Add rudimentary ingredient parsing and merging

src/commands/groceries.rs

@@ -85,15 +85,42 @@ where
     Ok(ingredients.into_iter().flatten().collect())
 }
 
-fn merge_ingredients(mut ingredients: Vec<(Ingredient, String)>) -> Vec<(Ingredient, String)> {
-    ingredients.sort();
+fn merge_ingredients(mut ingredients: Vec<(Ingredient, String)>) -> Vec<(Ingredient, Vec<String>)> {
+    if ingredients.is_empty() {
+        return vec![];
+    }
 
-    // TODO actual merging
+    // Prime merged_ingredients with the first ingredient in sorted order.
+    ingredients.sort_by(|(a, _), (b, _)| {
+        a.name.cmp(&b.name).then_with(|| {
+            // inefficient, but not so bad for now
+            a.unit.to_string().cmp(&b.unit.to_string())
+        })
+    });
+    let (mut merged_ingredients, ingredients): (Vec<(Ingredient, Vec<String>)>, _) = {
+        let v = ingredients.split_off(1);
+        (
+            ingredients.into_iter().map(|(i, s)| (i, vec![s])).collect(),
+            v,
+        )
+    };
 
-    ingredients
+    for (ingredient, recipe) in ingredients {
+        // If it can be summed to the last item of merged_ingredients, do it;
+        // else append it
+        let (last_i, last_rs) = merged_ingredients.last_mut().unwrap();
+        if last_i.name == ingredient.name && last_i.unit == ingredient.unit {
+            last_i.amount += ingredient.amount;
+            last_rs.push(recipe);
+        } else {
+            merged_ingredients.push((ingredient, vec![recipe]));
+        }
+    }
+
+    merged_ingredients
 }
 
-fn prepare_grocery_list(ingredients: &Vec<(Ingredient, String)>) -> Result<String> {
+fn prepare_grocery_list(ingredients: &Vec<(Ingredient, Vec<String>)>) -> Result<String> {
     let mut out = String::new();
     use std::fmt::Write;
 
@@ -103,9 +130,11 @@ fn prepare_grocery_list(ingredients: &Vec<(Ingredient, String)>) -> Result<Strin
         chrono::Local::now().format("%Y-%m-%d").to_string()
     )?;
     writeln!(out)?; // leave an empty line
-    for ingredient in ingredients {
-        let ingredient_s = ingredient.0 .0.as_str();
-        writeln!(out, "- [ ] {} ({})", ingredient_s, ingredient.1)?;
+    for (ingredient, recipes) in ingredients {
+        writeln!(out, "- [ ] {}", ingredient)?;
+        for recipe in recipes {
+            writeln!(out, "  * {}", recipe)?;
+        }
     }
 
     Ok(out)