Project-Image-Uploader/backend/src/routes/reorder.js

const express = require('express');
const router = express.Router();
const GroupRepository = require('../repositories/GroupRepository');

/**
 * PUT /api/groups/:groupId/reorder
 * Reorder images within a group
 * 
 * Request Body:
 * {
 *   "imageIds": [123, 456, 789] // Array of image IDs in new order
 * }
 * 
 * Response:
 * {
 *   "success": true,
 *   "message": "Image order updated successfully",
 *   "data": {
 *     "groupId": "abc123",
 *     "updatedImages": 3,
 *     "newOrder": [123, 456, 789]
 *   }
 * }
 */
router.put('/:groupId/reorder', async (req, res) => {
    try {
        const { groupId } = req.params;
        const { imageIds } = req.body;

        // Input validation
        if (!groupId) {
            return res.status(400).json({
                success: false,
                message: 'Group ID is required'
            });
        }

        if (!imageIds || !Array.isArray(imageIds) || imageIds.length === 0) {
            return res.status(400).json({
                success: false,
                message: 'imageIds array is required and cannot be empty'
            });
        }

        // Validate that all imageIds are numbers
        const invalidIds = imageIds.filter(id => !Number.isInteger(id) || id <= 0);
        if (invalidIds.length > 0) {
            return res.status(400).json({
                success: false,
                message: `Invalid image IDs: ${invalidIds.join(', ')}. Image IDs must be positive integers`
            });
        }

        // Log the reordering operation
        console.log(`[REORDER] Group ${groupId}: Reordering ${imageIds.length} images`);
        console.log(`[REORDER] New order: ${imageIds.join(' → ')}`);

        // Execute the reordering
        const result = await GroupRepository.updateImageOrder(groupId, imageIds);

        // Success response
        res.status(200).json({
            success: true,
            message: 'Image order updated successfully',
            data: result
        });

        // Log success
        console.log(`[REORDER] Success: Updated ${result.updatedImages} images in group ${groupId}`);

    } catch (error) {
        console.error(`[REORDER] Error reordering images in group ${req.params.groupId}:`, error.message);

        // Handle specific error types
        if (error.message.includes('not found')) {
            return res.status(404).json({
                success: false,
                message: error.message
            });
        }

        if (error.message.includes('Invalid image IDs') || 
            error.message.includes('Missing image IDs') ||
            error.message.includes('is required')) {
            return res.status(400).json({
                success: false,
                message: error.message
            });
        }

        // Generic server error
        res.status(500).json({
            success: false,
            message: 'Internal server error during image reordering',
            error: process.env.NODE_ENV === 'development' ? error.message : undefined
        });
    }
});

module.exports = router;