Add the PCZT Updater role

src/pczt.rs

@@ -24,6 +24,9 @@ pub use parse::ParseError;
 mod io_finalizer;
 pub use io_finalizer::IoFinalizerError;
 
+mod updater;
+pub use updater::{ActionUpdater, Updater, UpdaterError};
+
 mod prover;
 pub use prover::ProverError;
 

src/pczt/updater.rs

@@ -0,0 +1,69 @@
+use super::{Action, Bundle, Zip32Derivation};
+
+impl Bundle {
+    /// Updates the bundle with information provided in the given closure.
+    pub fn update_with<F>(&mut self, f: F) -> Result<(), UpdaterError>
+    where
+        F: FnOnce(Updater<'_>) -> Result<(), UpdaterError>,
+    {
+        f(Updater(self))
+    }
+}
+
+/// An updater for an Orchard PCZT bundle.
+#[derive(Debug)]
+pub struct Updater<'a>(&'a mut Bundle);
+
+impl<'a> Updater<'a> {
+    /// Provides read access to the bundle being updated.
+    pub fn bundle(&self) -> &Bundle {
+        &self.0
+    }
+
+    /// Updates the action at the given index with information provided in the given
+    /// closure.
+    pub fn update_action_with<F>(&mut self, index: usize, f: F) -> Result<(), UpdaterError>
+    where
+        F: FnOnce(ActionUpdater<'_>) -> Result<(), UpdaterError>,
+    {
+        f(ActionUpdater(
+            self.0
+                .actions
+                .get_mut(index)
+                .ok_or(UpdaterError::InvalidIndex)?,
+        ))
+    }
+}
+
+/// An updater for an Orchard PCZT action.
+#[derive(Debug)]
+pub struct ActionUpdater<'a>(&'a mut Action);
+
+impl<'a> ActionUpdater<'a> {
+    /// Sets the ZIP 32 derivation path for the spent note's signing key.
+    pub fn set_spend_zip32_derivation(&mut self, derivation: Zip32Derivation) {
+        self.0.spend.zip32_derivation = Some(derivation);
+    }
+
+    /// Stores the given spend-specific proprietary value at the given key.
+    pub fn set_spend_proprietary(&mut self, key: String, value: Vec<u8>) {
+        self.0.spend.proprietary.insert(key, value);
+    }
+
+    /// Sets the ZIP 32 derivation path for the new note's signing key.
+    pub fn set_output_zip32_derivation(&mut self, derivation: Zip32Derivation) {
+        self.0.output.zip32_derivation = Some(derivation);
+    }
+
+    /// Stores the given output-specific proprietary value at the given key.
+    pub fn set_output_proprietary(&mut self, key: String, value: Vec<u8>) {
+        self.0.output.proprietary.insert(key, value);
+    }
+}
+
+/// Errors that can occur while updating an Orchard bundle in a PCZT.
+#[derive(Debug)]
+pub enum UpdaterError {
+    /// An out-of-bounds index was provided when looking up an action.
+    InvalidIndex,
+}