rgee function for getting terrain data and returing a raster or extracted points

rgee_terrain_data.R

tar_extract_terrain <- function(
  geom_input,
  scale = 30,
  file_prefix = "rgee_terrain"
) {
  # --- 1. Compute Earth Engine Terrain Stack ---
  dem <- ee$ImageCollection('COPERNICUS/DEM/GLO30')$select('DEM')$mosaic()
  terrain_products <- ee$Terrain$products(dem)

  slope <- terrain_products$select('slope')
  aspect <- terrain_products$select('aspect')

  tpi_kernel <- ee$Kernel$circle(radius = 3, units = 'pixels')
  mean_dem <- dem$focal_mean(kernel = tpi_kernel)
  tpi <- dem$subtract(mean_dem)$rename('TPI')

  tri_kernel <- ee$Kernel$square(radius = 1, units = 'pixels')
  tri <- dem$reduceNeighborhood(
    reducer = ee$Reducer$stdDev(),
    kernel = tri_kernel
  )$rename('TRI')

  terrain_stack <- dem$addBands(slope)$addBands(aspect)$addBands(tpi)$addBands(
    tri
  )$rename(c('elevation', 'slope', 'aspect', 'TPI', 'TRI'))

  # --- 2. Polymorphic Input Normalization & Routing ---
  is_ee_raster <- inherits(geom_input, "ee.image.Image") ||
    inherits(geom_input, "ee.imagecollection.ImageCollection")

  if (is_ee_raster) {
    geom_type <- "Raster"
    ee_raster_geometry <- geom_input$geometry()
    processed_ee <- terrain_stack$clip(ee_raster_geometry)
  } else {
    if (inherits(geom_input, "sf") || inherits(geom_input, "sfc")) {
      message("Local R 'sf' layer detected. Converting to GEE environment...")
      geom_string <- as.character(sf::st_geometry_type(
        geom_input,
        by_geometry = FALSE
      ))
      ee_geom <- sf_as_ee(geom_input)
    } else {
      if (inherits(geom_input, "ee.geometry.Geometry")) {
        ee_type_obj <- geom_input$type()
        geom_string <- ee_type_obj$getInfo()
      } else {
        ee_geom_obj <- geom_input$geometry()
        ee_type_obj <- ee_geom_obj$type()
        geom_string <- ee_type_obj$getInfo()
      }
      ee_geom <- geom_input
    }

    if (grepl("Point", geom_string, ignore.case = TRUE)) {
      geom_type <- "Points"
      processed_ee <- terrain_stack$sampleRegions(
        collection = ee_geom,
        scale = scale,
        geometries = TRUE
      )
    } else {
      geom_type <- "Polygon"
      processed_ee <- terrain_stack$clip(ee_geom)
    }
  }

  task_desc <- paste0(file_prefix, "_", format(Sys.time(), "%Y%m%d_%H%M%S"))

  if (geom_type == "Points") {
    message("Launching GEE point extraction table export...")
    task <- ee$batch$Export$table$toDrive(
      collection = processed_ee,
      description = task_desc,
      fileFormat = "CSV"
    )
    ext <- ".csv"
  } else {
    message("Launching GEE regional raster mosaic export...")
    export_region <- if (is_ee_raster) geom_input$geometry() else ee_geom
    task <- ee$batch$Export$image$toDrive(
      image = processed_ee,
      description = task_desc,
      scale = scale,
      region = export_region,
      fileFormat = "GeoTIFF"
    )
    ext <- ".tif"
  }

  # --- 3. FIX: Custom Safe Monitoring Loop (Bypasses ee_monitoring Overflow) ---
  task$start()
  message(
    "Task dispatched safely to Earth Engine Cloud. Monitoring execution state..."
  )

  # Manual polling loop to avoid reticulate C long type casting errors
  repeat {
    status_state <- task$status()$state
    message(paste("Current Cloud State:", status_state))

    if (status_state %in% c("COMPLETED", "FAILED", "CANCELLED")) {
      break
    }
    Sys.sleep(10) # Check status every 10 seconds to keep targets synchronized
  }

  if (status_state != "COMPLETED") {
    stop(paste(
      "Earth Engine processing failed with cloud execution state:",
      status_state
    ))
  }

  # --- 4. Locate and Download the File via 'googledrive' ---
  message("Locating generated asset inside Google Drive filesystem...")
  target_filename <- paste0(task_desc, ext)

  Sys.sleep(5)

  drive_file <- drive_find(name = target_filename, n_max = 1)
  if (nrow(drive_file) == 0) {
    stop(paste(
      "Could not find file",
      target_filename,
      "in your Google Drive root directory."
    ))
  }

  tmp_path <- tempfile(fileext = ext)
  message(paste("Downloading dataset locally to path:", tmp_path))

  drive_download(
    file = as_id(drive_file$id),
    path = tmp_path,
    overwrite = TRUE
  )

  drive_rm(as_id(drive_file$id))

  # --- 5. Ingest Data Back into R Memory Context ---
  if (geom_type == "Points") {
    point_df <- read.csv(tmp_path)
    result <- st_read(point_df, geometry_column = ".geo", quiet = TRUE)
  } else {
    result <- terra::rast(tmp_path)
  }

  return(result)
}