node-data-modeling/src/create-type.js

"use strict";

const mapObj = require("map-obj");

const typeRules = require("./type-rules");
const generateDescriptor = require("./generate-descriptor");
const getSchemaKeys = require("./util/get-schema-keys");
const nullMissingFields = require("./util/null-missing-fields");
const generateTypeHash = require("./type-hash");
const serialize = require("./serialization/serialize");
const deserialize = require("./serialization/deserialize");

let registeredTypes = new Set();
let registeredTypesDirty = false;
let typeMap = new Map();

function hashAllTypes() {
	if (registeredTypesDirty) {
		registeredTypesDirty = false;

		for (let type of registeredTypes) {
			type._ensureHash();
		}
	}
}

module.exports = function createType(name, schema) {
	if (schema._isTypeRule === true) {
		return typeRules._createTypeRule({
			_typeName: name,
			_isTypeAlias: true,
			_alias: schema
		});
	} else {
		let propertyDescriptors = mapObj(schema, (key, rule) => {
			return generateDescriptor(rule, key, false);
		});

		let protoProperties = {
			_typeName: name,
			/* We pre-define this here so that instances can be monomorphic; this provides a 4x performance improvement. */
			_data: mapObj(schema, (key, _value) => {
				return [key, undefined];
			}),
			/* FIXME: Disallow overriding this. */
			serialize: function (serializer) {
				return serialize(this, {
					serializer: serializer
				});
			}
		};

		let proto = Object.create(protoProperties, propertyDescriptors);
		let schemaKeys = getSchemaKeys(schema);

		let factory = function createInstance(instanceProps) {
			factory._isUsed = true;

			let instance = Object.create(proto);
			instance._data = {};

			// for (let key of factory._schemaKeys) {
			// 	if (instanceProps[key] != null) {
			// 		instance[key] = instanceProps[key];
			// 	} else {
			// 		instance[key] = null;
			// 	}
			// }

			/* FIXME: Investigate ways to optimize this */
			let nullFields = nullMissingFields(instanceProps, factory._schemaKeys);
			Object.assign(instance, instanceProps, nullFields);

			return instance;
		};

		proto._type = factory;

		factory._schemaKeys = schemaKeys;
		factory._cumulativeSchema = Object.assign({}, schema);
		factory._isUsed = false;
		factory._typeHash = null;
		factory._isCustomType = true;
		factory._name = name;
		factory.prototype = proto;
		factory.description = name;

		factory._validator = function (value) {
			return (value instanceof factory);
		};

		factory._ensureHash = function () {
			if (this._typeHash == null) {
				this._isUsed = true;
				this._typeHash = generateTypeHash(this);
				typeMap.set(this._typeHash, this);
			}
		};

		/* FIXME: Is the below actually necessary? */
		proto._selfValidator = factory._validator;

		factory._implementedTraits = new Set();
		factory.implements = function (trait, implementation) {
			/* FIXME: Deregister old hash from global hash registry after mutating through trait implementation */
			if (this._isUsed !== false) {
				throw new Error("Cannot modify a custom type that has already been instantiated");
			} else {
				let {implementationDescriptors, slotSchemaKeys, implementationSchema} = trait.applyImplementation(implementation);

				let plainImplementationSchema = mapObj(implementationSchema, (key, value) => {
					return [key, value.rule];
				});

				// FIXME: Test this
				Object.keys(implementationDescriptors).forEach((key) => {
					if (proto.key != null) {
						throw new Error(`Trait implementation attempted to define a property '${key}' on the '${name}' type, but that property already exists`);
					}
				});

				Object.defineProperties(proto, implementationDescriptors);
				this._implementedTraits.add(trait);
				this._schemaKeys = this._schemaKeys.concat(slotSchemaKeys);
				Object.assign(this._cumulativeSchema, plainImplementationSchema);

				/* TODO: Verify that this produces the expected performance benefit for trait-having typesw. */
				for (let key of slotSchemaKeys) {
					protoProperties._data[key] = null;
				}

				return this;
			}
		};

		factory.deserialize = function (data, deserializer) {
			hashAllTypes();
			
			return deserialize(this, JSON.parse(data), typeMap, {
				deserializer: deserializer
			});
		};

		let rule = typeRules._createTypeRule(factory);
		registeredTypes.add(rule);
		registeredTypesDirty = true;
		return rule;
	}
};