feat: annotate scaled ingredient quantities

Refs #1, #2

lib/recipe-scaler.js

@@ -30,33 +30,53 @@ function formatQuantity(value) {
   ));
   if (Math.abs(fraction - remainder) <= 0.02) {
     const adjustedWhole = fraction === 1 ? whole + 1 : whole;
-    return `${adjustedWhole || ""}${adjustedWhole && symbol ? " " : ""}${symbol}` || "0";
+    return {
+      value: `${adjustedWhole || ""}${adjustedWhole && symbol ? " " : ""}${symbol}` || "0",
+      approximate: false
+    };
   }
-  return Number(value.toFixed(2)).toString();
+  return { value: Number(value.toFixed(2)).toString(), approximate: true };
+}
+
+function scaleIngredientWithStatus(ingredient, factor) {
+  if (typeof ingredient !== "string" || factor === 1) {
+    return { value: ingredient, status: "unchanged" };
+  }
+  const match = ingredient.match(/^(\s*)(?:(\d+)\s+)?(\d+\/\d+|\d+(?:\.\d+)?|[¼½¾⅓⅔⅛⅜⅝⅞])(?=\s|[a-zA-Z])/);
+  if (!match) {
+    const hasLeadingQuantity = /^\s*(?:\d|[¼½¾⅓⅔⅛⅜⅝⅞])/.test(ingredient);
+    return { value: ingredient, status: hasLeadingQuantity ? "unscalable" : "unquantified" };
+  }
+  const whole = Number(match[2] || 0);
+  const quantity = parseQuantity(match[3]);
+  if (!Number.isFinite(quantity)) return { value: ingredient, status: "unscalable" };
+  const formatted = formatQuantity((whole + quantity) * factor);
+  const replacement = `${match[1]}${formatted.value}`;
+  return {
+    value: replacement + ingredient.slice(match[0].length),
+    status: formatted.approximate ? "approximate" : "scaled"
+  };
 }
 
 function scaleIngredient(ingredient, factor) {
-  if (typeof ingredient !== "string" || factor === 1) return ingredient;
-  const match = ingredient.match(/^(\s*)(?:(\d+)\s+)?(\d+\/\d+|\d+(?:\.\d+)?|[¼½¾⅓⅔⅛⅜⅝⅞])(?=\s|[a-zA-Z])/);
-  if (!match) return ingredient;
-  const whole = Number(match[2] || 0);
-  const quantity = parseQuantity(match[3]);
-  if (!Number.isFinite(quantity)) return ingredient;
-  const replacement = `${match[1]}${formatQuantity((whole + quantity) * factor)}`;
-  return replacement + ingredient.slice(match[0].length);
+  return scaleIngredientWithStatus(ingredient, factor).value;
 }
 
 function scaleRecipe(recipe, portions) {
   const basePortions = parseYield(recipe?.recipeYield);
   if (!basePortions || !Number.isInteger(portions) || portions < 1) return recipe;
   const suffix = String(recipe.recipeYield).replace(/^\s*\d+(?:\.\d+)?\s*/, "");
+  const factor = portions / basePortions;
+  const ingredients = (recipe.recipeIngredient || []).map((ingredient) => (
+    scaleIngredientWithStatus(ingredient, factor)
+  ));
   return {
     ...recipe,
     recipeYield: suffix ? `${portions} ${suffix}` : portions,
-    recipeIngredient: (recipe.recipeIngredient || []).map((ingredient) => (
-      scaleIngredient(ingredient, portions / basePortions)
-    ))
+    originalRecipeYield: recipe.recipeYield,
+    recipeIngredient: ingredients.map(({ value }) => value),
+    recipeIngredientStatus: ingredients.map(({ status }) => status)
   };
 }
 
-module.exports = { parseYield, scaleIngredient, scaleRecipe };
+module.exports = { parseYield, scaleIngredient, scaleIngredientWithStatus, scaleRecipe };

test/recipe-scaler.test.js

@@ -1,6 +1,6 @@
 const test = require("node:test");
 const assert = require("node:assert/strict");
-const { parseYield, scaleIngredient, scaleRecipe } = require("../lib/recipe-scaler");
+const { parseYield, scaleIngredient, scaleIngredientWithStatus, scaleRecipe } = require("../lib/recipe-scaler");
 
 test("extracts the number of portions from a recipe yield", () => {
   assert.equal(parseYield("6 servings"), 6);
@@ -25,4 +25,21 @@ test("returns a scaled copy of a recipe", () => {
   assert.equal(scaled.recipeYield, "9 servings");
   assert.deepEqual(scaled.recipeIngredient, ["3 cups oats", "Salt to taste"]);
   assert.equal(original.recipeYield, "6 servings");
+  assert.equal(scaled.originalRecipeYield, "6 servings");
+  assert.deepEqual(scaled.recipeIngredientStatus, ["scaled", "unquantified"]);
+});
+
+test("reports ingredient scaling confidence", () => {
+  assert.deepEqual(scaleIngredientWithStatus("2 cups oats", 1.5), {
+    value: "3 cups oats", status: "scaled"
+  });
+  assert.deepEqual(scaleIngredientWithStatus("Salt to taste", 2), {
+    value: "Salt to taste", status: "unquantified"
+  });
+  assert.deepEqual(scaleIngredientWithStatus("1-2 tbsp oil", 2), {
+    value: "1-2 tbsp oil", status: "unscalable"
+  });
+  assert.deepEqual(scaleIngredientWithStatus("1 cup milk", 0.7), {
+    value: "0.7 cup milk", status: "approximate"
+  });
 });