feat: implementation of polyline decoding for S2, GMP Encoded, and JSON formats

Author: regeter

src/Map.js

@@ -275,7 +275,13 @@ function MapComponent({
     log("handlePolylineSubmit called.");
 
     const path = waypoints.map((wp) => new window.google.maps.LatLng(wp.latitude, wp.longitude));
-    const newPolyline = new window.google.maps.Polyline({ path, geodesic: true, ...properties });
+    const newPolyline = new window.google.maps.Polyline({
+      path,
+      geodesic: true,
+      strokeColor: properties.color,
+      strokeOpacity: properties.opacity,
+      strokeWeight: properties.strokeWeight,
+    });
     newPolyline.setMap(map);
     setPolylines((prev) => [...prev, newPolyline]);
   }, []);

src/PolylineCreation.js

@@ -1,8 +1,8 @@
 // src/PolylineCreation.js
 
 import { useState } from "react";
-import { decode } from "s2polyline-ts";
 import { log } from "./Utils";
+import { parsePolylineInput } from "./PolylineUtils";
 
 function PolylineCreation({ onSubmit, onClose, buttonPosition }) {
   const [input, setInput] = useState("");
@@ -13,60 +13,20 @@ function PolylineCreation({ onSubmit, onClose, buttonPosition }) {
   const handleSubmit = (e) => {
     e.preventDefault();
     try {
-      const trimmedInput = input.trim();
-
-      // Check if input looks like an encoded polyline (single string without spaces)
-      if (/^[A-Za-z0-9+/=\-_]+$/.test(trimmedInput)) {
-        log("Attempting to decode S2 polyline:", trimmedInput);
-        const decodedPoints = decode(trimmedInput);
-
-        if (decodedPoints && decodedPoints.length > 0) {
-          // Convert S2 points to our expected format
-          const validWaypoints = decodedPoints.map((point) => ({
-            latitude: point.latDegrees(),
-            longitude: point.lngDegrees(),
-          }));
-
-          log(`Decoded ${validWaypoints.length} points from S2 polyline`);
-          onSubmit(validWaypoints, { opacity, color, strokeWeight });
-          setInput("");
-          return;
-        }
-      }
-
-      // Existing JSON parsing logic
-      const jsonString = trimmedInput.replace(/(\w+):/g, '"$1":').replace(/\s+/g, " ");
-
-      const inputWithBrackets = jsonString.startsWith("[") && jsonString.endsWith("]") ? jsonString : `[${jsonString}]`;
-
-      const waypoints = JSON.parse(inputWithBrackets);
-
-      const validWaypoints = waypoints.filter(
-        (waypoint) =>
-          typeof waypoint === "object" &&
-          "latitude" in waypoint &&
-          "longitude" in waypoint &&
-          typeof waypoint.latitude === "number" &&
-          typeof waypoint.longitude === "number"
-      );
-
-      if (validWaypoints.length === 0) {
-        throw new Error("No valid waypoints found");
-      }
-
+      const validWaypoints = parsePolylineInput(input);
       log(`Parsed ${validWaypoints.length} valid waypoints`);
       onSubmit(validWaypoints, { opacity, color, strokeWeight });
+      setInput("");
     } catch (error) {
       log("Invalid input format:", error);
     }
-    setInput("");
   };
 
   let placeholder = `Paste waypoints here:
 { latitude: 52.5163, longitude: 13.2399 },
 { latitude: 52.5162, longitude: 13.2400 }
 
-Or paste an encoded S2 polyline string`;
+Or paste an encoded S2 or Google Maps polyline string`;
 
   return (
     <div

src/PolylineUtils.js

@@ -0,0 +1,109 @@
+import { decode as decodeS2 } from "s2polyline-ts";
+
+/**
+ * Decodes a Google Maps encoded polyline string into an array of LatLng objects.
+ * Based on the Google Polyline Algorithm.
+ * @param {string} encoded
+ * @returns {Array<{latitude: number, longitude: number}>}
+ */
+export function decodeGooglePolyline(encoded) {
+  const points = [];
+  let index = 0,
+    len = encoded.length;
+  let lat = 0,
+    lng = 0;
+
+  while (index < len) {
+    let b,
+      shift = 0,
+      result = 0;
+    do {
+      b = encoded.charCodeAt(index++) - 63;
+      result |= (b & 0x1f) << shift;
+      shift += 5;
+    } while (b >= 0x20);
+    const dlat = result & 1 ? ~(result >> 1) : result >> 1;
+    lat += dlat;
+
+    shift = 0;
+    result = 0;
+    do {
+      b = encoded.charCodeAt(index++) - 63;
+      result |= (b & 0x1f) << shift;
+      shift += 5;
+    } while (b >= 0x20);
+    const dlng = result & 1 ? ~(result >> 1) : result >> 1;
+    lng += dlng;
+
+    points.push({
+      latitude: lat / 1e5,
+      longitude: lng / 1e5,
+    });
+  }
+
+  return points;
+}
+
+/**
+ * Parses polyline input in various formats: S2, Google Encoded, JSON, or Plain Text.
+ * @param {string} input
+ * @returns {Array<{latitude: number, longitude: number}>}
+ */
+export function parsePolylineInput(input) {
+  const trimmedInput = input.trim();
+
+  // Check if it's obviously JSON or plain text coordinate list
+  const isJsonLike = (trimmedInput.startsWith("[") || trimmedInput.startsWith("{")) && trimmedInput.includes(":");
+
+  if (!isJsonLike) {
+    try {
+      // S2 strings usually don't have spaces or certain JSON characters
+      if (!trimmedInput.includes(" ") && !trimmedInput.includes('"')) {
+        const decodedPoints = decodeS2(trimmedInput);
+        if (decodedPoints && decodedPoints.length > 0) {
+          return decodedPoints.map((point) => ({
+            latitude: point.latDegrees(),
+            longitude: point.lngDegrees(),
+          }));
+        }
+      }
+    } catch (e) {
+      // Continue to next format
+    }
+
+    try {
+      // Sanity check: Google polylines shouldn't have spaces or newlines
+      if (!trimmedInput.includes("\n") && !trimmedInput.includes(" ")) {
+        const decodedPoints = decodeGooglePolyline(trimmedInput);
+        if (decodedPoints && decodedPoints.length > 0) {
+          return decodedPoints;
+        }
+      }
+    } catch (e) {
+      // Continue to next format
+    }
+  }
+
+  try {
+    const jsonString = trimmedInput.replace(/(\w+):/g, '"$1":').replace(/\s+/g, " ");
+    const inputWithBrackets = jsonString.startsWith("[") && jsonString.endsWith("]") ? jsonString : `[${jsonString}]`;
+    const waypoints = JSON.parse(inputWithBrackets);
+
+    const validWaypoints = waypoints.filter(
+      (waypoint) =>
+        typeof waypoint === "object" &&
+        "latitude" in waypoint &&
+        "longitude" in waypoint &&
+        typeof waypoint.latitude === "number" &&
+        typeof waypoint.longitude === "number"
+    );
+
+    if (validWaypoints.length > 0) {
+      return validWaypoints;
+    }
+  } catch (e) {
+    // Fall through to error
+  }
+
+  throw new Error("Invalid polyline format or no valid coordinates found.");
+}

src/PolylineUtils.test.js

@@ -0,0 +1,59 @@
+import { parsePolylineInput } from "./PolylineUtils";
+
+describe("PolylineUtils", () => {
+  const EXPECTED_POINTS = [
+    { latitude: 37.42213, longitude: -122.0848 },
+    { latitude: 37.4152, longitude: -122.0627 },
+    { latitude: 37.427, longitude: -122.0854 },
+  ];
+
+  test("decodes a GMP Encoded Polyline", () => {
+    const encoded = "i_lcF~tchVhj@ciCwhAzlC";
+    const decoded = parsePolylineInput(encoded);
+
+    expect(decoded).toHaveLength(EXPECTED_POINTS.length);
+    for (let i = 0; i < EXPECTED_POINTS.length; i++) {
+      expect(decoded[i].latitude).toBeCloseTo(EXPECTED_POINTS[i].latitude, 5);
+      expect(decoded[i].longitude).toBeCloseTo(EXPECTED_POINTS[i].longitude, 5);
+    }
+  });
+
+  test("decodes an S2 Polyline", () => {
+    const s2String =
+      "AQMAAAA7_tIhjf_avysne_M5iOW__WHh1yJy4z9MIcUK8Pvav7QbiLMRiuW_SWY5Y1lx4z-CIIuaN__av1Eb3-fUh-W_iPpHZ7By4z8=";
+    const decoded = parsePolylineInput(s2String);
+
+    expect(decoded).toHaveLength(EXPECTED_POINTS.length);
+    for (let i = 0; i < EXPECTED_POINTS.length; i++) {
+      expect(decoded[i].latitude).toBeCloseTo(EXPECTED_POINTS[i].latitude, 5);
+      expect(decoded[i].longitude).toBeCloseTo(EXPECTED_POINTS[i].longitude, 5);
+    }
+  });
+
+  test("decodes a GMP Unencoded Polyline (Plain Text)", () => {
+    const input =
+      "{ latitude: 37.42213, longitude: -122.0848 }, { latitude: 37.4152, longitude: -122.0627 }, { latitude: 37.427, longitude: -122.0854 }";
+    const decoded = parsePolylineInput(input);
+
+    expect(decoded).toHaveLength(EXPECTED_POINTS.length);
+    for (let i = 0; i < EXPECTED_POINTS.length; i++) {
+      expect(decoded[i].latitude).toBe(EXPECTED_POINTS[i].latitude);
+      expect(decoded[i].longitude).toBe(EXPECTED_POINTS[i].longitude);
+    }
+  });
+
+  test("decodes a JSON Polyline", () => {
+    const input = JSON.stringify(EXPECTED_POINTS);
+    const decoded = parsePolylineInput(input);
+
+    expect(decoded).toHaveLength(EXPECTED_POINTS.length);
+    for (let i = 0; i < EXPECTED_POINTS.length; i++) {
+      expect(decoded[i].latitude).toBe(EXPECTED_POINTS[i].latitude);
+      expect(decoded[i].longitude).toBe(EXPECTED_POINTS[i].longitude);
+    }
+  });
+
+  test("throws error on invalid input", () => {
+    expect(() => parsePolylineInput("not a polyline")).toThrow();
+  });
+});