feat: ensure tier ranges does not overlap

Author: adrianliz

exercises/tiered_pricing/solutions/adrianliz/java/src/main/java/tv/codely/checkout/SubscriptionTier.java

@@ -1,5 +1,7 @@
 package tv.codely.checkout;
 
+import java.util.Objects;
+
 public final class SubscriptionTier {
 
     private final SubscriptionTierRange range;
@@ -21,6 +23,10 @@ public boolean isLast() {
         return range.isLast();
     }
 
+    public boolean isAfter(final SubscriptionTier other) {
+        return range.isAfter(other.range);
+    }
+
     public boolean isInRange(int numberOfSubscriptions) {
         return this.range.isSuitableFor(numberOfSubscriptions);
     }
@@ -32,4 +38,21 @@ public double unitPrice() {
     public double getTotalPrice(int numberOfSubscriptions) {
         return unitPrice() * numberOfSubscriptions;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        SubscriptionTier that = (SubscriptionTier) o;
+        return Objects.equals(range, that.range) && Objects.equals(price, that.price);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(range, price);
+    }
 }

exercises/tiered_pricing/solutions/adrianliz/java/src/main/java/tv/codely/checkout/SubscriptionTierPrice.java

@@ -1,5 +1,7 @@
 package tv.codely.checkout;
 
+import java.util.Objects;
+
 public final class SubscriptionTierPrice {
 
     private final double value;
@@ -11,4 +13,21 @@ public SubscriptionTierPrice(double value) {
     public double unitPrice() {
         return value;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        SubscriptionTierPrice that = (SubscriptionTierPrice) o;
+        return Double.compare(that.value, value) == 0;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(value);
+    }
 }

exercises/tiered_pricing/solutions/adrianliz/java/src/main/java/tv/codely/checkout/SubscriptionTierRange.java

@@ -1,5 +1,7 @@
 package tv.codely.checkout;
 
+import java.util.Objects;
+
 public final class SubscriptionTierRange {
 
     private final int numberOfSubscriptionsFrom;
@@ -10,6 +12,10 @@ public SubscriptionTierRange(int numberOfSubscriptionsFrom, int numberOfSubscrip
         this.numberOfSubscriptionsTo = numberOfSubscriptionsTo;
     }
 
+    public static SubscriptionTierRange first(int numberOfSubscriptionsTo) {
+        return new SubscriptionTierRange(1, numberOfSubscriptionsTo);
+    }
+
     public static SubscriptionTierRange last(int numberOfSubscriptionsFrom) {
         return new SubscriptionTierRange(numberOfSubscriptionsFrom, Integer.MAX_VALUE);
     }
@@ -22,8 +28,30 @@ public boolean isLast() {
         return numberOfSubscriptionsTo == Integer.MAX_VALUE;
     }
 
+    public boolean isAfter(final SubscriptionTierRange other) {
+        return numberOfSubscriptionsFrom > other.numberOfSubscriptionsTo;
+    }
+
     public boolean isSuitableFor(int numberOfSubscriptions) {
         return numberOfSubscriptions >= numberOfSubscriptionsFrom
             && numberOfSubscriptions <= numberOfSubscriptionsTo;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        SubscriptionTierRange that = (SubscriptionTierRange) o;
+        return numberOfSubscriptionsFrom == that.numberOfSubscriptionsFrom
+            && numberOfSubscriptionsTo == that.numberOfSubscriptionsTo;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(numberOfSubscriptionsFrom, numberOfSubscriptionsTo);
+    }
 }

exercises/tiered_pricing/solutions/adrianliz/java/src/main/java/tv/codely/checkout/SubscriptionTiers.java

@@ -1,5 +1,6 @@
 package tv.codely.checkout;
 
+import java.util.HashSet;
 import java.util.List;
 
 public final class SubscriptionTiers {
@@ -23,6 +24,20 @@ private static void validate(final List<SubscriptionTier> tiers) {
         if (tiers.stream().noneMatch(SubscriptionTier::isLast)) {
             throw new InvalidSubscriptionTiers("There must be a last subscription tier");
         }
+
+        if (tiers.size() == 1) {
+            return;
+        }
+
+        final var validTiers = new HashSet<SubscriptionTier>();
+        for (final SubscriptionTier tier : tiers) {
+            if (tiers.stream()
+                .anyMatch(
+                    t -> !validTiers.contains(t) && !t.equals(tier) && !t.isAfter(tier))) {
+                throw new InvalidSubscriptionTiers("All tiers must be after the previous one");
+            }
+            validTiers.add(tier);
+        }
     }
 
     private SubscriptionTier findSuitableTier(int subscriptions) {

exercises/tiered_pricing/solutions/adrianliz/java/src/test/java/tv/codely/checkout/TieredPricingShould.java

@@ -17,7 +17,7 @@ public class TieredPricingShould {
     private static List<SubscriptionTier> defaultSubscriptionTiers() {
         return List.of(
             new SubscriptionTier(
-                new SubscriptionTierRange(1, 2),
+                SubscriptionTierRange.first(2),
                 new SubscriptionTierPrice(299)),
             new SubscriptionTier(
                 new SubscriptionTierRange(3, 10),
@@ -130,4 +130,17 @@ void throw_invalid_subscription_tiers_if_there_is_no_last_tier() {
 
         assertThrows(InvalidSubscriptionTiers.class, () -> new TieredPricing(subscriptionTiers));
     }
+
+    @Test
+    void throw_invalid_subscription_tiers_if_tiers_are_not_in_order() {
+        final var subscriptionTiers =
+            List.of(SubscriptionTierMother.create(SubscriptionTierRangeMother.first(10),
+                    SubscriptionTierPriceMother.random()),
+                SubscriptionTierMother.create(SubscriptionTierRangeMother.create(9, 20),
+                    SubscriptionTierPriceMother.random()),
+                SubscriptionTierMother.create(SubscriptionTierRangeMother.last(2),
+                    SubscriptionTierPriceMother.random()));
+
+        assertThrows(InvalidSubscriptionTiers.class, () -> new TieredPricing(subscriptionTiers));
+    }
 }

exercises/tiered_pricing/solutions/adrianliz/java/src/test/java/tv/codely/checkout/mother/SubscriptionTierRangeMother.java

@@ -13,6 +13,10 @@ public static SubscriptionTierRange create(
         return new SubscriptionTierRange(numberOfSubscriptionsFrom, numberOfSubscriptionsTo);
     }
 
+    public static SubscriptionTierRange first(final int numberOfSubscriptionsTo) {
+        return SubscriptionTierRange.first(numberOfSubscriptionsTo);
+    }
+
     public static SubscriptionTierRange last(final int numberOfSubscriptionsFrom) {
         return SubscriptionTierRange.last(numberOfSubscriptionsFrom);
     }