fix: replace write_text_file with backend dialog

Replaces `write_text_file` and `write_image_file` with backend commands
`save_text_file_dialog` and `save_image_file_dialog`. Instead of allowing
the frontend to pass an arbitrary absolute path, the Tauri backend now invokes
the OS save dialog directly, eliminating the risk of arbitrary file write
if the frontend is compromised.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>

package-lock.json

@@ -17,6 +17,7 @@
         "@tauri-apps/api": "^2.5.0",
         "@tauri-apps/plugin-autostart": "^2.3.0",
         "@tauri-apps/plugin-dialog": "^2.7.1",
+        "@tauri-apps/plugin-fs": "^2.5.1",
         "@tauri-apps/plugin-global-shortcut": "^2.2.0",
         "@tauri-apps/plugin-opener": "^2.2.0",
         "@tauri-apps/plugin-process": "^2.3.1",
@@ -1218,6 +1219,15 @@
         "@tauri-apps/api": "^2.11.0"
       }
     },
+    "node_modules/@tauri-apps/plugin-fs": {
+      "version": "2.5.1",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/plugin-fs/-/plugin-fs-2.5.1.tgz",
+      "integrity": "sha512-9Lz+Jopp6QyeEWhlpkMx4R/+P9HgR+AVAI4vOZhlT8Xaymtz8iVI/Ov984/XTqgJz/5gz5NretqPB/XEMS3NhQ==",
+      "license": "MIT OR Apache-2.0",
+      "dependencies": {
+        "@tauri-apps/api": "^2.11.0"
+      }
+    },
     "node_modules/@tauri-apps/plugin-global-shortcut": {
       "version": "2.3.2",
       "resolved": "https://registry.npmjs.org/@tauri-apps/plugin-global-shortcut/-/plugin-global-shortcut-2.3.2.tgz",

package.json

@@ -23,6 +23,7 @@
     "@tauri-apps/api": "^2.5.0",
     "@tauri-apps/plugin-autostart": "^2.3.0",
     "@tauri-apps/plugin-dialog": "^2.7.1",
+    "@tauri-apps/plugin-fs": "^2.5.1",
     "@tauri-apps/plugin-global-shortcut": "^2.2.0",
     "@tauri-apps/plugin-opener": "^2.2.0",
     "@tauri-apps/plugin-process": "^2.3.1",

src-tauri/src/main.rs

@@ -38,20 +38,41 @@ fn safe_name(name: &str) -> bool {
 }
 
 #[tauri::command]
-fn write_text_file(path: String, contents: String) -> Result<(), String> {
-    write_atomic(std::path::Path::new(&path), &contents)
+async fn save_text_file_dialog(app: tauri::AppHandle, contents: String, is_sum: bool) -> Result<bool, String> {
+    use tauri_plugin_dialog::DialogExt;
+    let dialog = app.dialog().file();
+    let dialog = if is_sum {
+        dialog.add_filter("Summarum Sheet", &["sum"])
+    } else {
+        dialog.add_filter("Text file", &["txt"])
+    };
+
+    if let Some(path) = dialog.blocking_save_file() {
+        let path = path.into_path().map_err(|_| "invalid path".to_string())?;
+        write_atomic(&path, &contents)?;
+        Ok(true)
+    } else {
+        Ok(false)
+    }
 }
 
 #[tauri::command]
-fn write_image_file(path: String, data_base64: String) -> Result<(), String> {
+async fn save_image_file_dialog(app: tauri::AppHandle, data_base64: String) -> Result<bool, String> {
+    use tauri_plugin_dialog::DialogExt;
     use std::io::Write;
-    let bytes = base64_decode(&data_base64)?;
-    let p = std::path::Path::new(&path);
-    let tmp = p.with_extension("tmp");
-    std::fs::File::create(&tmp)
-        .and_then(|mut f| f.write_all(&bytes))
-        .map_err(|e| e.to_string())?;
-    fs::rename(&tmp, p).map_err(|e| e.to_string())
+
+    if let Some(path) = app.dialog().file().add_filter("PNG Image", &["png"]).blocking_save_file() {
+        let path = path.into_path().map_err(|_| "invalid path".to_string())?;
+        let bytes = base64_decode(&data_base64)?;
+        let tmp = path.with_extension("tmp");
+        std::fs::File::create(&tmp)
+            .and_then(|mut f| f.write_all(&bytes))
+            .map_err(|e| e.to_string())?;
+        fs::rename(&tmp, &path).map_err(|e| e.to_string())?;
+        Ok(true)
+    } else {
+        Ok(false)
+    }
 }
 
 fn base64_decode(s: &str) -> Result<Vec<u8>, String> {
@@ -712,8 +733,8 @@ fn main() {
             read_text_file,
             exit_app,
             is_hidden_launch,
-            write_text_file,
-            write_image_file
+            save_text_file_dialog,
+            save_image_file_dialog
         ])
         .setup(|app| {
             let handle = app.handle().clone();

src/main.ts

@@ -907,17 +907,11 @@ async function boot(): Promise<void> {
     } else if (action === "print") {
       window.print();
     } else if (isTauri()) {
-      const { save } = await import("@tauri-apps/plugin-dialog");
       const { invoke } = await import("@tauri-apps/api/core");
       const isSum = action === "save-sum";
-      const path = await save({
-        filters: isSum
-          ? [{ name: "Summarum Sheet", extensions: ["sum"] }]
-          : [{ name: "Text file", extensions: ["txt"] }],
-      });
-      if (path) {
-        const content = isSum ? editor.getText() : editor.getSheetWithResults();
-        await invoke("write_text_file", { path, contents: content });
+      const content = isSum ? editor.getText() : editor.getSheetWithResults();
+      const saved = await invoke("save_text_file_dialog", { contents: content, isSum });
+      if (saved) {
         toast(t("saved"));
       }
     }

src/storage.ts

@@ -234,9 +234,9 @@ export async function fetchHistoricalRates(date: string): Promise<Record<string,
 
 // ---------- image export
 
-export async function writeImageFile(path: string, dataBase64: string): Promise<void> {
-  if (!isTauri()) return;
-  await invoke("write_image_file", { path, dataBase64 });
+export async function writeImageFile(dataBase64: string): Promise<boolean> {
+  if (!isTauri()) return false;
+  return await invoke<boolean>("save_image_file_dialog", { dataBase64 });
 }
 
 // ---------- market data

src/ui/export.ts

@@ -58,14 +58,10 @@ export async function exportSheetImage(deps: ExportImageDeps): Promise<void> {
   } catch {
     // clipboard API failed — save to file
     try {
-      const { save } = await import("@tauri-apps/plugin-dialog");
-      const path = await save({ filters: [{ name: "PNG Image", extensions: ["png"] }] });
-      if (path) {
-        const buf = await blob.arrayBuffer();
-        const b64 = bytesToBase64(new Uint8Array(buf));
-        await writeImageFile(path, b64);
-        toast(t("saved"));
-      }
+      const buf = await blob.arrayBuffer();
+      const b64 = bytesToBase64(new Uint8Array(buf));
+      const saved = await writeImageFile(b64);
+      if (saved) toast(t("saved"));
     } catch {
       toast(t("imageFailed"));
     }