package ru.project.finder;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import ru.project.collection.MyLinkedList;
import ru.project.collection.MyList;
import ru.project.student.Student;

public class StudentOccurrenceIndexFinderTest {
  private StudentOccurrenceIndexFinder finder;
  private MyList<Student> students;

  @BeforeEach
  void setUp() {
    finder = new StudentOccurrenceIndexFinder();
    students = new MyLinkedList<>();
  }

  @Test
  void shouldTesfindOccurrences_emptyList_returnsEmptyArray() {
    int[] result = finder.findOccurrences(students, new Student("A12", 4.5, 1));
    assertEquals(0, result.length);
  }

  @Test
  void shouldTesfindOccurrences_noMatches_returnsEmptyArray() {
    students.add(new Student("A12", 4.0, 101));
    students.add(new Student("B23", 3.5, 102));
    Student target = new Student("C34", 4.8, 103); // такого нет

    int[] result = finder.findOccurrences(students, target);
    assertEquals(0, result.length);
  }

  @Test
  void shouldTesfindOccurrences_singleMatch_returnsCorrectIndex() {
    students.add(new Student("A12", 4.0, 101));
    students.add(new Student("B23", 3.5, 102)); // target здесь
    students.add(new Student("C34", 4.8, 103));

    Student target = new Student("B23", 3.5, 102);
    int[] result = finder.findOccurrences(students, target);

    assertEquals(1, result.length);
    assertEquals(1, result[0]);
  }

  @Test
  void shouldTesfindOccurrences_multipleMatches_returnsAllIndicesSorted() {
    // индексы: 0, 2, 4 — должны вернуться в порядке возрастания
    students.add(new Student("A12", 4.5, 101)); // match
    students.add(new Student("B23", 3.8, 102));
    students.add(new Student("A12", 4.5, 101)); // match
    students.add(new Student("C34", 4.0, 103));
    students.add(new Student("A12", 4.5, 101)); // match

    Student target = new Student("A12", 4.5, 101);
    int[] result = finder.findOccurrences(students, target);

    assertEquals(3, result.length);
    assertArrayEquals(new int[] {0, 2, 4}, result);
  }

  @Test
  void shouldTesfindOccurrences_allElementsMatch_returnsAllIndices() {
    Student s = new Student("X99", 5.0, 999);
    students.add(s);
    students.add(s);
    students.add(s);

    int[] result = finder.findOccurrences(students, s);
    assertEquals(3, result.length);
    assertArrayEquals(new int[] {0, 1, 2}, result);
  }

  @Test
  void shouldTesfindOccurrences_differentAverageGrade_noMatch() {
    students.add(new Student("A12", 4.50, 101));
    Student target = new Student("A12", 4.51, 101); // отличается балл

    int[] result = finder.findOccurrences(students, target);
    assertEquals(0, result.length);
  }

  @Test
  void shouldTesfindOccurrences_differentGroupNumber_noMatch() {
    students.add(new Student("A12", 4.5, 101));
    Student target = new Student("B12", 4.5, 101); // другая группа

    int[] result = finder.findOccurrences(students, target);
    assertEquals(0, result.length);
  }

  @Test
  void shouldTesfindOccurrences_differentRecordBookNumber_noMatch() {
    students.add(new Student("A12", 4.5, 101));
    Student target = new Student("A12", 4.5, 102); // другой номер зачетки

    int[] result = finder.findOccurrences(students, target);
    assertEquals(0, result.length);
  }

  @Test
  void shouldTesfindOccurrences_nullList_throwsException() {
    Student target = new Student("A12", 4.5, 101);
    assertThrows(IllegalArgumentException.class, () -> finder.findOccurrences(null, target));
  }

  @Test
  void shouldTesfindOccurrences_nullTarget_throwsException() {
    assertThrows(IllegalArgumentException.class, () -> finder.findOccurrences(students, null));
  }

  @Test
  void shouldTesfindOccurrences_resultIsSorted() {
    String[] validGroups = {"A00", "A01", "B12", "C99", "X55"};

    for (int i = 0; i < 50; i++) {
      String group = validGroups[i % validGroups.length];
      double grade = (3.0 + (i % 3)) / 2.0;
      if (i % 3 == 0) {

        students.add(new Student("A12", 4.5, 101));
      } else {
        students.add(new Student(group, grade, 200 + i));
      }
    }
    Student target = new Student("A12", 4.5, 101);
    int[] result = finder.findOccurrences(students, target);

    for (int i = 1; i < result.length; i++) {
      assertTrue(result[i] > result[i - 1], "Результат должен быть отсортирован");
    }
  }
}