LLeMbas Desktop: the server in a window, the CLI's agent on this computer

Tauri 2, no Node. A first-run page chooses the server; then the window is
the server's web UI, whose pages get no IPC. The bundled LLeMbas CLI
(fetched and signature-checked by scripts/fetch-cli.sh) links the computer
with 'lembas login --json' and runs as 'lembas service' while the app runs.
A tray menu starts and stops it. Linux packages from GitHub Actions on a tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src-tauri/src/settings.rs

@@ -0,0 +1,92 @@
+//! What the app remembers: which server it opens, and whether the agent should run. One small
+//! JSON file in the app's config directory; nothing secret is in it (the device's key is the
+//! LLeMbas CLI's, in its own config).
+
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::{Path, PathBuf};
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq)]
+#[serde(default)]
+pub struct Settings {
+    /// The server's base address, `https://host[:port]`, with no trailing slash.
+    pub server: Option<String>,
+    /// Run the agent while the app runs (once this computer is linked to the server).
+    pub agent: bool,
+}
+
+pub fn file(config_dir: &Path) -> PathBuf {
+    config_dir.join("settings.json")
+}
+
+pub fn load(config_dir: &Path) -> Settings {
+    fs::read_to_string(file(config_dir))
+        .ok()
+        .and_then(|s| serde_json::from_str(&s).ok())
+        .unwrap_or_default()
+}
+
+pub fn save(config_dir: &Path, s: &Settings) -> std::io::Result<()> {
+    fs::create_dir_all(config_dir)?;
+    let tmp = config_dir.join("settings.json.tmp");
+    fs::write(&tmp, serde_json::to_string_pretty(s)? + "\n")?;
+    fs::rename(tmp, file(config_dir))
+}
+
+/// An address as typed (`ai.example`, `https://ai.example/`, `http://10.1.2.3:8080/chat`)
+/// as a base: https unless it says http, scheme and host and port only. The same rule as
+/// `lembas login`, so both name the instance alike.
+pub fn normalise(address: &str) -> Result<String, String> {
+    let a = address.trim();
+    if a.is_empty() {
+        return Err("Enter the address of your LLeMbas server.".into());
+    }
+    let with_scheme = if a.contains("://") {
+        a.to_string()
+    } else {
+        format!("https://{a}")
+    };
+    let url = tauri::Url::parse(&with_scheme).map_err(|e| format!("Not an address: {e}"))?;
+    if url.scheme() != "https" && url.scheme() != "http" {
+        return Err("The address must start with https:// or http://.".into());
+    }
+    let host = url.host_str().ok_or("The address has no host.")?;
+    Ok(match url.port() {
+        Some(p) => format!("{}://{}:{}", url.scheme(), host, p),
+        None => format!("{}://{}", url.scheme(), host),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn an_address_becomes_a_base() {
+        assert_eq!(normalise("ai.example").unwrap(), "https://ai.example");
+        assert_eq!(
+            normalise(" https://ai.example/ ").unwrap(),
+            "https://ai.example"
+        );
+        assert_eq!(
+            normalise("http://10.1.2.3:8080/chat?x=1").unwrap(),
+            "http://10.1.2.3:8080"
+        );
+        assert!(normalise("").is_err());
+        assert!(normalise("ftp://ai.example").is_err());
+    }
+
+    #[test]
+    fn settings_round_trip_and_survive_a_missing_file() {
+        let dir = std::env::temp_dir().join(format!("llembas-desktop-test-{}", std::process::id()));
+        let _ = fs::remove_dir_all(&dir);
+        assert_eq!(load(&dir), Settings::default());
+        let s = Settings {
+            server: Some("https://ai.example".into()),
+            agent: true,
+        };
+        save(&dir, &s).unwrap();
+        assert_eq!(load(&dir), s);
+        fs::remove_dir_all(&dir).unwrap();
+    }
+}