Customizable isMergeable behavior (#100)

Make the `ShoppingCart::isMergeable()` behavior customizable for users
of the SDK.

Author: cmaier

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

@@ -29,9 +29,9 @@
 import io.snabble.sdk.codes.templates.CodeTemplate;
 import io.snabble.sdk.coupons.Coupon;
 import io.snabble.sdk.coupons.CouponType;
+import io.snabble.sdk.customization.IsMergeable;
 import io.snabble.sdk.utils.Dispatch;
 import io.snabble.sdk.utils.GsonHolder;
-import io.snabble.sdk.utils.Logger;
 
 /**
  * Class representing the snabble shopping cart
@@ -232,7 +232,7 @@ public Iterator<Item> iterator() {
     /**
      * Returns a cart item that contains the given product, if that cart item
      * can be merged.
-     *
+     * <p>
      * A cart item is not mergeable if it uses encoded data of a scanned code (e.g. a different price)
      */
     public Item getExistingMergeableProduct(Product product) {
@@ -288,7 +288,7 @@ public void remove(int index) {
 
     /**
      * The number items in the cart.
-     *
+     * <p>
      * This is not the sum of articles.
      */
     public int size() {
@@ -304,7 +304,7 @@ public boolean isEmpty() {
 
     /**
      * Backups the cart, so it can be restured using {@link #restore()} later.
-     *
+     * <p>
      * A cart is restorable for up to 5 minutes.
      */
     public void backup() {
@@ -336,7 +336,7 @@ public void restore() {
         if (isRestorable()) {
             data = oldData;
             data.applyShoppingCart(this);
-            
+
             clearBackup();
             checkLimits();
             updatePrices(false);
@@ -346,6 +346,7 @@ public void restore() {
 
     /**
      * The last time the cart was backed up by using {@link #backup()}
+     *
      * @return
      */
     public long getBackupTimestamp() {
@@ -481,10 +482,10 @@ public int getModCount() {
 
     /**
      * Generate a new uuid.
-     *
+     * <p>
      * UUID's are used to uniquely identify a specific purchase made by the user. If a new UUID
      * is generated a new checkout can be made.
-     *
+     * <p>
      * If a checkout already exist with the same UUID, the checkout will get continued.
      */
     public void generateNewUUID() {
@@ -494,10 +495,10 @@ public void generateNewUUID() {
 
     /**
      * The UUID of the cart
-     *
+     * <p>
      * UUID's are used to uniquely identify a specific purchase made by the user. If a new UUID
      * is generated a new checkout can be made.
-     *
+     * <p>
      * If a checkout already exist with the same UUID, the checkout will get continued.
      */
     public String getUUID() {
@@ -540,7 +541,7 @@ public boolean hasInvalidDepositReturnVoucher() {
 
     /**
      * Returns the total price of the cart.
-     *
+     * <p>
      * If the cart was updated by the backend, the online price is used. If no update was made
      * a locally calculated price will be used
      */
@@ -923,15 +924,24 @@ public boolean isEditableInDialog() {
          * Returns true if the item can be merged with items that conain the same product and type
          */
         public boolean isMergeable() {
+            @Nullable final IsMergeable isMergeableOverride = Snabble.getInstance().isMergeable();
+            final boolean isMergeable = isMergeableDefault();
+            if (isMergeableOverride == null) {
+                return isMergeable;
+            } else {
+                return isMergeableOverride.isMergeable(this, isMergeable);
+            }
+        }
+
+        private boolean isMergeableDefault() {
             if (product == null && lineItem != null) return false;
             if (coupon != null) return false;
 
-            boolean b = product.getType() == Product.Type.Article
+            return product.getType() == Product.Type.Article
                     && getUnit() != PIECE
                     && product.getPrice(cart.project.getCustomerCardId()) != 0
                     && scannedCode.getEmbeddedData() == 0
                     && !isUsingSpecifiedQuantity;
-            return b;
         }
 
         /**
@@ -1043,7 +1053,7 @@ public String getDisplayName() {
 
         /**
          * Gets text displaying quantity, can be a weight or price depending on the type
-         *
+         * <p>
          * E.g. "1" or "100g" or "2,03 €"
          */
         public String getQuantityText() {
@@ -1070,7 +1080,7 @@ public String getQuantityText() {
 
         /**
          * Gets text displaying price, including the calculation.
-         *
+         * <p>
          * E.g. "2 * 3,99 € = 7,98 €"
          */
         public String getFullPriceText() {
@@ -1115,7 +1125,7 @@ public String getTotalPriceText() {
 
         /**
          * Gets text displaying price, including the calculation.
-         *
+         * <p>
          * E.g. "3,99 €" or "2,99 € /kg = 0,47 €"
          */
         public String getPriceText() {
@@ -1530,13 +1540,16 @@ public void onTaxationChanged(ShoppingCart list, Taxation taxation) {
         }
 
         @Override
-        public void onCheckoutLimitReached(ShoppingCart list) {}
+        public void onCheckoutLimitReached(ShoppingCart list) {
+        }
 
         @Override
-        public void onOnlinePaymentLimitReached(ShoppingCart list) {}
+        public void onOnlinePaymentLimitReached(ShoppingCart list) {
+        }
 
         @Override
-        public void onViolationDetected(@NonNull List<ViolationNotification> violations) {}
+        public void onViolationDetected(@NonNull List<ViolationNotification> violations) {
+        }
 
         @Override
         public void onCartDataChanged(ShoppingCart list) {
@@ -1648,4 +1661,4 @@ private void notifyCleared(final ShoppingCart list) {
             }
         });
     }
-}
+}

core/src/main/java/io/snabble/sdk/Snabble.kt

@@ -17,6 +17,7 @@ import com.google.gson.JsonObject
 import io.snabble.sdk.auth.TokenRegistry
 import io.snabble.sdk.checkin.CheckInLocationManager
 import io.snabble.sdk.checkin.CheckInManager
+import io.snabble.sdk.customization.IsMergeable
 import io.snabble.sdk.payment.PaymentCredentialsStore
 import io.snabble.sdk.utils.*
 import okhttp3.OkHttpClient
@@ -36,6 +37,7 @@ import java.util.concurrent.atomic.AtomicBoolean
  * The heart of the snabble SDK. Initialization and object access is provided via this facade.
  */
 object Snabble {
+
     /**
      * Retrieve the global instance of snabble.
      *
@@ -303,7 +305,12 @@ object Snabble {
      */
     var error: Error? = null
         private set
-    
+
+    /**
+     * Set to take control over [ShoppingCart.Item.isMergeable] default behavior.
+     */
+    var isMergeable: IsMergeable? = null
+
     /**
      * Setup the snabble SDK.
      *
@@ -355,7 +362,8 @@ object Snabble {
         Logger.setLogEventHandler { message, args -> Events.logErrorEvent(null, message, *args) }
 
         if (!this.config.endpointBaseUrl.startsWith("http://")
-         && !this.config.endpointBaseUrl.startsWith("https://")) {
+            && !this.config.endpointBaseUrl.startsWith("https://")
+        ) {
             dispatchError(Error.CONFIG_ERROR)
             return
         }
@@ -382,14 +390,16 @@ object Snabble {
         paymentCredentialsStore = PaymentCredentialsStore()
 
         checkInLocationManager = CheckInLocationManager(application)
-        checkInManager = CheckInManager(this,
+        checkInManager = CheckInManager(
+            this,
             checkInLocationManager,
             this.config.checkInRadius,
             this.config.checkOutRadius,
             this.config.lastSeenThreshold
         )
 
-        metadataDownloader = MetadataDownloader(okHttpClient, this.config.bundledMetadataAssetPath, this.config.bundledMetadataRawResId)
+        metadataDownloader =
+            MetadataDownloader(okHttpClient, this.config.bundledMetadataAssetPath, this.config.bundledMetadataRawResId)
 
         if (this.config.bundledMetadataAssetPath != null || this.config.bundledMetadataRawResId != 0) {
             dispatchOnReady()
@@ -478,10 +488,12 @@ object Snabble {
 
     private fun registerNetworkCallback(app: Application) {
         val cm = app.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
-        cm.registerNetworkCallback(NetworkRequest.Builder()
-            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
-            .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR).build(),
-            networkCallback)
+        cm.registerNetworkCallback(
+            NetworkRequest.Builder()
+                .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
+                .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR).build(),
+            networkCallback
+        )
     }
 
     /**
@@ -708,6 +720,7 @@ object Snabble {
      * Interface for notifying when our metadata is getting updated
      */
     fun interface OnMetadataUpdateListener {
+
         /**
          * Gets called when our metadata has updated
          */
@@ -760,6 +773,7 @@ object Snabble {
      * Exception used for SDK initialization errors
      */
     class SnabbleException internal constructor(val error: Error?) : Exception() {
+
         override fun toString(): String {
             return "SnabbleException{" +
                     "error=" + error +
@@ -771,6 +785,7 @@ object Snabble {
      * Enum describing the error types, which can occur during initialization of the SDK
      */
     enum class Error {
+
         UNSPECIFIED_ERROR,
         NO_APPLICATION_SET,
         CONFIG_ERROR,
@@ -784,4 +799,4 @@ object Snabble {
     fun setDebugLoggingEnabled(enabled: Boolean) {
         Logger.setEnabled(enabled)
     }
-}
+}

core/src/main/java/io/snabble/sdk/customization/IsMergeable.kt

@@ -0,0 +1,12 @@
+package io.snabble.sdk.customization
+
+import io.snabble.sdk.ShoppingCart
+
+/**
+ * Implement the interface and set [Snabble.isMergeable] to make use of the
+ * custom ShoppingCart.Item.isMergeable implementation
+ */
+fun interface IsMergeable {
+
+    fun isMergeable(item: ShoppingCart.Item, isMergeable: Boolean): Boolean
+}