example.js

import { spec, valid, explain, conform } from "./index";

const point = spec.map("point", {
  x: spec.int,
  y: spec.int
});
const line = spec.map("line", {
  p1: point,
  p2: point
});
const point_or_line = spec.or("point or line", {
  point: point,
  line
});

const p = {
  x: 0
};
valid(point_or_line, p);
// => false

// what is wrong?
explain(point_or_line, p);
// point or line → point → point → Keys(point): hasKey failed for undefined at [y].
// point or line → line → line → Keys(line): hasKey failed for undefined at [p1].
// point or line → line → line → Keys(line): hasKey failed for undefined at [p2].

// let's try again
const p2 = {
  x: 0,
  y: 0
};

valid(point_or_line, p2);
// => true

// but which spec did it match?
conform(point_or_line, p2);
// => [ 'point', { x: 0, y: 0 } ]

// regexes work also (only cat/alt currently though)
const line2 = spec.cat("source", point, "target", point);
conform(line2, [p2, p2]);
// => {source: {x: 0, y: 0}, target: {x: 0, y: 0}}
explain(line2, [p2, p]);
// cat · → target → point → Keys(point): hasKey failed for undefined at [1, y].
explain(line2, [p2]);
// cat ·: hasLength failed for undefined at [].