src/lib/server/photo.ts

import sharp from 'sharp';
import { collections, withTransaction } from '$lib/server/db';
import { generateId } from '$lib/utils/generateId';
import type { ClientSession } from 'mongodb';
import { error } from '@sveltejs/kit';

export async function generatePicture(
	buffer: Buffer,
	name: string,
	opts?: { productId?: string; cb?: (session: ClientSession) => Promise<void> }
): Promise<void> {
	const image = sharp(buffer);
	const { width, height } = await image.metadata();

	if (!width || !height) {
		throw error(400, 'Invalid image: no height or width');
	}

	const formats: Array<{ width: number; height: number; data: Buffer }> = [];

	if (width <= 2048 && height <= 2048) {
		formats.push({
			width,
			height,
			data: await image.toFormat('webp').toBuffer()
		});
	}

	for (const size of [2048, 1024, 512, 256, 128]) {
		if (width > size || height > size) {
			const buffer = await image
				.resize(width > height ? { width: size } : { height: size })
				.toFormat('webp')
				.toBuffer();
			const metadata = await sharp(buffer).metadata();

			formats.push({
				width: metadata.width!,
				height: metadata.height!,
				data: buffer
			});
		}
	}

	const _id = generateId(name);

	await withTransaction(async (session) => {
		await collections.pictures.insertOne(
			{
				_id,
				name,
				storage: formats.map((format) => ({
					_id: `${_id}-${format.width}x${format.height}`,
					width: format.width,
					height: format.height,
					size: format.data.length
				})),
				...(opts?.productId && { productId: opts.productId }),
				createdAt: new Date(),
				updatedAt: new Date()
			},
			{ session }
		);

		await collections.picturesFs.insertMany(
			formats.map(
				(format) => ({
					_id: `${_id}-${format.width}x${format.height}`,
					createdAt: new Date(),
					updatedAt: new Date(),
					size: format.data.length,
					data: format.data,
					picture: _id
				}),
				{ session }
			)
		);

		if (opts?.cb) {
			await opts.cb(session);
		}
	});
}