<?php
// db/config.php

// --- Database Credentials ---
// We are using environment variables for configuration.
$db_host = getenv('DB_HOST') ?: '127.0.0.1';
$db_port = getenv('DB_PORT') ?: '3306';
$db_name = getenv('DB_DATABASE') ?: 'app';
$db_user = getenv('DB_USERNAME') ?: 'app';
$db_pass = getenv('DB_PASSWORD') ?: 'app';

/**
 * Establishes a PDO database connection.
 *
 * @return PDO|null A PDO connection object on success, or null on failure.
 */
function db() {
    global $db_host, $db_port, $db_name, $db_user, $db_pass;
    static $pdo = null;

    if ($pdo !== null) {
        return $pdo;
    }

    $dsn = "mysql:host={$db_host};port={$db_port};dbname={$db_name};charset=utf8mb4";
    $options = [
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES   => false,
    ];

    try {
        $pdo = new PDO($dsn, $db_user, $db_pass, $options);
        return $pdo;
    } catch (PDOException $e) {
        // In a real application, you would log this error and show a generic error page.
        // For this development environment, we'll just show the error.
        error_log('Database Connection Error: ' . $e->getMessage());
        // Returning null or you could throw an exception.
        return null;
    }
}

/**
 * Runs database migrations.
 * It finds all .php files in the migrations directory and runs them in order.
 * Each migration file should contain a function with the same name as the file (without .php).
 */
function run_migrations() {
    $pdo = db();
    if (!$pdo) {
        // Cannot run migrations without a database connection.
        return;
    }

    $migration_dir = __DIR__ . '/migrations';
    if (!is_dir($migration_dir)) {
        return; // No migrations directory.
    }

    $files = glob($migration_dir . '/*.php');
    sort($files);

    // Check if migrations table exists, create if not
    $pdo->exec("CREATE TABLE IF NOT EXISTS migrations (migration VARCHAR(255) PRIMARY KEY)");

    // Get all executed migrations
    $executed_migrations = $pdo->query("SELECT migration FROM migrations")->fetchAll(PDO::FETCH_COLUMN);

    foreach ($files as $file) {
        $migration_name = basename($file, '.php');

        if (in_array($migration_name, $executed_migrations)) {
            continue; // Skip already executed migration
        }

        require_once $file;
        // The function name inside the migration file must match the filename.
        // e.g., 001_create_agenda_table.php must contain a function named 'migration_001_create_agenda_table'
        $migration_function_name = 'migration_' . str_replace(['-'], '_', $migration_name);


        if (function_exists($migration_function_name)) {
            try {
                $pdo->beginTransaction();
                $migration_function_name($pdo);
                // Record the migration
                $stmt = $pdo->prepare("INSERT INTO migrations (migration) VALUES (?)");
                $stmt->execute([$migration_name]);
                $pdo->commit();
            } catch (Exception $e) {
                $pdo->rollBack();
                error_log("Migration failed: {$migration_name}. Error: " . $e->getMessage());
                // Stop on first failed migration
                return;
            }
        }
    }
}