<?php

require_once __DIR__ . '/../UserProviderInterface.php';
require_once __DIR__ . '/../User.php';

/**
 * MysqlUserProvider stores users in MySQL database
 */
class MysqlUserProvider implements UserProviderInterface
{
    private PDO $db;
    private string $table;

    public function __construct(array $config, string $table = 'users')
    {
        $this->table = $table;
        
        $dsn = sprintf(
            'mysql:host=%s;port=%s;dbname=%s;charset=%s',
            $config['host'] ?? 'localhost',
            $config['port'] ?? 3306,
            $config['database'],
            $config['charset'] ?? 'utf8mb4'
        );

        try {
            $this->db = new PDO(
                $dsn,
                $config['username'],
                $config['password'],
                [
                    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                    PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8mb4"
                ]
            );
            $this->createTable();
        } catch (PDOException $e) {
            throw new Exception("Failed to connect to MySQL database: " . $e->getMessage());
        }
    }

    /**
     * Create users table if it doesn't exist
     */
    private function createTable(): void
    {
        $sql = "CREATE TABLE IF NOT EXISTS {$this->table} (
            id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
            username VARCHAR(255) UNIQUE,
            email VARCHAR(255) UNIQUE,
            password VARCHAR(255) NOT NULL,
            remember_token VARCHAR(255),
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            attributes JSON,
            INDEX idx_email (email),
            INDEX idx_username (username),
            INDEX idx_remember_token (remember_token)
        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci";

        $this->db->exec($sql);
    }

    /**
     * Map database row to User object
     */
    private function mapToUser(array $row): User
    {
        $attributes = isset($row['attributes']) ? json_decode($row['attributes'], true) ?? [] : [];
        
        return new User([
            'id' => $row['id'],
            'username' => $row['username'],
            'email' => $row['email'],
            'password' => $row['password'],
            'rememberToken' => $row['remember_token'],
            'createdAt' => $row['created_at'],
            'updatedAt' => $row['updated_at'],
            'attributes' => $attributes
        ]);
    }

    public function findById(int|string $id): ?User
    {
        $stmt = $this->db->prepare("SELECT * FROM {$this->table} WHERE id = :id");
        $stmt->execute(['id' => $id]);
        
        $row = $stmt->fetch();
        return $row ? $this->mapToUser($row) : null;
    }

    public function findByEmail(string $email): ?User
    {
        $stmt = $this->db->prepare("SELECT * FROM {$this->table} WHERE email = :email");
        $stmt->execute(['email' => $email]);
        
        $row = $stmt->fetch();
        return $row ? $this->mapToUser($row) : null;
    }

    public function findByUsername(string $username): ?User
    {
        $stmt = $this->db->prepare("SELECT * FROM {$this->table} WHERE username = :username");
        $stmt->execute(['username' => $username]);
        
        $row = $stmt->fetch();
        return $row ? $this->mapToUser($row) : null;
    }

    public function findByCredentials(string $identifier): ?User
    {
        $stmt = $this->db->prepare(
            "SELECT * FROM {$this->table} WHERE email = :identifier OR username = :identifier"
        );
        $stmt->execute(['identifier' => $identifier]);
        
        $row = $stmt->fetch();
        return $row ? $this->mapToUser($row) : null;
    }

    public function findByRememberToken(string $token): ?User
    {
        $stmt = $this->db->prepare("SELECT * FROM {$this->table} WHERE remember_token = :token");
        $stmt->execute(['token' => $token]);
        
        $row = $stmt->fetch();
        return $row ? $this->mapToUser($row) : null;
    }

    public function create(array $data): User
    {
        $attributes = $data['attributes'] ?? [];
        unset($data['attributes']);

        $stmt = $this->db->prepare(
            "INSERT INTO {$this->table} (username, email, password, remember_token, attributes) 
             VALUES (:username, :email, :password, :remember_token, :attributes)"
        );

        $stmt->execute([
            'username' => $data['username'] ?? null,
            'email' => $data['email'] ?? null,
            'password' => $data['password'],
            'remember_token' => $data['remember_token'] ?? null,
            'attributes' => json_encode($attributes)
        ]);

        $data['id'] = $this->db->lastInsertId();
        $data['attributes'] = $attributes;

        // Fetch created/updated timestamps
        $user = $this->findById($data['id']);
        return $user;
    }

    public function update(User $user, array $data): bool
    {
        $attributes = array_merge($user->attributes, $data['attributes'] ?? []);
        unset($data['attributes']);

        $fields = [];
        $params = ['id' => $user->id];

        foreach (['username', 'email', 'password'] as $field) {
            if (isset($data[$field])) {
                $fields[] = "$field = :$field";
                $params[$field] = $data[$field];
                $user->$field = $data[$field];
            }
        }

        if (!empty($attributes)) {
            $fields[] = "attributes = :attributes";
            $params['attributes'] = json_encode($attributes);
            $user->attributes = $attributes;
        }

        if (empty($fields)) {
            return true;
        }

        $sql = "UPDATE {$this->table} SET " . implode(', ', $fields) . " WHERE id = :id";
        $stmt = $this->db->prepare($sql);

        return $stmt->execute($params);
    }

    public function updateRememberToken(User $user, ?string $token): bool
    {
        $stmt = $this->db->prepare(
            "UPDATE {$this->table} SET remember_token = :token WHERE id = :id"
        );

        return $stmt->execute([
            'id' => $user->id,
            'token' => $token
        ]);
    }

    public function verifyPassword(User $user, string $password): bool
    {
        return password_verify($password, $user->password);
    }
}