Splitwise: Solved the problem

README.md

@@ -3,3 +3,8 @@ Welcome to the 2nd Mock Machine Coding Round by [workat.tech](http://workat.tech
 
 Please visit [this link](https://workat.tech/machine-coding/practice/splitwise-problem-0kp2yneec2q2) to participate.
 
+Compile and package:
+mvn clean package
+
+Run
+java -jar target/splitwise-1.0-SNAPSHOT.jar

pom.xml

@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>mc-prep</artifactId>
+        <groupId>com.sameerpandit</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>splitwise</artifactId>
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+        <main>com.sameerpandit.Main</main>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.glassfish.hk2</groupId>
+            <artifactId>hk2-locator</artifactId>
+            <version>3.0.2</version>
+        </dependency>
+    </dependencies>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.2.4</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <transformers>
+                                <transformer
+                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>${main}</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.glassfish.hk2</groupId>
+                <artifactId>hk2-inhabitant-generator</artifactId>
+                <version>3.0.2</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>generate-inhabitants</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

src/main/java/com/sameerpandit/Driver.java

@@ -0,0 +1,76 @@
+package com.sameerpandit;
+
+import com.sameerpandit.db.InMemRepository;
+
+import org.jvnet.hk2.annotations.Service;
+
+import jakarta.inject.Inject;
+
+@Service
+public class Driver {
+    @Inject
+    Splitwise splitwise;
+    @Inject
+    InMemRepository repository;
+    public void run(){
+        System.out.println("Running Driver");
+        test1();
+        repository.clear();
+        test2();
+    }
+
+    public void test1(){
+        System.out.println("------------------------------------------------------");
+        String user1 = splitwise.addUser("User1", "user1@gmail.com", "9986368688");
+        String user2 = splitwise.addUser("User2", "user2@gmail.com", "9986368689");
+        String user3 = splitwise.addUser("User3", "user3@gmail.com", "9986368682");
+        String user4 = splitwise.addUser("User4", "user4@gmail.com", "9986368683");
+        splitwise.show();
+//        System.out.println("------------------------------------------------------");
+        splitwise.show(user1);
+//        System.out.println("------------------------------------------------------");
+        //EXPENSE u1 1000 4 u1 u2 u3 u4 EQUAL
+        splitwise.addExpense(1000,"EQUAL",user1, new String[]{user1, user2, user3,user4});
+        splitwise.show(user4);
+//        System.out.println("------------------------------------------------------");
+        splitwise.show(user1);
+//        System.out.println("------------------------------------------------------");
+        //EXPENSE u1 1250 2 u2 u3 EXACT 370 880
+        splitwise.addExpense(1250,"EXACT",user1, new String[]{user1, user2, user3}, new Integer[]{0, 370, 880});
+        splitwise.show();
+//        System.out.println("------------------------------------------------------");
+        //EXPENSE u4 1200 4 u1 u2 u3 u4 PERCENT 40 20 20 20
+        splitwise.addExpense(1200,"PERCENT",user4, new String[]{user1, user2, user3, user4}, new Integer[]{40, 20, 20, 20});
+        splitwise.show(user1);
+//        System.out.println("------------------------------------------------------");
+        splitwise.show();
+//        System.out.println("------------------------------------------------------");
+    }
+
+    public void test2(){
+        System.out.println("------------------------------------------------------");
+        String user1 = splitwise.addUser("User1", "user1@gmail.com", "9986368688");
+        String user2 = splitwise.addUser("User2", "user2@gmail.com", "9986368689");
+        String user3 = splitwise.addUser("User3", "user3@gmail.com", "9986368682");
+        splitwise.show();
+        //        System.out.println("------------------------------------------------------");
+        splitwise.show(user1);
+        //        System.out.println("------------------------------------------------------");
+        //EXPENSE u1 1000 4 u1 u2 u3 u4 EQUAL
+        splitwise.addExpense(1000,"EQUAL",user1, new String[]{user1, user2, user3});
+        splitwise.show(user3);
+        //        System.out.println("------------------------------------------------------");
+        splitwise.show(user1);
+        //        System.out.println("------------------------------------------------------");
+        //EXPENSE u1 1250 2 u2 u3 EXACT 370 880
+        splitwise.addExpense(1250,"EXACT",user1, new String[]{user1, user2,user3 }, new Integer[]{0, 370, 880});
+        splitwise.show();
+        //        System.out.println("------------------------------------------------------");
+        //EXPENSE u4 1200 4 u1 u2 u3 u4 PERCENT 40 20 20 20
+        splitwise.addExpense(1200,"PERCENT",user3, new String[]{user1, user2, user3}, new Integer[]{60, 20, 20});
+        splitwise.show(user1);
+        //        System.out.println("------------------------------------------------------");
+        splitwise.show();
+        //        System.out.println("------------------------------------------------------");
+    }
+}

src/main/java/com/sameerpandit/Main.java

@@ -0,0 +1,12 @@
+package com.sameerpandit;
+
+import org.glassfish.hk2.api.ServiceLocator;
+import org.glassfish.hk2.utilities.ServiceLocatorUtilities;
+
+public class Main {
+    public static void main(String[] args){
+        ServiceLocator locator = ServiceLocatorUtilities.createAndPopulateServiceLocator();
+        Driver driver = locator.getService(Driver.class);
+        driver.run();
+    }
+}

src/main/java/com/sameerpandit/Splitwise.java

@@ -0,0 +1,38 @@
+package com.sameerpandit;
+
+import com.sameerpandit.service.ExpenseManagerService;
+import com.sameerpandit.service.UserService;
+
+import org.jvnet.hk2.annotations.Service;
+
+import jakarta.inject.Inject;
+
+@Service
+public class Splitwise {
+
+    @Inject
+    ExpenseManagerService expenseManagerService;
+
+    @Inject
+    UserService userService;
+
+    public String  addUser(String name, String email, String phone) {
+        return userService.addUser(name,email,phone);
+    }
+
+    public void addExpense(Integer amount, String type, String initiatorId, String[] participants){
+        expenseManagerService.addExpense(amount,type,initiatorId,participants);
+    }
+
+    public void addExpense(Integer amount, String type, String initiatorId, String[] participants, Integer[] splits){
+        expenseManagerService.addExpense(amount,type,initiatorId,participants,splits);
+    }
+
+    public void show(){
+        expenseManagerService.show();
+    }
+
+    public void show(String userId){
+        expenseManagerService.show(userId);
+    }
+}

src/main/java/com/sameerpandit/business/Constants.java

@@ -0,0 +1,6 @@
+package com.sameerpandit.business;
+
+public class Constants {
+    public static Integer PERCENT_SCALE = 100;
+    public static Integer EXPENSE_SCALING_FACTOR = 100;
+}

src/main/java/com/sameerpandit/business/EqualSplitStrategy.java

@@ -0,0 +1,33 @@
+package com.sameerpandit.business;
+
+import com.sameerpandit.models.Expense;
+
+import org.jvnet.hk2.annotations.Service;
+
+import jakarta.inject.Named;
+
+@Service
+@Named("EQUAL")
+public class EqualSplitStrategy  implements  SplitStrategy{
+    @Override
+    public Integer[] split(Expense expense) {
+        int amountUnScaled = expense.getUnscaledAmount();
+        int totalParts = (expense.getParticipants().length);
+        boolean cleanSplit = (amountUnScaled%totalParts == 0);
+        Integer[] splitAmounts = new Integer[totalParts];
+        int start = 0;
+        if(!cleanSplit){
+            while(amountUnScaled!=0){
+                int part = amountUnScaled/(totalParts-start);
+                splitAmounts[start] = part;
+                amountUnScaled-=part;
+                start++;
+            }
+        }else{
+            for(;start<splitAmounts.length;start++){
+                splitAmounts[start] = (amountUnScaled/totalParts);
+            }
+        }
+        return splitAmounts;
+    }
+}

src/main/java/com/sameerpandit/business/ExactStrategy.java

@@ -0,0 +1,17 @@
+package com.sameerpandit.business;
+
+import com.sameerpandit.models.Expense;
+
+import org.jvnet.hk2.annotations.Service;
+
+import jakarta.inject.Named;
+
+@Service
+@Named("EXACT")
+public class ExactStrategy implements SplitStrategy {
+
+    @Override
+    public Integer[] split(Expense expense) {
+        return expense.getUnscaledSplitAmounts();
+    }
+}

src/main/java/com/sameerpandit/business/PercentSplitStrategy.java

@@ -0,0 +1,26 @@
+package com.sameerpandit.business;
+
+import com.sameerpandit.models.Expense;
+
+import org.jvnet.hk2.annotations.Service;
+
+import jakarta.inject.Named;
+
+@Service
+@Named("PERCENT")
+public class PercentSplitStrategy implements SplitStrategy {
+    @Override
+    public Integer[] split(Expense expense) {
+        int amountUnScaled = expense.getUnscaledAmount();
+        int totalParts = (expense.getParticipants().length);
+        Integer[] splitUnscaledPercentages = expense.getSplitPercentages();
+        Integer[] splitAmounts = new Integer[totalParts];
+        int total = 0;
+        for (int i = 0; i < splitAmounts.length; i++) {
+            splitAmounts[i] = (splitUnscaledPercentages[i] * amountUnScaled) / Constants.PERCENT_SCALE;
+            total += splitAmounts[i];
+        }
+        splitAmounts[0] += (amountUnScaled - total);
+        return splitAmounts;
+    }
+}

src/main/java/com/sameerpandit/business/SplitStrategy.java

@@ -0,0 +1,10 @@
+package com.sameerpandit.business;
+
+import com.sameerpandit.models.Expense;
+
+import org.jvnet.hk2.annotations.Contract;
+
+@Contract
+public interface SplitStrategy {
+    public Integer[] split(Expense expense);
+}

src/main/java/com/sameerpandit/business/validator/ExpenseConfigurationValidator.java

@@ -0,0 +1,4 @@
+package com.sameerpandit.business.validator;
+
+public class ExpenseConfigurationValidator {
+}

src/main/java/com/sameerpandit/db/InMemRepository.java

@@ -0,0 +1,82 @@
+package com.sameerpandit.db;
+
+import com.sameerpandit.models.Expense;
+import com.sameerpandit.models.Transaction;
+import com.sameerpandit.models.User;
+
+import org.jvnet.hk2.annotations.Service;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import jakarta.inject.Singleton;
+
+@Service
+@Singleton
+public class InMemRepository {
+    private ConcurrentHashMap<String, List<Transaction>> creditorMap         = new ConcurrentHashMap<>();
+    private ConcurrentHashMap<String, List<Transaction>> debitorMap          = new ConcurrentHashMap<>();
+    private ConcurrentHashMap<String, User>              userMap             = new ConcurrentHashMap<>();
+    private ConcurrentHashMap<String, List<Expense>>     expenseInitiatorMap = new ConcurrentHashMap<>();
+    private AtomicInteger                                userIdNumber        = new AtomicInteger(0);
+
+    public void clear(){
+        creditorMap         = new ConcurrentHashMap<>();
+        debitorMap          = new ConcurrentHashMap<>();
+        userMap             = new ConcurrentHashMap<>();
+        expenseInitiatorMap = new ConcurrentHashMap<>();
+        userIdNumber        = new AtomicInteger(0);
+    }
+
+    public List<Transaction> getCreditTransactionsByUserId(String userId) {
+        return creditorMap.getOrDefault(userId, new LinkedList<>());
+    }
+
+    public List<Transaction> getDebitTransactionsByUserId(String userId) {
+        return debitorMap.getOrDefault(userId, new LinkedList<>());
+    }
+
+    public List<Expense> getExpensesInitiatedByUserId(String userId) {
+        return expenseInitiatorMap.get(userId);
+    }
+
+    public User getUserDetailsById(String userId) {
+        return userMap.get(userId);
+    }
+
+    public List<User> getUsers(){
+        LinkedList<User> users = new LinkedList<>();
+        users.addAll(userMap.values());
+        return users;
+    }
+
+    public String addUser(String name, String email, String phone) {
+        String userId = "u" + userIdNumber.incrementAndGet();
+        userMap.put(userId, new User(userId, name, email, phone));
+        return userId;
+    }
+
+    public Expense addExpense(Integer amount, String type, String initiatorId, String[] participants) {
+        Expense expense = new Expense(amount, type, initiatorId, participants);
+        expenseInitiatorMap.computeIfAbsent(initiatorId, k -> new LinkedList<>()).add(expense);
+        return expense;
+    }
+
+    public Expense addExpense(Integer amount, String type, String initiatorId, String[] participants, Integer[] splits) {
+        Expense expense = new Expense(amount, type, initiatorId, participants,splits);
+        expenseInitiatorMap.computeIfAbsent(initiatorId, k -> new LinkedList<>()).add(expense);
+        return expense;
+    }
+
+
+    public void addCreditorTransaction(String creditorId, Transaction tx) {
+        creditorMap.computeIfAbsent(creditorId, k -> new LinkedList<>()).add(tx);
+    }
+
+    public void addDebitorTransaction(String debitorId, Transaction tx) {
+        debitorMap.computeIfAbsent(debitorId, k -> new LinkedList<>()).add(tx);
+    }
+
+}