Move ChangePolicy to drain.rs

src/change_policy.rs

@@ -1,54 +1 @@
-//! This module contains a collection of change policies.
-//!
-//! A change policy determines whether a given coin selection (presented by [`CoinSelector`]) should
-//! construct a transaction with a change output. A change policy is represented as a function of
-//! type `Fn(&CoinSelector, Target) -> Drain`.
 
-#[allow(unused)] // some bug in <= 1.48.0 sees this as unused when it isn't
-use crate::float::FloatExt;
-use crate::{DrainWeights, FeeRate};
-
-/// Describes when a change output (although it could represent several) should be added that drains
-/// the excess in the coin selection. It includes the `drain_weights` to account for the cost of
-/// adding this outupt(s).
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub struct ChangePolicy {
-    /// The minimum amount of excesss there needs to be add a change output.
-    pub min_value: u64,
-    /// The weights of the drain that would be added according to the policy.
-    pub drain_weights: DrainWeights,
-}
-
-impl ChangePolicy {
-    /// Construct a change policy that creates change when the change value is greater than
-    /// `min_value`.
-    pub fn min_value(drain_weights: DrainWeights, min_value: u64) -> Self {
-        Self {
-            drain_weights,
-            min_value,
-        }
-    }
-
-    /// Construct a change policy that creates change when it would reduce the transaction waste
-    /// given that `min_value` is respected.
-    pub fn min_value_and_waste(
-        drain_weights: DrainWeights,
-        min_value: u64,
-        target_feerate: FeeRate,
-        long_term_feerate: FeeRate,
-    ) -> Self {
-        // The output waste of a changeless solution is the excess.
-        let waste_with_change = drain_weights
-            .waste(
-                target_feerate,
-                long_term_feerate,
-                0, /* ignore varint cost for now */
-            )
-            .ceil() as u64;
-
-        Self {
-            drain_weights,
-            min_value: waste_with_change.max(min_value),
-        }
-    }
-}

src/coin_selector.rs

@@ -1,7 +1,7 @@
 use super::*;
 #[allow(unused)] // some bug in <= 1.48.0 sees this as unused when it isn't
 use crate::float::FloatExt;
-use crate::{bnb::BnbMetric, change_policy::ChangePolicy, float::Ordf32, FeeRate, Target};
+use crate::{bnb::BnbMetric, float::Ordf32, ChangePolicy, FeeRate, Target};
 use alloc::{borrow::Cow, collections::BTreeSet, vec::Vec};
 
 /// [`CoinSelector`] selects/deselects coins from a set of canididate coins.

src/drain.rs

@@ -1,3 +1,5 @@
+#[allow(unused)] // some bug in <= 1.48.0 sees this as unused when it isn't
+use crate::float::FloatExt;
 use crate::{varint_size, FeeRate, TR_KEYSPEND_TXIN_WEIGHT, TR_SPK_WEIGHT, TXOUT_BASE_WEIGHT};
 
 /// Represents the weight costs of a drain (a.k.a. change) output.
@@ -93,3 +95,48 @@ impl Drain {
         !self.is_none()
     }
 }
+
+/// Describes when a change output (although it could represent several) should be added that drains
+/// the excess in the coin selection. It includes the `drain_weights` to account for the cost of
+/// adding this outupt(s).
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct ChangePolicy {
+    /// The minimum amount of excesss there needs to be add a change output.
+    pub min_value: u64,
+    /// The weights of the drain that would be added according to the policy.
+    pub drain_weights: DrainWeights,
+}
+
+impl ChangePolicy {
+    /// Construct a change policy that creates change when the change value is greater than
+    /// `min_value`.
+    pub fn min_value(drain_weights: DrainWeights, min_value: u64) -> Self {
+        Self {
+            drain_weights,
+            min_value,
+        }
+    }
+
+    /// Construct a change policy that creates change when it would reduce the transaction waste
+    /// given that `min_value` is respected.
+    pub fn min_value_and_waste(
+        drain_weights: DrainWeights,
+        min_value: u64,
+        target_feerate: FeeRate,
+        long_term_feerate: FeeRate,
+    ) -> Self {
+        // The output waste of a changeless solution is the excess.
+        let waste_with_change = drain_weights
+            .waste(
+                target_feerate,
+                long_term_feerate,
+                0, /* ignore varint cost for now */
+            )
+            .ceil() as u64;
+
+        Self {
+            drain_weights,
+            min_value: waste_with_change.max(min_value),
+        }
+    }
+}

src/lib.rs

@@ -22,8 +22,6 @@ pub mod metrics;
 
 mod feerate;
 pub use feerate::*;
-mod change_policy;
-pub use change_policy::*;
 mod target;
 pub use target::*;
 mod drain;

src/metrics.rs

@@ -1,8 +1,6 @@
 //! Branch and bound metrics that can be passed to [`CoinSelector::bnb_solutions`] or
 //! [`CoinSelector::run_bnb`].
-use crate::{
-    bnb::BnbMetric, change_policy::ChangePolicy, float::Ordf32, CoinSelector, Drain, Target,
-};
+use crate::{bnb::BnbMetric, float::Ordf32, ChangePolicy, CoinSelector, Drain, Target};
 mod lowest_fee;
 pub use lowest_fee::*;
 mod changeless;

src/metrics/changeless.rs

@@ -1,5 +1,5 @@
 use super::change_lower_bound;
-use crate::{bnb::BnbMetric, change_policy::ChangePolicy, float::Ordf32, CoinSelector, Target};
+use crate::{bnb::BnbMetric, float::Ordf32, ChangePolicy, CoinSelector, Target};
 
 #[derive(Clone, Debug)]
 /// Metric for finding changeless solutions only.

src/metrics/lowest_fee.rs

@@ -1,6 +1,4 @@
-use crate::{
-    change_policy::ChangePolicy, float::Ordf32, BnbMetric, CoinSelector, Drain, FeeRate, Target,
-};
+use crate::{float::Ordf32, BnbMetric, ChangePolicy, CoinSelector, Drain, FeeRate, Target};
 
 /// Metric that aims to minimize transaction fees. The future fee for spending the change output is
 /// included in this calculation.