import assert from 'node:assert/strict';
import { afterEach, describe, it } from 'node:test';
import { SchulcloudClient, SchulcloudApiError } from '../src/core/client.ts';

/**
 * Retry behaviour, driven by a stubbed fetch. Observed live: a full crawl made
 * the instance answer 4 of 26 course pages with a 503 front-page, all of which
 * succeeded on retry — so this is the difference between a complete index and a
 * quietly incomplete one.
 */
const config = {
	baseUrl: 'https://example.test',
	jwt: 'x',
	authToken: undefined,
	port: 1,
	bindHost: '127.0.0.1',
	maxDownloadBytes: 1000,
	maxExtractedChars: 1000,
	requestTimeoutMs: 1000,
	keepaliveIntervalMs: 0,
	databaseUrl: undefined,
	mirrorDir: '/tmp',
	mirrorMaxBytes: 1000,
	crawlIntervalMs: 0,
};

const realFetch = globalThis.fetch;
afterEach(() => {
	globalThis.fetch = realFetch;
});

function stubFetch(responses: (Response | Error)[]): () => number {
	let calls = 0;
	globalThis.fetch = (async () => {
		const next = responses[calls++] ?? responses.at(-1)!;
		if (next instanceof Error) throw next;
		return next;
	}) as typeof fetch;
	return () => calls;
}

const json = (body: unknown, status = 200) =>
	new Response(JSON.stringify(body), { status, headers: { 'content-type': 'application/json' } });

describe('SchulcloudClient retries', () => {
	it('retries a 503 and succeeds', async () => {
		const calls = stubFetch([json({}, 503), json({ school: { id: 's' } })]);
		const client = new SchulcloudClient(config);
		await client.me();
		assert.equal(calls(), 2);
	});

	it('retries transient network errors', async () => {
		const calls = stubFetch([new Error('ECONNRESET'), json({ school: { id: 's' } })]);
		await new SchulcloudClient(config).me();
		assert.equal(calls(), 2);
	});

	it('does not retry a 401 — a dead token will not recover', async () => {
		const calls = stubFetch([json({}, 401)]);
		await assert.rejects(() => new SchulcloudClient(config).me(), (error: SchulcloudApiError) => {
			assert.equal(error.status, 401);
			return true;
		});
		assert.equal(calls(), 1, 'retrying an expired token just wastes time');
	});

	it('does not retry a 404', async () => {
		const calls = stubFetch([json({}, 404)]);
		await assert.rejects(() => new SchulcloudClient(config).me());
		assert.equal(calls(), 1);
	});

	it('gives up after the retry budget and reports the real status', async () => {
		const calls = stubFetch([json({}, 503)]);
		await assert.rejects(() => new SchulcloudClient(config).me(), (error: SchulcloudApiError) => {
			assert.equal(error.status, 503);
			return true;
		});
		assert.equal(calls(), 4, 'one attempt plus three retries');
	});
});

describe('getCards chunking', () => {
	it('never sends more than 20 ids in one request', async () => {
		// The API's query parser turns >20 repeated params into an object, and
		// validation then rejects every id with a message blaming the ids rather
		// than their number. Verified live: 20 -> 200, 21 -> 400.
		const seen: number[] = [];
		globalThis.fetch = (async (url: string | URL) => {
			const count = [...new globalThis.URL(String(url)).searchParams.getAll('ids')].length;
			seen.push(count);
			return json({ data: [] });
		}) as typeof fetch;

		const ids = Array.from({ length: 47 }, (_, i) => String(i).padStart(24, '0'));
		await new SchulcloudClient(config).getCards(ids);

		assert.deepEqual(seen, [20, 20, 7], 'should split 47 ids into 20/20/7');
		assert.ok(Math.max(...seen) <= 20);
	});

	it('merges the chunked responses into one list', async () => {
		let call = 0;
		globalThis.fetch = (async () =>
			json({ data: [{ id: `card${call++}`, height: 1, elements: [] }] })) as typeof fetch;
		const ids = Array.from({ length: 25 }, (_, i) => String(i).padStart(24, '0'));
		const cards = await new SchulcloudClient(config).getCards(ids);
		assert.equal(cards.length, 2, 'one card from each of the two chunks');
	});
});

describe('download timeouts', () => {
	/**
	 * A real local server, because the timing is the point: a stubbed fetch
	 * cannot model bytes that keep arriving slowly. requestTimeoutMs is 1000ms.
	 */
	async function withServer(
		handler: (res: import('node:http').ServerResponse) => void,
		run: (base: string) => Promise<void>,
	) {
		const { createServer } = await import('node:http');
		const server = createServer((_req, res) => handler(res));
		await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
		const { port } = server.address() as import('node:net').AddressInfo;
		try {
			await run(`http://127.0.0.1:${port}`);
		} finally {
			server.closeAllConnections();
			await new Promise<void>((resolve) => server.close(() => resolve()));
		}
	}

	const slowButSteady = (res: import('node:http').ServerResponse) => {
		res.writeHead(200, { 'content-type': 'application/pdf' });
		let sent = 0;
		const tick = setInterval(() => {
			res.write(Buffer.alloc(10, 65));
			if (++sent === 4) {
				clearInterval(tick);
				res.end();
			}
		}, 400);
	};

	it('lets a download run past the request timeout while bytes keep arriving', async () => {
		await withServer(slowButSteady, async (base) => {
			// 4 chunks, 400ms apart: 1.6s in total against a 1s timeout, never 1s of silence.
			const client = new SchulcloudClient({ ...config, baseUrl: base } as never);
			const file = await client.getBytes('/file', 'slow.pdf');
			assert.equal(file.bytes.length, 40);
			assert.equal(file.truncated, false);
		});
	});

	it('abandons a download that stalls', async () => {
		await withServer(
			(res) => {
				res.writeHead(200, { 'content-type': 'application/pdf' });
				res.write(Buffer.alloc(10, 65));
				// …and then nothing, well past the 1s idle limit.
			},
			async (base) => {
				const client = new SchulcloudClient({ ...config, baseUrl: base } as never);
				await assert.rejects(client.getBytes('/file', 'stalled.pdf'), /no data received for 1s/);
			},
		);
	});
});