node-data-modeling/src/util/get-value-type.js

"use strict";

const util = require("util");
const capitalize = require("capitalize");

const isConstructor = require("./is-constructor");
const isNamedFunction = require("./is-named-function");

/* TODO: Add property tracking throughout calls, to determine exactly where the wrong value was specified. */

module.exports = getValueType;
function getValueType(value, withArticle = true) {
	let [article, description] = getValueTypeData(value);

	if (withArticle) {
		if (article != null) {
			return `${article} ${description}`;
		} else {
			return description;
		}
	} else {
		return description;
	}
}

function getValueTypeData(value) {
	if (value != null && value._isTypeRule) {
		/*
			_baseType
				boolean
				string
				number
				nothing?
				null
				undefined
				function?
				guardedFunction
			_collectionType
				set
				map
				array
			_modifierType
				either
			_constructorType
				(for instanceOf)
			_isSlotRule
			_isSelfRule
			custom type
		*/
		if (value._isSlotRule) {
			return [null, "(slot)"];
		} else if (value._isSelfRule) {
			return [null, "(self)"];
		} else if (value._constructorType != null) {
			let constructorName;

			if (value._constructorType.name != null) {
				constructorName = value._constructorType.name;
			} else {
				constructorName = "(unnamed type)";
			}

			return ["an", `instance of ${constructorName}`];
		} else if (value._baseType != null) {
			if (value._baseType === "guardedFunction") {
				let argList = value._options.args
					.map((arg) => getValueType(arg, false))
					.join(", ");

				return ["a", `guarded function (${argList}) → ${getValueType(value._options.returnType, false)}`];
			} else {
				if (value._baseType === "string") {
					return ["a", "string"];
				} else if (value._baseType === "number") {
					return ["a", "number"];
				} else if (value._baseType === "boolean") {
					return ["a", "boolean"];
				} else {
					return [null, value._baseType];
				}
			}
		} else if (value._modifierType != null) {
			if (value._modifierType === "either") {
				let typeList = value._types
					.map((type) => getValueType(type, false))
					.join(" | ");

				return [null, `Either<${typeList}>`];
			} else {
				throw new Error(`Encountered unrecognized modifier type: ${value._modifierType}`);
			}
		} else if (value._collectionType != null) {
			let collectionTypeName = capitalize(value._collectionType);

			if (value._keyType != null) {
				return ["a", `${collectionTypeName}<${getValueType(value._keyType, false)} → ${getValueType(value._itemType, false)}>`];
			} else {
				return ["a", `${collectionTypeName}<${getValueType(value._itemType, false)}>`];
			}
		} else if (value._isCustomType || value._isCustomRegistryType) {
			return ["an", `instance of ${value._name}`];
		} else if (value._isTrait || value._isRegistryTrait) {
			return ["an", `instance of a type with the ${value._name} trait`];
		} else {
			throw new Error(`Encountered unrecognized type rule: ${util.inspect(value, {breakLength: Infinity})}`);
		}
	} else {
		/* Assume this is a value, rather than a type rule. */
		if (value === undefined) {
			return [null, "undefined"];
		} else if (value === null) {
			return [null, "null"];
		} else if (typeof value === "boolean") {
			return ["a", "boolean"];
		} else if (typeof value === "number") {
			if (value === Number.POSITIVE_INFINITY) {
				return [null, "Infinity"];
			} else if (value === Number.NEGATIVE_INFINITY) {
				return [null, "negative Infinity"];
			} else if (isNaN(value)) {
				return [null, "NaN"];
			} else {
				return ["a", "number"];
			}
		} else if (typeof value === "string") {
			return ["a", "string"];
		} else if (typeof value === "function") {
			if (value._guardedFunction != null) {
				let functionName;

				if (isNamedFunction(value._guardedFunction)) {
					functionName = `guarded function[${value._guardedFunction.name}]`;
				} else {
					functionName = "guarded function";
				}

				/* TODO: Deduplicate this code? */
				let argList = value._guardedArgs
					.map((arg) => getValueType(arg, false))
					.join(", ");

				return ["a", `${functionName} (${argList}) → ${getValueType(value._guardedReturnType, false)}`];
			} else if (isConstructor(value)) {
				if (isNamedFunction(value)) {
					return ["a", `constructor[${value.name}]`];
				} else {
					return ["a", "constructor"];
				}
			} else {
				if (isNamedFunction(value)) {
					return ["a", `function[${value.name}]`];
				} else {
					return ["a", "function"];
				}
			}
		} else if (Array.isArray(value)) {
			return ["an", "array"];
		} else if (value instanceof RegExp) {
			return ["a", "regular expression"];
		} else if (typeof value === "object") {
			if (value._guardedCollectionType === "set") {
				return ["a", `Set<${getValueType(value._itemType, false)}>`];
			} else if (value._guardedCollectionType === "map") {
				return ["a", `Map<${getValueType(value._keyType, false)} → ${getValueType(value._itemType, false)}>`];
			} else if (value instanceof Map) {
				return ["a", "Map"];
			} else if (value instanceof Set) {
				return ["a", "Set"];
			} else if (value._type != null && value._type._isCustomType != null) {
				return ["an", `instance of ${value._type._name}`];
			} else if (value.__proto__.constructor === Object) {
				/* Object literal */
				return ["an", "object"];
			} else if (isNamedFunction(value.__proto__.constructor)) {
				return ["an", `instance of ${value.__proto__.constructor.name}`];
			} else {
				return ["an", "instance of an unknown type"];
			}
		} else {
			throw new Error("Encountered unrecognized value type");
		}
	}
}