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src/modules/cart/utils/geographic.utils.ts

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+/**
+ * Utility class for geographic calculations
+ */
+export class GeographicUtils {
+  /**
+   * Check if a point is inside a polygon using ray-casting algorithm
+   * @param point - [longitude, latitude]
+   * @param polygon - Array of [longitude, latitude] pairs
+   */
+  static isPointInPolygon(point: [number, number], polygon: [number, number][]): boolean {
+    const x = point[0];
+    const y = point[1];
+    let inside = false;
+
+    for (let i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
+      const xi = polygon[i][0];
+      const yi = polygon[i][1];
+      const xj = polygon[j][0];
+      const yj = polygon[j][1];
+
+      const intersect =
+        yi > y !== yj > y && x < ((xj - xi) * (y - yi)) / (yj - yi + Number.EPSILON) + xi;
+      if (intersect) inside = !inside;
+    }
+
+    return inside;
+  }
+
+  /**
+   * Convert degrees to radians
+   */
+  private static toRad(value: number): number {
+    return (value * Math.PI) / 180;
+  }
+
+  /**
+   * Calculate distance between two points in kilometers using Haversine formula
+   */
+  static getDistanceKm(lat1: number, lng1: number, lat2: number, lng2: number): number {
+    const R = 6371; // Earth radius in KM
+
+    const dLat = this.toRad(lat2 - lat1);
+    const dLng = this.toRad(lng2 - lng1);
+
+    const a =
+      Math.sin(dLat / 2) ** 2 +
+      Math.cos(this.toRad(lat1)) * Math.cos(this.toRad(lat2)) * Math.sin(dLng / 2) ** 2;
+
+    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+
+    return R * c;
+  }
+
+  /**
+   * Calculate distance between two points in kilometers (rounded)
+   */
+  static getDistanceKmRounded(
+    lat1: number,
+    lng1: number,
+    lat2: number,
+    lng2: number,
+    precision = 2,
+  ): number {
+    const distance = this.getDistanceKm(lat1, lng1, lat2, lng2);
+    return Number(distance.toFixed(precision));
+  }
+}
+