check-nesting-depth

Nesting Depth Check

Analyze PHP code for excessive nesting depth and complexity.

Detection Thresholds

Depth	Classification
1-2	✅ Ideal
3	⚠️ Acceptable
4	🟡 Deep - refactor recommended
5+	🟠 Too deep - must refactor

Detection Patterns

1. Deep Nesting

// DEPTH 5: Arrow code / pyramid of doom
public function process(Request $request): Response
{
    if ($request->isValid()) {                           // 1
        if ($user = $request->getUser()) {               // 2
            if ($user->hasPermission('edit')) {          // 3
                foreach ($request->getItems() as $item) { // 4
                    if ($item->isActive()) {              // 5
                        $this->handle($item);
                    }
                }
            }
        }
    }
}

// DEPTH 2: Using early returns
public function process(Request $request): Response
{
    if (!$request->isValid()) {
        return $this->badRequest();
    }

    $user = $request->getUser();
    if (!$user) {
        return $this->unauthorized();
    }

    if (!$user->hasPermission('edit')) {
        return $this->forbidden();
    }

    $activeItems = array_filter(
        $request->getItems(),
        fn($item) => $item->isActive()
    );

    foreach ($activeItems as $item) {
        $this->handle($item);
    }
}

2. Complex Conditionals

// COMPLEX: Multiple nested conditions
if ($order->isPaid()) {
    if ($order->isShipped()) {
        if ($order->isDelivered()) {
            if (!$order->isReturned()) {
                $this->complete($order);
            }
        }
    }
}

// SIMPLIFIED: Combined condition
if ($order->canBeCompleted()) {
    $this->complete($order);
}

// Or with early return
if (!$order->isPaid()) return;
if (!$order->isShipped()) return;
if (!$order->isDelivered()) return;
if ($order->isReturned()) return;

$this->complete($order);

3. Nested Loops

// DEEP: Triple nested loop
foreach ($categories as $category) {
    foreach ($category->getProducts() as $product) {
        foreach ($product->getVariants() as $variant) {
            foreach ($variant->getOptions() as $option) {
                $this->process($option);
            }
        }
    }
}

// BETTER: Extract methods
foreach ($categories as $category) {
    $this->processCategory($category);
}

private function processCategory(Category $category): void
{
    foreach ($category->getProducts() as $product) {
        $this->processProduct($product);
    }
}

private function processProduct(Product $product): void
{
    foreach ($product->getVariants() as $variant) {
        $this->processVariant($variant);
    }
}

4. Callback Nesting (Callback Hell)

// DEEP: Nested callbacks
$this->service->fetch($id, function($result) {
    $this->processor->process($result, function($processed) {
        $this->sender->send($processed, function($sent) {
            $this->logger->log($sent, function($logged) {
                $this->cleanup($logged);
            });
        });
    });
});

// FLAT: Sequential or promise-based
$result = $this->service->fetch($id);
$processed = $this->processor->process($result);
$sent = $this->sender->send($processed);
$this->logger->log($sent);
$this->cleanup($sent);

5. Switch in If in Loop

// DEEP: Mixed control structures
foreach ($items as $item) {
    if ($item->isActive()) {
        switch ($item->getType()) {
            case 'A':
                if ($item->hasFeature()) {
                    $this->handleTypeA($item);
                }
                break;
            case 'B':
                if ($item->isValid()) {
                    $this->handleTypeB($item);
                }
                break;
        }
    }
}

// BETTER: Strategy pattern + filter
$activeItems = array_filter($items, fn($i) => $i->isActive());
foreach ($activeItems as $item) {
    $handler = $this->handlerFactory->create($item->getType());
    $handler->handle($item);
}

Refactoring Techniques

Early Return / Guard Clauses

// Before
function process($data) {
    if ($data !== null) {
        if ($data->isValid()) {
            if ($data->canProcess()) {
                // actual logic
            }
        }
    }
}

// After
function process($data) {
    if ($data === null) return;
    if (!$data->isValid()) return;
    if (!$data->canProcess()) return;

    // actual logic (no nesting)
}

Extract Method

// Before
foreach ($orders as $order) {
    if ($order->isPaid()) {
        foreach ($order->getItems() as $item) {
            if ($item->needsShipping()) {
                $this->ship($item);
            }
        }
    }
}

// After
foreach ($orders as $order) {
    $this->processOrder($order);
}

private function processOrder(Order $order): void
{
    if (!$order->isPaid()) return;
    $this->shipItems($order->getItems());
}

private function shipItems(array $items): void
{
    foreach ($items as $item) {
        if ($item->needsShipping()) {
            $this->ship($item);
        }
    }
}

Replace Conditional with Polymorphism

// Before: Deep switch
switch ($type) {
    case 'email':
        if ($config['html']) {
            // ...
        } else {
            // ...
        }
        break;
    case 'sms':
        // ...
}

// After: Strategy pattern
interface NotificationChannel {
    public function send(Notification $notification): void;
}

class EmailChannel implements NotificationChannel { }
class SmsChannel implements NotificationChannel { }

Decompose Conditional

// Before
if ($date->before($SUMMER_START) || $date->after($SUMMER_END)) {
    $charge = $quantity * $winterRate + $winterServiceCharge;
} else {
    $charge = $quantity * $summerRate;
}

// After
if ($this->isWinter($date)) {
    $charge = $this->winterCharge($quantity);
} else {
    $charge = $this->summerCharge($quantity);
}

Grep Patterns

# Find nested if statements
Grep: "if\s*\([^)]+\)\s*\{[^}]*if\s*\(" --glob "**/*.php"

# Find nested foreach
Grep: "foreach.*foreach" --glob "**/*.php"

# Count indentation levels (manual analysis)

Severity Classification

Depth	Severity
4	🟡 Minor
5	🟠 Major
6+	🔴 Critical

Output Format

### Nesting Depth: [Description]

**Severity:** 🟠/🟡
**Location:** `file.php:line`
**Depth:** 5 levels

**Issue:**
Method `processOrder` has 5 levels of nesting, making it difficult to follow.

**Code Structure:**

if ($request->isValid()) // Level 1 if ($user = getUser()) // Level 2 if ($user->hasPermission()) // Level 3 foreach ($items) // Level 4 if ($item->isActive()) // Level 5

**Suggested Refactoring:**
```php
// Use early returns to flatten
if (!$request->isValid()) return;
if (!$user = getUser()) return;
if (!$user->hasPermission()) return;

$activeItems = $this->filterActiveItems($items);
foreach ($activeItems as $item) {
    $this->handle($item);
}