Many imorovments

core/dr-sync-nextcloud/src/session.rs

@@ -20,6 +20,41 @@ use serde::{Deserialize, Serialize};
 
 use crate::AppCredentials;
 
+/// Where configuration is written, when the platform has told us.
+///
+/// Android has no `$HOME` and no XDG directories, so the guess below resolves
+/// to a path the app cannot write. Nothing failed loudly: the session list went
+/// to a doomed path, so credentials survived only as long as the process did and
+/// backgrounding the app lost the account (ARCH §6.9 — no core API may assume a
+/// filesystem path on Android).
+///
+/// The platform layer sets this once at startup, before any store is opened.
+static DATA_DIR: std::sync::OnceLock<PathBuf> = std::sync::OnceLock::new();
+
+/// TRACES: FR-NC-2
+/// Declare the per-app directory configuration belongs in.
+///
+/// Call before opening any store; later calls are ignored rather than racing.
+/// On Android this is `AndroidApp::internal_data_path`, which is private to the
+/// app and survives being backgrounded. Desktop needs no call — the XDG
+/// fallback is correct there.
+pub fn set_data_dir(dir: PathBuf) {
+    let _ = DATA_DIR.set(dir);
+}
+
+/// The directory configuration lives in.
+fn config_dir() -> PathBuf {
+    if let Some(d) = DATA_DIR.get() {
+        return d.clone();
+    }
+    std::env::var_os("XDG_CONFIG_HOME")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| {
+            PathBuf::from(std::env::var("HOME").unwrap_or_default()).join(".config")
+        })
+        .join("darkroom")
+}
+
 /// A configured account, minus its credential.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Session {
@@ -119,17 +154,16 @@ impl SessionStore {
     /// Linux: `$XDG_CONFIG_HOME/darkroom/sessions.json`, falling back to
     /// `~/.config` (FR-PLAT-LIN-1).
     pub fn open(secrets: Box<dyn SecretStore>) -> Self {
-        let dir = std::env::var_os("XDG_CONFIG_HOME")
-            .map(PathBuf::from)
-            .unwrap_or_else(|| {
-                PathBuf::from(std::env::var("HOME").unwrap_or_default()).join(".config")
-            })
-            .join("darkroom");
-        Self::open_at(dir.join("sessions.json"), secrets)
+        Self::open_at(config_dir().join("sessions.json"), secrets)
     }
 
     /// Open at an explicit path — used by tests, and by anything wanting a
     /// non-default config location.
+    /// Where configuration lives, for callers that need to sit files beside it.
+    pub fn data_dir() -> PathBuf {
+        config_dir()
+    }
+
     pub fn open_at(config_path: PathBuf, secrets: Box<dyn SecretStore>) -> Self {
         Self {
             config_path,