wip: infer default viewport

src/geoarrow/bbox.ts

@@ -0,0 +1,132 @@
+import * as arrow from "apache-arrow";
+import {
+  LineStringVector,
+  MultiPolygonVector,
+  PointData,
+  PointVector,
+  PolygonVector,
+} from "../types";
+import {
+  getLineStringChild,
+  getMultiPolygonChild,
+  getPointChild,
+  getPolygonChild,
+} from "../utils";
+import { EXTENSION_NAME } from "../constants";
+
+class Bbox {
+  minX: number;
+  minY: number;
+  maxX: number;
+  maxY: number;
+
+  constructor() {
+    this.minX = Infinity;
+    this.minY = Infinity;
+    this.maxX = -Infinity;
+    this.maxY = -Infinity;
+  }
+
+  updateBbox(other: Bbox) {
+    if (other.minX < this.minX) {
+      this.minX = other.minX;
+    }
+    if (other.minY < this.minY) {
+      this.minY = other.minY;
+    }
+    if (other.maxX > this.maxX) {
+      this.maxX = other.maxX;
+    }
+    if (other.maxY > this.maxY) {
+      this.maxY = other.maxY;
+    }
+  }
+
+  updateCoord(x: number, y: number) {
+    if (x < this.minX) {
+      this.minX = x;
+    }
+    if (y < this.minY) {
+      this.minY = y;
+    }
+    if (x > this.maxX) {
+      this.maxX = x;
+    }
+    if (y > this.maxY) {
+      this.maxY = y;
+    }
+  }
+}
+
+export function totalBounds(vector: arrow.Vector, field: arrow.Field): Bbox {
+  switch (field.metadata.get("ARROW:extension:name")) {
+    case EXTENSION_NAME.POINT:
+      return totalBoundsNest0(vector);
+    case EXTENSION_NAME.LINESTRING:
+    case EXTENSION_NAME.MULTIPOINT:
+      return totalBoundsNest1(vector);
+    case EXTENSION_NAME.POLYGON:
+    case EXTENSION_NAME.MULTILINESTRING:
+      return totalBoundsNest2(vector);
+    case EXTENSION_NAME.MULTIPOLYGON:
+      return totalBoundsNest3(vector);
+    default:
+      throw new Error("Unknown ext type name");
+  }
+}
+
+function coordsBbox(data: PointData): Bbox {
+  const coordsData = getPointChild(data);
+  const flatCoords = coordsData.values;
+  const bbox = new Bbox();
+
+  for (let coordIdx = 0; coordIdx < data.length; coordIdx++) {
+    const x = flatCoords[coordIdx * 2];
+    const y = flatCoords[coordIdx * 2 + 1];
+    bbox.updateCoord(x, y);
+  }
+
+  return bbox;
+}
+
+function totalBoundsNest0(vector: PointVector): Bbox {
+  const bbox = new Bbox();
+  for (const data of vector.data) {
+    bbox.updateBbox(coordsBbox(data));
+  }
+
+  return bbox;
+}
+
+function totalBoundsNest1(vector: LineStringVector): Bbox {
+  const bbox = new Bbox();
+  for (const data of vector.data) {
+    const pointData = getLineStringChild(data);
+    bbox.updateBbox(coordsBbox(pointData));
+  }
+
+  return bbox;
+}
+
+function totalBoundsNest2(vector: PolygonVector): Bbox {
+  const bbox = new Bbox();
+  for (const data of vector.data) {
+    const lineStringData = getPolygonChild(data);
+    const pointData = getLineStringChild(lineStringData);
+    bbox.updateBbox(coordsBbox(pointData));
+  }
+
+  return bbox;
+}
+
+function totalBoundsNest3(vector: MultiPolygonVector): Bbox {
+  const bbox = new Bbox();
+  for (const data of vector.data) {
+    const polygonData = getMultiPolygonChild(data);
+    const lineStringData = getPolygonChild(polygonData);
+    const pointData = getLineStringChild(lineStringData);
+    bbox.updateBbox(coordsBbox(pointData));
+  }
+
+  return bbox;
+}

src/geoarrow/index.ts

@@ -0,0 +1,2 @@
+// This folder contains operations that are candidates to be moved into a
+// geoarrow-js library in the future