From f3f27293df83986ba29fb03f8af26a2177518e20 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Wed, 4 Jan 2023 13:07:13 +0100
Subject: Uniform framework for bg variable management

---
 src/util/background/mod.rs  |   1 +
 src/util/background/vars.rs | 107 ++++++++++++++++++++++++++++++++++++++++++++
 src/util/persister.rs       |  34 ++++++++++++++
 3 files changed, 142 insertions(+)
 create mode 100644 src/util/background/vars.rs

(limited to 'src/util')

diff --git a/src/util/background/mod.rs b/src/util/background/mod.rs
index 41b48e93..607cd7a3 100644
--- a/src/util/background/mod.rs
+++ b/src/util/background/mod.rs
@@ -1,5 +1,6 @@
 //! Job runner for futures and async functions
 
+pub mod vars;
 pub mod worker;
 
 use std::collections::HashMap;
diff --git a/src/util/background/vars.rs b/src/util/background/vars.rs
new file mode 100644
index 00000000..fe54268e
--- /dev/null
+++ b/src/util/background/vars.rs
@@ -0,0 +1,107 @@
+use std::collections::HashMap;
+use std::str::FromStr;
+
+use crate::error::{Error, OkOrMessage};
+use crate::migrate::Migrate;
+use crate::persister::PersisterShared;
+
+pub struct BgVars {
+	vars: HashMap<&'static str, Box<dyn BgVarTrait>>,
+}
+
+impl BgVars {
+	pub fn new() -> Self {
+		Self {
+			vars: HashMap::new(),
+		}
+	}
+
+	pub fn register_rw<V, T, GF, SF>(
+		&mut self,
+		p: &PersisterShared<V>,
+		name: &'static str,
+		get_fn: GF,
+		set_fn: SF,
+	) where
+		V: Migrate + Default + Send + Sync,
+		T: FromStr + ToString + Send + Sync + 'static,
+		GF: Fn(&PersisterShared<V>) -> T + Send + Sync + 'static,
+		SF: Fn(&PersisterShared<V>, T) -> Result<(), Error> + Send + Sync + 'static,
+	{
+		let p1 = p.clone();
+		let get_fn = move || get_fn(&p1);
+
+		let p2 = p.clone();
+		let set_fn = move |v| set_fn(&p2, v);
+
+		self.vars.insert(name, Box::new(BgVar { get_fn, set_fn }));
+	}
+
+	pub fn register_ro<V, T, GF>(&mut self, p: &PersisterShared<V>, name: &'static str, get_fn: GF)
+	where
+		V: Migrate + Default + Send + Sync,
+		T: FromStr + ToString + Send + Sync + 'static,
+		GF: Fn(&PersisterShared<V>) -> T + Send + Sync + 'static,
+	{
+		let p1 = p.clone();
+		let get_fn = move || get_fn(&p1);
+
+		let set_fn = move |_| Err(Error::Message(format!("Cannot set value of {}", name)));
+
+		self.vars.insert(name, Box::new(BgVar { get_fn, set_fn }));
+	}
+
+	pub fn get(&self, var: &str) -> Result<String, Error> {
+		Ok(self
+			.vars
+			.get(var)
+			.ok_or_message("variable does not exist")?
+			.get())
+	}
+
+	pub fn get_all(&self) -> Vec<(&'static str, String)> {
+		self.vars.iter().map(|(k, v)| (*k, v.get())).collect()
+	}
+
+	pub fn set(&self, var: &str, val: &str) -> Result<(), Error> {
+		self.vars
+			.get(var)
+			.ok_or_message("variable does not exist")?
+			.set(val)
+	}
+}
+
+// ----
+
+trait BgVarTrait: Send + Sync + 'static {
+	fn get(&self) -> String;
+	fn set(&self, v: &str) -> Result<(), Error>;
+}
+
+struct BgVar<T, GF, SF>
+where
+	T: FromStr + ToString + Send + Sync + 'static,
+	GF: Fn() -> T + Send + Sync + 'static,
+	SF: Fn(T) -> Result<(), Error> + Sync + Send + 'static,
+{
+	get_fn: GF,
+	set_fn: SF,
+}
+
+impl<T, GF, SF> BgVarTrait for BgVar<T, GF, SF>
+where
+	T: FromStr + ToString + Sync + Send + 'static,
+	GF: Fn() -> T + Sync + Send + 'static,
+	SF: Fn(T) -> Result<(), Error> + Sync + Send + 'static,
+{
+	fn get(&self) -> String {
+		(self.get_fn)().to_string()
+	}
+
+	fn set(&self, vstr: &str) -> Result<(), Error> {
+		let value = vstr
+			.parse()
+			.map_err(|_| Error::Message(format!("invalid value: {}", vstr)))?;
+		(self.set_fn)(value)
+	}
+}
diff --git a/src/util/persister.rs b/src/util/persister.rs
index 4b9adf51..5c66bbed 100644
--- a/src/util/persister.rs
+++ b/src/util/persister.rs
@@ -1,5 +1,6 @@
 use std::io::{Read, Write};
 use std::path::{Path, PathBuf};
+use std::sync::{Arc, RwLock};
 
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
@@ -84,3 +85,36 @@ impl<T: Migrate> Persister<T> {
 		Ok(())
 	}
 }
+
+pub struct PersisterShared<V: Migrate + Default>(Arc<(Persister<V>, RwLock<V>)>);
+
+impl<V: Migrate + Default> Clone for PersisterShared<V> {
+	fn clone(&self) -> PersisterShared<V> {
+		PersisterShared(self.0.clone())
+	}
+}
+
+impl<V: Migrate + Default> PersisterShared<V> {
+	pub fn new(base_dir: &Path, file_name: &str) -> Self {
+		let persister = Persister::new(base_dir, file_name);
+		let value = persister.load().unwrap_or_default();
+		Self(Arc::new((persister, RwLock::new(value))))
+	}
+
+	pub fn get_with<F, R>(&self, f: F) -> R
+	where
+		F: FnOnce(&V) -> R,
+	{
+		let value = self.0 .1.read().unwrap();
+		f(&value)
+	}
+
+	pub fn set_with<F>(&self, f: F) -> Result<(), Error>
+	where
+		F: FnOnce(&mut V),
+	{
+		let mut value = self.0 .1.write().unwrap();
+		f(&mut value);
+		self.0 .0.save(&value)
+	}
+}
-- 
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