/**

* Direct unit tests for the JSON-LD → Turtle converter.

*

* The focus is on regression coverage for properties that would otherwise

* be easy to regress silently:

* - cycle-safety in expandUri (DoS guard — a malicious context must not

* cause unbounded recursion / stack overflow)

* - duplicate @id across top-level docs must NOT suppress emission

* (the visited-set refactor previously dropped data)

* - cyclical nested node references must not hang the BFS

*/

import { describe, it } from 'node:test';

import assert from 'node:assert';

import { fromJsonLd } from '../src/rdf/conneg.js';

describe('turtle converter — unit (#320 follow-ups)', () => {

it('expandUri does not recurse forever on a cyclic context (a → b → a)', async () => {

const doc = {

'@context': {

// Pathological: each term points at another term via CURIE, forming a loop.

'a': { '@id': 'b:x' },

'b': { '@id': 'a:y' }

},

'@id': 'https://example.test/s',

'a': 'hello'

};

// The converter should finish — not stack-overflow — regardless of what

// the output happens to look like. We only assert it completes with a

// string result.

const { content } = await fromJsonLd(doc, 'text/turtle', 'https://example.test/', true);

assert.ok(typeof content === 'string');

});

it('expandUri does not recurse forever on a self-loop (a → a)', async () => {

const doc = {

'@context': {

'selfy': 'selfy'

},

'@id': 'https://example.test/s',

'selfy': 'hello'

};

const { content } = await fromJsonLd(doc, 'text/turtle', 'https://example.test/', true);

assert.ok(typeof content === 'string');

});

it('duplicate top-level @id is not silently dropped', async () => {

// Two docs describing the same subject — both claims must survive.

// (Previously the visited-set in the BFS skipped the second pass.)

const docs = [

{

'@context': { 'foaf': 'http://xmlns.com/foaf/0.1/' },

'@id': 'https://example.test/alice',

'foaf:name': 'Alice'

},

{

'@context': { 'foaf': 'http://xmlns.com/foaf/0.1/' },

'@id': 'https://example.test/alice',

'foaf:age': 30

}

];

const { content } = await fromJsonLd(docs, 'text/turtle', 'https://example.test/', true);

assert.ok(content.includes('Alice'), `Turtle should contain the name claim, got:\n${content}`);

assert.ok(/30|"30"/.test(content), `Turtle should contain the age claim, got:\n${content}`);

});

it('prefix-looking context key defined as an object is not string-concatenated', async () => {

// A user-supplied context can legally define a prefix-looking key as a

// term-definition object (not a namespace string). The converter must

// not treat it as a namespace — string-concatenating the object would

// produce invalid IRIs like "[object Object]foo".

const doc = {

'@context': {

// `bogus` is defined as a term object, not a namespace string.

'bogus': { '@id': 'https://example.test/ns#bogus' }

},

'@id': 'https://example.test/s',

// This looks like a CURIE `bogus:foo` but `bogus` is not a valid

// namespace — the converter should leave it alone.

'bogus:foo': 'hello'

};

const { content } = await fromJsonLd(doc, 'text/turtle', 'https://example.test/', true);

assert.ok(typeof content === 'string');

assert.ok(!content.includes('[object Object]'),

`Turtle output must not contain object-stringification, got:\n${content}`);

});

it('cyclical nested node reference does not hang', async () => {

// Two nested nodes reference each other. BFS must not loop.

const a = { '@id': 'https://example.test/a', 'ex:knows': null };

const b = { '@id': 'https://example.test/b', 'ex:knows': a };

a['ex:knows'] = b;

const doc = {

'@context': { 'ex': 'https://example.test/ns#' },

'@id': 'https://example.test/root',

'ex:knows': a

};

const { content } = await fromJsonLd(doc, 'text/turtle', 'https://example.test/', true);

assert.ok(typeof content === 'string');

assert.ok(content.includes('https://example.test/a'), 'node a should appear');

assert.ok(content.includes('https://example.test/b'), 'node b should appear');

});

});