Solution

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

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+package core.basesyntax;
+
+import core.basesyntax.model.FruitTransaction;
+import core.basesyntax.service.DataConverter;
+import core.basesyntax.service.DataConverterImpl;
+import core.basesyntax.service.FileReaderService;
+import core.basesyntax.service.FileReaderServiceImpl;
+import core.basesyntax.service.FileWriterService;
+import core.basesyntax.service.FileWriterServiceImpl;
+import core.basesyntax.service.ReportGenerator;
+import core.basesyntax.service.ReportGeneratorImpl;
+import core.basesyntax.service.ShopService;
+import core.basesyntax.service.ShopServiceImpl;
+import core.basesyntax.strategy.BalanceOperationHandler;
+import core.basesyntax.strategy.OperationHandler;
+import core.basesyntax.strategy.OperationStrategy;
+import core.basesyntax.strategy.OperationStrategyImpl;
+import core.basesyntax.strategy.PurchaseOperationHandler;
+import core.basesyntax.strategy.ReturnOperationHandler;
+import core.basesyntax.strategy.SupplyOperationHandler;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Main {
+    public static void main(String[] arg) {
+        FileReaderService fileReader = new FileReaderServiceImpl();
+        List<String> inputReport = fileReader.readFile("reportToRead.csv");
+
+        // 2. Convert the incoming data into FruitTransactions list
+        DataConverter dataConverter = new DataConverterImpl();
+        final List<FruitTransaction> transactions = dataConverter.convertToTransaction(inputReport);
+
+        Map<FruitTransaction.Operation, OperationHandler> operationHandlers = new HashMap<>();
+        operationHandlers.put(FruitTransaction.Operation.BALANCE, new BalanceOperationHandler());
+        operationHandlers.put(FruitTransaction.Operation.PURCHASE, new PurchaseOperationHandler());
+        operationHandlers.put(FruitTransaction.Operation.RETURN, new ReturnOperationHandler());
+        operationHandlers.put(FruitTransaction.Operation.SUPPLY, new SupplyOperationHandler());
+        OperationStrategy operationStrategy = new OperationStrategyImpl(operationHandlers);
+
+        // 4. Process the incoming transactions with applicable OperationHandler implementations
+        ShopService shopService = new ShopServiceImpl(operationStrategy);
+        shopService.process(transactions);
+        ReportGenerator reportGenerator = new ReportGeneratorImpl();
+        String resultingReport = reportGenerator.getReport();
+
+        // 6. Write the received report into the destination file
+        FileWriterService fileWriter = new FileWriterServiceImpl();
+        fileWriter.writeFile(resultingReport, "finalReport.csv");
+    }
+}

src/main/java/core/basesyntax/reportToRead.csv

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+type,fruit,quantity
+b,banana,20
+b,apple,100
+s,banana,100
+p,banana,13
+r,apple,10
+p,apple,20
+p,banana,5
+s,banana,50

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

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.List;
+
+public interface DataConverter {
+    List<FruitTransaction> convertToTransaction(List<String> data);
+}

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

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.ArrayList;
+import java.util.List;
+
+public class DataConverterImpl implements DataConverter {
+    @Override
+    public List<FruitTransaction> convertToTransaction(List<String> data) {
+        List<FruitTransaction> transactions = new ArrayList<>();
+        for (String line: data) {
+            String[] elements = line.split(",");
+            FruitTransaction fruitTransaction =
+                    new FruitTransaction(FruitTransaction.Operation.fromCode(elements[0]),
+                            elements[1], Integer.parseInt(elements[2]));
+            transactions.add(fruitTransaction);
+        }
+        return transactions;
+    }
+}

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

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+package core.basesyntax.service;
+
+import java.util.List;
+
+public interface FileReaderService {
+    List<String> readFile(String fileName);
+}

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

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+package core.basesyntax.service;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class FileReaderServiceImpl implements FileReaderService {
+    @Override
+    public List<String> readFile(String filepath) {
+        List<String> lines = new ArrayList<>();
+        try (BufferedReader br = new BufferedReader(new FileReader(filepath))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                lines.add(line);
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return lines;
+    }
+}

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

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+package core.basesyntax.service;
+
+public interface FileWriterService {
+    void writeFile(String report, String fileName);
+}

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

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+package core.basesyntax.service;
+
+import java.io.BufferedWriter;
+import java.io.FileWriter;
+import java.io.IOException;
+
+public class FileWriterServiceImpl implements FileWriterService {
+    @Override
+    public void writeFile(String report, String filePath) {
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filePath))) {
+            writer.write(report);
+        } catch (IOException e) {
+            throw new RuntimeException("Can't write a " + filePath, e);
+        }
+    }
+}

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

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+package core.basesyntax.service;
+
+public interface ReportGenerator {
+    String getReport();
+}

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

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+package core.basesyntax.service;
+
+import core.basesyntax.storage.Storage;
+
+public class ReportGeneratorImpl implements ReportGenerator {
+    @Override
+    public String getReport() {
+        StringBuilder report = new StringBuilder("fruit,quantity\n");
+        Storage.fruits.forEach((fruit, quantity) -> report.append(fruit)
+                .append(",").append(quantity).append("\n"));
+        return report.toString();
+    }
+}

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

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.List;
+
+public interface ShopService {
+    void process(List<FruitTransaction> transactions);
+}

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

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+package core.basesyntax.service;
+
+import core.basesyntax.model.FruitTransaction;
+import core.basesyntax.strategy.OperationStrategy;
+import java.util.List;
+
+public class ShopServiceImpl implements ShopService {
+    private OperationStrategy operationStrategy;
+
+    public ShopServiceImpl(OperationStrategy operationStrategy) {
+        this.operationStrategy = operationStrategy;
+    }
+
+    @Override
+    public void process(List<FruitTransaction> transactions) {
+        for (FruitTransaction fruitTransaction: transactions) {
+            operationStrategy.getHandler(
+                    fruitTransaction.getOperation()).apply(fruitTransaction.getFruit(),
+                    fruitTransaction.getQuantity());
+        }
+    }
+}

src/main/java/core/basesyntax/storage/Storage.java

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+package core.basesyntax.storage;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Storage {
+    public static final Map<String, Integer> fruits = new HashMap<>();
+}

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

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+package core.basesyntax.strategy;
+
+import core.basesyntax.storage.Storage;
+
+public class BalanceOperationHandler implements OperationHandler {
+    @Override
+    public void apply(String fruit, int quantity) {
+        Storage.fruits.put(fruit, quantity);
+    }
+}

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

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+package core.basesyntax.strategy;
+
+public interface OperationHandler {
+    void apply(String fruit, int quantity);
+}

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

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

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

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+package core.basesyntax.strategy;
+
+import core.basesyntax.model.FruitTransaction;
+import java.util.Map;
+
+public class OperationStrategyImpl implements OperationStrategy {
+    private final Map<FruitTransaction.Operation, OperationHandler> operationHandlers;
+
+    public OperationStrategyImpl(Map<FruitTransaction.Operation,
+            OperationHandler> operationHandlers) {
+        this.operationHandlers = operationHandlers;
+    }
+
+    @Override
+    public OperationHandler getHandler(FruitTransaction.Operation operation) {
+        return operationHandlers.get(operation);
+    }
+}

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

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+package core.basesyntax.strategy;
+
+import core.basesyntax.storage.Storage;
+
+public class PurchaseOperationHandler implements OperationHandler {
+    @Override
+    public void apply(String fruit, int quantity) {
+        Storage.fruits.put(fruit, Storage.fruits.get(fruit) + quantity);
+    }
+}

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

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+package core.basesyntax.strategy;
+
+import core.basesyntax.storage.Storage;
+
+public class ReturnOperationHandler implements OperationHandler {
+    @Override
+    public void apply(String fruit, int quantity) {
+        Storage.fruits.put(fruit, Storage.fruits.get(fruit) + quantity);
+    }
+}

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

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+package core.basesyntax.strategy;
+
+import core.basesyntax.storage.Storage;
+
+public class SupplyOperationHandler implements OperationHandler {
+    @Override
+    public void apply(String fruit, int quantity) {
+        Storage.fruits.put(fruit, Storage.fruits.get(fruit) + quantity);
+    }
+}