// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

import assert from 'node:assert/strict';
import {describe, it, type TestContext} from 'node:test';

import {AxiosError, type AxiosAdapter, type AxiosResponse, type InternalAxiosRequestConfig} from 'axios';

import {client, isHtmlInterstitialError, isPreConnectionFailure, PRE_CONNECTION_MAX_RETRIES} from './client';

/**
 * Trimmed from a real failure body in PR 10050's 40b8e5ea run: Cloudflare answered the Detox
 * runners' API calls with its bot check instead of proxying to Mattermost. Kept verbatim in the
 * parts that matter, because the defect this file guards was a matcher that did not recognise
 * this exact markup — a paraphrased fixture would not have caught it.
 */
const CHALLENGE_HTML = [
    '<!DOCTYPE html><html lang="en"><head><meta charset="utf-8">',
    '<title>Mattermost captcha challenge</title></head><body>',
    '<h1>Just a moment...</h1><h2>Enable JavaScript and cookies to continue</h2>',
    "<script>(function(){window._cf_chl_opt = {cFPWv: 'b'};})();</script>",
    '</body></html>',
].join('');

const COLD_START_HTML = '<!DOCTYPE html><html><body>cloud/inaccessible</body></html>';

const ok = (config: InternalAxiosRequestConfig, data: unknown, status = 200): AxiosResponse => ({
    config, data, status, statusText: 'OK', headers: {},
});

/**
 * Installs an adapter that replays `steps` in order and holds the last one, then restores the
 * previous adapter. Driving the real instance means the interceptors under test run exactly as
 * they do in CI; only the transport is replaced.
 */
const withAdapter = async (
    steps: Array<{status: number; data: unknown}>,
    run: (calls: () => number) => Promise<void>,
) => {
    const previous = client.defaults.adapter;
    let calls = 0;

    const adapter: AxiosAdapter = async (config) => {
        const step = steps.at(Math.min(calls, steps.length - 1));
        assert.ok(step, 'adapter step fixture must exist');
        calls += 1;
        const response = ok(config, step.data, step.status);
        if (step.status >= 400) {
            const error = new Error(`Request failed with status code ${step.status}`) as Error & {
                config: InternalAxiosRequestConfig;
                response: AxiosResponse;
                isAxiosError: boolean;
            };
            error.config = config;
            error.response = response;
            error.isAxiosError = true;
            throw error;
        }
        return response;
    };

    client.defaults.adapter = adapter;
    try {
        await run(() => calls);
    } finally {
        client.defaults.adapter = previous;
    }
};

const tickRetryDelays = async (t: TestContext, delaysMs: number[]) => {
    const yieldEventLoop = () => new Promise<void>((resolve) => {
        setImmediate(resolve);
    });

    for (const delayMs of delaysMs) {
        // Let the interceptor schedule setTimeout before advancing mocked time.
        // eslint-disable-next-line no-await-in-loop -- retry delays are sequential
        await yieldEventLoop();
        t.mock.timers.tick(delayMs);
    }
    await yieldEventLoop();
};

describe('client HTML interstitial retry', () => {
    it('should retry a Cloudflare challenge served as 403 and return the eventual API response', async (t) => {
        t.mock.timers.enable({apis: ['setTimeout']});
        await withAdapter(
            [{status: 403, data: CHALLENGE_HTML}, {status: 200, data: {status: 'OK'}}],
            async (calls) => {
                const pending = client.get('http://example.test/api/v4/system/ping');
                await tickRetryDelays(t, [3000]);
                const response = await pending;

                assert.deepEqual(response.data, {status: 'OK'});
                assert.equal(calls(), 2, 'the challenge should have been retried exactly once');
            },
        );
    });

    it('should retry a Cloudflare challenge twice, advancing the 3s then 6s backoff before succeeding', async (t) => {
        t.mock.timers.enable({apis: ['setTimeout']});
        await withAdapter(
            [
                {status: 403, data: CHALLENGE_HTML},
                {status: 403, data: CHALLENGE_HTML},
                {status: 200, data: {status: 'OK'}},
            ],
            async (calls) => {
                const pending = client.get('http://example.test/api/v4/system/ping');
                await tickRetryDelays(t, [3000, 6000]);
                const response = await pending;

                assert.deepEqual(response.data, {status: 'OK'});
                assert.equal(calls(), 3, 'the challenge should have been retried twice');
            },
        );
    });

    it('should retry a cold-start page served as 200, which axios resolves rather than rejects', async (t) => {
        t.mock.timers.enable({apis: ['setTimeout']});
        await withAdapter(
            [{status: 200, data: COLD_START_HTML}, {status: 200, data: {status: 'OK'}}],
            async (calls) => {
                const pending = client.get('http://example.test/api/v4/system/ping');
                await tickRetryDelays(t, [3000]);
                const response = await pending;

                assert.deepEqual(response.data, {status: 'OK'});
                assert.equal(calls(), 2);
            },
        );
    });

    it('should leave an ordinary 403 alone, so a real permission error still fails fast', async () => {
        await withAdapter(
            [{status: 403, data: {id: 'api.context.permissions.app_error', status_code: 403}}],
            async (calls) => {
                await assert.rejects(() => client.get('http://example.test/api/v4/system/ping'));
                assert.equal(calls(), 1, 'a JSON 403 must not be retried');
            },
        );
    });

    it('should report an exhausted interstitial as such, so apiInit can spend its own budget on it', () => {
        assert.equal(isHtmlInterstitialError(new Error('Server returned "_cf_chl_opt" HTML for /x (retries exhausted or retry budget spent)')), true);
        assert.equal(isHtmlInterstitialError(new Error('Request failed with status code 403')), false);
        assert.equal(isHtmlInterstitialError(undefined), false);
    });
});

const URL = 'http://unit-test.invalid/api/v4/channels';
const BODY = {name: 'channel-1'};

type Step = {code: string} | {status: number; data?: unknown};
type CallCounter = {calls: number};

// Adapter that replays `script` in order and holds the last step forever, so a single-step
// script models "fails every time". Errors are raised the way axios' http adapter raises
// them: an AxiosError carrying `code` and `config`, with `response` only for HTTP answers.
const scriptedAdapter = (script: readonly Step[], counter: CallCounter): AxiosAdapter => async (config: InternalAxiosRequestConfig) => {
    const step = script[Math.min(counter.calls, script.length - 1)]!;
    counter.calls++;

    if ('code' in step) {
        throw new AxiosError(`${step.code} ${config.url}`, step.code, config);
    }

    const response: AxiosResponse = {data: step.data ?? {}, status: step.status, statusText: '', headers: {}, config};
    if (step.status >= 400) {
        throw new AxiosError(`Request failed with status code ${step.status}`, AxiosError.ERR_BAD_REQUEST, config, undefined, response);
    }
    return response;
};

const post = (script: readonly Step[], counter: CallCounter) => client.post(URL, BODY, {adapter: scriptedAdapter(script, counter)});

describe('server_api client pre-connection retry', () => {
    it('should classify only response-less DNS / connect failures as pre-connection', () => {
        assert.equal(isPreConnectionFailure({code: 'ENOTFOUND'}), true);
        assert.equal(isPreConnectionFailure({code: 'ECONNREFUSED'}), true);
        assert.equal(isPreConnectionFailure({code: 'ECONNRESET'}), false, 'a reset can happen after the request was sent');
        assert.equal(isPreConnectionFailure({code: 'ECONNABORTED'}), false, 'timeouts are owned by the timeout interceptor');
        assert.equal(isPreConnectionFailure({code: 'ENOTFOUND', response: {status: 502}}), false, 'an HTTP answer means the request was sent');
    });

    it('should replay a POST after DNS failures and return the eventual answer', async () => {
        const counter: CallCounter = {calls: 0};
        const response = await post([{code: 'ENOTFOUND'}, {code: 'ENOTFOUND'}, {status: 201, data: {id: 'c1'}}], counter);

        assert.equal(counter.calls, 3, 'two failed attempts then the success');
        assert.equal(response.status, 201);
        assert.deepEqual(response.data, {id: 'c1'});
    });

    it('should give up after PRE_CONNECTION_MAX_RETRIES and surface the original error', async () => {
        const counter: CallCounter = {calls: 0};
        await assert.rejects(post([{code: 'ECONNREFUSED'}], counter), (error: AxiosError) => error.code === 'ECONNREFUSED' && error.response === undefined);

        assert.equal(counter.calls, 1 + PRE_CONNECTION_MAX_RETRIES, 'the first attempt plus every retry');
    });

    it('should not replay a POST on an ambiguous socket error', async () => {
        const counter: CallCounter = {calls: 0};
        await assert.rejects(post([{code: 'ECONNRESET'}], counter), (error: AxiosError) => error.code === 'ECONNRESET');

        assert.equal(counter.calls, 1, 'the request may have reached the server, so it must not be replayed');
    });

    it('should not replay a POST the server answered', async () => {
        const counter: CallCounter = {calls: 0};
        await assert.rejects(post([{status: 400, data: {message: 'bad request'}}], counter), (error: AxiosError) => error.response?.status === 400);

        assert.equal(counter.calls, 1);
    });
});