<?php
/**
 * Session Manager for Multi-User Support
 * Handles isolated sessions, file-based image storage, and automatic cleanup
 */

class SessionManager {
    private $sessionId;
    private $uploadDir;
    private $sessionDir;

    public function __construct() {
        // Configure session for better security
        ini_set('session.cookie_httponly', 1);
        ini_set('session.use_only_cookies', 1);
        ini_set('session.cookie_lifetime', 86400); // 24 hours
        ini_set('session.gc_maxlifetime', 86400); // 24 hours

        // Start session if not already started
        if (session_status() === PHP_SESSION_NONE) {
            session_start();
        }

        // Regenerate session ID on first access for security
        if (!isset($_SESSION['initialized'])) {
            session_regenerate_id(true);
            $_SESSION['initialized'] = true;
            $_SESSION['created_at'] = time();
        }

        $this->sessionId = session_id();
        $this->uploadDir = __DIR__ . '/uploads/sessions';
        $this->sessionDir = $this->uploadDir . '/' . $this->sessionId;

        // Create session directory if it doesn't exist
        if (!is_dir($this->sessionDir)) {
            mkdir($this->sessionDir, 0755, true);
            mkdir($this->sessionDir . '/images', 0755, true);
        }

        // Initialize session data
        $this->initializeSessionData();

        // Clean up invalid history entries
        $this->cleanupImageHistory();

        // Auto-cleanup expired images (runs randomly ~10% of the time)
        // This replaces the need for a cron job
        if (rand(1, 10) === 1) {
            $this->autoCleanupExpiredImages();
        }
    }

    private function initializeSessionData() {
        if (!isset($_SESSION['conversation_history'])) {
            $_SESSION['conversation_history'] = [];
        }
        if (!isset($_SESSION['image_history'])) {
            $_SESSION['image_history'] = [];
        }
        if (!isset($_SESSION['current_image_path'])) {
            $_SESSION['current_image_path'] = null;
        }
    }

    public function getSessionId() {
        return $this->sessionId;
    }

    public function getSessionDir() {
        return $this->sessionDir;
    }

    public function getImagesDir() {
        return $this->sessionDir . '/images';
    }

    /**
     * Save image to disk and return file path
     */
    public function saveImage($imageData, $mimeType = 'image/png') {
        $extension = $this->getExtensionFromMime($mimeType);
        $timestamp = time();
        $filename = 'image_' . $timestamp . '_' . uniqid() . '.' . $extension;
        $filepath = $this->getImagesDir() . '/' . $filename;

        // Decode base64 if needed
        if (base64_decode($imageData, true) !== false) {
            $imageData = base64_decode($imageData);
        }

        // Save image
        if (file_put_contents($filepath, $imageData) === false) {
            throw new Exception('Failed to save image to disk');
        }

        // Save metadata
        $metadataFile = $filepath . '.meta';
        $metadata = [
            'created_at' => $timestamp,
            'mime_type' => $mimeType,
            'session_id' => $this->sessionId,
            'expires_at' => $timestamp + 86400 // 24 hours
        ];
        file_put_contents($metadataFile, json_encode($metadata));

        return $filename;
    }

    /**
     * Get image data from disk
     */
    public function getImage($filename) {
        $filepath = $this->getImagesDir() . '/' . $filename;

        // Check if file exists and is actually a file (not a directory)
        if (!file_exists($filepath) || !is_file($filepath)) {
            return null;
        }

        // Check if image has expired
        $metadataFile = $filepath . '.meta';
        if (file_exists($metadataFile) && is_file($metadataFile)) {
            $metadata = json_decode(file_get_contents($metadataFile), true);
            if ($metadata && isset($metadata['expires_at']) && $metadata['expires_at'] < time()) {
                // Image expired, delete it
                $this->deleteImage($filename);
                return null;
            }
        }

        return [
            'data' => base64_encode(file_get_contents($filepath)),
            'mime_type' => $this->getMimeTypeFromFile($filepath)
        ];
    }

    /**
     * Delete image from disk
     */
    public function deleteImage($filename) {
        $filepath = $this->getImagesDir() . '/' . $filename;
        $metadataFile = $filepath . '.meta';

        if (file_exists($filepath)) {
            unlink($filepath);
        }
        if (file_exists($metadataFile)) {
            unlink($metadataFile);
        }
    }

    /**
     * Set current image and add to history
     */
    public function setCurrentImage($filename, $mimeType = 'image/png') {
        $_SESSION['current_image_path'] = $filename;
        $_SESSION['current_image_mime'] = $mimeType;

        // Add to history (keep last 10)
        $this->addToImageHistory($filename, $mimeType);
    }

    /**
     * Add image to history
     */
    private function addToImageHistory($filename, $mimeType) {
        if (!isset($_SESSION['image_history'])) {
            $_SESSION['image_history'] = [];
        }

        // Add to beginning of array
        array_unshift($_SESSION['image_history'], [
            'filename' => $filename,
            'mime_type' => $mimeType,
            'timestamp' => time()
        ]);

        // Keep only last 10
        if (count($_SESSION['image_history']) > 10) {
            $_SESSION['image_history'] = array_slice($_SESSION['image_history'], 0, 10);
        }
    }

    /**
     * Get image history
     */
    public function getImageHistory() {
        return $_SESSION['image_history'] ?? [];
    }

    /**
     * Clean up invalid image history entries
     * Removes entries without filename or with missing files
     */
    private function cleanupImageHistory() {
        if (!isset($_SESSION['image_history']) || !is_array($_SESSION['image_history'])) {
            $_SESSION['image_history'] = [];
            return;
        }

        $validHistory = [];

        foreach ($_SESSION['image_history'] as $item) {
            // Check if item has filename key and file exists
            if (isset($item['filename']) && !empty($item['filename'])) {
                $filepath = $this->getImagesDir() . '/' . $item['filename'];
                if (file_exists($filepath) && is_file($filepath)) {
                    $validHistory[] = $item;
                }
            }
        }

        $_SESSION['image_history'] = $validHistory;
    }

    /**
     * Restore image from history
     */
    public function restoreImageFromHistory($filename) {
        $image = $this->getImage($filename);
        if ($image) {
            $this->setCurrentImage($filename, $image['mime_type']);
            return true;
        }
        return false;
    }

    /**
     * Get current image
     */
    public function getCurrentImage() {
        if (!isset($_SESSION['current_image_path']) || !$_SESSION['current_image_path']) {
            return null;
        }

        return $this->getImage($_SESSION['current_image_path']);
    }

    /**
     * Clear current image
     */
    public function clearCurrentImage() {
        if (isset($_SESSION['current_image_path']) && $_SESSION['current_image_path']) {
            $this->deleteImage($_SESSION['current_image_path']);
        }
        $_SESSION['current_image_path'] = null;
        $_SESSION['current_image_mime'] = 'image/png';
    }

    /**
     * Add to conversation history
     */
    public function addToHistory($prompt, $type = 'edit') {
        $_SESSION['conversation_history'][] = [
            'prompt' => $prompt,
            'type' => $type,
            'timestamp' => time()
        ];

        // Keep only last 50 items
        if (count($_SESSION['conversation_history']) > 50) {
            $_SESSION['conversation_history'] = array_slice($_SESSION['conversation_history'], -50);
        }
    }

    /**
     * Get conversation history
     */
    public function getHistory() {
        return $_SESSION['conversation_history'] ?? [];
    }

    /**
     * Clear all session data and images
     */
    public function reset() {
        // Delete all images in session directory
        $imagesDir = $this->getImagesDir();
        if (is_dir($imagesDir)) {
            $files = glob($imagesDir . '/*');
            foreach ($files as $file) {
                if (is_file($file)) {
                    unlink($file);
                }
            }
        }

        // Clear session data
        $_SESSION['conversation_history'] = [];
        $_SESSION['image_history'] = [];
        $_SESSION['current_image_path'] = null;
        $_SESSION['current_image_mime'] = 'image/png';
    }

    /**
     * Get file extension from MIME type
     */
    private function getExtensionFromMime($mimeType) {
        $mimeMap = [
            'image/jpeg' => 'jpg',
            'image/jpg' => 'jpg',
            'image/png' => 'png',
            'image/webp' => 'webp',
            'image/gif' => 'gif'
        ];

        return $mimeMap[$mimeType] ?? 'png';
    }

    /**
     * Get MIME type from file
     */
    private function getMimeTypeFromFile($filepath) {
        $extension = strtolower(pathinfo($filepath, PATHINFO_EXTENSION));

        $extMap = [
            'jpg' => 'image/jpeg',
            'jpeg' => 'image/jpeg',
            'png' => 'image/png',
            'webp' => 'image/webp',
            'gif' => 'image/gif'
        ];

        return $extMap[$extension] ?? 'image/png';
    }

    /**
     * Auto-cleanup expired images (called on session init)
     * Runs the cleanup in the background without blocking
     */
    private function autoCleanupExpiredImages() {
        try {
            // Run cleanup silently
            $result = self::cleanupExpiredImages($this->uploadDir);

            // Log cleanup results if any images were cleaned
            if ($result['cleaned'] > 0) {
                error_log("Auto-cleanup: Removed {$result['cleaned']} expired images");
            }
        } catch (Exception $e) {
            // Silently fail - don't break the app if cleanup fails
            error_log("Auto-cleanup failed: " . $e->getMessage());
        }
    }

    /**
     * Static method to clean up expired images across all sessions
     */
    public static function cleanupExpiredImages($uploadDir = null) {
        if ($uploadDir === null) {
            $uploadDir = __DIR__ . '/uploads/sessions';
        }

        if (!is_dir($uploadDir)) {
            return ['cleaned' => 0, 'errors' => []];
        }

        $cleaned = 0;
        $errors = [];
        $currentTime = time();

        // Scan all session directories
        $sessionDirs = glob($uploadDir . '/*', GLOB_ONLYDIR);

        foreach ($sessionDirs as $sessionDir) {
            $imagesDir = $sessionDir . '/images';

            if (!is_dir($imagesDir)) {
                continue;
            }

            // Find all metadata files
            $metadataFiles = glob($imagesDir . '/*.meta');

            foreach ($metadataFiles as $metadataFile) {
                try {
                    $metadata = json_decode(file_get_contents($metadataFile), true);

                    // Check if expired
                    if ($metadata && isset($metadata['expires_at']) && $metadata['expires_at'] < $currentTime) {
                        // Delete image and metadata
                        $imageFile = str_replace('.meta', '', $metadataFile);

                        if (file_exists($imageFile)) {
                            unlink($imageFile);
                        }
                        unlink($metadataFile);

                        $cleaned++;
                    }
                } catch (Exception $e) {
                    $errors[] = $e->getMessage();
                }
            }

            // Remove empty session directories
            $remainingFiles = glob($imagesDir . '/*');
            if (empty($remainingFiles)) {
                rmdir($imagesDir);
                rmdir($sessionDir);
            }
        }

        return [
            'cleaned' => $cleaned,
            'errors' => $errors,
            'timestamp' => date('Y-m-d H:i:s')
        ];
    }
}