feat(shortcut): area

components/label/utils/geometry/areaFilter.ts

@@ -0,0 +1,69 @@
+import {
+  normalizeMultiPolygon,
+  type NormalizedMultiPolygon,
+  type NormalizedRing,
+} from "./booleanAdapter"
+
+export interface AreaFilterResult {
+  geometry: NormalizedMultiPolygon
+  removedOuterCount: number
+  removedHoleCount: number
+}
+
+const getRingArea = (ring: NormalizedRing) => {
+  let area = 0
+  for (let index = 0; index < ring.length - 1; index += 1) {
+    const [x1, y1] = ring[index]
+    const [x2, y2] = ring[index + 1]
+    area += x1 * y2 - x2 * y1
+  }
+  return Math.abs(area / 2)
+}
+
+export const filterMultiPolygonByAreaThreshold = ({
+  geometry,
+  minArea,
+}: {
+  geometry: NormalizedMultiPolygon | null | undefined
+  minArea: number
+}): AreaFilterResult => {
+  const normalizedGeometry = normalizeMultiPolygon(geometry)
+  const normalizedMinArea = Math.max(0, Number(minArea) || 0)
+
+  if (!normalizedMinArea) {
+    return {
+      geometry: normalizedGeometry,
+      removedOuterCount: 0,
+      removedHoleCount: 0,
+    }
+  }
+
+  let removedOuterCount = 0
+  let removedHoleCount = 0
+
+  const nextGeometry = normalizedGeometry.flatMap((polygon) => {
+    const [outerRing, ...holeRings] = polygon
+    if (!outerRing) return []
+
+    if (getRingArea(outerRing) < normalizedMinArea) {
+      removedOuterCount += 1
+      return []
+    }
+
+    const nextHoleRings = holeRings.filter((ring) => {
+      const keep = getRingArea(ring) >= normalizedMinArea
+      if (!keep) {
+        removedHoleCount += 1
+      }
+      return keep
+    })
+
+    return [[outerRing, ...nextHoleRings]]
+  })
+
+  return {
+    geometry: nextGeometry,
+    removedOuterCount,
+    removedHoleCount,
+  }
+}