feat: added density conversion

lib/measurements/densities.js

@@ -0,0 +1,58 @@
+/**
+ * Ingredient density table for automatic weight/volume conversion.
+ *
+ * Each entry has keywords (ingredient names) and a density in g/ml.
+ * Conversion:
+ *   Weight -> Volume: ml = grams / density
+ *   Volume -> Weight: grams = ml * density
+ *
+ * Entries are sorted longest-keyword-first so that "brown sugar" matches
+ * before "sugar", "olive oil" before "oil", etc.
+ */
+
+const DENSITIES = [
+  { keywords: ['all-purpose flour', 'all purpose flour', 'ap flour'], density: 0.53 },
+  { keywords: ['powdered sugar', 'confectioners sugar', 'icing sugar'], density: 0.50 },
+  { keywords: ['vanilla extract'], density: 1.03 },
+  { keywords: ['baking powder'], density: 0.90 },
+  { keywords: ['cocoa powder'], density: 0.43 },
+  { keywords: ['brown sugar'], density: 0.93 },
+  { keywords: ['maple syrup'], density: 1.32 },
+  { keywords: ['baking soda', 'bicarbonate'], density: 1.10 },
+  { keywords: ['bread flour'], density: 0.55 },
+  { keywords: ['sour cream'], density: 1.05 },
+  { keywords: ['olive oil'], density: 0.92 },
+  { keywords: ['cornstarch', 'corn starch'], density: 0.54 },
+  { keywords: ['butter'], density: 0.96 },
+  { keywords: ['cream'], density: 1.01 },
+  { keywords: ['flour'], density: 0.53 },
+  { keywords: ['sugar'], density: 0.85 },
+  { keywords: ['honey'], density: 1.42 },
+  { keywords: ['milk'], density: 1.03 },
+  { keywords: ['water'], density: 1.0 },
+  { keywords: ['salt'], density: 1.22 },
+  { keywords: ['rice'], density: 0.80 },
+  { keywords: ['oil'], density: 0.92 },
+];
+
+/**
+ * Check if text contains a known ingredient and return its density.
+ * Lowercases the text and checks keywords longest-first.
+ *
+ * @param {string} text - text preceding the measurement (ingredient context)
+ * @returns {number|null} density in g/ml, or null if no match
+ */
+function matchDensity(text) {
+  if (!text) return null;
+  const lower = text.toLowerCase().trim();
+  for (const entry of DENSITIES) {
+    for (const keyword of entry.keywords) {
+      if (lower.includes(keyword)) {
+        return entry.density;
+      }
+    }
+  }
+  return null;
+}
+
+module.exports = { DENSITIES, matchDensity };