Added solution

report.csv

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+fruit,quantity
+apple,160
+banana,115
+pear,140

src/main/java/core/basesyntax/Main.java

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+package core.basesyntax;
+
+import core.basesyntax.model.FruitTransaction;
+import core.basesyntax.service.FileReader;
+import core.basesyntax.service.FileReaderImpl;
+import core.basesyntax.service.ParseService;
+import core.basesyntax.service.ParseServiceImpl;
+import core.basesyntax.service.PurchaseOperationHandler;
+import core.basesyntax.service.RemnantOperationHandler;
+import core.basesyntax.service.ReportService;
+import core.basesyntax.service.ReportServiceImpl;
+import core.basesyntax.service.SupplyOperationHandler;
+import core.basesyntax.strategy.OperationStrategy;
+import core.basesyntax.strategy.OperationStrategyImpl;
+import java.io.File;
+import java.net.URL;
+import java.util.HashMap;
+import java.util.List;
+
+public class Main {
+    private static final String[] FILE_NAMES =
+            new String[]{"input1.csv", "input2.csv", "input3.csv"};
+
+    public static void main(String[] args) {
+        FileReader fileReader = new FileReaderImpl();
+        ParseService parseService = new ParseServiceImpl();
+        ReportService reportService = new ReportServiceImpl();
+        OperationStrategy operationStrategy = new OperationStrategyImpl(new HashMap<>() {{
+                put(FruitTransaction.Operation.BALANCE, new RemnantOperationHandler());
+                put(FruitTransaction.Operation.PURCHASE, new PurchaseOperationHandler());
+                put(FruitTransaction.Operation.RETURN, new SupplyOperationHandler());
+                put(FruitTransaction.Operation.SUPPLY, new SupplyOperationHandler());
+                }}
+        );
+        ClassLoader classLoader = Main.class.getClassLoader();
+        for (String fileName : FILE_NAMES) {
+            URL resources = classLoader.getResource(fileName);
+            List<FruitTransaction> fruitTransactions = parseService.parse(
+                    fileReader.readFromFile(new File(resources.getFile())));
+            for (FruitTransaction fruitTransaction : fruitTransactions) {
+                operationStrategy
+                        .get(fruitTransaction.getOperation())
+                        .handle(fruitTransaction.getFruit(), fruitTransaction.getQuantity());
+            }
+            System.out.println(reportService.generateReport() + System.lineSeparator());
+        }
+    }
+}

src/main/java/core/basesyntax/dao/FruitDao.java

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+package core.basesyntax.dao;
+
+public interface FruitDao {
+    void add(String name, int quantity);
+
+    void set(String name, int quantity);
+
+    void remove(String name, int quantity);
+}

src/main/java/core/basesyntax/dao/FruitDaoImpl.java

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+package core.basesyntax.dao;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class FruitDaoImpl implements FruitDao {
+    private static final Map<String, Integer> fruits = new HashMap<>();
+
+    public static Map<String, Integer> getFruits() {
+        Map<String, Integer> fruitsCopy = new HashMap<>();
+        for (String key : fruits.keySet()) {
+            fruitsCopy.put(key, fruits.get(key));
+
+        }
+        return fruitsCopy;
+    }
+
+    @Override
+    public void add(String name, int quantity) {
+        if (quantity < 0) {
+            throw new RuntimeException("Cannot add such quantity: " + quantity);
+        }
+        int currentAmount = fruits.getOrDefault(name, 0);
+        fruits.put(name, currentAmount + quantity);
+    }
+
+    @Override
+    public void remove(String name, int quantity) {
+        if (fruits.get(name) < quantity) {
+            throw new RuntimeException("Not enough " + name + " to purchase");
+        }
+        fruits.put(name, fruits.get(name) - quantity);
+    }
+
+    @Override
+    public void set(String name, int quantity) {
+        if (quantity < 0) {
+            throw new RuntimeException("Cannot put such quantity: " + quantity);
+        }
+        fruits.put(name, quantity);
+    }
+}

src/main/java/core/basesyntax/model/FruitTransaction.java

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+package core.basesyntax.model;
+
+import java.util.NoSuchElementException;
+import java.util.Objects;
+
+public class FruitTransaction {
+    private Operation operation;
+    private String fruit;
+    private int quantity;
+
+    public FruitTransaction(String fruit, int quantity, Operation operation) {
+        this.fruit = fruit;
+        this.quantity = quantity;
+        this.operation = operation;
+    }
+
+    public Operation getOperation() {
+        return operation;
+    }
+
+    public void setOperation(Operation operation) {
+        this.operation = operation;
+    }
+
+    public String getFruit() {
+        return fruit;
+    }
+
+    public void setFruit(String fruit) {
+        this.fruit = fruit;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public void setQuantity(int quantity) {
+        this.quantity = quantity;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || obj.getClass() != FruitTransaction.class) {
+            return false;
+        }
+        FruitTransaction fruitTransaction = (FruitTransaction) obj;
+        return Objects.equals(this.fruit, fruitTransaction.fruit)
+                && Objects.equals(this.quantity, fruitTransaction.quantity)
+                && Objects.equals(this.operation, fruitTransaction.operation);
+    }
+
+    public enum Operation {
+        BALANCE("b"),
+        SUPPLY("s"),
+        PURCHASE("p"),
+        RETURN("r");
+
+        private final String operation;
+
+        Operation(String operation) {
+            this.operation = operation;
+        }
+
+        public String getOperation() {
+            return operation;
+        }
+
+        public static Operation getByCode(String code) {
+            for (Operation operation : values()) {
+                if (operation.getOperation().equals(code)) {
+                    return operation;
+                }
+            }
+            throw new NoSuchElementException("Unknown operation: " + code);
+        }
+    }
+}

src/main/java/core/basesyntax/service/FileReader.java

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+package core.basesyntax.service;
+
+import java.io.File;
+import java.util.List;
+
+public interface FileReader {
+    List<String> readFromFile(File file);
+}

src/main/java/core/basesyntax/service/FileReaderImpl.java

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+
+public class FileReaderImpl implements FileReader {
+    private static final String SEPARATOR = ",";
+    private static final int HEADER_INDEX = 0;
+    private static final int OPERATION_INDEX = 0;
+    private static final int FRUIT_INDEX = 1;
+    private static final int AMOUNT_INDEX = 2;
+
+    @Override
+    public List<String> readFromFile(File file) {
+        ArrayList<FruitTransaction> fruitTransactions = new ArrayList<>();
+        try {
+            return Files.readAllLines(file.toPath());
+        } catch (IOException ioException) {
+            throw new RuntimeException("Cannot read data from file: " + file, ioException);
+        }
+    }
+}

src/main/java/core/basesyntax/service/FileWriter.java

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+package core.basesyntax.service;
+
+import java.io.File;
+
+public interface FileWriter {
+    void writeToFile(File file, String report);
+}

src/main/java/core/basesyntax/service/FileWriterImpl.java

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+package core.basesyntax.service;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
+public class FileWriterImpl implements core.basesyntax.service.FileWriter {
+    @Override
+    public void writeToFile(File file, String report) {
+        try (BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(file))) {
+            bufferedWriter.write(report);
+        } catch (IOException ioException) {
+            throw new RuntimeException("Cannot write data to file: " + file, ioException);
+        }
+    }
+}

src/main/java/core/basesyntax/service/OperationHandler.java

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+package core.basesyntax.service;
+
+public interface OperationHandler {
+    void handle(String name, int amount);
+}

src/main/java/core/basesyntax/service/ParseService.java

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.List;
+
+public interface ParseService {
+    List<FruitTransaction> parse(List<String> fruits);
+}

src/main/java/core/basesyntax/service/ParseServiceImpl.java

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+public class ParseServiceImpl implements ParseService {
+    private static final String SEPARATOR = ",";
+    private static final int HEADER_INDEX = 0;
+    private static final int OPERATION_INDEX = 0;
+    private static final int FRUIT_INDEX = 1;
+    private static final int AMOUNT_INDEX = 2;
+
+    @Override
+    public List<FruitTransaction> parse(List<String> fruits) {
+        ArrayList<FruitTransaction> fruitTransactions = new ArrayList<>();
+        fruits.remove(HEADER_INDEX);
+        for (String fruit : fruits) {
+            String[] parsedFruit = fruit.split(SEPARATOR);
+            try {
+                int amount = Integer.parseInt(parsedFruit[AMOUNT_INDEX]);
+                if (amount < 0) {
+                    throw new NumberFormatException();
+                }
+                FruitTransaction.Operation operation
+                        = FruitTransaction.Operation.getByCode(parsedFruit[OPERATION_INDEX]);
+                fruitTransactions.add(new FruitTransaction(parsedFruit[FRUIT_INDEX],
+                        amount, operation));
+            } catch (NumberFormatException numberFormatException) {
+                throw new RuntimeException("Invalid amount: " + parsedFruit[AMOUNT_INDEX],
+                        numberFormatException);
+            } catch (NoSuchElementException noSuchElementException) {
+                throw new RuntimeException("No such operation code: "
+                        + parsedFruit[OPERATION_INDEX],
+                        noSuchElementException);
+            }
+        }
+        return fruitTransactions;
+    }
+}

src/main/java/core/basesyntax/service/PurchaseOperationHandler.java

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+package core.basesyntax.service;
+
+import core.basesyntax.dao.FruitDao;
+import core.basesyntax.dao.FruitDaoImpl;
+
+public class PurchaseOperationHandler implements OperationHandler {
+    private FruitDao fruitDao = new FruitDaoImpl();
+
+    @Override
+    public void handle(String name, int amount) {
+        fruitDao.remove(name, amount);
+    }
+}

src/main/java/core/basesyntax/service/RemnantOperationHandler.java

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+package core.basesyntax.service;
+
+import core.basesyntax.dao.FruitDao;
+import core.basesyntax.dao.FruitDaoImpl;
+
+public class RemnantOperationHandler implements OperationHandler {
+    private FruitDao fruitDao = new FruitDaoImpl();
+
+    @Override
+    public void handle(String name, int amount) {
+        fruitDao.set(name, amount);
+    }
+}

src/main/java/core/basesyntax/service/ReportService.java

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+package core.basesyntax.service;
+
+public interface ReportService {
+    public String generateReport();
+}

src/main/java/core/basesyntax/service/ReportServiceImpl.java

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+package core.basesyntax.service;
+
+import core.basesyntax.dao.FruitDaoImpl;
+import java.util.TreeSet;
+
+public class ReportServiceImpl implements ReportService {
+    private static final String SEPARATOR = ",";
+    private static final String HEADER = "fruit,quantity";
+    private FruitDaoImpl fruitDao = new FruitDaoImpl();
+
+    @Override
+    public String generateReport() {
+        StringBuilder stringBuilder = new StringBuilder(HEADER);
+        for (String key : new TreeSet<>(fruitDao.getFruits().keySet())) {
+            stringBuilder.append(System.lineSeparator())
+                    .append(key)
+                    .append(SEPARATOR).append(fruitDao.getFruits().get(key));
+        }
+        return stringBuilder.toString();
+    }
+}

src/main/java/core/basesyntax/service/SupplyOperationHandler.java

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+package core.basesyntax.service;
+
+import core.basesyntax.dao.FruitDao;
+import core.basesyntax.dao.FruitDaoImpl;
+
+public class SupplyOperationHandler implements OperationHandler {
+    private FruitDao fruitDao = new FruitDaoImpl();
+
+    @Override
+    public void handle(String name, int amount) {
+        fruitDao.add(name, amount);
+    }
+}

src/main/java/core/basesyntax/strategy/OperationStrategy.java

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+package core.basesyntax.strategy;
+
+import core.basesyntax.model.FruitTransaction;
+import core.basesyntax.service.OperationHandler;
+
+public interface OperationStrategy {
+    OperationHandler get(FruitTransaction.Operation operation);
+}