BE-#94: Working on calculation

backend/src/main/java/com/dhbw/get2gether/backend/widget/model/expensesplit/Dept.java

@@ -0,0 +1,15 @@
+package com.dhbw.get2gether.backend.widget.model.expensesplit;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Builder
+@Getter
+@NoArgsConstructor
+@AllArgsConstructor
+public class Dept {
+    private String userId;
+    private double deptAmount;
+}

backend/src/main/java/com/dhbw/get2gether/backend/widget/model/expensesplit/ExpenseSplitWidget.java

@@ -9,6 +9,8 @@
 import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
 
 @Builder(toBuilder = true)
 @Getter
@@ -40,5 +42,47 @@ public boolean replaceEntry(ExpenseEntry oldEntry, ExpenseEntry newEntry) {
         entries.set(index, newEntry);
         return true;
     }
+
+    public List<Dept> calculateDeptsForUserId(String userId){
+        List<Dept> depts = new ArrayList<>();
+        for(ExpenseEntry expenseEntry : entries){
+            if(expenseEntry.getCreatorId().equals(userId)){
+                // Add every involved user except the buyer to List of dept
+                for(UserWithPercentage userWithPercentage: expenseEntry.getInvolvedUsers()){
+                    if(!Objects.equals(userWithPercentage.getUserId(), userId)){
+                        depts = addDept(depts, userWithPercentage.getUserId(), expenseEntry.getPrice()*userWithPercentage.getPercentage());
+                    }
+                }
+            } else {
+                Optional<UserWithPercentage> userWithPercentage = expenseEntry.getInvolvedUsers().stream()
+                        .findFirst().filter(user -> user.getUserId().equals(userId));
+                if(userWithPercentage.isPresent()){
+                    // Add the Dept of the user to the Dept List
+                    // In this case the user for whom we calculate all depts is a involved user and not the payer
+                    depts = addDept(depts, expenseEntry.getCreatorId(), expenseEntry.getPrice()*userWithPercentage.get().getPercentage()*-1.0);
+                }
+            }
+        }
+        return depts;
+    }
+
+    // This method extracts the logic if the deptor is already in the list or not
+    private List<Dept> addDept(List<Dept> depts, String debtorId, double deptAmount){
+        Optional<Dept> optionalDept = depts.stream().findFirst()
+                .filter(dept -> dept.getUserId().equals(debtorId));
+        // todo somehow in second entry with second user this optional is empty but should not be
+
+        if(optionalDept.isPresent()){
+            // Calculate new deptAmount if already exists
+            Dept newDept = new Dept(debtorId, optionalDept.get().getDeptAmount()+deptAmount);
+            int index = depts.indexOf(optionalDept.get());
+            depts.set(index, newDept);
+
+        } else {
+            // Add new dept if not exists already
+            depts.add(new Dept(debtorId, deptAmount));
+        }
+        return depts;
+    }
 }
 

backend/src/test/java/com/dhbw/get2gether/backend/widget/application/ExpenseSplitWidgetServiceTest.java

@@ -178,6 +178,60 @@ void shouldAddEntry() {
         assertThat(returnedWidget.getEntries().get(0).getId()).isNotBlank();
     }
 
+    @Test
+    @WithMockOAuth2User
+    void shouldCalculateDeptsCorrectly(){
+        // given
+        UserWithPercentage mainUser = UserWithPercentage.builder()
+                .userId("test")
+                .percentage(0.25)
+                .build();
+        UserWithPercentage user2 = UserWithPercentage.builder()
+                .userId("user2")
+                .percentage(0.25)
+                .build();
+        UserWithPercentage user3 = UserWithPercentage.builder()
+                .userId("user3")
+                .percentage(0.25)
+                .build();
+        UserWithPercentage user4 = UserWithPercentage.builder()
+                .userId("user4")
+                .percentage(0.25)
+                .build();
+        ExpenseEntry entry1 = ExpenseEntry.builder()
+                .id("1")
+                .price(10)
+                .description("Bier")
+                .creatorId("test")
+                .involvedUsers(List.of(mainUser, user2, user3, user4))
+                .build();
+        ExpenseEntry entry2 = ExpenseEntry.builder()
+                .id("2")
+                .price(20)
+                .description("Bier2")
+                .creatorId("test")
+                .involvedUsers(List.of(mainUser, user2, user3, user4))
+                .build();
+
+        ExpenseSplitWidget widget = ExpenseSplitWidget.builder()
+                .id("wi-123")
+                .entries(List.of(entry1, entry2))
+                .build();
+
+        // when
+        List<Dept> depts = widget.calculateDeptsForUserId(mainUser.getUserId());
+
+        // then
+        assertThat(depts.get(0).getUserId()).isEqualTo(user2.getUserId());
+        assertThat(depts.get(0).getDeptAmount()).isEqualTo(user2.getPercentage()*entry1.getPrice()+user2.getPercentage()*entry2.getPrice());
+        assertThat(depts.get(1).getUserId()).isEqualTo(user3.getUserId());
+        assertThat(depts.get(1).getDeptAmount()).isEqualTo(user3.getPercentage()*entry1.getPrice()+user3.getPercentage()*entry2.getPrice());
+        assertThat(depts.get(2).getUserId()).isEqualTo(user4.getUserId());
+        assertThat(depts.get(2).getDeptAmount()).isEqualTo(user4.getPercentage()*entry1.getPrice()+user4.getPercentage()*entry2.getPrice());
+        assertThat(depts.size()==3).isTrue();
+    }
+
+
 //    @Test
 //    @WithMockGuestUser
 //    void shouldNotAddEntryIfUserIsGuest() {