<?php

namespace App\Services\Database;

use PDO;

class MigrationRunner
{
    private PDO $pdo;
    private string $migrationsDir;

    public function __construct(Connection $connection)
    {
        $this->pdo = $connection->getPdo();
        $this->migrationsDir = __DIR__ . '/../../../database/migrations';
    }

    /**
     * Run all pending migrations.
     */
    public function migrate(): void
    {
        $this->createMigrationsTable();

        $executed = $this->getExecutedMigrations();
        
        if (!is_dir($this->migrationsDir)) {
            mkdir($this->migrationsDir, 0755, true);
        }
        
        $files = glob($this->migrationsDir . '/*.sql');
        if ($files === false) {
            $files = [];
        }
        sort($files);

        $count = 0;
        foreach ($files as $file) {
            $name = basename($file);
            if (!in_array($name, $executed)) {
                echo "Running migration: {$name}...\n";
                $this->executeSqlFile($file);
                $this->logMigration($name);
                echo "Successfully ran: {$name}\n";
                $count++;
            }
        }

        if ($count === 0) {
            echo "Nothing to migrate. Database is up to date!\n";
        }
    }

    /**
     * Create the tracking migrations table if it does not exist.
     */
    private function createMigrationsTable(): void
    {
        $sql = "CREATE TABLE IF NOT EXISTS migrations (
            id INT AUTO_INCREMENT PRIMARY KEY,
            migration VARCHAR(255) NOT NULL,
            executed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;";
        $this->pdo->exec($sql);
    }

    /**
     * Get list of already executed migrations.
     */
    private function getExecutedMigrations(): array
    {
        $stmt = $this->pdo->query("SELECT migration FROM migrations");
        $results = $stmt->fetchAll(PDO::FETCH_COLUMN);
        return $results ?: [];
    }

    /**
     * Execute SQL file.
     */
    private function executeSqlFile(string $filePath): void
    {
        $sql = file_get_contents($filePath);
        if (!$sql) {
            return;
        }

        try {
            // Run SQL commands
            $this->pdo->exec($sql);
        } catch (\PDOException $e) {
            echo "Error running migration from file: " . basename($filePath) . "\n";
            echo "Details: " . $e->getMessage() . "\n";
            throw $e;
        }
    }

    /**
     * Log executed migration.
     */
    private function logMigration(string $name): void
    {
        $stmt = $this->pdo->prepare("INSERT INTO migrations (migration) VALUES (?)");
        $stmt->execute([$name]);
    }
}