// Unit tests for src/main.js, run with Node's built-in test runner by the
// test script in package.json. Importing the module does not start the
// page.

import { beforeEach, test } from "node:test";
import assert from "node:assert/strict";
import {
    AppState,
    CONFIG,
    greyOutUI,
    hostRowHTML,
    HostState,
    humanDuration,
    latencyClass,
    latencyHex,
    measureLatency,
    tick,
} from "../../src/main.js";

// There is no page here, so the tests stand in for it. The debug log looks
// for its panel by id and finds none. Each element of a host's row that
// tick or greyOutUI draws into is a plain object, made the first time a
// test looks it up and kept in elements under its selector until the next
// test starts. As on a page, writing its text replaces its markup; the
// status dot greyOutUI looks for in it is not there. Drawing a sparkline
// does nothing; it looks for the pixel ratio on window and finds none.
let elements;
beforeEach(() => {
    elements = {};
});
const doNothing = () => {};
const canvasContext = {
    clearRect: doNothing,
    beginPath: doNothing,
    moveTo: doNothing,
    lineTo: doNothing,
    stroke: doNothing,
    fill: doNothing,
    fillRect: doNothing,
    fillText: doNothing,
    arc: doNothing,
};
globalThis.window = {};
globalThis.document = {
    getElementById: () => null,
    querySelector: (selector) =>
        (elements[selector] ??= {
            getContext: () => canvasContext,
            querySelector: () => null,
            set textContent(text) {
                this.innerHTML = text;
            },
        }),
};

// What tick last wrote into the latency figure in host's row, or undefined
// if it has written nothing there.
function latencyFigure(state, host) {
    const index = state.allHosts.indexOf(host);
    return elements[`.latency-value[data-host="${index}"]`]?.innerHTML;
}

// What was last written into the status text in host's row.
function statusText(state, host) {
    const index = state.allHosts.indexOf(host);
    return elements[`.status-text[data-host="${index}"]`]?.innerHTML;
}

// Mocks the clock for test t, so that a check lasting seconds takes no real
// time, and replaces fetch with targets that each answer after
// answerAfter(url) milliseconds of that clock, or never when that is
// Infinity. Both are restored when the test ends.
function mockTargets(t, answerAfter) {
    t.mock.timers.enable({ apis: ["setTimeout", "Date"] });
    t.mock.method(performance, "now", () => Date.now());
    t.mock.method(
        globalThis,
        "fetch",
        (url, { signal }) =>
            new Promise((resolve, reject) => {
                if (answerAfter(url) !== Infinity) {
                    setTimeout(resolve, answerAfter(url));
                }
                signal.addEventListener("abort", () => reject(signal.reason));
            }),
    );
}

// The result of check if it has ended, otherwise "still waiting".
function settled(check) {
    return Promise.race([
        check,
        new Promise((resolve) => setImmediate(resolve, "still waiting")),
    ]);
}

for (const interval of [10000, 30000]) {
    const timeout = interval * 0.8;
    // Over 3 seconds, which the timeout used to be capped at.
    const slowAnswer = timeout - 1000;

    test(`at a ${interval}ms interval, an answer after ${slowAnswer}ms is recorded with its real time`, async (t) => {
        CONFIG.updateInterval = interval;
        mockTargets(t, () => slowAnswer);
        const check = measureLatency("https://target.test");
        t.mock.timers.tick(slowAnswer);
        assert.deepEqual(await settled(check), {
            latency: slowAnswer,
            error: null,
        });
    });

    test(`at a ${interval}ms interval, a target that never answers is recorded as a timeout after ${timeout}ms`, async (t) => {
        CONFIG.updateInterval = interval;
        mockTargets(t, () => Infinity);
        const check = measureLatency("https://target.test");
        t.mock.timers.tick(timeout - 1);
        assert.equal(await settled(check), "still waiting");
        t.mock.timers.tick(1);
        assert.deepEqual(await settled(check), {
            latency: null,
            error: "timeout",
        });
    });
}

test("at a 30000ms interval, a target answering after 1000ms shows in its row while another target's check is still waiting", async (t) => {
    CONFIG.updateInterval = 30000;
    const state = new AppState([
        { name: "Answering", url: "https://answering.test" },
    ]);
    const answering = state.local[0];
    const waiting = state.wan[0];
    // No target but the answering one ever answers.
    mockTargets(t, (url) => (url.startsWith(answering.url) ? 1000 : Infinity));
    // The third tick: the first is discarded as a whole, and the second ends
    // by sorting the rows, which rebuilds a page that is not here.
    state.tickCount = 2;

    const round = tick(state, new AbortController().signal);
    t.mock.timers.tick(1000);
    assert.equal(await settled(round), "still waiting");
    assert.match(latencyFigure(state, answering), />1000</);
    assert.equal(latencyFigure(state, waiting), undefined);
    assert.equal(state.tickCount, 2);

    // The round ends, once, when the last check times out.
    t.mock.timers.tick(CONFIG.requestTimeout - 1000);
    assert.notEqual(await settled(round), "still waiting");
    assert.equal(state.tickCount, 3);
});

// In the next three tests, the answering target's check is still waiting
// when something happens after which its result must not show.

test("at a 30000ms interval, a check still waiting when its round is given up does not show in its row", async (t) => {
    CONFIG.updateInterval = 30000;
    const state = new AppState([
        { name: "Answering", url: "https://answering.test" },
    ]);
    const answering = state.local[0];
    mockTargets(t, (url) => (url.startsWith(answering.url) ? 1000 : Infinity));
    state.tickCount = 2;

    const roundChecks = new AbortController();
    const round = tick(state, roundChecks.signal);
    t.mock.timers.tick(500);
    // As a round started early does to the last round's checks.
    roundChecks.abort();
    assert.notEqual(await settled(round), "still waiting");
    assert.equal(latencyFigure(state, answering), undefined);
});

test("at a 30000ms interval, a check still waiting when the user pauses does not show in its row", async (t) => {
    CONFIG.updateInterval = 30000;
    const state = new AppState([
        { name: "Answering", url: "https://answering.test" },
    ]);
    const answering = state.local[0];
    mockTargets(t, (url) => (url.startsWith(answering.url) ? 1000 : Infinity));
    state.tickCount = 2;

    const round = tick(state, new AbortController().signal);
    t.mock.timers.tick(500);
    state.paused = true;
    t.mock.timers.tick(500);
    assert.equal(await settled(round), "still waiting");
    assert.equal(latencyFigure(state, answering), undefined);
});

test("at a 30000ms interval, a check in the first round does not show in its row", async (t) => {
    CONFIG.updateInterval = 30000;
    const state = new AppState([
        { name: "Answering", url: "https://answering.test" },
    ]);
    const answering = state.local[0];
    mockTargets(t, (url) => (url.startsWith(answering.url) ? 1000 : Infinity));

    const round = tick(state, new AbortController().signal);
    t.mock.timers.tick(1000);
    assert.equal(await settled(round), "still waiting");
    assert.equal(latencyFigure(state, answering), undefined);
});

test("at a 30000ms interval, after the user pauses and resumes during a round, no row reads paused once its last check ends", async (t) => {
    CONFIG.updateInterval = 30000;
    const state = new AppState([
        { name: "Answering", url: "https://answering.test" },
    ]);
    const answering = state.local[0];
    mockTargets(t, (url) => (url.startsWith(answering.url) ? 1000 : Infinity));
    state.tickCount = 2;

    const round = tick(state, new AbortController().signal);
    t.mock.timers.tick(1000);
    assert.equal(await settled(round), "still waiting");
    // The user pauses, which greys out every row, and resumes, which leaves
    // the rows as they are, as togglePause does. The answering target's
    // check has already ended, so only the redraw of every row at the end
    // of the round can take "paused" out of its row.
    state.paused = true;
    greyOutUI(state);
    state.paused = false;
    assert.equal(statusText(state, answering), "paused");

    // The round ends when the last check times out.
    t.mock.timers.tick(CONFIG.requestTimeout - 1000);
    assert.notEqual(await settled(round), "still waiting");
    for (const host of state.allHosts) {
        assert.notEqual(statusText(state, host), "paused", host.name);
    }
});

// The page shows &lt; &gt; &quot; &amp; and &#39; in a row's markup as
// < > " & and '.
test(`a target whose name and URL hold < > " & and ' shows those characters in its row`, () => {
    const host = new HostState({
        name: `<b>"x" & 'y'</b>`,
        url: `https://x.test/<b>?a="x"&b='y'`,
    });
    const row = hostRowHTML(host, 0);
    assert.doesNotMatch(row, /<b>/);
    assert.ok(
        row.includes(
            ">&lt;b&gt;&quot;x&quot; &amp; &#39;y&#39;&lt;/b&gt;</span>",
        ),
    );
    assert.ok(
        row.includes(
            'href="https://x.test/&lt;b&gt;?a=&quot;x&quot;&amp;b=&#39;y&#39;"',
        ),
    );
    assert.ok(
        row.includes(
            ">https://x.test/&lt;b&gt;?a=&quot;x&quot;&amp;b=&#39;y&#39;</a>",
        ),
    );
});

for (const [seconds, text] of [
    [0, "0s"],
    [1, "1s"],
    [59, "59s"],
    [60, "1m"],
    [61, "1m1s"],
    [3599, "59m59s"],
    [3600, "1h"],
    [3601, "1h1s"],
    [3660, "1h1m"],
    [3661, "1h1m1s"],
]) {
    test(`humanDuration writes ${seconds} seconds as ${text}`, () => {
        assert.equal(humanDuration(seconds), text);
    });
}

// The colour of a target's latency figure, as a class, and of its sparkline
// for an answer after latency ms, as the colour coding in README.md gives
// them. The rows sit either side of each boundary.
for (const [latency, figure, sparkline] of [
    [0, "text-green-500", "#22c55e"],
    [49, "text-green-500", "#22c55e"],
    [50, "text-lime-500", "#84cc16"],
    [99, "text-lime-500", "#84cc16"],
    [100, "text-yellow-500", "#eab308"],
    [199, "text-yellow-500", "#eab308"],
    [200, "text-orange-500", "#f97316"],
    [499, "text-orange-500", "#f97316"],
    [500, "text-red-500", "#ef4444"],
]) {
    test(`an answer after ${latency}ms has a ${figure} figure and a ${sparkline} sparkline`, () => {
        assert.equal(latencyClass(latency, "online"), figure);
        assert.equal(latencyHex(latency), sparkline);
    });
}

test("a check that timed out or found its target unreachable has a grey figure and sparkline", () => {
    assert.equal(latencyClass(null, "error"), "text-gray-500");
    assert.equal(latencyClass(null, "offline"), "text-gray-500");
    assert.equal(latencyHex(null), "#6b7280");
});

// A target whose checks, in turn, answered after each of latencies ms, or,
// for null, found it unreachable.
function hostAfter(latencies) {
    const host = new HostState({ name: "Target", url: "https://target.test" });
    for (const latency of latencies) {
        host.pushSample(
            Date.now(),
            latency === null
                ? { latency: null, error: "unreachable" }
                : { latency, error: null },
        );
    }
    return host;
}

for (const { history, latencies, statistics } of [
    {
        history: "no checks",
        latencies: [],
        statistics: { min: null, max: null, average: null, median: null },
    },
    {
        history: "only unreachable checks",
        latencies: [null, null, null],
        statistics: { min: null, max: null, average: null, median: null },
    },
    {
        history: "three answers and an unreachable check",
        latencies: [30, null, 10, 20],
        statistics: { min: 10, max: 30, average: 20, median: 20 },
    },
    {
        // The median of an even number of answers is the mean of the
        // middle two. It and the average, 23.75, are rounded.
        history: "four answers",
        latencies: [10, 40, 20, 25],
        statistics: { min: 10, max: 40, average: 24, median: 23 },
    },
    {
        // Sorted as text rather than as numbers, these answers would put
        // 100 in the middle. The average, 39.67, is rounded.
        history: "answers with different numbers of digits",
        latencies: [100, 9, 10],
        statistics: { min: 9, max: 100, average: 40, median: 10 },
    },
]) {
    test(`a target's min, max, average and median latency over ${history}`, () => {
        const host = hostAfter(latencies);
        assert.deepEqual(
            {
                min: host.minLatency(),
                max: host.maxLatency(),
                average: host.averageLatency(),
                median: host.medianLatency(),
            },
            statistics,
        );
    });
}

// The summary's figures come from each WAN target's last check, by the same
// rules as a target's own: here four answered, one was found unreachable
// and the rest have not been checked yet. The median, 22.5, and the
// average, 21.25, are rounded.
test("the summary's min, max, median and average latency over the WAN targets' last checks", () => {
    const state = new AppState([]);
    [30, 10, null, 25, 20].forEach((latency, i) =>
        state.wan[i].pushSample(
            Date.now(),
            latency === null
                ? { latency: null, error: "unreachable" }
                : { latency, error: null },
        ),
    );
    assert.deepEqual(state.wanStats(), {
        reachable: 4,
        total: state.wan.length,
        min: 10,
        max: 30,
        med: 23,
        avg: 21,
    });
});

// An app state in which, of the WAN targets, the first timedOut timed out,
// the next unreachable were found unreachable, the next answered answered
// after latency ms, and the rest have not been checked yet.
function stateAfter({ timedOut, unreachable, answered, latency }) {
    const state = new AppState([]);
    const results = [
        ...Array(timedOut).fill({ latency: null, error: "timeout" }),
        ...Array(unreachable).fill({ latency: null, error: "unreachable" }),
        ...Array(answered).fill({ latency, error: null }),
    ];
    results.forEach((result, i) => state.wan[i].pushSample(Date.now(), result));
    return state;
}

// For each number the health is decided by, the rows put it one under, at
// and one over its threshold.
for (const { timedOut, unreachable = 0, answered, latency, health } of [
    // Offline: more than 10 timed out and at most 4 answered.
    { timedOut: 9, answered: 4, latency: 30, health: "degraded" },
    { timedOut: 10, answered: 4, latency: 30, health: "degraded" },
    { timedOut: 11, answered: 4, latency: 30, health: "offline" },
    { timedOut: 11, answered: 3, latency: 30, health: "offline" },
    { timedOut: 11, answered: 5, latency: 30, health: "degraded" },
    // Otherwise degraded: more than 4 timed out.
    { timedOut: 3, answered: 10, latency: 30, health: "healthy" },
    { timedOut: 4, answered: 10, latency: 30, health: "healthy" },
    { timedOut: 5, answered: 10, latency: 30, health: "degraded" },
    // Otherwise slow: more than 3 answered after more than 1000ms.
    { timedOut: 0, answered: 4, latency: 999, health: "healthy" },
    { timedOut: 0, answered: 4, latency: 1000, health: "healthy" },
    { timedOut: 0, answered: 4, latency: 1001, health: "slow" },
    { timedOut: 0, answered: 2, latency: 1001, health: "healthy" },
    { timedOut: 0, answered: 3, latency: 1001, health: "healthy" },
    // A target found unreachable counts as one that timed out.
    {
        timedOut: 5,
        unreachable: 6,
        answered: 4,
        latency: 30,
        health: "offline",
    },
    {
        timedOut: 0,
        unreachable: 5,
        answered: 10,
        latency: 30,
        health: "degraded",
    },
]) {
    test(`with ${timedOut} WAN targets timed out, ${unreachable} found unreachable and ${answered} answering after ${latency}ms, the health is ${health}`, () => {
        const state = stateAfter({ timedOut, unreachable, answered, latency });
        assert.equal(state.healthStatus(), health);
    });
}