R/caching.R

In seandavi/sars2pack: COVID-19 data resources and analysis tools

#' get the BiocFileCache for sars2pack
#'
#' Set up or get location of BiocFileCache. By default,
#' this uses the name BiocFileCache.
#'
#' @importFrom BiocFileCache BiocFileCache bfcneedsupdate bfcupdate bfcadd bfcquery bfcrpath
#' 
#' @param cache character(1), the path to the cache directory. See [BiocFileCache::BiocFileCache()].
#'
#' @return a `BiocFileCache` instance
#'
#' @keywords internal
s2p_get_cache <- function(cache = rappdirs::user_cache_dir(appname='sars2pack')) {
    BiocFileCache::BiocFileCache(cache=cache)
}

#' @importFrom BiocFileCache bfcneedsupdate bfcdownload bfcadd bfcquery bfcrpath
#' 
s2p_cached_url <- function(url, rname = url, ask_on_update=FALSE,
                           max_cache_age=getOption('sars2pack.max_cache_age', '2 days'),
                           ...) {
    bfc = s2p_get_cache()
    bfcres = bfcquery(bfc,rname,'rname')

    rid = bfcres$rid
    # Not found
    fileage = 0
    if(!length(rid)) {
        rid = names(bfcadd(bfc, rname, url))
    } else {
        fileage = lubridate::as_datetime(Sys.time()) -
            lubridate::parse_date_time2(bfcres$access_time, "YmdHMS", tz=Sys.timezone())
    }
    # if needs update, do the download
    if(isTRUE(bfcneedsupdate(bfc, rid))) {
        bfcdownload(bfc, rid, ask=FALSE, ...)
    } else if (fileage > lubridate::as.period(max_cache_age)) {
        bfcdownload(bfc, rid, ask=FALSE, ...)
    }
    bfcrpath(bfc, rids = rid)
}