From 461b41695b106265a40111940f2ae158c216d4ea Mon Sep 17 00:00:00 2001
From: SeanOMik <seanomik@gmail.com>
Date: Sat, 16 Sep 2023 11:52:20 -0400
Subject: [PATCH] Add a change tracker type

---
 src/change_tracker.rs | 103 ++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs            |   1 +
 2 files changed, 104 insertions(+)
 create mode 100644 src/change_tracker.rs

diff --git a/src/change_tracker.rs b/src/change_tracker.rs
new file mode 100644
index 0000000..211ad77
--- /dev/null
+++ b/src/change_tracker.rs
@@ -0,0 +1,103 @@
+use std::ops::{DerefMut, Deref};
+
+/// A change tracker. This tracks changes of the data it owns.
+/// Tracking changes can cause false positives since it actually tracks calls to `deref_mut()`
+/// If you mutably dereference this, make sure its only when you change the data.
+pub struct Ct<T> {
+    data: T,
+    changed: bool,
+}
+
+impl<T> Ct<T> {
+    pub fn new(data: T) -> Self {
+        Self {
+            data,
+            changed: false,
+        }
+    }
+
+    /// Create a new change tracker with data
+    pub fn new_true(data: T) -> Self {
+        Self {
+            data,
+            changed: true,
+        }
+    }
+
+    /// Returns true if there was a change. Will reset back to false after this is called.
+    pub fn changed(&mut self) -> bool {
+        let before = self.changed;
+        self.reset();
+        before
+    }
+
+    /// Resets the changed tracker to be false
+    pub fn reset(&mut self) {
+        self.changed = false;
+    }
+
+    /// Silently mutate the inner data, this wont be tracked
+    pub fn silent_mutate(&mut self) -> &mut T {
+        &mut self.data
+    }
+
+    /// Consumes self and returns the data stored inside.
+    pub fn take(self) -> T {
+        self.data
+    }
+}
+
+impl<T> Deref for Ct<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T> DerefMut for Ct<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.changed = true;
+        &mut self.data
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Ct;
+
+    #[test]
+    fn new() {
+        let mut c = Ct::new(100);
+        assert!(!c.changed());
+
+        let mut c = Ct::new_true(100);
+        assert!(c.changed());
+    }
+
+    #[test]
+    fn change_tracking() {
+        let mut c = Ct::new(100);
+        assert!(!c.changed());
+
+        *c = 10;
+        assert!(c.changed());
+        assert!(!c.changed()); // should now be not changed
+    }
+
+    #[test]
+    fn silent_mutate() {
+        let mut c = Ct::new(100);
+        let a = c.silent_mutate();
+        *a = 10;
+        assert!(!c.changed());
+    }
+
+    #[test]
+    fn reset() {
+        let mut c = Ct::new(100);
+        *c = 10;
+        c.reset();
+        assert!(!c.changed()); // should not be changed because of reset
+    }
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index d599eed..4c01741 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,7 @@ pub mod math;
 pub mod input;
 pub mod castable_any;
 pub mod plugin;
+pub mod change_tracker;
 
 pub use lyra_resource as assets;