Added Writable implementation

src/main/java/org/writer/Main.java

@@ -1,7 +1,29 @@
 package org.writer;
 
+import org.writer.model.Months;
+import org.writer.model.Person;
+import org.writer.model.Student;
+
+import java.util.List;
+
 public class Main {
     public static void main(String[] args) {
-        System.out.println("Hello world!");
+        Writable writable = new WritableImpl();
+
+        List<Student> students = List.of(
+                new Student("Student 1", List.of("5", "4", "3", "2")),
+                new Student("Student 2", List.of("2", "1", "1", "2")),
+                new Student("Student 3", List.of("2", "3", "4", "5"))
+        );
+        writable.writeToFile(students, "Students.csv");
+
+        List<Person> persons = List.of(
+                new Person("Имя 1", "Фамилия 1", 17, Months.SEPTEMBER, 1996),
+                new Person("Имя 2", "Фамилия 2", 18, Months.OCTOBER, 1995),
+                new Person("Имя 3", "Фамилия 3", 19, Months.NOVEMBER, 1994),
+                new Person("Имя 4", "Фамилия 4", 20, Months.DECEMBER, 1993),
+                new Person("Имя 5", "Фамилия 5", 21, Months.JANUARY, 1992)
+        );
+        writable.writeToFile(persons, "Persons.csv");
     }
 }

src/main/java/org/writer/WritableImpl.java

@@ -0,0 +1,76 @@
+package org.writer;
+
+import java.io.BufferedWriter;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.*;
+import java.util.stream.Collectors;
+
+
+public class WritableImpl implements Writable {
+
+    /**
+     * Writes CSV file from List.
+     *
+     * @param data List containing data to be written into CSV file.
+     * @param fileName Name of CSV file.
+     */
+    @Override
+    public void writeToFile(List<?> data, String fileName) {
+        List<List<String>> fullDataList = new ArrayList<>();
+        Set<String> fieldNames = new LinkedHashSet<>();
+
+        for (Object object : data) {
+            List<String> subList = new ArrayList<>();
+            Field[] fields = object.getClass().getDeclaredFields();
+            for (Field field : fields) {
+                field.setAccessible(true);
+                fieldNames.add(field.getName());
+                Object fieldValue;
+                try {
+                    fieldValue = field.get(object);
+                } catch (IllegalAccessException e) {
+                    throw new RuntimeException(e);
+                }
+
+                String stringToAdd;
+                if (fieldValue instanceof Collection<?> collection) {
+                    String joined = collection.stream()
+                            .map(Object::toString)
+                            .map(this::escapeCsv)
+                            .collect(Collectors.joining(", "));
+                    stringToAdd = escapeCsv(joined);
+                } else {
+                    stringToAdd = escapeCsv(fieldValue.toString());
+                }
+                subList.add(stringToAdd);
+
+            }
+            fullDataList.add(subList);
+        }
+
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(fileName))) {
+            writer.append(String.join(",", fieldNames));
+            writer.newLine();
+
+            List<String> tempList = fullDataList.stream()
+                    .map(strings -> String.join(",", strings))
+                    .toList();
+            for (String string : tempList) {
+                writer.append(string);
+                writer.newLine();
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private String escapeCsv(String value) {
+        if (value == null) return "";
+        if (value.contains("\"") || value.contains(",") || value.contains("\n")) {
+            return "\"" + value.replace("\"", "\"\"") + "\"";
+        }
+        return value;
+    }
+}

src/test/java/org/writer/WritableImplTest.java

@@ -0,0 +1,134 @@
+package org.writer;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.writer.model.Student;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+class WritableImplTest {
+
+    @TempDir
+    Path tempDir;
+
+    @Test
+    void simpleWriteToFile() throws IOException {
+        WritableImpl writable = new WritableImpl();
+        String fileName = "CorrectFileName";
+        Path csvFile = tempDir.resolve(fileName);
+        List<Student> students = List.of(
+                new Student("Student 1", List.of("5", "4", "3", "2")),
+                new Student("Student 2", List.of("2", "1", "1", "2")),
+                new Student("Student 3", List.of("2", "3", "4", "5"))
+        );
+
+        writable.writeToFile(students, csvFile.toString());
+
+        assertAll(
+                () -> assertTrue(Files.exists(csvFile), "���� ������ ������������"),
+                () -> assertTrue(Files.isRegularFile(csvFile), "������ ���� ����, � �� ����������"),
+                () -> assertTrue(Files.size(csvFile) > 0, "���� �� ������ ���� ������")
+        );
+
+        List<String> actual = Files.readAllLines(csvFile);
+        List<String> expected = List.of(
+                "name,score",
+                "Student 1,\"5, 4, 3, 2\"",
+                "Student 2,\"2, 1, 1, 2\"",
+                "Student 3,\"2, 3, 4, 5\""
+        );
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void dataHasDoubleQuotes() throws IOException {
+        WritableImpl writable = new WritableImpl();
+        String fileName = "CorrectFileName";
+        Path csvFile = tempDir.resolve(fileName);
+        List<Student> students = List.of(
+                new Student("St\"ude\"nt 1", List.of("5", "4", "3", "2")),
+                new Student("S\"tud\"ent 2", List.of("2", "1", "1", "2")),
+                new Student("\"Stu\"dent 3", List.of("2", "3", "4", "5"))
+        );
+
+        writable.writeToFile(students, csvFile.toString());
+
+        assertAll(
+                () -> assertTrue(Files.exists(csvFile), "���� ������ ������������"),
+                () -> assertTrue(Files.isRegularFile(csvFile), "������ ���� ����, � �� ����������"),
+                () -> assertTrue(Files.size(csvFile) > 0, "���� �� ������ ���� ������")
+        );
+
+        List<String> actual = Files.readAllLines(csvFile);
+        List<String> expected = List.of(
+                "name,score",
+                "\"St\"\"ude\"\"nt 1\",\"5, 4, 3, 2\"",
+                "\"S\"\"tud\"\"ent 2\",\"2, 1, 1, 2\"",
+                "\"\"\"Stu\"\"dent 3\",\"2, 3, 4, 5\""
+        );
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void dataHasComma() throws IOException {
+        WritableImpl writable = new WritableImpl();
+        String fileName = "CorrectFileName";
+        Path csvFile = tempDir.resolve(fileName);
+        List<Student> students = List.of(
+                new Student("St,udent 1", List.of("5", "4", "3", "2")),
+                new Student("Stu,dent 2", List.of("2", "1", "1", "2")),
+                new Student("Stud,ent 3", List.of("2", "3", "4", "5"))
+        );
+
+        writable.writeToFile(students, csvFile.toString());
+
+        assertAll(
+                () -> assertTrue(Files.exists(csvFile), "���� ������ ������������"),
+                () -> assertTrue(Files.isRegularFile(csvFile), "������ ���� ����, � �� ����������"),
+                () -> assertTrue(Files.size(csvFile) > 0, "���� �� ������ ���� ������")
+        );
+
+        List<String> actual = Files.readAllLines(csvFile);
+        List<String> expected = List.of(
+                "name,score",
+                "\"St,udent 1\",\"5, 4, 3, 2\"",
+                "\"Stu,dent 2\",\"2, 1, 1, 2\"",
+                "\"Stud,ent 3\",\"2, 3, 4, 5\""
+        );
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void dataHasEmptyCollection() throws IOException {
+        WritableImpl writable = new WritableImpl();
+        String fileName = "CorrectFileName";
+        Path csvFile = tempDir.resolve(fileName);
+        List<Student> students = List.of(
+                new Student("Student 1", Collections.emptyList()),
+                new Student("Student 2", Collections.emptyList()),
+                new Student("Student 3", Collections.emptyList())
+        );
+
+        writable.writeToFile(students, csvFile.toString());
+
+        assertAll(
+                () -> assertTrue(Files.exists(csvFile), "���� ������ ������������"),
+                () -> assertTrue(Files.isRegularFile(csvFile), "������ ���� ����, � �� ����������"),
+                () -> assertTrue(Files.size(csvFile) > 0, "���� �� ������ ���� ������")
+        );
+
+        List<String> actual = Files.readAllLines(csvFile);
+        List<String> expected = List.of(
+                "name,score",
+                "Student 1,",
+                "Student 2,",
+                "Student 3,"
+        );
+        assertEquals(expected, actual);
+    }
+}