From 6677f41af2d59f232f0bc8ec26d4c29dd1245f7b Mon Sep 17 00:00:00 2001
From: Sebastian Kuzminsky <seb@highlab.com>
Date: Thu, 13 Mar 2025 15:58:47 -0600
Subject: [PATCH] move Quantity to its own module, add some Traits for
 convenience

---
 tools/src/lib.rs      |  3 ++
 tools/src/quantity.rs | 64 +++++++++++++++++++++++++++++++++++++++++++
 tools/src/recipe.rs   | 36 ++----------------------
 tools/src/repo.rs     |  2 +-
 tools/src/repos.rs    |  9 ++----
 5 files changed, 73 insertions(+), 41 deletions(-)
 create mode 100644 tools/src/quantity.rs

diff --git a/tools/src/lib.rs b/tools/src/lib.rs
index c9b6ed3..1a93fbd 100644
--- a/tools/src/lib.rs
+++ b/tools/src/lib.rs
@@ -1,3 +1,6 @@
+pub mod quantity;
+pub use quantity::*;
+
 pub mod recipe;
 pub use recipe::Recipe;
 
diff --git a/tools/src/quantity.rs b/tools/src/quantity.rs
new file mode 100644
index 0000000..54a8f0c
--- /dev/null
+++ b/tools/src/quantity.rs
@@ -0,0 +1,64 @@
+#[derive(Clone, Copy, Debug, PartialEq, serde::Deserialize)]
+pub enum Unit {
+    Foot,
+    Gram,
+    Liter,
+    Meter,
+    USDollar,
+}
+
+/// `Quantity` measures the amount of a resource (Input or Output).
+#[derive(Clone, Copy, PartialEq, serde::Deserialize)]
+pub struct Quantity {
+    pub amount: f32,
+    pub unit: Option<Unit>,
+}
+
+impl std::default::Default for Quantity {
+    fn default() -> Self {
+        Self {
+            amount: 1.0,
+            unit: None,
+        }
+    }
+}
+
+impl std::fmt::Debug for Quantity {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &self.unit {
+            None => write!(f, "{:#}", self.amount),
+            Some(unit) => write!(f, "{:#} {:?}", self.amount, unit),
+        }
+    }
+}
+
+impl std::ops::Mul<f32> for Quantity {
+    type Output = Self;
+    fn mul(self, rhs: f32) -> Self {
+        Self {
+            unit: self.unit,
+            amount: self.amount * rhs,
+        }
+    }
+}
+
+impl std::ops::Mul<usize> for Quantity {
+    type Output = Self;
+    fn mul(self, rhs: usize) -> Self {
+        Self {
+            unit: self.unit,
+            amount: self.amount * (rhs as f32),
+        }
+    }
+}
+
+impl std::ops::Add<&Quantity> for Quantity {
+    type Output = Self;
+    fn add(self, rhs: &Self) -> Self {
+        assert_eq!(self.unit, rhs.unit);
+        Self {
+            unit: self.unit,
+            amount: self.amount + rhs.amount,
+        }
+    }
+}
diff --git a/tools/src/recipe.rs b/tools/src/recipe.rs
index 009b55c..a03d9f9 100644
--- a/tools/src/recipe.rs
+++ b/tools/src/recipe.rs
@@ -1,3 +1,5 @@
+use crate::quantity::*;
+
 #[derive(Debug, thiserror::Error)]
 pub enum RecipeLoadError {
     #[error(transparent)]
@@ -6,40 +8,6 @@ pub enum RecipeLoadError {
     TomlDeserializeError(#[from] toml::de::Error),
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, serde::Deserialize)]
-pub enum Unit {
-    Foot,
-    Gram,
-    Liter,
-    Meter,
-    USDollar,
-}
-
-/// `Quantity` measures the amount of a resource (Input or Output).
-#[derive(Clone, Copy, PartialEq, serde::Deserialize)]
-pub struct Quantity {
-    pub amount: f32,
-    pub unit: Option<Unit>,
-}
-
-impl std::default::Default for Quantity {
-    fn default() -> Self {
-        Self {
-            amount: 1.0,
-            unit: None,
-        }
-    }
-}
-
-impl std::fmt::Debug for Quantity {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match &self.unit {
-            None => write!(f, "{:#}", self.amount),
-            Some(unit) => write!(f, "{:#} {:?}", self.amount, unit),
-        }
-    }
-}
-
 #[derive(Debug, serde::Deserialize, PartialEq)]
 pub struct Input {
     // Quantity defaults to "amount=1" if omitted.
diff --git a/tools/src/repo.rs b/tools/src/repo.rs
index bfb1d5f..0a8b795 100644
--- a/tools/src/repo.rs
+++ b/tools/src/repo.rs
@@ -134,7 +134,7 @@ impl Repo {
                             .ok_or(anyhow::Error::msg(format!(
                                 "can't find input capital for {input_name}"
                             )))?;
-                    if input_capital.quantity.unit != Some(crate::recipe::Unit::USDollar) {
+                    if input_capital.quantity.unit != Some(crate::quantity::Unit::USDollar) {
                         return Err(anyhow::Error::msg(format!(
                             "{} input capital does not have units USDollar",
                             input_name
diff --git a/tools/src/repos.rs b/tools/src/repos.rs
index 7859070..c79491d 100644
--- a/tools/src/repos.rs
+++ b/tools/src/repos.rs
@@ -128,17 +128,14 @@ impl Repos {
             // A Recipe whose only input is Capital is a Vitamin.
             let cost = match input_recipe.is_vitamin() {
                 true => {
-                    let amount_needed = crate::recipe::Quantity {
-                        unit: input_info.quantity.unit,
-                        amount: quantity as f32 * input_info.quantity.amount,
-                    };
+                    let amount_needed = input_info.quantity * quantity;
 
                     // FIXME: for now Vitamins must have exactly one Input, and it must be Capital.
                     assert_eq!(input_recipe.inputs.len(), 1);
                     let input_capital = input_recipe.inputs.get("capital").ok_or_else(|| {
                         RecipeCompileError::VitaminLacksCapital(input_name.into())
                     })?;
-                    if input_capital.quantity.unit != Some(crate::recipe::Unit::USDollar) {
+                    if input_capital.quantity.unit != Some(crate::quantity::Unit::USDollar) {
                         return Err(RecipeCompileError::VitaminCapitalHasWrongUnit(
                             input_name.into(),
                         ));
@@ -218,7 +215,7 @@ impl Repos {
             if !input_recipe.is_vitamin() {
                 self.compile_inner(
                     puml_file,
-                    (quantity as f32 * input_info.quantity.amount) as usize, // FIXME: pretty dodgy
+                    (input_info.quantity * quantity).amount as usize, // FIXME: pretty dodgy
                     input_name,
                     input_recipe,
                     indent + 4,