<?php

namespace Infrastructure\Logging;

use Infrastructure\Config\DatabaseFactory;
use PDO;

/**
 * Audit Logger for tracking all important application events.
 *
 * Features:
 * - Correlation ID for request tracing
 * - Structured event logging with context
 * - Entity-action pattern for CRUD operations
 * - Automatic user and IP tracking
 */
final class AuditLogger
{
    private string $correlationId;
    private PDO $db;

    private const LOG_LEVELS = ['debug', 'info', 'warning', 'error'];

    public function __construct(?string $correlationId = null)
    {
        $this->correlationId = $correlationId
            ?? $_SERVER['HTTP_X_CORRELATION_ID']
            ?? $_SERVER['CORRELATION_ID']
            ?? $this->generateCorrelationId();

        $this->db = DatabaseFactory::dev();
    }

    /**
     * Generate a unique correlation ID.
     */
    private function generateCorrelationId(): string
    {
        return bin2hex(random_bytes(8));
    }

    /**
     * Get the current correlation ID.
     */
    public function getCorrelationId(): string
    {
        return $this->correlationId;
    }

    /**
     * Log a generic event.
     *
     * @param string $event Event name (e.g., "user.login", "chat.message.sent")
     * @param array<string, mixed> $context Additional context data
     * @param string $level Log level: debug, info, warning, error
     */
    public function log(string $event, array $context = [], string $level = 'info'): void
    {
        if (!in_array($level, self::LOG_LEVELS, true)) {
            $level = 'info';
        }

        $stmt = $this->db->prepare('
            INSERT INTO audit_log
            (correlation_id, event, context, level, user_id, ip_address, created_at)
            VALUES (?, ?, ?, ?, ?, ?, NOW())
        ');

        $stmt->execute([
            $this->correlationId,
            $event,
            json_encode($context, JSON_UNESCAPED_UNICODE),
            $level,
            $this->getUserId(),
            $this->getIpAddress(),
        ]);
    }

    /**
     * Log an entity action (CRUD operation).
     *
     * @param string $action Action performed: create, read, update, delete, etc.
     * @param string $entity Entity type: user, task, content, etc.
     * @param int|null $entityId Entity ID (null for create before ID is known)
     * @param array<string, mixed> $data Additional data about the action
     */
    public function logAction(
        string $action,
        string $entity,
        ?int $entityId = null,
        array $data = []
    ): void {
        $event = "{$entity}.{$action}";

        $stmt = $this->db->prepare('
            INSERT INTO audit_log
            (correlation_id, event, entity_type, entity_id, context, level, user_id, ip_address, created_at)
            VALUES (?, ?, ?, ?, ?, ?, ?, ?, NOW())
        ');

        $stmt->execute([
            $this->correlationId,
            $event,
            $entity,
            $entityId,
            json_encode($data, JSON_UNESCAPED_UNICODE),
            'info',
            $this->getUserId(),
            $this->getIpAddress(),
        ]);
    }

    /**
     * Log an error event.
     */
    public function logError(string $event, string $message, array $context = []): void
    {
        $context['error_message'] = $message;
        $this->log($event, $context, 'error');
    }

    /**
     * Log a warning event.
     */
    public function logWarning(string $event, string $message, array $context = []): void
    {
        $context['warning_message'] = $message;
        $this->log($event, $context, 'warning');
    }

    /**
     * Log debug information (only in development).
     */
    public function debug(string $event, array $context = []): void
    {
        // Only log debug in development
        if ($_ENV['APP_ENV'] ?? 'production' === 'development') {
            $this->log($event, $context, 'debug');
        }
    }

    /**
     * Get the current user ID from session.
     */
    private function getUserId(): ?int
    {
        return isset($_SESSION['user_id']) ? (int) $_SESSION['user_id'] : null;
    }

    /**
     * Get the client IP address.
     */
    private function getIpAddress(): ?string
    {
        return $_SERVER['HTTP_X_FORWARDED_FOR']
            ?? $_SERVER['HTTP_X_REAL_IP']
            ?? $_SERVER['REMOTE_ADDR']
            ?? null;
    }

    /**
     * Query logs by correlation ID.
     *
     * @return array<int, array<string, mixed>>
     */
    public function getByCorrelationId(string $correlationId): array
    {
        $stmt = $this->db->prepare('
            SELECT * FROM audit_log
            WHERE correlation_id = ?
            ORDER BY created_at ASC
        ');
        $stmt->execute([$correlationId]);

        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * Query recent logs for an entity.
     *
     * @return array<int, array<string, mixed>>
     */
    public function getByEntity(string $entityType, int $entityId, int $limit = 50): array
    {
        $stmt = $this->db->prepare('
            SELECT * FROM audit_log
            WHERE entity_type = ? AND entity_id = ?
            ORDER BY created_at DESC
            LIMIT ?
        ');
        $stmt->execute([$entityType, $entityId, $limit]);

        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
}