[PATCH proxmox 2/5] notify: Add state file handling

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

Add State struct abstracting state file deserialization, updates and
persistence, as well as an EndpointState marker trait stateful endpoints
may implement.

Also add a state_file_path method to the crate's Context trait, which
allows
tests to build their own context instead of depending on statics.

As far as SMTP endpoints are concerned, file locks are not necessary.
Old Microsoft tokens stay valid for 90 days after refreshes [1], and
Google
tokens' lifetime is just extended at every use [2], so concurrent reads
should not
be an issue here.

[1]
https://learn.microsoft.com/en-us/entra/identity-platform/refresh-tokens#token-lifetime
[2]
https://stackoverflow.com/questions/8953983/do-google-refresh-tokens-expire

Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
 proxmox-notify/Cargo.toml          |  1 +
 proxmox-notify/debian/control      |  2 +
 proxmox-notify/src/context/mod.rs  |  2 +
 proxmox-notify/src/context/pbs.rs  |  4 ++
 proxmox-notify/src/context/pve.rs  |  4 ++
 proxmox-notify/src/context/test.rs |  4 ++
 proxmox-notify/src/lib.rs          | 60 ++++++++++++++++++++++++++++++
 7 files changed, 77 insertions(+)

diff --git a/proxmox-notify/Cargo.toml b/proxmox-notify/Cargo.toml
index 52493ef7..daa10296 100644
--- a/proxmox-notify/Cargo.toml
+++ b/proxmox-notify/Cargo.toml
@@ -40,6 +40,7 @@ proxmox-sendmail = { workspace = true, optional = true }
 proxmox-sys = { workspace = true, optional = true }
 proxmox-time.workspace = true
 proxmox-uuid = { workspace = true, features = ["serde"] }
+nix.workspace = true
 
 [features]
 default = ["sendmail", "gotify", "smtp", "webhook"]
diff --git a/proxmox-notify/debian/control b/proxmox-notify/debian/control
index 7770f5ee..76b8a1fa 100644
--- a/proxmox-notify/debian/control
+++ b/proxmox-notify/debian/control
@@ -11,6 +11,7 @@ Build-Depends-Arch: cargo:native <!nocheck>,
  librust-handlebars-5+default-dev <!nocheck>,
  librust-http-1+default-dev <!nocheck>,
  librust-lettre-0.11+default-dev (>= 0.11.1-~~) <!nocheck>,
+ librust-nix-0.29+default-dev <!nocheck>,
  librust-oauth2-5+default-dev <!nocheck>,
  librust-openssl-0.10+default-dev <!nocheck>,
  librust-percent-encoding-2+default-dev (>= 2.1-~~) <!nocheck>,
@@ -52,6 +53,7 @@ Depends:
  librust-anyhow-1+default-dev,
  librust-const-format-0.2+default-dev,
  librust-handlebars-5+default-dev,
+ librust-nix-0.29+default-dev,
  librust-oauth2-5+default-dev,
  librust-openssl-0.10+default-dev,
  librust-proxmox-http-error-1+default-dev,
diff --git a/proxmox-notify/src/context/mod.rs b/proxmox-notify/src/context/mod.rs
index 8b6e2c43..86130409 100644
--- a/proxmox-notify/src/context/mod.rs
+++ b/proxmox-notify/src/context/mod.rs
@@ -32,6 +32,8 @@ pub trait Context: Send + Sync + Debug {
         namespace: Option<&str>,
         source: TemplateSource,
     ) -> Result<Option<String>, Error>;
+    /// Return the state file, or None if no state file exists for this context.
+    fn state_file_path(&self) -> &'static str;
 }
 
 #[cfg(not(test))]
diff --git a/proxmox-notify/src/context/pbs.rs b/proxmox-notify/src/context/pbs.rs
index 3e5da59c..67010060 100644
--- a/proxmox-notify/src/context/pbs.rs
+++ b/proxmox-notify/src/context/pbs.rs
@@ -125,6 +125,10 @@ impl Context for PBSContext {
             .map_err(|err| Error::Generic(format!("could not load template: {err}")))?;
         Ok(template_string)
     }
+
+    fn state_file_path(&self) -> &'static str {
+        "/etc/proxmox-backup/notifications.state.json"
+    }
 }
 
 #[cfg(test)]
diff --git a/proxmox-notify/src/context/pve.rs b/proxmox-notify/src/context/pve.rs
index a97cce26..0dffbb11 100644
--- a/proxmox-notify/src/context/pve.rs
+++ b/proxmox-notify/src/context/pve.rs
@@ -74,6 +74,10 @@ impl Context for PVEContext {
             .map_err(|err| Error::Generic(format!("could not load template: {err}")))?;
         Ok(template_string)
     }
+
+    fn state_file_path(&self) -> &'static str {
+        "/etc/pve/priv/notifications.state.json"
+    }
 }
 
 pub static PVE_CONTEXT: PVEContext = PVEContext;
diff --git a/proxmox-notify/src/context/test.rs b/proxmox-notify/src/context/test.rs
index 2c236b4c..e0236b9c 100644
--- a/proxmox-notify/src/context/test.rs
+++ b/proxmox-notify/src/context/test.rs
@@ -40,4 +40,8 @@ impl Context for TestContext {
     ) -> Result<Option<String>, Error> {
         Ok(Some(String::new()))
     }
+
+    fn state_file_path(&self) -> &'static str {
+        "/tmp/notifications.state.json"
+    }
 }
diff --git a/proxmox-notify/src/lib.rs b/proxmox-notify/src/lib.rs
index 1134027c..a40342cc 100644
--- a/proxmox-notify/src/lib.rs
+++ b/proxmox-notify/src/lib.rs
@@ -6,6 +6,7 @@ use std::fmt::Display;
 use std::str::FromStr;
 
 use context::context;
+use serde::de::DeserializeOwned;
 use serde::{Deserialize, Serialize};
 use serde_json::json;
 use serde_json::Value;
@@ -272,6 +273,65 @@ impl Notification {
     }
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq, Eq)]
+pub struct State {
+    #[serde(flatten)]
+    pub sections: HashMap<String, Value>,
+}
+
+impl FromStr for State {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        serde_json::from_str(s).map_err(|e| Error::ConfigDeserialization(e.into()))
+    }
+}
+
+/// Marker trait to be implemented by the state structs for stateful endpoints.
+pub trait EndpointState: Serialize + DeserializeOwned + Default {}
+
+impl State {
+    pub fn from_path<P: AsRef<std::path::Path>>(path: P) -> Result<Self, Error> {
+        let contents = proxmox_sys::fs::file_read_string(path)
+            .map_err(|e| Error::ConfigDeserialization(e.into()))?;
+        Self::from_str(&contents)
+    }
+
+    pub fn persist<P: AsRef<std::path::Path>>(&self, path: P) -> Result<(), Error> {
+        let state_str =
+            serde_json::to_string_pretty(self).map_err(|e| Error::ConfigSerialization(e.into()))?;
+
+        let mode = nix::sys::stat::Mode::from_bits_truncate(0o600);
+        let options = proxmox_sys::fs::CreateOptions::new().perm(mode);
+
+        proxmox_sys::fs::replace_file(path, state_str.as_bytes(), options, true)
+            .map_err(|e| Error::ConfigSerialization(e.into()))
+    }
+
+    pub fn get<S: EndpointState>(&self, name: &str) -> Result<Option<S>, Error> {
+        match self.sections.get(name) {
+            Some(v) => Ok(Some(
+                S::deserialize(v).map_err(|e| Error::ConfigDeserialization(e.into()))?,
+            )),
+            None => Ok(None),
+        }
+    }
+
+    pub fn get_or_default<S: EndpointState>(&self, name: &str) -> Result<S, Error> {
+        Ok(self.get(name)?.unwrap_or_default())
+    }
+
+    pub fn set<S: EndpointState>(&mut self, name: &str, state: &S) -> Result<(), Error> {
+        let v = serde_json::to_value(state).map_err(|e| Error::ConfigSerialization(e.into()))?;
+        self.sections.insert(name.to_string(), v);
+        Ok(())
+    }
+
+    pub fn remove(&mut self, name: &str) {
+        self.sections.remove(name);
+    }
+}
+
 /// Notification configuration
 #[derive(Debug, Clone)]
 pub struct Config {
-- 
2.47.3