Add scan cancellation when device is selected

Scanner now stops immediately when user selects a device or closes the
modal. Returns ScanController with cancel() function. Prevents wasted
battery and network usage from continuing to scan after selection.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: ryanmio

boat-telemetry-app/src/components/DeviceScannerModal.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect } from 'react';
+import React, { useState, useEffect, useRef } from 'react';
 import {
   View,
   Text,
@@ -9,7 +9,7 @@ import {
   ActivityIndicator,
 } from 'react-native';
 import AsyncStorage from '@react-native-async-storage/async-storage';
-import { ScannedDevice, scanForDevices } from '../services/networkScanService';
+import { ScannedDevice, scanForDevices, ScanController } from '../services/networkScanService';
 import { COLORS, FONTS } from '../constants/Theme';
 
 interface DeviceScannerModalProps {
@@ -36,6 +36,7 @@ export const DeviceScannerModal: React.FC<DeviceScannerModalProps> = ({
   const [totalToScan, setTotalToScan] = useState(0);
   const [scanComplete, setScanComplete] = useState(false);
   const [recentlyUsedIPs, setRecentlyUsedIPs] = useState<string[]>([]);
+  const scanControllerRef = useRef<ScanController | null>(null);
 
   // Load recently found IPs on mount
   useEffect(() => {
@@ -81,7 +82,7 @@ export const DeviceScannerModal: React.FC<DeviceScannerModalProps> = ({
     setTotalToScan(0);
 
     try {
-      const finalDevices = await scanForDevices(
+      const controller = scanForDevices(
         (foundDevices, checked, total) => {
           // Real-time updates: show devices as they're found
           setIpsChecked(checked);
@@ -99,6 +100,11 @@ export const DeviceScannerModal: React.FC<DeviceScannerModalProps> = ({
         recentlyUsedIPs
       );
 
+      // Store controller so we can cancel scan later
+      scanControllerRef.current = controller;
+      
+      const finalDevices = await controller.promise;
+      
       console.log(`[DeviceScanner] Scan complete. Found ${finalDevices.length} devices`);
 
       // Final update with type filtering
@@ -114,15 +120,24 @@ export const DeviceScannerModal: React.FC<DeviceScannerModalProps> = ({
     } finally {
       setScanning(false);
       setScanComplete(true);
+      scanControllerRef.current = null;
     }
   };
 
   const handleSelectDevice = (ip: string) => {
+    // Cancel ongoing scan when device is selected
+    if (scanControllerRef.current) {
+      scanControllerRef.current.cancel();
+    }
     onSelectDevice(ip);
     handleClose();
   };
 
   const handleClose = () => {
+    // Cancel ongoing scan when modal is closed
+    if (scanControllerRef.current) {
+      scanControllerRef.current.cancel();
+    }
     setDevices([]);
     setDevicesFound(0);
     setScanComplete(false);

boat-telemetry-app/src/services/networkScanService.ts

@@ -13,6 +13,11 @@ export interface ScannedDevice {
   lastSeen: number;
 }
 
+export interface ScanController {
+  cancel: () => void;
+  promise: Promise<ScannedDevice[]>;
+}
+
 const TIMEOUT_MS = 2000; // 2 second timeout per device
 const QUICK_PROBE_TIMEOUT_MS = 1000; // Faster timeout for known IPs
 
@@ -185,108 +190,109 @@ async function getLocalIP(): Promise<string | null> {
  * 
  * @param onProgress - Callback called as devices are found (passes devices array for real-time display)
  * @param recentlyUsedIPs - IPs that were recently found (should be provided by component)
- * @returns Promise that resolves when scan is complete
+ * @returns ScanController with cancel() and promise
  */
-export async function scanForDevices(
+export function scanForDevices(
   onProgress?: (devices: ScannedDevice[], checked: number, total: number) => void,
   recentlyUsedIPs: string[] = []
-): Promise<ScannedDevice[]> {
-  const devices: ScannedDevice[] = [];
-  let checkedCount = 0;
-  
-  // #region agent log - scan start
-  fetch('http://127.0.0.1:7242/ingest/d3a9473c-c512-41da-a870-4c36bb5dd5ec',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({location:'networkScanService.ts:195',message:'scanForDevices start',data:{recentIPsLength:recentlyUsedIPs.length},timestamp:Date.now(),hypothesisId:'H3_scan_progress'})}).catch(()=>{});
-  // #endregion
+): ScanController {
+  let cancelled = false;
 
-  console.log('[NetworkScan] Starting progressive device scan...');
-  console.log('[NetworkScan] Recently used IPs:', recentlyUsedIPs);
-
-  // Phase 1: Quickly probe recently used IPs (should be instant if devices are online)
-  if (recentlyUsedIPs.length > 0) {
-    console.log(`[NetworkScan] Phase 1: Probing ${recentlyUsedIPs.length} recently used IPs...`);
+  const promise = (async (): Promise<ScannedDevice[]> => {
+    const devices: ScannedDevice[] = [];
+    let checkedCount = 0;
 
-    const recentResults = await Promise.all(
-      recentlyUsedIPs.map(ip => probeIP(ip, QUICK_PROBE_TIMEOUT_MS))
-    );
-
-    recentResults.forEach((result, idx) => {
-      if (result) {
-        console.log(`[NetworkScan] Found recent device at ${result.ip}`);
-        devices.push(result);
-      }
-      checkedCount++;
-    });
-
-    // #region agent log - phase 1 complete
-    fetch('http://127.0.0.1:7242/ingest/d3a9473c-c512-41da-a870-4c36bb5dd5ec',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({location:'networkScanService.ts:219',message:'Phase 1 complete',data:{devicesFound:devices.length,checkedCount},timestamp:Date.now(),hypothesisId:'H3_scan_progress'})}).catch(()=>{});
-    // #endregion
-
-    // Report progress after recent IPs checked - pass devices array for real-time display
-    const totalEstimate = recentlyUsedIPs.length + COMMON_IP_RANGES.reduce((sum, r) => sum + (r.end - r.start + 1), 0);
-    onProgress?.([...devices], checkedCount, totalEstimate);
-  }
+    console.log('[NetworkScan] Starting progressive device scan...');
+    console.log('[NetworkScan] Recently used IPs:', recentlyUsedIPs);
+
+    // Phase 1: Quickly probe recently used IPs (should be instant if devices are online)
+    if (recentlyUsedIPs.length > 0) {
+      console.log(`[NetworkScan] Phase 1: Probing ${recentlyUsedIPs.length} recently used IPs...`);
+      
+      const recentResults = await Promise.all(
+        recentlyUsedIPs.map(ip => probeIP(ip, QUICK_PROBE_TIMEOUT_MS))
+      );
+
+      recentResults.forEach((result, idx) => {
+        if (result) {
+          console.log(`[NetworkScan] Found recent device at ${result.ip}`);
+          devices.push(result);
+        }
+        checkedCount++;
+      });
 
-  // Phase 2: Scan subnet ranges in parallel for faster coverage
-  console.log('[NetworkScan] Phase 2: Scanning full subnets in parallel...');
-  
-  const allIPs: string[] = [];
-  for (const range of COMMON_IP_RANGES) {
-    for (let i = range.start; i <= range.end; i++) {
-      allIPs.push(`${range.base}.${i}`);
+      // Report progress after recent IPs checked - pass devices array for real-time display
+      const totalEstimate = recentlyUsedIPs.length + COMMON_IP_RANGES.reduce((sum, r) => sum + (r.end - r.start + 1), 0);
+      onProgress?.([...devices], checkedCount, totalEstimate);
     }
-  }
-
-  // Filter out IPs we already checked
-  const recentIPSet = new Set(recentlyUsedIPs);
-  const uncheckedIPs = allIPs.filter(ip => !recentIPSet.has(ip));
-  
-  console.log(`[NetworkScan] Scanning ${uncheckedIPs.length} unchecked IP addresses`);
-
-  // #region agent log - phase 2 start
-  fetch('http://127.0.0.1:7242/ingest/d3a9473c-c512-41da-a870-4c36bb5dd5ec',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({location:'networkScanService.ts:244',message:'Phase 2 start',data:{uncheckedIPsLength:uncheckedIPs.length},timestamp:Date.now(),hypothesisId:'H3_scan_progress'})}).catch(()=>{});
-  // #endregion
 
-  // Probe in parallel batches for speed
-  const batchSize = 15; // Increased batch size since we're doing it faster
-  
-  for (let i = 0; i < uncheckedIPs.length; i += batchSize) {
-    const batch = uncheckedIPs.slice(i, i + batchSize);
+    // Phase 2: Scan subnet ranges in parallel for faster coverage
+    console.log('[NetworkScan] Phase 2: Scanning full subnets in parallel...');
 
-    const results = await Promise.all(batch.map(ip => probeIP(ip)));
-
-    results.forEach(result => {
-      if (result) {
-        console.log(`[NetworkScan] Found device at ${result.ip} (type: ${result.type})`);
-        
-        // Avoid duplicates
-        if (!devices.find(d => d.ip === result.ip)) {
-          devices.push(result);
-          saveRecentIP(result.ip);
-        }
+    const allIPs: string[] = [];
+    for (const range of COMMON_IP_RANGES) {
+      for (let i = range.start; i <= range.end; i++) {
+        allIPs.push(`${range.base}.${i}`);
       }
-    });
+    }
 
-    checkedCount += batch.length;
+    // Filter out IPs we already checked
+    const recentIPSet = new Set(recentlyUsedIPs);
+    const uncheckedIPs = allIPs.filter(ip => !recentIPSet.has(ip));
 
-    // Call progress callback with current devices array for real-time UI updates
-    onProgress?.([...devices], recentlyUsedIPs.length + checkedCount, recentlyUsedIPs.length + allIPs.length);
-  }
-
-  console.log(`[NetworkScan] Scan complete. Found ${devices.length} devices.`);
+    console.log(`[NetworkScan] Scanning ${uncheckedIPs.length} unchecked IP addresses`);
 
-  // #region agent log - scan complete
-  fetch('http://127.0.0.1:7242/ingest/d3a9473c-c512-41da-a870-4c36bb5dd5ec',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({location:'networkScanService.ts:279',message:'Scan complete',data:{devicesFound:devices.length},timestamp:Date.now(),hypothesisId:'H3_scan_progress'})}).catch(()=>{});
-  // #endregion
+    // Probe in parallel batches for speed
+    const batchSize = 15;
+    
+    for (let i = 0; i < uncheckedIPs.length; i += batchSize) {
+      // Check if scan was cancelled
+      if (cancelled) {
+        console.log('[NetworkScan] Scan cancelled by user');
+        break;
+      }
+      
+      const batch = uncheckedIPs.slice(i, i + batchSize);
+      
+      const results = await Promise.all(batch.map(ip => probeIP(ip)));
+
+      results.forEach(result => {
+        if (result) {
+          console.log(`[NetworkScan] Found device at ${result.ip} (type: ${result.type})`);
+          
+          // Avoid duplicates
+          if (!devices.find(d => d.ip === result.ip)) {
+            devices.push(result);
+            saveRecentIP(result.ip);
+          }
+        }
+      });
 
-  // Sort by type (telemetry first), then by IP
-  devices.sort((a, b) => {
-    if (a.type !== b.type) {
-      return a.type === 'telemetry' ? -1 : 1;
+      checkedCount += batch.length;
+      
+      // Call progress callback with current devices array for real-time UI updates
+      onProgress?.([...devices], recentlyUsedIPs.length + checkedCount, recentlyUsedIPs.length + allIPs.length);
     }
-    return a.ip.localeCompare(b.ip);
-  });
 
-  return devices;
+    console.log(`[NetworkScan] Scan ${cancelled ? 'cancelled' : 'complete'}. Found ${devices.length} devices.`);
+
+    // Sort by type (telemetry first), then by IP
+    devices.sort((a, b) => {
+      if (a.type !== b.type) {
+        return a.type === 'telemetry' ? -1 : 1;
+      }
+      return a.ip.localeCompare(b.ip);
+    });
+
+    return devices;
+  })();
+  
+  return {
+    cancel: () => {
+      cancelled = true;
+    },
+    promise,
+  };
 }
 
 /**