (!is.logical(val)) {
    .error(paste(
      "Select expressions must be evaluated as logical.",
      "If you want select assets by name, use `asset_names`",
      "parameter."
    ))
  }
  if (length(val) != 1) {
    .error("Select function must return a logical value of length 1.")
  }
}

select_eval <- function(key, asset, expr) {
  old <- asset_install(key, asset)
  on.exit(asset_install(old$key, old$asset))
  val <- tryCatch({
    eval(expr, envir = asset, enclos = parent.env(parent.frame()))
  }, error = function(e) {
    return(FALSE)
  })
  if (length(val) == 0)
    return(FALSE)
  select_check_eval(val)
  return(val)
}

select_exec <- function(key, asset, select_fn) {
  args <- if (length(formals(select_fn)) >= 2)
    list(asset, key) else list(asset)
  val <- do.call(select_fn, args = args, envir = parent.env(parent.frame()))
  select_check_eval(val)
  return(val)
}