const querySchema = {
name: { type: "string", min: 3, max: 255 },
};

const customErrorHandler = (err, req, res, next) => {
console.log('error at the customErrorHandler:');
console.log(err);
res.sendStatus(418);
}

const validationMiddleware = RequestValidator({
// also you can pass the "body" and "params" fields
query: querySchema,
});

const middlewareWithCustomHandler = RequestValidator(
{ query: querySchema },
customErrorHandler,
);

const fastMiddleware = RequestValidator(
{ query: querySchema },
null, // define a custom error handler if you want to

/* you can pass some options for a fastest-validator instance
it should implements a ValidatorConstructorOptions interface
note that this package set a "useNewCustomCheckerFunction" option in true by default
so you should override it to use a v1 syntax for built-in rules */
{ haltOnFirstError: true }
);

// also this package provides BodyValidator and ParamsValidator short validators
const shortQueryMiddleware = QueryValidator(
querySchema,
// also you can pass a custom error handler in a second argument,
// also you can pass a ValidatorConstructorOptions in a third argument
);

app.get('/', validationMiddleware, (req, res) => {
console.log('a query object is:');
console.log(req.query);
res.send('Hello World');
});

app.get('/custom', middlewareWithCustomHandler, (req, res) => {
console.log('a query object at the custom route is:');
console.log(req.query);
res.send('Hello Custom');
});

app.get('/fast', fastMiddleware, (req, res) => {
console.log('a query object at the fast route is:');
console.log(req.query);
res.send('It was fast');
});

app.get('/short', shortQueryMiddleware, (req, res) => {
console.log('a query object at the short route is:');
console.log(req.query);
res.send('Hello Short');
});

// This middleware already have a default validation error handling behaviour -
// send 404 on params validation error
// and 422 (with error details at response body) on query and body validation error.
const defaultQueryValidationMiddleware = DefaultRequestValidator(
{ query: schema / body, params / },
// you can pass a ValidatorConstructorOptions here
);
app.get('/default', defaultQueryValidationMiddleware, (req, res) => {
console.log('a query object at the default route is:');
console.log(req.query);
res.send('Hello Default');
});

app.use((err, req, res, next) => {
console.log('OMG!');
console.error(err);
res.status(500).send('Something broke!');
});