validateComplexModel.ts

import * as V from "../src/validation";
import * as PV from "../src/predValidation";

// a custom error type
interface ErrorType {
  path: string;
  error: string;
}

// some validations
const notBlank = (property: string, s: string): V.Validation<ErrorType> =>
  (s || "").length > 0
    ? V.success()
    : V.failure([{ path: property, error: `${property} was blank` }]);

const positive = (property: string, n: number): V.Validation<ErrorType> =>
  n > 0
    ? V.success()
    : V.failure([{ path: property, error: `${property} was negative` }]);

// a non trivial model with child relationship
type Package = { label: string; qty: number };
type Item = { itemNumber: string; packages: Package[] };

// validate a single package
const packageValidation: PV.PredValidation<Package, ErrorType> = (p: Package) =>
  V.combine(positive("qty", p.qty), notBlank("label", p.label));

// a helper that allows us to prepend error paths with index info
const prefixIndex = (property: string) => (
  e: ErrorType,
  i: number
): ErrorType => ({
  ...e,
  path: `${property}[${i}].${e.path}`
});

// lift packageValidation to work on an array of Packages.  
// if an item has an error prefix the path with packages[indexInArray]
const packagesValidation: PV.PredValidation<Package[], ErrorType> = PV.all(
  packageValidation,
  prefixIndex("packages")
);

// combine packagesValidation with a notBlank to validate an Item
const itemValidation: PV.PredValidation<Item, ErrorType> = PV.combine(
  (i: Item) => notBlank("itemNumber", i.itemNumber),
  (i: Item) => packagesValidation(i.packages)
);

// an invalid item
const invalidItem = {
  itemNumber: "",
  packages: [
    { label: "", qty: -2 },
    { label: "", qty: 2 },
    { label: "pack", qty: 10 }
  ]
};

console.log(itemValidation(invalidItem));
// { kind: 'Failure',
//  errors:
//   [ { path: 'itemNumber', error: 'itemNumber was blank' },
//     { path: 'packages[0].qty', error: 'qty was negative' },
//     { path: 'packages[0].label', error: 'label was blank' },
//     { path: 'packages[1].label', error: 'label was blank' } ] }

// a valid item
const validItem = {
  itemNumber: "123",
  packages: [{ label: "each", qty: 1 }, { label: "pack", qty: 10 }]
};

console.log(itemValidation(validItem));
// { kind: 'Success' }

// lift itemValidation to work with an array of Items
const itemsValidation: PV.PredValidation<Item[], ErrorType> = PV.all(
  itemValidation,
  prefixIndex("")
);

const items = [validItem, invalidItem];

console.log(itemsValidation(items));
// { kind: 'Failure',
//  errors:
//   [ { path: '[1].itemNumber', error: 'itemNumber was blank' },
//     { path: '[1].packages[0].qty', error: 'qty was negative' },
//     { path: '[1].packages[0].label', error: 'label was blank' },
//     { path: '[1].packages[1].label', error: 'label was blank' } ] }