fix(bindings): atomically replace persisted store

crates/core/Cargo.toml

@@ -11,3 +11,6 @@ serde_json = "1"
 rspotify = { version = "0.15.3", default-features = false, features = ["client-reqwest", "reqwest-rustls-tls"] }
 url = "2"
 rand = "0.9"
+
+[target.'cfg(windows)'.dependencies]
+windows-sys = { version = "0.59", features = ["Win32_Storage_FileSystem"] }

crates/core/src/bindings.rs

@@ -6,7 +6,11 @@ use crate::{
 use anyhow::{bail, Context, Result};
 use rand::{distr::Alphanumeric, Rng};
 use serde::{Deserialize, Serialize};
-use std::{fs, path::PathBuf};
+use std::{
+    fs::{self, OpenOptions},
+    io::Write,
+    path::PathBuf,
+};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "snake_case")]
@@ -128,11 +132,84 @@ fn write_store(store: &BindingStore) -> Result<()> {
     }
 
     let raw = serde_json::to_string_pretty(store).context("failed to serialize bindings")?;
-    fs::write(&path, raw)
-        .with_context(|| format!("failed to write bindings file at {}", path.display()))?;
+    let temp_path = path.with_extension(format!("json.tmp-{}", generate_binding_id()));
+    let write_result = (|| -> Result<()> {
+        let mut file = OpenOptions::new()
+            .write(true)
+            .create_new(true)
+            .open(&temp_path)
+            .with_context(|| {
+                format!(
+                    "failed to create temporary bindings file at {}",
+                    temp_path.display()
+                )
+            })?;
+        file.write_all(raw.as_bytes()).with_context(|| {
+            format!(
+                "failed to write temporary bindings file at {}",
+                temp_path.display()
+            )
+        })?;
+        file.sync_all().with_context(|| {
+            format!(
+                "failed to sync temporary bindings file at {}",
+                temp_path.display()
+            )
+        })?;
+        Ok(())
+    })();
+
+    if let Err(error) = write_result {
+        let _ = fs::remove_file(&temp_path);
+        return Err(error);
+    }
+
+    if let Err(error) = replace_file(&temp_path, &path) {
+        let _ = fs::remove_file(&temp_path);
+        return Err(error)
+            .with_context(|| format!("failed to replace bindings file at {}", path.display()));
+    }
+
     Ok(())
 }
 
+#[cfg(not(windows))]
+fn replace_file(temp_path: &PathBuf, path: &PathBuf) -> std::io::Result<()> {
+    fs::rename(temp_path, path)
+}
+
+#[cfg(windows)]
+fn replace_file(temp_path: &PathBuf, path: &PathBuf) -> std::io::Result<()> {
+    use std::os::windows::ffi::OsStrExt;
+    use windows_sys::Win32::Storage::FileSystem::{
+        MoveFileExW, MOVEFILE_REPLACE_EXISTING, MOVEFILE_WRITE_THROUGH,
+    };
+
+    let source: Vec<u16> = temp_path
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+    let destination: Vec<u16> = path
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+
+    if unsafe {
+        MoveFileExW(
+            source.as_ptr(),
+            destination.as_ptr(),
+            MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH,
+        )
+    } == 0
+    {
+        Err(std::io::Error::last_os_error())
+    } else {
+        Ok(())
+    }
+}
+
 fn generate_binding_id() -> String {
     rand::rng()
         .sample_iter(&Alphanumeric)
@@ -176,7 +253,9 @@ fn normalized_favorite_order(
 mod tests {
     use super::*;
     use crate::firetv::FireTvAction;
-    use std::{env, fs, path::PathBuf};
+    use std::{env, fs, path::PathBuf, sync::Mutex};
+
+    static TEST_ENV_LOCK: Mutex<()> = Mutex::new(());
 
     fn binding(id: &str, label: &str, favorite: bool, favorite_order: u32) -> Binding {
         Binding {
@@ -192,6 +271,7 @@ mod tests {
     }
 
     fn with_temp_home(test: impl FnOnce()) {
+        let _env_guard = TEST_ENV_LOCK.lock().expect("lock test environment");
         let original_home = env::var_os("HOME");
         let original_appdata = env::var_os("APPDATA");
         let temp_home =
@@ -286,4 +366,20 @@ mod tests {
             assert_eq!(reloaded.bindings[0].favorite_order, 2);
         });
     }
+
+    #[test]
+    fn replaces_bindings_without_leaving_temporary_files() {
+        with_temp_home(|| {
+            save_binding(binding("home", "Home", false, 0)).expect("save binding");
+            let mut updated = binding("home", "Updated", false, 0);
+            updated.hotkey = "Ctrl+H".to_string();
+            save_binding(updated).expect("replace binding");
+
+            let path = stored_bindings_path();
+            let reloaded = list_bindings().expect("reload binding");
+            assert_eq!(reloaded.bindings[0].label, "Updated");
+            assert_eq!(reloaded.bindings[0].hotkey, "Ctrl+H");
+            assert!(fs::read_to_string(path).is_ok());
+        });
+    }
 }