Alex2Node/dist/esm/registry/schema.js
David aa0ffd64ea registry: describe an Alexa interface as data
src/registry/ holds what the library knows about an interface: namespace, version, the page it was read from,
properties with their value schemas and directives with their payload schemas. Five interfaces are described
(Alexa, PowerController, BrightnessController, TemperatureSensor, EndpointHealth); the other 65 names of
AlexaInterfaceType are stubs with the version and property names of 1.5.2. schema.ts is the run-time check behind
it (241 lines, no new dependency), catalog.ts the vocabularies of the pages: 103 assets (23 units), 6 actions,
9 states, 56 display categories, 22 reserved words, 73 error types under 11 namespaces.

AlexaInterface.getVersion() and getProps() read the registry; the two switch statements are gone (-167 lines).
On the wire: Alexa.EndpointHealth is announced at 3.1 (was 3.3; the page is titled 3.1 and no page mentions 3.3),
and TimeHoldController and Camera.LiveViewController at 3 and 1.7 (1.5.2 sent the string "UNKNOWN").
DisplayCategory gains VACUUM. New exports: registry, DeclarationError, SchemaError, Assets, Units, Actions,
States, DisplayCategories and the descriptor types.

Tests: 20 JSON examples of the five pages under test/fixtures/alexa-docs; every directive payload and property
value in them parses with its descriptor. npm test: 57 pass (was 30) in 10.8 s, also on Node 18.20.8 and 20.20.2.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
2026-09-28 15:18:22 +00:00

186 lines
7.3 KiB
JavaScript

// Values checked at run time and typed at compile time. A descriptor states its property values, directive payloads
// and declaration options with these; parse() returns the value or throws a SchemaError that names where it went
// wrong. Written here rather than taken from a package: mqtt stays the only runtime dependency.
/** A value that does not fit its schema: path is where ("payload.targetSetpoint.scale"), problem is what. */
export class SchemaError extends Error {
constructor(path, problem) {
super(path ? `${path}: ${problem}` : problem);
this.path = path;
this.problem = problem;
this.name = "SchemaError";
}
}
// The input as an error message shows it: short, and quoted when it is text.
function shown(input) {
if (input === undefined)
return "nothing";
if (typeof input === "function")
return "a function";
const text = JSON.stringify(input) ?? String(input);
return text.length > 60 ? `${text.slice(0, 57)}...` : text;
}
function mismatch(path, expects, input) {
return new SchemaError(path, `expected ${expects}, got ${shown(input)}`);
}
const at = (path, key) => (path ? `${path}.${key}` : key);
function isRecord(input) {
return typeof input === "object" && input !== null && !Array.isArray(input);
}
function schema(expects, accepts) {
return {
expects,
parse(input, path = "") {
if (!accepts(input))
throw mismatch(path, expects, input);
return input;
},
};
}
function numberText({ min, max, gt, integer }) {
const kind = integer ? "an integer" : "a number";
if (min !== undefined && max !== undefined)
return `${kind} from ${min} to ${max}`;
if (min !== undefined)
return `${kind} of ${min} or more`;
if (max !== undefined)
return `${kind} of ${max} or less`;
if (gt !== undefined)
return `${kind} greater than ${gt}`;
return kind;
}
function number(rules = {}) {
const { min = -Infinity, max = Infinity, gt = -Infinity, integer = false } = rules;
return schema(numberText(rules), (input) => typeof input === "number" && Number.isFinite(input) && input >= min && input <= max && input > gt
&& (!integer || Number.isInteger(input)));
}
function string(rules = {}) {
const { min = 0, max = Infinity, pattern } = rules;
const length = max === Infinity ? (min > 0 ? ` of ${min} or more characters` : "") : ` of ${min} to ${max} characters`;
return schema(rules.expects ?? `a string${length}`, (input) => typeof input === "string" && input.length >= min && input.length <= max && (!pattern || pattern.test(input)));
}
function boolean() {
return schema("true or false", (input) => typeof input === "boolean");
}
function literal(value) {
return schema(JSON.stringify(value), (input) => input === value);
}
function enumeration(...values) {
return { ...schema(values.join(" | "), (input) => values.includes(input)), values };
}
function unknown() {
return schema("any value", () => true);
}
function optional(inner) {
return {
expects: inner.expects,
optional: true,
parse: (input, path = "") => (input === undefined ? undefined : inner.parse(input, path)),
};
}
function nullable(inner) {
const expects = `${inner.expects} or null`;
return {
expects,
parse(input, path = "") {
if (input === null)
return null;
try {
return inner.parse(input, path);
}
catch (err) {
// The value itself is of the wrong kind: null was a choice too. An error further in keeps its own path.
if (err instanceof SchemaError && err.path === path)
throw mismatch(path, expects, input);
throw err;
}
},
};
}
function array(item, rules = {}) {
const { min = 0, max = Infinity } = rules;
const count = max === Infinity ? (min > 0 ? ` with ${min} or more entries` : "") : ` with ${min} to ${max} entries`;
const expects = `a list${count}`;
return {
expects,
parse(input, path = "") {
if (!Array.isArray(input) || input.length < min || input.length > max)
throw mismatch(path, expects, input);
return input.map((entry, i) => item.parse(entry, `${path}[${i}]`));
},
};
}
/**
* An object with the keys of shape. Keys the shape does not name are kept as they are: a field Alexa adds to a
* directive reaches the handler. unknownKeys "reject" is for what a developer writes, where such a key is a typo.
*/
function object(shape, rules = {}) {
const known = Object.keys(shape);
const expects = known.length > 0 ? `an object with ${known.join(", ")}` : "an object";
return {
expects,
parse(input, path = "") {
if (!isRecord(input))
throw mismatch(path, expects, input);
const others = Object.keys(input).filter((key) => !known.includes(key));
if (others.length > 0 && rules.unknownKeys === "reject") {
throw new SchemaError(at(path, others[0]), `unknown key, the known ones are ${known.join(", ") || "none"}`);
}
const parsed = {};
for (const key of known) {
const value = shape[key].parse(input[key], at(path, key));
if (value !== undefined)
parsed[key] = value;
}
for (const key of others)
parsed[key] = input[key];
return parsed;
},
};
}
// alexa-property-schemas.html "Temperature", "Temperature scales"
function temperature() {
return object({ value: number(), scale: enumeration("CELSIUS", "FAHRENHEIT", "KELVIN") });
}
// alexa-property-schemas.html "DateTime": UTC, no offsets. The seconds are optional here because the TimeInterval
// examples on the same page leave them out ("2017-10-04T14:00Z").
const DATE_TIME = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}(:\d{2}(\.\d+)?)?Z$/;
function dateTime() {
return schema("a UTC time like 2017-08-30T01:18:21Z", (input) => typeof input === "string" && DATE_TIME.test(input) && !Number.isNaN(Date.parse(input)));
}
// alexa-property-schemas.html "Duration": the time portion of ISO 8601, negative for a delta ("PT-30S")
const DURATION = /^PT(?=.)(-?\d+H)?(-?\d+M)?(-?\d+S)?$/;
function duration() {
return string({ pattern: DURATION, expects: "a duration like PT3M15S" });
}
// alexa-property-schemas.html "TimeInterval": "Specify one or two of the time interval fields. If you specify all
// three fields, an error occurs."
function timeInterval() {
const fields = object({ start: optional(dateTime()), end: optional(dateTime()), duration: optional(duration()) });
const expects = "a time interval with one or two of start, end, duration";
return {
expects,
parse(input, path = "") {
const interval = fields.parse(input, path);
const given = [interval.start, interval.end, interval.duration].filter((field) => field !== undefined).length;
if (given < 1 || given > 2)
throw mismatch(path, expects, input);
return interval;
},
};
}
export const s = {
string,
number,
boolean,
literal,
enum: enumeration,
unknown,
optional,
nullable,
array,
object,
temperature,
dateTime,
duration,
timeInterval,
};