import {Instantiable} from '../di'
import {FormRequest} from './FormRequest'
import {ValidationError} from './Validator'
import {ResponseObject, RouteHandler} from '../http/routing/Route'
import {Request} from '../http/lifecycle/Request'

/**
 * Builds a middleware function that validates a request's input against
 * the given form request class and registers the FormRequest class into
 * the request container.
 *
 * @example
 * ```typescript
 * Route.group(...).pre(formRequest(MyFormRequestClass))
 * ```
 *
 * @param formRequestClass
 */
export function formRequest<T>(formRequestClass: Instantiable<FormRequest<T>>): RouteHandler {
    return async function formRequestRouteHandler(request: Request): Promise<ResponseObject> {
        const formRequestInstance = <FormRequest<T>> request.make(formRequestClass)

        try {
            await formRequestInstance.get()
            request.registerSingletonInstance<FormRequest<T>>(formRequestClass, formRequestInstance)
        } catch (e: unknown) {
            if ( e instanceof ValidationError ) {
                return e.errors.toJSON()
            }

            throw e
        }
    }
}