refinement.js

var assert = require('./assert');
var isTypeName = require('./isTypeName');
var isFunction = require('./isFunction');
var forbidNewOperator = require('./forbidNewOperator');
var isIdentity = require('./isIdentity');
var create = require('./create');
var is = require('./is');
var getTypeName = require('./getTypeName');
var getFunctionName = require('./getFunctionName');

function getDefaultName(type, predicate) {
  return '{' + getTypeName(type) + ' | ' + getFunctionName(predicate) + '}';
}

function refinement(type, predicate, name) {

  if (process.env.NODE_ENV !== 'production') {
    assert(isFunction(type), function () { return 'Invalid argument type ' + assert.stringify(type) + ' supplied to refinement(type, predicate, [name]) combinator (expected a type)'; });
    assert(isFunction(predicate), function () { return 'Invalid argument predicate supplied to refinement(type, predicate, [name]) combinator (expected a function)'; });
    assert(isTypeName(name), function () { return 'Invalid argument name ' + assert.stringify(name) + ' supplied to refinement(type, predicate, [name]) combinator (expected a string)'; });
  }

  var displayName = name || getDefaultName(type, predicate);
  var identity = isIdentity(type);

  function Refinement(value, path) {

    if (process.env.NODE_ENV !== 'production') {
      if (identity) {
        forbidNewOperator(this, Refinement);
      }
      path = path || [displayName];
    }

    var x = create(type, value, path);

    if (process.env.NODE_ENV !== 'production') {
      assert(predicate(x), function () { return 'Invalid value ' + assert.stringify(value) + ' supplied to ' + path.join('/'); });
    }

    return x;
  }

  Refinement.meta = {
    kind: 'subtype',
    type: type,
    predicate: predicate,
    name: name,
    identity: identity
  };

  Refinement.displayName = displayName;

  Refinement.is = function (x) {
    return is(x, type) && predicate(x);
  };

  Refinement.update = function (instance, patch) {
    return Refinement(assert.update(instance, patch));
  };

  return Refinement;
}

refinement.getDefaultName = getDefaultName;
module.exports = refinement;