Added Haversine Formula calculation to get the radius of circles for study groups required for rendering

src/components/CustomMapCallout/CustomMapCallout.tsx

@@ -1,12 +1,12 @@
 import { Callout } from "react-native-maps";
-import { LocationType } from "../../interfaces/Interfaces";
+import { RawLocationType } from "../../interfaces/Interfaces";
 import styles from "../../styles";
 import { Text } from "react-native";
 
 // Map popup for user's location
 
 type props = {
-  location: LocationType;
+  location: RawLocationType;
   studying: boolean;
   subject?: string;
 };

src/components/ParseStudyGroupList/ParseStudyGroupList.tsx

@@ -0,0 +1,125 @@
+import * as React from "react";
+import { View, Text } from "react-native";
+import {
+  StudentStatusFilterType,
+  LocationType,
+  subjectUserMapType,
+  StudentStatusListType,
+  StudentStatusFilterTypeFlattened,
+} from "../../interfaces/Interfaces";
+import { Double, Float } from "react-native/Libraries/Types/CodegenTypes";
+
+export default function ParseStudyGroupList(data: any) {
+  let result: any[] = [];
+  // Circle generation for students in a study group
+  // We first flatten the data to remove nested entries
+  console.log("Initial Data:", data);
+  let flattened_data = data
+    .filter((item: StudentStatusFilterType) => item.study_group !== "")
+    .map((item: StudentStatusFilterType) => ({
+      active: item.active,
+      distance: item.distance,
+      landmark: item.landmark,
+      latitude: item.location.latitude,
+      longitude: item.location.longitude,
+      study_group: item.study_group,
+      subject: item.subject,
+      user: item.user,
+      weight: 1,
+    }));
+  console.log("Filtered Data:", flattened_data);
+
+  // We get each unique subject
+  let unique_subjects = [
+    ...new Set(
+      flattened_data.map((item: StudentStatusFilterType) => item.subject)
+    ),
+  ];
+
+  // Then append all entries belonging to that subject to its own array
+  unique_subjects.forEach((subject, index: number) => {
+    index++;
+    let filteredData = flattened_data.filter(
+      (item: StudentStatusFilterTypeFlattened) => item.subject === subject
+    );
+    console.log("Subject #", index, "-", filteredData[0].subject, filteredData);
+    // We get the circle's center by averaging all the points
+    // Calculate the average latitude and longitude
+    const totalLat = filteredData.reduce(
+      (sum: Double, point: LocationType) => sum + point.latitude,
+      0
+    );
+    const totalLng = filteredData.reduce(
+      (sum: Double, point: LocationType) => sum + point.longitude,
+      0
+    );
+
+    const avgLat = totalLat / filteredData.length;
+    const avgLng = totalLng / filteredData.length;
+
+    console.log("Center Latitude:", avgLat);
+    console.log("Center Longitude:", avgLng);
+
+    // We now calculate the radius of the circle using the Haversine Distance Formula
+
+    function haversineDistance(
+      lat1: number,
+      lon1: number,
+      lat2: number,
+      lon2: number
+    ) {
+      function toRad(x: number) {
+        return (x * Math.PI) / 180;
+      }
+
+      var R = 6371; // km
+      var x1 = lat2 - lat1;
+      var dLat = toRad(x1);
+      var x2 = lon2 - lon1;
+      var dLon = toRad(x2);
+      var a =
+        Math.sin(dLat / 2) * Math.sin(dLat / 2) +
+        Math.cos(toRad(lat1)) *
+          Math.cos(toRad(lat2)) *
+          Math.sin(dLon / 2) *
+          Math.sin(dLon / 2);
+      var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+      var d = R * c;
+      return d;
+    }
+
+    let circle_radius =
+      Math.max(
+        ...filteredData.map((item: StudentStatusFilterTypeFlattened) =>
+          haversineDistance(avgLat, avgLng, item.latitude, item.longitude)
+        )
+      ) * 1000;
+    console.log("Radius:", circle_radius);
+
+    // We now build the object
+    const subjectUserMap: subjectUserMapType = {
+      subject: "",
+      users: [],
+      latitude: 0,
+      longitude: 0,
+      radius: 0,
+    };
+    filteredData.forEach((item: StudentStatusFilterType) => {
+      if (!subjectUserMap["users"]) {
+        subjectUserMap["users"] = [];
+      }
+      subjectUserMap["subject"] = item.subject;
+      subjectUserMap["latitude"] = avgLat;
+      subjectUserMap["longitude"] = avgLng;
+      subjectUserMap["radius"] = circle_radius;
+      subjectUserMap["users"].push(item.user);
+    });
+    console.log(subjectUserMap);
+
+    result = result.concat([subjectUserMap]);
+  });
+
+  // console.log("Final Result:", result);
+
+  return result;
+}