feat: add lab

.devcontainer/Dockerfile

@@ -0,0 +1,11 @@
+ARG VARIANT=8.5-bookworm
+FROM mcr.microsoft.com/devcontainers/php:4-${VARIANT}
+
+RUN apt-get update \
+    && export DEBIAN_FRONTEND=noninteractive \
+    && apt-get install -y --no-install-recommends libsqlite3-dev \
+    && docker-php-ext-install pdo_sqlite \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY php-memory-limit.ini /usr/local/etc/php/conf.d/php-memory-limit.ini

.devcontainer/devcontainer.json

@@ -1,6 +1,11 @@
 {
   "name": "PHP Technical Assessment",
-  "image": "mcr.microsoft.com/devcontainers/php:4-8.3-bookworm",
+  "build": {
+    "dockerfile": "Dockerfile",
+    "args": {
+      "VARIANT": "8.5-bookworm"
+    }
+  },
 
   "features": {
     "ghcr.io/devcontainers/features/github-cli:1": {},

.devcontainer/php-memory-limit.ini

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+memory_limit = 32M

.gitignore

@@ -0,0 +1,4 @@
+/data/*.sqlite
+/data/*.sqlite-shm
+/data/*.sqlite-wal
+/data/*.jsonl

README.md

@@ -1,32 +1,103 @@
-# PHP Technical Assessment
-
-This repository contains the starter project for the technical interview.
+# Senior Interview Lab
 
 ## Getting started
 
 1. Open this repository in GitHub Codespaces.
 2. Wait for the Codespace setup to finish.
 3. Open a terminal in the Codespace.
 
-Run the starter program:
+## Introduction
+
+This repository contains two independent PHP exercises:
+
+1. **User maintenance**
+2. **Order processing**
+
+The lab is dependency-free and uses file-backed **SQLite** databases. You do not
+need Docker, MySQL, PostgreSQL, Composer, or any third-party packages.
+
+You can also list the available lab commands:
+
+```bash
+php lab.php help
+```
+
+## Candidate instructions
+
+For each exercise:
 
-```sh
-php index.php
+1. Explain how the existing implementation works.
+2. Identify anything you think should be improved.
+3. Make appropriate changes while preserving intended behavior.
+4. Explain your decisions and trade-offs.
+
+You are encouraged to use your judgment about what to investigate and how far to refactor the
+exercise. You may make code changes wherever appropriate.
+
+Do not add external dependencies or require additional infrastructure.
+
+The exercises are independent. Complete them in the order directed by your interviewer.
+
+## Exercise 1 — User maintenance
+
+Prepare a fresh user database:
+
+```bash
+php lab.php setup:users
 ```
 
-The expected starter output is:
+Review and improve:
 
 ```text
-Hello, World!
+code exercises/01_user_maintenance.php
 ```
 
-## Coding agent
+Run the exercise:
+
+```bash
+php exercises/01_user_maintenance.php
+```
 
-Codex is available from the Codespace terminal:
+Inspect the resulting user statuses:
 
-```sh
-codex
+```bash
+php lab.php inspect:users
 ```
 
-Follow the interviewer's instructions for the assessment and submission
-process.
+Re-run the reset command whenever you need to restore the original dataset:
+
+```bash
+php lab.php reset:users
+```
+
+## Exercise 2 — Order processing
+
+Prepare a fresh order database:
+
+```bash
+php lab.php setup:orders
+```
+
+Review and improve:
+
+```text
+code exercises/02_order_processing.php
+```
+
+Run the exercise:
+
+```bash
+php exercises/02_order_processing.php
+```
+
+Inspect products, orders, order items, and payments:
+
+```bash
+php lab.php inspect:orders
+```
+
+Re-run the setup command whenever you need a clean database:
+
+```bash
+php lab.php reset:orders
+```

exercises/01_user_maintenance.php

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+<?php
+
+declare(strict_types=1);
+
+// =============================================================================
+// Setup
+// =============================================================================
+
+// Load dependencies.
+require_once __DIR__ . '/../support/Database.php';
+
+// Connect to the exercise database.
+$dbPath = __DIR__ . '/../data/users.sqlite';
+$pdo = Database::connect($dbPath);
+
+// =============================================================================
+// Exercise
+// =============================================================================
+
+$users = $pdo->query(<<<'SQL'
+    SELECT *
+    FROM users
+    WHERE status = 'active'
+      AND last_login_at < '2025-08-13'
+    ORDER BY id
+SQL)->fetchAll();
+
+foreach ($users as $user) {
+    $stmt = $pdo->prepare("UPDATE users SET status = 'inactive' WHERE id = ?");
+    $stmt->execute([$user['id']]);
+}

exercises/02_order_processing.php

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+<?php
+
+declare(strict_types=1);
+
+// =============================================================================
+// Setup
+// =============================================================================
+
+// Load dependencies.
+require_once __DIR__ . '/../support/Database.php';
+
+// Parse command-line options and connect to the exercise database.
+$pdo = Database::connect(__DIR__ . '/../data/orders.sqlite');
+
+// =============================================================================
+// Exercise
+// =============================================================================
+
+// Define the products and quantities in the order.
+$items = [
+    ['product_id' => 1, 'quantity' => 2],
+    ['product_id' => 2, 'quantity' => 1],
+    ['product_id' => 3, 'quantity' => 3],
+];
+
+// Start processing the order
+try {
+    $pdo->exec("INSERT INTO orders(status, total_cents, created_at) VALUES ('pending', 0, datetime('now'))");
+    $orderId = (int) $pdo->lastInsertId();
+
+    $total = 0;
+    foreach ($items as $item) {
+        $productStmt = $pdo->prepare('SELECT price_cents, stock FROM products WHERE id = ?');
+        $productStmt->execute([$item['product_id']]);
+        $product = $productStmt->fetch();
+
+        if (!$product) {
+            throw new RuntimeException('Product not found');
+        }
+
+        if ((int) $product['stock'] < $item['quantity']) {
+            throw new RuntimeException('Insufficient stock');
+        }
+
+        $lineTotal = (int) $product['price_cents'] * $item['quantity'];
+        $total += $lineTotal;
+
+        $insertItem = $pdo->prepare(<<<'SQL'
+            INSERT INTO order_items(order_id, product_id, quantity, unit_price_cents)
+            VALUES (?, ?, ?, ?)
+        SQL);
+        $insertItem->execute([$orderId, $item['product_id'], $item['quantity'], $product['price_cents']]);
+
+        $newStock = (int) $product['stock'] - $item['quantity'];
+        $updateStock = $pdo->prepare('UPDATE products SET stock = ? WHERE id = ?');
+        $updateStock->execute([$newStock, $item['product_id']]);
+    }
+
+    $updateOrder = $pdo->prepare("UPDATE orders SET total_cents = ?, status = 'ready_for_payment' WHERE id = ?");
+    $updateOrder->execute([$total, $orderId]);
+
+    $payment = $pdo->prepare("INSERT INTO payments(order_id, amount_cents, status) VALUES (?, ?, 'pending')");
+    $payment->execute([$orderId, $total]);
+
+    echo "Order {$orderId} completed successfully.\n";
+} catch (Throwable $e) {
+    fwrite(STDERR, "FAILED: {$e->getMessage()}\n");
+    fwrite(STDERR, "Inspect the DB now. Partial writes may remain.\n");
+    exit(1);
+}