feat(desktop): #77 B5 port auto-increment si 17890 occupe (pick_free_port) + 3 tests Rust

desktop/src/main.rs

@@ -9,11 +9,40 @@ use log::{error, info, warn};
 use serde::{Deserialize, Serialize};
 use std::fs::{self, OpenOptions};
 use std::io::Write;
+use std::net::TcpListener;
 use std::path::PathBuf;
 use std::process::{Child, Command, Stdio};
+use std::sync::atomic::{AtomicU16, Ordering};
 use std::sync::Mutex;
 use std::time::Duration;
 
+// ── Backend port (ROADMAP #77 B: auto-increment if 17890 is busy) ────
+
+const DEFAULT_BACKEND_PORT: u16 = 17890;
+const PORT_SCAN_ATTEMPTS: u16 = 10;
+
+static BACKEND_PORT: AtomicU16 = AtomicU16::new(DEFAULT_BACKEND_PORT);
+
+fn backend_url() -> String {
+    format!("http://127.0.0.1:{}", BACKEND_PORT.load(Ordering::Relaxed))
+}
+
+/// First free TCP port starting at DEFAULT_BACKEND_PORT.
+fn pick_free_port() -> u16 {
+    for offset in 0..PORT_SCAN_ATTEMPTS {
+        let port = DEFAULT_BACKEND_PORT + offset;
+        if TcpListener::bind(("127.0.0.1", port)).is_ok() {
+            if offset > 0 {
+                info!("Port {} busy — using {} instead", DEFAULT_BACKEND_PORT, port);
+            }
+            return port;
+        }
+    }
+    warn!("No free port in {}..{}, falling back to default",
+          DEFAULT_BACKEND_PORT, DEFAULT_BACKEND_PORT + PORT_SCAN_ATTEMPTS - 1);
+    DEFAULT_BACKEND_PORT
+}
+
 #[cfg(target_os = "windows")]
 use std::os::windows::process::CommandExt;
 use tauri::Manager;
@@ -172,12 +201,15 @@ fn spawn_backend(exe_dir: &PathBuf) -> Result<Child, String> {
         cmd.env(format!("DIR_{}_PATH", n), &dir.path);
     }
 
+    let port = pick_free_port();
+    BACKEND_PORT.store(port, Ordering::Relaxed);
+
     let child = cmd
         .args([
             "-m", "uvicorn",
             "backend.main:app",
             "--host", "127.0.0.1",
-            "--port", "17890",
+            "--port", &port.to_string(),
             "--log-level", "info",
         ])
         .stdout(Stdio::from(log.try_clone().map_err(|e| format!("{}", e))?))
@@ -191,10 +223,10 @@ fn spawn_backend(exe_dir: &PathBuf) -> Result<Child, String> {
 
 async fn wait_for_backend() -> Result<(), String> {
     let client = reqwest::Client::new();
-    let url = "http://127.0.0.1:17890/api/health";
+    let url = format!("{}/api/health", backend_url());
 
     for i in 0..30 {
-        match client.get(url).timeout(Duration::from_secs(2)).send().await {
+        match client.get(&url).timeout(Duration::from_secs(2)).send().await {
             Ok(resp) if resp.status().is_success() => {
                 info!("Backend ready (attempt {})", i + 1);
                 return Ok(());
@@ -235,7 +267,7 @@ fn kill_backend(child: &mut Child) {
 
 #[tauri::command]
 fn get_backend_url() -> String {
-    "http://127.0.0.1:17890".to_string()
+    backend_url()
 }
 
 #[tauri::command]
@@ -390,7 +422,7 @@ async fn check_backend_health(state: tauri::State<'_, BackendProcess>) -> Result
     }
 
     // Health check HTTP
-    match reqwest::get("http://127.0.0.1:17890/api/health").await {
+    match reqwest::get(format!("{}/api/health", backend_url())).await {
         Ok(resp) if resp.status().is_success() => Ok("healthy".to_string()),
         _ => Ok("unhealthy".to_string()),
     }
@@ -570,7 +602,7 @@ fn main() {
                             let _ = window.eval(
                                 r#"if (window.__setBootStatus) window.__setBootStatus("Backend prêt — chargement de l'interface…")"#,
                             );
-                            match window.eval("window.location.href = 'http://127.0.0.1:17890'") {
+                            match window.eval(&format!("window.location.href = '{}'", backend_url())) {
                                 Ok(_) => info!("Redirect to backend OK"),
                                 Err(e) => error!("Redirect eval failed: {}", e),
                             }
@@ -580,8 +612,9 @@ fn main() {
                         error!("Backend failed: {}", e);
                         if let Some(window) = handle.get_webview_window("main") {
                             let _ = window.eval(&format!(
-                                r#"document.body.innerHTML = '<div style="padding:40px;text-align:center;font-family:sans-serif"><h2 style="color:#c0392b">ObsiGate n\'a pas pu démarrer</h2><p style="color:#666">{}</p><p><button onclick="location.reload()" style="padding:10px 20px;font-size:16px;cursor:pointer;background:#7C3AED;color:white;border:none;border-radius:6px">Réessayer</button></p><p style="margin-top:20px;font-size:12px;color:#999">Backend: http://127.0.0.1:17890 | Logs: {}</p></div>'"#,
+                                r#"document.body.innerHTML = '<div style="padding:40px;text-align:center;font-family:sans-serif"><h2 style="color:#c0392b">ObsiGate n\'a pas pu démarrer</h2><p style="color:#666">{}</p><p><button onclick="location.reload()" style="padding:10px 20px;font-size:16px;cursor:pointer;background:#7C3AED;color:white;border:none;border-radius:6px">Réessayer</button></p><p style="margin-top:20px;font-size:12px;color:#999">Backend: {} | Logs: {}</p></div>'"#,
                                 e.replace('\'', "\\'").replace('"', "\\\""),
+                                backend_url(),
                                 backend_log_path().display().to_string().replace('\\', "\\\\"),
                             ));
                         }
@@ -934,7 +967,35 @@ mod tests {
 
     #[test]
     fn test_backend_url() {
-        assert_eq!(get_backend_url(), "http://127.0.0.1:17890");
+        let port = BACKEND_PORT.load(Ordering::Relaxed);
+        assert_eq!(get_backend_url(), format!("http://127.0.0.1:{}", port));
+    }
+
+    #[test]
+    fn test_pick_free_port_is_free() {
+        let port = pick_free_port();
+        assert!((DEFAULT_BACKEND_PORT..DEFAULT_BACKEND_PORT + PORT_SCAN_ATTEMPTS).contains(&port));
+        assert!(TcpListener::bind(("127.0.0.1", port)).is_ok());
+    }
+
+    #[test]
+    fn test_pick_free_port_skips_busy_port() {
+        let blocker = match TcpListener::bind(("127.0.0.1", DEFAULT_BACKEND_PORT)) {
+            Ok(l) => l,
+            Err(_) => return, // default port already busy on this machine — skip
+        };
+        let port = pick_free_port();
+        assert_ne!(port, DEFAULT_BACKEND_PORT);
+        assert!(port < DEFAULT_BACKEND_PORT + PORT_SCAN_ATTEMPTS);
+        drop(blocker);
+    }
+
+    #[test]
+    fn test_backend_url_reflects_port() {
+        let saved = BACKEND_PORT.load(Ordering::Relaxed);
+        BACKEND_PORT.store(17893, Ordering::Relaxed);
+        assert_eq!(backend_url(), "http://127.0.0.1:17893");
+        BACKEND_PORT.store(saved, Ordering::Relaxed);
     }
 
     #[test]