Fix npe in shopping cart (#203)

Author: Fabtron

core/src/main/java/io/snabble/sdk/Unit.java

@@ -1,5 +1,7 @@
 package io.snabble.sdk;
 
+import androidx.annotation.NonNull;
+
 import java.math.BigDecimal;
 import java.math.MathContext;
 import java.util.ArrayList;
@@ -195,7 +197,7 @@ private static void addConversion(Unit from, Unit to, int factor, int divisor) {
      * <p>
      * Returns the same value if a conversion is not possible. (e.g. KILOGRAM -> MILLIMETER)
      */
-    public static BigDecimal convert(BigDecimal value, Unit from, Unit to) {
+    public static @NonNull BigDecimal convert(@NonNull BigDecimal value, @NonNull Unit from, @NonNull Unit to) {
         if (from == to) return value;
 
         for (Conversion conversion : conversions) {

ui/src/main/java/io/snabble/sdk/ui/cart/shoppingcart/Extensions.kt

@@ -9,8 +9,8 @@ import java.math.RoundingMode
 
 fun PriceModifier.convertPriceModifier(
     amount: Int,
-    weightedUnit: String?,
-    referencedUnit: String?
+    weightedUnit: String,
+    referencedUnit: String
 ): Int {
     val convertedValue = convert(BigDecimal(amount), fromString(weightedUnit), fromString(referencedUnit))
     val mode = Snabble.checkedInProject.value?.roundingMode ?: RoundingMode.HALF_UP

ui/src/main/java/io/snabble/sdk/ui/cart/shoppingcart/ShoppingCartViewModel.kt

@@ -149,16 +149,32 @@ class ShoppingCartViewModel : ViewModel() {
                 val discounts = mutableListOf<DiscountItem>()
                 item.item.lineItem?.priceModifiers?.forEach { priceModifier ->
                     val name = priceModifier.name.orEmpty()
-                    val modifiedPrice = priceModifier
-                        .convertPriceModifier(
-                            item.quantity,
-                            item.item.lineItem?.weightUnit,
-                            item.item.lineItem?.referenceUnit
-                        )
-                        .let { priceFormatter?.format(it).orEmpty() }
+                    val weightUnit = item.item.lineItem?.weightUnit
+                    val referenceUnit = item.item.lineItem?.referenceUnit
+                    val modifiedPrice = if (weightUnit != null && referenceUnit != null) {
+                        priceModifier
+                            .convertPriceModifier(
+                                amount = item.quantity,
+                                weightedUnit = weightUnit,
+                                referencedUnit = referenceUnit
+                            )
+                            .let { priceFormatter?.format(it).orEmpty() }
+                    } else {
+                        (priceModifier.price * item.quantity).let {
+                            priceFormatter?.format(it).orEmpty()
+                        }
+                    }
                     // Set this to zero because the backend already subtracted the discount from the total price:
                     val discountValue = 0
-                    discounts.add(DiscountItem(name = name, discount = modifiedPrice, discountValue = discountValue))
+                    modifiedPrice.let {
+                        discounts.add(
+                            DiscountItem(
+                                name = name,
+                                discount = modifiedPrice,
+                                discountValue = discountValue
+                            )
+                        )
+                    }
                 }
                 item.copy(discounts = item.discounts + discounts)
             }

ui/src/main/java/io/snabble/sdk/ui/cart/shoppingcart/product/model/ProductItem.kt

@@ -32,9 +32,17 @@ internal data class ProductItem(
         // price modifiers on top of the total price to get the unmodified total price.
         // In the other case we can directly work with the total price.
         val depositPrice = deposit?.depositPrice ?: 0
-        val sumOfModifierPriceDiscounts = item.lineItem?.priceModifiers.orEmpty()
-            .sumOf { it.convertPriceModifier(quantity, unit, item.lineItem?.referenceUnit) }
-            .let(::abs)
+        val weightUnit = item.lineItem?.weightUnit
+        val referenceUnit = item.lineItem?.referenceUnit
+        val sumOfModifierPriceDiscounts = if (weightUnit != null && referenceUnit != null) {
+            item.lineItem?.priceModifiers.orEmpty()
+                .sumOf { it.convertPriceModifier(quantity, weightUnit, referenceUnit) }
+                .let(::abs)
+        } else {
+            item.lineItem?.priceModifiers.orEmpty()
+                .sumOf { it.price * quantity }
+                .let(::abs)
+        }
         return totalPrice + depositPrice + sumOfModifierPriceDiscounts
     }