R/source-api.R

In osmar: OpenStreetMap and R

#' @include get.R
#' @include source.R
{}



#' API OSM data source
#'
#' OSM API version 0.6 data source; see
#' \url{http://wiki.openstreetmap.org/wiki/API_v0.6}.
#'
#' @section Supported request elements:
#'
#' \describe{
#'   \item{Bounding box:}{
#'
#'     Use \code{\link{corner_bbox}} or \code{\link{center_bbox}} to
#'     retrieve:
#'
#'     \itemize{
#'
#'       \item all nodes that are inside a given bounding box and any
#'         relations that reference them;
#'
#'       \item all ways that reference at least one node that is
#'         inside a given bounding box, any relations that reference
#'         them [the ways], and any nodes outside the bounding box
#'         that the ways may reference;
#'
#'       \item all relations that reference one of the nodes or ways
#'         included due to the above rules (does not apply
#'         recursively);
#'     }
#'   }
#'
#'   \item{Basic request elements:}{
#'     Use \code{\link[=osm_descriptors]{node}},
#'     \code{\link[=osm_descriptors]{way}},
#'     \code{\link[=osm_descriptors]{relation}} to retrieve an element
#'     by its ID.
#'
#'     Use \code{full = TRUE} as additional argument to the
#'     \code{\link{get_osm}} function. This means that all members of
#'     the specified elements are retrieved as well:
#'
#'     \itemize{
#'
#'       \item For a way, it will return the way specified plus all
#'         nodes referenced by the way.
#'
#'       \item For a relation, it will return: (1) the relation itself;
#'         (2) all nodes, ways, and relations that are members of the
#'         relation; and (3) all nodes used by ways from the previous step.
#'
#'     }
#'   }
#'
#' }
#'
#' @param url URL of the API
#'
#' @examples
#'   \dontrun{
#'     api <- osmsource_api()
#'
#'     box <- corner_bbox(11.579341, 48.15102, 11.582852, 48.1530)
#'     gschw <- get_osm(box, source = api)
#'
#'     kaufstr <- get_osm(way(3810479))
#'     kaufstr_full <- get_osm(way(3810479), full = TRUE)
#'   }
#'
#' @references
#'   \url{http://wiki.openstreetmap.org/wiki/API_v0.6}
#' @seealso \code{\link{get_osm}}, \code{\link{bbox}},
#'   \code{\link{osm_descriptors}}
#' @family osmsource
#'
#' @export
osmsource_api <- function(url = "http://api.openstreetmap.org/api/0.6/") {
  osmsource(list(url = url), "api")
}



get_osm_data.api <- function(source, what, ...) {
  request <- osm_request(source, what, ...)
  response <- getURL(request, .encoding = "UTF-8")

  response
}



setMethod("osm_request", signature = c("api", "bbox"),
function(source, what, ...) {
  if ( size(what) >= 0.25 )
    stop("BoundingBox is bigger than 0.25-Square-Degrees\n")

  sprintf("%smap/?bbox=%s,%s,%s,%s", source$url,
          what["left"], what["bottom"], what["right"], what["top"])
})



setMethod("osm_request", signature = c("api", "element"),
function(source, what, full = FALSE, ...) {
  element <- class(what)[1]
  r <- sprintf("%s%s/%s", source$url, element, what["id"])
  if ( full )
    r <- sprintf("%s/full", r)

  r
})