feat: graceful Npcap handling - show download dialog when not installed

- Add /DELAYLOAD:wpcap.dll to prevent app crash when Npcap is missing
- Add runtime Npcap check via LoadLibraryA on Windows
- Guard pcap-dependent commands (lan_scan, start_arp_spoof) with Npcap check
- Add NpcapDialog component to prompt users to download Npcap
- Add useNpcapCheck hook for frontend Npcap availability checking
- Add tauri-plugin-shell for opening external URLs in browser
- Add tests for NpcapDialog, useNpcapCheck, and npcap defaults

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: T3pp31

package-lock.json

@@ -13,12 +13,15 @@
     "@tauri-apps/api": "^2.10.1",
     "@tauri-apps/plugin-dialog": "^2.6.0",
     "@tauri-apps/plugin-fs": "^2.4.5",
+    "@tauri-apps/plugin-shell": "^2.3.5",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-router-dom": "^7.13.1"
   },
   "devDependencies": {
     "@eslint/js": "^9.13.0",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "^18.3.12",
     "@types/react-dom": "^18.3.1",
     "@vitejs/plugin-react": "^4.3.3",
@@ -27,6 +30,7 @@
     "eslint-plugin-react-hooks": "^5.0.0",
     "eslint-plugin-react-refresh": "^0.4.14",
     "globals": "^15.11.0",
+    "happy-dom": "^20.8.4",
     "typescript": "~5.6.2",
     "typescript-eslint": "^8.11.0",
     "vite": "^5.4.10",

package.json

@@ -19,6 +19,7 @@ tauri-build = { version = "2", features = [] }
 tauri = { version = "2", features = [] }
 tauri-plugin-dialog = "2"
 tauri-plugin-fs = "2"
+tauri-plugin-shell = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 tokio = { version = "1", features = ["full"] }

src-tauri/Cargo.lock

@@ -89,7 +89,19 @@ fn configure_npcap_link_search() {
 #[cfg(not(target_os = "windows"))]
 fn configure_npcap_link_search() {}
 
+/// Windows: wpcap.dll を遅延ロードに設定し、未インストール時もアプリが起動できるようにする
+#[cfg(target_os = "windows")]
+fn configure_delay_load() {
+    println!("cargo:rustc-link-arg=/DELAYLOAD:wpcap.dll");
+    println!("cargo:rustc-link-lib=delayimp");
+}
+
+/// Linux / macOS では遅延ロード設定は不要
+#[cfg(not(target_os = "windows"))]
+fn configure_delay_load() {}
+
 fn main() {
     configure_npcap_link_search();
+    configure_delay_load();
     tauri_build::build();
 }

src-tauri/Cargo.toml

@@ -1,5 +1,6 @@
 use serde::Serialize;
 
+use crate::config::NPCAP_DOWNLOAD_URL;
 use crate::error::AppError;
 use crate::AppState;
 
@@ -17,6 +18,9 @@ pub async fn start_arp_spoof(
     packet_count: u32,
     state: tauri::State<'_, AppState>,
 ) -> Result<String, AppError> {
+    if !crate::network::npcap::is_npcap_available() {
+        return Err(AppError::NpcapNotFound(NPCAP_DOWNLOAD_URL.to_string()));
+    }
     crate::network::arp_spoof::start(
         &target_ip,
         &gateway_ip,

src-tauri/build.rs

@@ -1,6 +1,7 @@
 use serde::Serialize;
 use tauri::Window;
 
+use crate::config::NPCAP_DOWNLOAD_URL;
 use crate::error::AppError;
 use crate::AppState;
 
@@ -19,5 +20,8 @@ pub async fn lan_scan(
     state: tauri::State<'_, AppState>,
     window: Window,
 ) -> Result<Vec<DeviceInfo>, AppError> {
+    if !crate::network::npcap::is_npcap_available() {
+        return Err(AppError::NpcapNotFound(NPCAP_DOWNLOAD_URL.to_string()));
+    }
     crate::network::lan_scan::scan(start, end, &state.config, &state.http_client, &window).await
 }

src-tauri/src/commands/arp_spoof.rs

@@ -2,4 +2,5 @@ pub mod arp_spoof;
 pub mod binary;
 pub mod lan_scan;
 pub mod network_info;
+pub mod npcap;
 pub mod port_scan;

src-tauri/src/commands/lan_scan.rs

@@ -0,0 +1,17 @@
+use serde::Serialize;
+
+use crate::config::NPCAP_DOWNLOAD_URL;
+
+#[derive(Debug, Serialize)]
+pub struct NpcapStatus {
+    pub available: bool,
+    pub download_url: String,
+}
+
+#[tauri::command]
+pub async fn check_npcap() -> NpcapStatus {
+    NpcapStatus {
+        available: crate::network::npcap::is_npcap_available(),
+        download_url: NPCAP_DOWNLOAD_URL.to_string(),
+    }
+}

src-tauri/src/commands/mod.rs

@@ -1,6 +1,9 @@
 use serde::Deserialize;
 use std::path::PathBuf;
 
+/// Npcap ダウンロードページの URL
+pub const NPCAP_DOWNLOAD_URL: &str = "https://npcap.com/#download";
+
 #[derive(Debug, Deserialize, Clone)]
 pub struct AppConfig {
     pub scan: ScanConfig,