import { Either, left, right } from 'fp-ts/lib/Either';

type File = {
	name: string;
	ext: string;
	size: number;
};

const checkName = (f: File): Either<string, File> =>
	f.name.length < 20 ? right(f) : left('File length should be less then 20 characters');

const checkExt = (f: File): Either<string, File> =>
	['ts', 'tsx'].includes(f.ext) ? right(f) : left('File extension should be either ts or tsx');

const checkSize = (f: File): Either<string, File> => (f.size < 1000 ? right(f) : left('Error message about size'));


const file = {
	name: 'file',
	ext: 'tss',
	size: 123,
};

// we'll have Either Right<File> or Left<string> here
const validatedFile = checkName(file)
	.chain(checkExt)
	.chain(checkSize);