<?php
// Start session if not already started
if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

// Set proper content type
header('Content-Type: application/json');

// Basic authentication check
if (!isset($_SESSION['user_id'])) {
    http_response_code(403);
    echo json_encode(['success' => false, 'message' => 'Authentication required.']);
    exit;
}

// Check if image path is provided
if (!isset($_POST['path']) || empty($_POST['path'])) {
    http_response_code(400);
    echo json_encode(['success' => false, 'message' => 'Image path not provided.']);
    exit;
}

$imagePath = $_POST['path'];

// Sanitize the path: remove any query string to prevent issues with realpath()
$path_parts = parse_url($imagePath);
$imagePath = $path_parts['path'];

$baseDir = realpath(__DIR__ . '/../data/images/backgrounds');
$fullPath = realpath(__DIR__ . '/../' . $imagePath);

// Security check: ensure the file is within the backgrounds directory
if (!$fullPath || strpos($fullPath, $baseDir) !== 0 || !file_exists($fullPath)) {
    http_response_code(400);
    echo json_encode(['success' => false, 'message' => 'Invalid or non-existent image path.']);
    exit;
}

// --- Image Optimization Logic ---
$maxWidth = 1920;
$quality = 85;

try {
    // Get image info
    list($width, $height, $type) = getimagesize($fullPath);
    
    // Check if image is too large for memory (more conservative estimate)
    $estimatedMemory = ($width * $height * 4) + (1920 * 1080 * 4); // Rough estimate
    if ($estimatedMemory > (400 * 1024 * 1024)) { // 400MB (leave some headroom)
        echo json_encode(['success' => false, 'message' => 'Image too large to process safely. Please use a smaller image or reduce the image dimensions.']);
        exit;
    }

    // Don't optimize if the image is already reasonably sized
    if ($width <= $maxWidth) {
        // Still, re-save JPEG to apply quality setting, which might reduce size
        if ($type == IMAGETYPE_JPEG) {
            $source = imagecreatefromjpeg($fullPath);
            if ($source === false) {
                throw new Exception('Could not load image for quality adjustment.');
            }
            imagejpeg($source, $fullPath, $quality);
            imagedestroy($source);
            echo json_encode(['success' => true, 'message' => 'Image quality adjusted, but no resize needed.']);
            exit;
        }
        // For other types, if no resize is needed, there's nothing to do.
        echo json_encode(['success' => true, 'message' => 'Image is already optimized (width is within limit).']);
        exit;
    }

    // Continue with resizing for images wider than maxWidth
    $newWidth = $maxWidth;
    $newHeight = (int) (($newWidth / $width) * $height);
    
    // Create image resource based on type
    $source = false;
    switch ($type) {
        case IMAGETYPE_JPEG:
            $source = @imagecreatefromjpeg($fullPath);
            break;
        case IMAGETYPE_PNG:
            $source = @imagecreatefrompng($fullPath);
            break;
        case IMAGETYPE_GIF:
            $source = @imagecreatefromgif($fullPath);
            break;
        case IMAGETYPE_WEBP:
            $source = @imagecreatefromwebp($fullPath);
            break;
        default:
            throw new Exception('Unsupported image type.');
    }

    if ($source === false) {
        throw new Exception('Could not create image resource. The image may be corrupted or too large.');
    }
    
    // Create a new true color image
    $thumb = imagecreatetruecolor($newWidth, $newHeight);

    // Handle transparency for PNG
    if ($type == IMAGETYPE_PNG) {
        imagealphablending($thumb, false);
        imagesavealpha($thumb, true);
        $transparent = imagecolorallocatealpha($thumb, 255, 255, 255, 127);
        imagefilledrectangle($thumb, 0, 0, $newWidth, $newHeight, $transparent);
    }

    // Resize
    imagecopyresampled($thumb, $source, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);

    // Save the optimized image, overwriting the original
    switch ($type) {
        case IMAGETYPE_JPEG:
            imagejpeg($thumb, $fullPath, $quality);
            break;
        case IMAGETYPE_PNG:
            // PNG quality is 0-9. 85 quality -> level 1-2.
            imagepng($thumb, $fullPath, 1);
            break;
        case IMAGETYPE_GIF:
            imagegif($thumb, $fullPath);
            break;
        case IMAGETYPE_WEBP:
            imagewebp($thumb, $fullPath, $quality);
            break;
    }

    // Free up memory
    imagedestroy($source);
    imagedestroy($thumb);

    echo json_encode(['success' => true, 'message' => 'Image optimized successfully.']);

} catch (Exception $e) {
    http_response_code(500);
    echo json_encode(['success' => false, 'message' => 'Error optimizing image: ' . $e->getMessage()]);
}