OperServ: add SET READONLY lockdown

modules/operserv/src/set.rs

@@ -0,0 +1,35 @@
+use echo_api::{Priv, Sender, ServiceCtx, Store};
+
+// SET READONLY {ON|OFF}: put services into (or out of) read-only lockdown.
+// While on, no new registrations or changes are accepted; existing data and
+// gossip replication keep working. Admin-only. No argument reports the state.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    if !from.privs.has(Priv::Admin) {
+        ctx.notice(me, from.uid, "Access denied — SET is for services operators.");
+        return;
+    }
+    match args.get(1).map(|s| s.to_ascii_uppercase()).as_deref() {
+        Some("READONLY") => {
+            let Some(on) = args.get(2).and_then(|s| parse_toggle(s)) else {
+                let state = if db.readonly() { "ON" } else { "OFF" };
+                ctx.notice(me, from.uid, format!("READONLY is currently \x02{state}\x02. Syntax: SET READONLY {{ON|OFF}}"));
+                return;
+            };
+            db.set_readonly(on);
+            if on {
+                ctx.notice(me, from.uid, "Services are now \x02read-only\x02 — no changes will be accepted.");
+            } else {
+                ctx.notice(me, from.uid, "Services are no longer read-only.");
+            }
+        }
+        _ => ctx.notice(me, from.uid, "Syntax: SET READONLY {ON|OFF}"),
+    }
+}
+
+fn parse_toggle(s: &str) -> Option<bool> {
+    match s.to_ascii_uppercase().as_str() {
+        "ON" | "TRUE" | "YES" => Some(true),
+        "OFF" | "FALSE" | "NO" => Some(false),
+        _ => None,
+    }
+}