Grade school

src/GradeSchool.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+use Assert\Assert;
+use Tightenco\Collect\Support\Collection;
+
+final class GradeSchool
+{
+    private Collection $students;
+
+    public function __construct()
+    {
+        $this->students = new Collection();
+    }
+
+    public function addStudentToGrade(string $name, int $grade): void
+    {
+        Assert::that($name)->notEmpty('Name cannot be blank');
+
+        Assert::that($grade)
+            ->greaterOrEqualThan(1, 'Grade must be greater than or equal to 1');
+
+        $this->students->push(['name' => $name, 'grade' => $grade]);
+    }
+
+    public function getAllStudents(): Collection
+    {
+        return $this->students->pluck('grade')
+            ->unique()
+            ->map(fn (int $grade): Collection => new Collection([
+                'grade' => $grade,
+                'students' => $this->getStudentsByGrade($grade),
+            ]))
+            ->sortBy('grade')
+            ->values();
+    }
+
+    public function getStudentsByGrade(int $grade): Collection
+    {
+        return $this->students
+            ->filter(fn (array $student): bool => $grade == $student['grade'])
+            ->pluck('name')
+            ->sort()
+            ->values();
+    }
+}