fix(map): make area analysis scale-aware

frontend/src/components/map/mapWorkspaceUtils.ts

@@ -73,6 +73,63 @@ export function selectionAreaSquareMetres(bbox: VectorSelectionBBox | null): num
   return Math.max(0, widthMetres * heightMetres)
 }
 
+export interface SelectionDimensions {
+  widthMetres: number
+  heightMetres: number
+  areaSquareMetres: number
+}
+
+export type SelectionAnalysisScale = 'detail' | 'regional' | 'overview'
+
+export function selectionDimensions(bbox: VectorSelectionBBox): SelectionDimensions {
+  const middleLatitudeRadians = ((bbox.min_y + bbox.max_y) / 2) * (Math.PI / 180)
+  const widthMetres = Math.max(0, (bbox.max_x - bbox.min_x) * 111_320 * Math.cos(middleLatitudeRadians))
+  const heightMetres = Math.max(0, (bbox.max_y - bbox.min_y) * 110_574)
+  return {
+    widthMetres,
+    heightMetres,
+    areaSquareMetres: widthMetres * heightMetres,
+  }
+}
+
+export function selectionAnalysisScale(bbox: VectorSelectionBBox): SelectionAnalysisScale {
+  const { widthMetres, heightMetres } = selectionDimensions(bbox)
+  const longestSide = Math.max(widthMetres, heightMetres)
+  if (longestSide <= 20_000) return 'detail'
+  if (longestSide <= 50_000) return 'regional'
+  return 'overview'
+}
+
+export function splitSelectionBbox(
+  bbox: VectorSelectionBBox,
+  maxTileSideMetres = 18_000,
+  maxTiles = 16,
+): VectorSelectionBBox[] {
+  const { widthMetres, heightMetres } = selectionDimensions(bbox)
+  const columns = Math.max(1, Math.ceil(widthMetres / maxTileSideMetres))
+  const rows = Math.max(1, Math.ceil(heightMetres / maxTileSideMetres))
+  if (columns * rows > maxTiles) {
+    throw new Error(
+      `De selectie vereist ${columns * rows} detailpartities; maximaal ${maxTiles} zijn toegestaan.`,
+    )
+  }
+  const longitudeStep = (bbox.max_x - bbox.min_x) / columns
+  const latitudeStep = (bbox.max_y - bbox.min_y) / rows
+  const tiles: VectorSelectionBBox[] = []
+  for (let row = 0; row < rows; row += 1) {
+    for (let column = 0; column < columns; column += 1) {
+      tiles.push({
+        min_x: bbox.min_x + longitudeStep * column,
+        min_y: bbox.min_y + latitudeStep * row,
+        max_x: column === columns - 1 ? bbox.max_x : bbox.min_x + longitudeStep * (column + 1),
+        max_y: row === rows - 1 ? bbox.max_y : bbox.min_y + latitudeStep * (row + 1),
+        crs: 'EPSG:4326',
+      })
+    }
+  }
+  return tiles
+}
+
 export function bboxesEqual(left: VectorSelectionBBox | null, right: VectorSelectionBBox | null): boolean {
   if (!left || !right) {
     return false