utils.R

library(dplyr)
library(duckdbfs)
library(sf)

as_dataset.sf <- function(sf, ...) {
  # cludgy way to get polygon into duckdb as spatial data
  tmp <- tempfile(fileext = ".fgb")
  sf |>
    sf::st_transform(4326) |>
    sf::write_sf(tmp, append = FALSE, quiet = TRUE)
  aoi <- duckdbfs::open_dataset(tmp, ...)

  aoi
}

# promote bbox to polygon
as_poly <- function(aoi) {
  crs <- st_crs(aoi)
  if (crs$input != "EPSG:4326") {
    aoi <- aoi |> st_transform(4326)
  }
  if (inherits(aoi, "bbox")) {
    aoi <- aoi |>
      st_as_sfc() |>
      st_as_sf() |>
      rename(geom = x)
  }
  aoi
}


get_h3_aoi <- function(aoi, zoom = 0L, precision = 6L, upper = FALSE) {
  duckdbfs::load_h3()

  zoom <- as.integer(zoom)
  # consider auto-retry at higher precision if subset is empty.
  precision <- as.integer(precision)
  res <- paste0("h", precision)

  if (inherits(aoi, "sf") || inherits(aoi, "bbox")) {
    aoi <- as_poly(aoi)
    aoi <- as_dataset.sf(aoi)
  }

  # multipolygon dump may not be needed for draw tools.
  h3_aoi <- aoi |>
    dplyr::mutate(
      poly = array_extract(unnest(st_dump(geom)), "geom"),
      h3id = h3_polygon_wkt_to_cells(poly, {
        precision
      }),
      h3id = unnest(h3id)
    ) |>
    dplyr::mutate(
      h0 = h3_h3_to_string(h3_cell_to_parent(h3id, {
        zoom
      })),
      h3id = h3_h3_to_string(h3id)
    )

  if (upper) {
    h3_aoi <- h3_aoi |>
      dplyr::mutate(h0 = toupper(h0), h3id = toupper(h3id))
  }

  h3_aoi |>
    dplyr::select(h0, h3id) |>
    duckdbfs::as_view("h3_aoi")
}

hex_res <- function(x) {
  x |>
    utils::head(1) |>
    dplyr::mutate(res = h3_get_resolution(h3id)) |>
    dplyr::pull(res)
}

hex_join <- function(x, y) {
  res_x <- hex_res(x)
  res_y <- hex_res(y)

  if (res_x > res_y) {
    y <- y |>
      dplyr::mutate(
        h3id = unnest(h3_cell_to_children(h3id, {
          res_x
        })),
        h3id = toupper(h3id)
      )
  }
  if (res_x < res_y) {
    y <- y |>
      dplyr::mutate(
        h3id = h3_cell_to_parent(h3id, {
          res_x
        })
      )
  }

  dplyr::inner_join(x, y)
}

antimeridian_hexes <- function(zoom = 4, con = duckdbfs::cached_connection()) {
  duckdbfs::load_h3(con)
  duckdbfs::load_spatial(con)
  DBI::dbExecute(
    con,
    "
  CREATE OR REPLACE TABLE antimeridian AS (
    SELECT ST_GeomFromText(
    'POLYGON ((170 85, 190 85, 190 -85, 170 -85, 170 85))'
    ) AS geometry
  )
  "
  )
  zoom <- as.integer(zoom)

  am <-
    dplyr::tbl(con, "antimeridian") |>
    dplyr::mutate(
      h3id = unnest(
        h3_polygon_wkt_to_cells_string(geometry, {
          zoom
        })
      )
    ) |>
    dplyr::select(h3id)

  am
}


viridis_pal <-
  function(column = "height", n = 61, min_v = 0, max_v = 1) {
    pal <- viridisLite::viridis(n)
    fill_color = mapgl::step_expr(
      column = column,
      base = pal[1],
      stops = pal[2:n],
      values = seq(min_v, max_v, length.out = n - 1),
      na_color = "white"
    )

    fill_color
  }