import { json, error } from '@sveltejs/kit';
import { S3Client, ListObjectsV2Command, GetObjectCommand } from '@aws-sdk/client-s3';
import { getSignedUrl } from '@aws-sdk/s3-request-presigner';
import { env } from '$env/dynamic/private';

export async function GET({ url }) {
	const nextToken = url.searchParams.get('next') || undefined;
	
	try {
		const s3 = new S3Client({
			endpoint: env.B2_ENDPOINT,
			region: env.B2_REGION,
			credentials: {
				accessKeyId: env.B2_ACCESS_KEY_ID,
				secretAccessKey: env.B2_SECRET_ACCESS_KEY
			}
		});

		const tokenDuration = parseInt(env.B2_TOKEN_DURATION, 10) || 600;

		// Fetch a batch of files from the thumbs/ folder
		const listCommand = new ListObjectsV2Command({
			Bucket: env.B2_BUCKET_NAME,
			Prefix: 'thumbs/',
			MaxKeys: 40,
			ContinuationToken: nextToken
		});

		const listResponse = await s3.send(listCommand);
		const contents = listResponse.Contents || [];

		// Strict Filter: Only allow actual .jpg or .jpeg extensions
		const imageFiles = contents.filter(file => {
			const lowerKey = file.Key.toLowerCase();
			return lowerKey.endsWith('.jpg') || lowerKey.endsWith('.jpeg');
		});

		// Generate presigned URLs for validated items
		const photos = await Promise.all(
			imageFiles.map(async (file) => {
				const id = file.Key.replace('thumbs/', '');
				const fullSizeKey = `images/${id}`;

				const thumbCommand = new GetObjectCommand({ Bucket: env.B2_BUCKET_NAME, Key: file.Key });
				const fullCommand = new GetObjectCommand({ Bucket: env.B2_BUCKET_NAME, Key: fullSizeKey });

				// 10 minutes = 600 seconds
				const [thumbUrl, fullUrl] = await Promise.all([
					getSignedUrl(s3, thumbCommand, { expiresIn: tokenDuration }),
					getSignedUrl(s3, fullCommand, { expiresIn: tokenDuration })
				]);

				return { id, thumbUrl, fullUrl };
			})
		);

		return json({
			photos,
			nextContinuationToken: listResponse.NextContinuationToken || null
		});
	} catch (err) {
		console.error(err);
		throw error(500, 'Failed to process images from storage.');
	}
}