notify: add context

Since `proxmox-notify` is intended to be used by multiple products,
there needs to be a way to inject product-specific behavior.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>

proxmox-notify/Cargo.toml

@@ -11,6 +11,7 @@ exclude.workspace = true
 handlebars = { workspace = true }
 lazy_static.workspace = true
 log.workspace = true
+once_cell.workspace = true
 openssl.workspace = true
 proxmox-http = { workspace = true, features = ["client-sync"], optional = true }
 proxmox-human-byte.workspace = true

proxmox-notify/src/context.rs

@@ -0,0 +1,14 @@
+use once_cell::sync::OnceCell;
+use std::fmt::Debug;
+
+pub trait Context: Send + Sync + Debug {}
+
+static CONTEXT: OnceCell<&'static dyn Context> = OnceCell::new();
+
+pub fn set_context(context: &'static dyn Context) {
+    CONTEXT.set(context).expect("context has already been set");
+}
+
+pub(crate) fn context() -> &'static dyn Context {
+    *CONTEXT.get().expect("context has not been yet")
+}

proxmox-notify/src/lib.rs

@@ -13,6 +13,7 @@ use std::error::Error as StdError;
 
 pub mod api;
 mod config;
+pub mod context;
 pub mod endpoints;
 pub mod filter;
 pub mod group;