spaceplace: Function-Based Search of Space

#' Download OSM data and return as sf object
#'
#' Download OSM data with specified parameters and return sf object.
#'
#' @param bbox \code{vector} of corner coordinates of the area to download.
#' @param crs output coordinate reference system.
#' @param geom_type OSM geometry type.
#' @param key OSM key to download.
#' @param value OSM value to download.
#' @param timeout (optional) overpass timeout time in seconds.
#'
#' @return \code{sf} object of downloaded data.
#'
#' @export
#'
#' @examples
#' \dontrun{
#' # London
#' bb <- c (-0.90, 51.30, 0.0, 51.40)
#' crs <- 32630
#' geom_type <- "osm_points"
#' key <- "highway"
#' value <- "bus_stop"
#'
#' bus_stops <- osm_to_sf (bb, crs, geom_type, key, value)
#' }
osm_to_sf <- function (bbox, crs, geom_type, key, value, timeout = 25)
{
  feat <- osmdata::opq (bbox = bbox, timeout = timeout)
  if (missing (value))
  {
    feat <- osmdata::add_osm_feature (feat, key = key)
  } else {
    feat <- osmdata::add_osm_feature (feat, key = key, value = value)
  }

  feat_out <- NULL
  if (geom_type != "osm_points")
  {
    dat <- osmdata::osmdata_sf(feat) [[geom_type]]
    if (dim (dat) [1] > 0)
      feat_out <- sf::st_transform (sf::st_as_sf (dat), crs)
  } else
  {
    dat_pts <- osmdata::osmdata_sf(feat) [["osm_points"]]
    dat_poly <- osmdata::osmdata_sf(feat) [["osm_polygons"]]

    mergepts <- FALSE
    if (dim (dat_pts) [1] > 0)
    {
      dat_pts <- sf::st_transform (sf::st_as_sf (dat_pts), crs)
      feat_out <- dat_pts
    } else {
      return (feat_out)
    }

    if (dim (dat_poly) [1] > 0)
    {
      dat_poly <- sf::st_transform (sf::st_as_sf (dat_poly), crs)
      mergepts <- TRUE
    }

    if (mergepts)
    {
      dups <- sf::st_intersects(dat_pts$geometry, dat_poly$geometry)
      keep <- apply (dups, 1, any)
      dat_pts <- dat_pts [keep, ]
      cents <- sf::st_centroid(dat_poly$geometry)
      dat_poly <- sf::st_set_geometry (dat_poly, cents)

       if ("name" %in% names (dat_pts) & "name" %in% names (dat_poly))
       {
         dat_pts <- dat_pts [c ("name", "geometry")]
         dat_poly <- dat_poly [c ("name", "geometry")]
       } else {
         dat_pts <- dat_pts ["geometry"]
         dat_poly <- dat_poly ["geometry"]
       }
      feat_out <- rbind (dat_pts, dat_poly)
    }
  }

  return (feat_out)
}

#' Download OSM data, store it and and return as sf object
#'
#' Wrapper function for osm_to_sf that creates a unique file name from the
#' passed parameters, downloads the requested data if necessary and returns the
#' resulting sf object.
#'
#' @param bbox \code{vector} of corner coordinates of the area to download.
#' @param crs output coordinate reference system.
#' @param geom_type OSM geometry type.
#' @param key OSM key to download.
#' @param value OSM value to download.
#' @param clip_by_outline (optional) city name based on which the outline should be cut.
#' @param timeout (optional) overpass timeout time in seconds.
#'
#' @return \code{sf} object of downloaded data.
#'
#' @export
#'
#' @examples
#' \dontrun{
#' # London
#' bb <- c (-0.90, 51.30, 0.0, 51.40)
#' crs <- 32630
#' geom_type <- "osm_points"
#' key <- "highway"
#' value <- "bus_stop"
#' clip_by <- "London"
#'
#' bus_stops <- load_osm_data (bb, crs, geom_type, key, value, clip_by)
#' }
load_osm_data <- function (bbox, crs, geom_type, key, value, clip_by_outline,
                           timeout = 25)
{
  fname <- paste0 (paste (c (crs, geom_type, key, value), collapse = "-"),
                   ".gpkg")

  lyr <- paste (key, value, sep = " - ")

  dat <- NA
  if (!fname %in% dir())
  {
    dat <- osm_to_sf(bbox, crs, geom_type, key, value, timeout)
    if (is.null(dat))
      return (NULL)
    if ("name" %in% names (dat))
    {
      dat <- dat [c ("name", "geometry")]
    } else
    {
      dat <- dat ["geometry"]
    }
    sf::st_write (dat, layer = lyr, fname)
  }
  dat <- sf::read_sf(fname)

  if (exists(clip_by_outline))
  {
    aoi <- get_city_outline (clip_by_outline)
    keep <- sf::st_contains(sf::st_geometry(aoi), sf::st_geometry(dat)) [[1]]
    dat <- dat [keep, ]
  }
  return (dat)
}
#' Download OSM data with multiple values, combine and store them, and and
#' return as sf object
#'
#' Wrapper function for osm_to_sf that creates a unique file name from the
#' passed parameters, downloads the requested data if necessary and returns the
#' resulting sf object.
#'
#' @param bbox \code{vector} of corner coordinates of the area to download.
#' @param crs output coordinate reference system.
#' @param geom_type OSM geometry type.
#' @param keys vector of OSM keys to download.
#' @param values vector of OSM values to download.
#' @param group group name for the downloaded data.
#' @param clip_by_outline (optional) city name based on which the outline should be cut.
#' @param timeout (optional) overpass timeout time in seconds.
#'
#' @return \code{sf} object of downloaded data.
#'
#' @export
#'
#' @examples
#' \dontrun{
#' # London
#' bb <- c (-0.90, 51.30, 0.0, 51.40)
#' crs <- 32630
#' geom_type <- "osm_points"
#' key <- "amenity"
#' values <- c ("atm", "bank")
#' group_name <- "finance"
#' clip_by <- "London"
#'
#' finance_london <- load_osm_value_groups (bb, crs, geom_type, key, values,
#'                                          group_name, clip_by)
#' }
load_osm_value_groups <- function (bbox, crs, geom_type, keys, values, group,
                                   clip_by_outline, timeout = 25)
{
  fname <- paste0 (paste (c (crs, key), collapse = "-"), ".gpkg")

  for (key in keys)
  {
    for (value in values)
    {
      dat <- load_osm_data (bbox, crs, geom_type, key, value, clip_by_outline,
                            timeout)
      if (is.null(dat))
        next

      lyrname <- paste (c (group, value), collapse = " - ")
      append <- TRUE
      if (fname %in% dir ())
      {
        layers <- rgdal::ogrListLayers(fname)
        if (lyrname %in% layers)
          append <- FALSE
      }
      if (append)
      {
        sf::st_write(dat, fname, layer = lyrname, update = TRUE,
                     layer_options = c ("OVERWRITE=yes"))
      }
    }
  }
  dat <- sf::read_sf(fname)
  return (dat)
}

#' Download city outline from OSM and return as sf object
#'
#' @param city_name Name of the city outline to download.
#'
#' @return \code{sf} object of downloaded data.
#'
#' @export
get_city_outline <- function (city_name)
{
  osm_l <- osmdata::getbb (city_name, format_out = "polygon") [[1]] [[1]]
  wkt <- paste0 ("SRID=4326;POLYGON((",
                 paste (paste (osm_l [, 1], osm_l [, 2]), collapse
                        = ","),
                 "))")
  aoi <- sf::st_set_crs (sf::st_as_sfc (wkt), 4326)
  return (aoi)
}