Kalkulator średniej ocen

{
  "grades": [
    {
      "id": 1,
      "grade": 5,
      "weight": 2,
      "description": "Sprawdzian - równania",
      "created_at": "2026-02-10 14:30:00"
    },
    {
      "id": 2,
      "grade": 4,
      "weight": 1,
      "description": "Kartkówka",
      "created_at": "2026-02-12 10:15:00"
    },
    {
      "id": 3,
      "grade": 3,
      "weight": 3,
      "description": "Praca klasowa",
      "created_at": "2026-02-15 11:00:00"
    },
    {
      "id": 4,
      "grade": 6,
      "weight": 1,
      "description": "Aktywność",
      "created_at": "2026-02-17 09:45:00"
    }
  ]
}

$grade = filter_var($_POST['grade'] ?? '', FILTER_VALIDATE_INT);
$weight = filter_var($_POST['weight'] ?? 1, FILTER_VALIDATE_INT);

if ($grade === false || $grade < 1 || $grade > 6) {
    $errors[] = "Ocena musi być liczbą od 1 do 6";
}

if ($weight < 1 || $weight > 3) {
    $errors[] = "Waga musi być od 1 do 3";
}

function calculateArithmeticAverage(array $grades): float {
    if (empty($grades)) {
        return 0;
    }

    $sum = array_sum(array_column($grades, 'grade'));
    return round($sum / count($grades), 2);
}

function calculateWeightedAverage(array $grades): float {
    if (empty($grades)) {
        return 0;
    }

    $weightedSum = 0;
    $totalWeight = 0;

    foreach ($grades as $g) {
        $weight = $g['weight'] ?? 1;
        $weightedSum += $g['grade'] * $weight;
        $totalWeight += $weight;
    }

    if ($totalWeight === 0) {
        return 0;
    }

    return round($weightedSum / $totalWeight, 2);
}

function getGradeStatistics(array $grades): array {
    if (empty($grades)) {
        return [
            'count' => 0,
            'min' => null,
            'max' => null,
            'distribution' => [],
        ];
    }

    $gradeValues = array_column($grades, 'grade');

    // Rozkład ocen
    $distribution = array_count_values($gradeValues);
    ksort($distribution);

    return [
        'count' => count($grades),
        'min' => min($gradeValues),
        'max' => max($gradeValues),
        'distribution' => $distribution,
    ];
}

function predictNeededGrade(array $grades, float $targetAvg, int $newWeight = 1): ?array {
    if (empty($grades)) {
        return ['grade' => ceil($targetAvg), 'possible' => true];
    }

    $currentWeightedSum = 0;
    $currentTotalWeight = 0;

    foreach ($grades as $g) {
        $weight = $g['weight'] ?? 1;
        $currentWeightedSum += $g['grade'] * $weight;
        $currentTotalWeight += $weight;
    }

    // Wzór: (currentSum + X * newWeight) / (currentWeight + newWeight) = targetAvg
    // X = (targetAvg * (currentWeight + newWeight) - currentSum) / newWeight
    $neededGrade = ($targetAvg * ($currentTotalWeight + $newWeight) - $currentWeightedSum) / $newWeight;

    if ($neededGrade <= 0) {
        return ['grade' => 1, 'possible' => true, 'message' => 'Już masz wystarczającą średnią'];
    }

    if ($neededGrade > 6) {
        return ['grade' => null, 'possible' => false, 'message' => 'Niemożliwe do osiągnięcia jedną oceną'];
    }

    return [
        'grade' => ceil($neededGrade),
        'exact' => round($neededGrade, 2),
        'possible' => true,
    ];
}

// Użycie
$prediction = predictNeededGrade($grades, 4.5, 2);
if ($prediction['possible']) {
    echo "Potrzebujesz oceny {$prediction['grade']} z wagą 2";
} else {
    echo $prediction['message'];
}

function getGradeColor(int $grade): string {
    $colors = [
        1 => '#e74c3c', // czerwony
        2 => '#e74c3c', // czerwony
        3 => '#f39c12', // pomarańczowy
        4 => '#f1c40f', // żółty
        5 => '#2ecc71', // zielony
        6 => '#27ae60', // ciemny zielony
    ];

    return $colors[$grade] ?? '#95a5a6';
}

function getGradeEmoji(int $grade): string {
    $emojis = [
        1 => '😢',
        2 => '😕',
        3 => '😐',
        4 => '🙂',
        5 => '😊',
        6 => '🎉',
    ];

    return $emojis[$grade] ?? '❓';
}