Fix summary amount calculation and add Öresutjämning row

- Amount = round(volume, 2) * round(avg_price, 2)
- Add Öresutjämning showing difference between transaction sum and calculated total

src/main.rs

@@ -86,6 +86,7 @@ struct Summary {
     total_volume: String,
     grand_total: String,
     products: Vec<ProductSummary>,
+    oresutjamning: String,
 }
 
 #[derive(Clone)]
@@ -150,10 +151,12 @@ impl PreparedCustomer {
             .collect();
 
         let mut product_totals: HashMap<String, (f64, f64)> = HashMap::new();
+        let mut total_from_transactions: f64 = 0.0;
         for card in &cards {
             for tx in &card.transactions {
                 let volume: f64 = tx.volume.parse().unwrap();
                 let amount: f64 = tx.amount.parse::<f64>().unwrap();
+                total_from_transactions += amount;
                 let entry = product_totals
                     .entry(tx.quality_name.clone())
                     .or_insert((0.0, 0.0));
@@ -166,11 +169,13 @@ impl PreparedCustomer {
             .into_iter()
             .map(|(name, (volume, amount))| {
                 let avg_price = if volume > 0.0 { amount / volume } else { 0.0 };
-                let calculated_amount = volume * avg_price;
+                let rounded_volume = (volume * 100.0).round() / 100.0;
+                let rounded_avg_price = (avg_price * 100.0).round() / 100.0;
+                let calculated_amount = rounded_volume * rounded_avg_price;
                 ProductSummary {
                     name,
-                    volume: fmt(volume),
-                    avg_price: fmt(avg_price),
+                    volume: fmt(rounded_volume),
+                    avg_price: fmt(rounded_avg_price),
                     amount: fmt(calculated_amount),
                 }
             })
@@ -187,10 +192,13 @@ impl PreparedCustomer {
             .map(|p| p.amount.parse::<f64>().unwrap())
             .sum();
 
+        let oresutjamning = total_from_transactions - grand_total;
+
         let summary = Summary {
             total_volume: fmt(total_volume),
             grand_total: fmt(grand_total),
             products,
+            oresutjamning: fmt(oresutjamning),
         };
 
         PreparedCustomer {