HARD

Author: Subham1999

.idea/workspace.xml

@@ -3,4 +3,7 @@
 /**
  * @author: Subham Santra
  */
-public abstract class BalanceSheet {}
+public abstract class BalanceSheet {
+
+  abstract void update(User paidBy, User borrower, Double amount);
+}

low-level-design/src/main/java/com/thealgorithm/splitwise/BalanceSheet.java

@@ -1,11 +1,13 @@
 package com.thealgorithm.splitwise;
 
+import lombok.AllArgsConstructor;
 import lombok.Data;
 
 /**
  * @author: Subham Santra
  */
 @Data
+@AllArgsConstructor
 public class BalanceSheetEntry {
   User owner;
   User other;

low-level-design/src/main/java/com/thealgorithm/splitwise/BalanceSheetEntry.java

@@ -3,14 +3,16 @@
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Data;
+import lombok.ToString;
 
 /**
  * @author: Subham Santra
  */
 @Data
+@ToString(onlyExplicitlyIncluded = true)
 public class Group {
-  String name;
-  List<User> users;
+  @ToString.Include String name;
+  @ToString.Include List<User> users;
   ResolverStrategy resolverStrategy;
   GroupBalanceSheet groupBalanceSheet;
   GroupExpenseValidator groupExpenseValidator;
@@ -21,6 +23,7 @@ public Group(String name) {
     resolverStrategy = null;
     groupBalanceSheet = new GroupBalanceSheet();
     groupExpenseValidator = new GroupExpenseValidator(this);
+    groupBalanceSheet.setGroup(this);
   }
 
   void changeDebtResolver(DebtResolverType debtResolverType) {
@@ -29,12 +32,27 @@ void changeDebtResolver(DebtResolverType debtResolverType) {
 
   void add(User user) {
     this.users.add(user);
+    this.getGroupBalanceSheet().add(user);
   }
 
   void add(Expense expense) throws UserIsNotPartOfGroupException, InvalidSplitException {
     groupExpenseValidator.validate(expense);
 
-    // add expense now
+    Double totalAmount = expense.getTotalAmount();
+    for (UserSplit eachUserSplit : expense.getUserSplits()) {
+      User user = eachUserSplit.getUser();
+      Double shareAmount = eachUserSplit.getShareAmount();
+      if (user.equals(expense.getPaidBy())) {
+        double totalGetBack =
+            user.getPersonalBalanceSheet().getTotalGetBack() + (totalAmount - shareAmount);
+        user.getPersonalBalanceSheet().setTotalGetBack(totalGetBack);
+      } else {
+        PersonalBalanceSheet personalBalanceSheet = user.getPersonalBalanceSheet();
+        Double totalOweAmount = personalBalanceSheet.getTotalOwe() + eachUserSplit.getShareAmount();
+        personalBalanceSheet.setTotalOwe(totalOweAmount);
+        groupBalanceSheet.update(expense.getPaidBy(), user, eachUserSplit.getShareAmount());
+      }
+    }
   }
 
   void resolve() throws OperationNotSupportedException {

low-level-design/src/main/java/com/thealgorithm/splitwise/Group.java

@@ -1,5 +1,6 @@
 package com.thealgorithm.splitwise;
 
+import java.util.HashMap;
 import java.util.Map;
 import lombok.Data;
 import lombok.EqualsAndHashCode;
@@ -10,5 +11,37 @@
 @Data
 @EqualsAndHashCode(callSuper = true)
 public class GroupBalanceSheet extends BalanceSheet {
-  Map<User, Map<User, BalanceSheetEntry>> balanceSheetEntryMap;
+  private Group group;
+  private Map<User, Map<User, BalanceSheetEntry>> balanceSheetEntryMap = new HashMap<>();
+
+  public void add(User user) {
+    balanceSheetEntryMap.put(user, new HashMap<>());
+  }
+
+  @Override
+  void update(User paidBy, User borrower, Double amount) {
+    update0(paidBy, borrower, amount);
+    update0(borrower, paidBy, -amount);
+  }
+
+  private void update0(User paidBy, User borrower, Double amount) {
+    Map<User, BalanceSheetEntry> paidUserBalanceSheet = balanceSheetEntryMap.get(paidBy);
+    paidUserBalanceSheet.putIfAbsent(borrower, new BalanceSheetEntry(paidBy, borrower, 0D));
+    paidUserBalanceSheet
+        .get(borrower)
+        .setAmount(paidUserBalanceSheet.get(borrower).getAmount() + amount);
+  }
+
+  public void print() {
+    System.out.println("SHOWING BALANCESHEET FOR " + group.name);
+    balanceSheetEntryMap.forEach(
+        (user, map) -> {
+          System.out.printf("BALANCE FOR %s\n", user);
+
+          map.forEach(
+              (u, e) -> {
+                System.out.printf("%s %s\n", u, e.getAmount());
+              });
+        });
+  }
 }

low-level-design/src/main/java/com/thealgorithm/splitwise/GroupBalanceSheet.java

@@ -37,12 +37,25 @@ public static void main(String[] args)
     picnicWala.add(
         Expense.builder()
             .paidBy(subham)
-            .totalAmount(100D)
+            .totalAmount(60D)
             .userSplits(
                 List.of(
-                    UserSplit.builder().user(subham).shareAmount(33D).build(),
-                    UserSplit.builder().user(shyam).shareAmount(33D).build(),
-                    UserSplit.builder().user(ram).shareAmount(34D).build()))
+                    UserSplit.builder().user(subham).shareAmount(20D).build(),
+                    UserSplit.builder().user(shyam).shareAmount(20D).build(),
+                    UserSplit.builder().user(ram).shareAmount(20D).build()))
             .build());
+
+    picnicWala.add(
+      Expense.builder()
+        .paidBy(shyam)
+        .totalAmount(60D)
+        .userSplits(
+          List.of(
+            UserSplit.builder().user(subham).shareAmount(20D).build(),
+            UserSplit.builder().user(shyam).shareAmount(20D).build(),
+            UserSplit.builder().user(ram).shareAmount(20D).build()))
+        .build());
+
+    picnicWala.getGroupBalanceSheet().print();
   }
 }

low-level-design/src/main/java/com/thealgorithm/splitwise/Main.java

@@ -1,5 +1,6 @@
 package com.thealgorithm.splitwise;
 
+import java.util.HashMap;
 import java.util.Map;
 import lombok.Data;
 
@@ -8,7 +9,12 @@
  */
 @Data
 public class PersonalBalanceSheet extends BalanceSheet {
-  Double totalOwe;
-  Double totalGetBack;
-  Map<User, BalanceSheetEntry> balanceSheetEntryMap; // otherUser --> entry
+  Double totalOwe = 0D;
+  Double totalGetBack = 0D;
+  Map<User, BalanceSheetEntry> balanceSheetEntryMap = new HashMap<>(); // otherUser --> entry
+
+  @Override
+  void update(User paidBy, User borrower, Double amount) {
+
+  }
 }

low-level-design/src/main/java/com/thealgorithm/splitwise/PersonalBalanceSheet.java

@@ -3,15 +3,22 @@
 import java.util.ArrayList;
 import java.util.List;
 import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
 
 /**
  * @author: Subham Santra
  */
 @Data
+@ToString(onlyExplicitlyIncluded = true)
+@EqualsAndHashCode(onlyExplicitlyIncluded = true)
 public class User {
-  String name;
-  List<Group> groups;
-  PersonalBalanceSheet personalBalanceSheet;
+  @EqualsAndHashCode.Include
+  @ToString.Include
+  private String name;
+  @ToString.Include
+  private List<Group> groups;
+  private PersonalBalanceSheet personalBalanceSheet;
 
   public User(String name) {
     this.name = name;