Validates a selected image for a fake "articles" table by mime type

directus-image-validation-hook.js

// This example uses a "articles" collection with an "image" field that we only want to allow JPEGs in

module.exports = function registerHook({ filter, action }, { exceptions, services, logger }) {
	const { InvalidPayloadException } = exceptions;
	const { FilesService } = services;

	//===============================================================================================
	// Make sure only JPEGs can be associated to the collection
	const imageFieldValidator = async (payload, _meta, { database, schema }) => {
		// Note how the "database" object is passed in from the filter handler to the service, this
		// allows the service to operate against the same transaction that the current filter is using
		const filesService = new FilesService({ schema, database });

		// Only execute the check if the image field was actually set/altered
		if (payload.image) {
			const { type } = await filesService.readOne(payload.image, { fields: ['type'] });

			if (type !== 'image/jpeg') {
				// This message will be shown to the user in a dialog on save, alternatively, a
				// FailedValidationException can be used
				throw new InvalidPayloadException('Image has to be a JPEG');
			}
		}
	};

	filter('articles.items.create', imageFieldValidator);
	filter('articles.items.update', imageFieldValidator);

	//===============================================================================================
	// Prevent non-jpegs from being uploaded in the first place.
	//
	// This currently has to be handled "reactionary", as there's no blocking filter hook for file
	// file uploads. The solution here will respond to a file upload, and immediately delete/undo the
	// upload when a non-jpeg is detected.
	action('files.upload', async ({ key, payload }, { database, schema }) => {
		const filesService = new FilesService({ database, schema });

		if (payload.type !== 'image/jpeg') {
			logger.warn('Illegal file type uploaded');
			await filesService.deleteOne(key);
		}
	});
};