import { strict as assert } from "assert";

import { UserID } from "matrix-bot-sdk";
import { Suite } from "mocha";
import { Mjolnir } from "../../src/Mjolnir";
import { DetectFederationLag, LAG_STATE_EVENT } from "../../src/protections/DetectFederationLag";
import { getFirstReply } from "./commands/commandUtils";
import { newTestUser } from "./clientHelper";

const LOCAL_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS = 180_000;
const LOCAL_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS = 100_000;
const FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS = 300_000;
const FEDERATED_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS = 200_000;
const BUCKET_DURATION_MS = 100;
const SAMPLE_SIZE = 100;
const NUMBER_OF_LAGGING_FEDERATED_HOMESERVERS_ENTER_WARNING_ZONE = 2;

const RE_STATS = /(\{(:?.|\n)*\})[^}]*$/m;

describe("Test: DetectFederationLag protection", function() {
    // In this entire test, we call `handleEvent` directly, injecting
    // - events that simulate lag;
    // - a progression through time, to make sure that histograms get processed.
    beforeEach(async function() {
        // Setup an instance of DetectFederationLag
        this.detector = new DetectFederationLag();
        await this.mjolnir.registerProtection(this.detector);
        await this.mjolnir.enableProtection("DetectFederationLag");

        // Setup a moderator.
        this.moderator = await newTestUser(this.config.homeserverUrl, { name: { contains: "moderator" } });
        await this.moderator.joinRoom(this.mjolnir.managementRoomId);

        const SETTINGS = {
            // The protection should kick in immediately.
            initialDelayGrace: 0,
            // Make histograms progress quickly.
            bucketDuration: BUCKET_DURATION_MS,
            // Three homeservers should be sufficient to raise an alert.
            numberOfLaggingFederatedHomeserversEnterWarningZone: NUMBER_OF_LAGGING_FEDERATED_HOMESERVERS_ENTER_WARNING_ZONE,

            localHomeserverLagEnterWarningZone: LOCAL_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS,
            localHomeserverLagExitWarningZone: LOCAL_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS,

            federatedHomeserverLagEnterWarningZone: FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS,
            federatedHomeserverLagExitWarningZone: FEDERATED_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS,
        };
        for (let key of Object.keys(SETTINGS)) {
            this.detector.settings[key].setValue(SETTINGS[key]);
        }
        this.localDomain = new UserID(await this.mjolnir.client.getUserId()).domain;
        this.protectedRoomId = `!room1:${this.localDomain}`;
        this.mjolnir.addProtectedRoom(this.protectedRoomId);

        this.simulateLag = async (senders: string[], lag: number, start: Date) => {
            const content = {};
            const origin_server_ts = start.getTime() - lag;
            for (let i = 0; i < SAMPLE_SIZE; ++i) {
                // We call directly `this.detector.handleEvent` to be able to forge old values of `origin_server_ts`.
                await this.detector.handleEvent(this.mjolnir, this.protectedRoomId, {
                    sender: senders[i % senders.length],
                    origin_server_ts,
                    content,
                },
                    // Make sure that time progresses through histogram buckets.
                    simulateDate(start, i)
                );
            }
        };

        this.getAlertEvent = async () => {
            try {
                let event = await this.mjolnir.client.getRoomStateEvent(this.mjolnir.managementRoomId, LAG_STATE_EVENT, this.protectedRoomId);
                if (Object.keys(event).length == 0) {
                    // Event was redacted.
                    return null;
                }
                return event;
            } catch (ex) {
                // No such event.
                return null;
            }
        };

        this.getCommandStatus = async () => {
            const protectedRoomReply = await getFirstReply(this.mjolnir.client, this.mjolnir.managementRoomId, () => {
                const command = `!mjolnir status protection DetectFederationLag ${this.protectedRoomId}`;
                return this.moderator.sendMessage(this.mjolnir.managementRoomId, { msgtype: 'm.text', body: command });
            });
            const globalReply = await getFirstReply(this.mjolnir.client, this.mjolnir.managementRoomId, () => {
                const command = `!mjolnir status protection DetectFederationLag *`;
                return this.moderator.sendMessage(this.mjolnir.managementRoomId, { msgtype: 'm.text', body: command });
            });
            const protectedRoomStatsStr = protectedRoomReply.content.body.match(RE_STATS)[0];
            const globalStatsStr = globalReply.content.body.match(RE_STATS)[0];
            return {
                protectedRoomStats: protectedRoomStatsStr ? JSON.parse(protectedRoomStatsStr) : null,
                globalStats: globalStatsStr ? JSON.parse(globalStatsStr) : null,
            }
        }
    });

    afterEach(async function() {
        await this.detector.cleanup();
        this.detector.dispose();
        await this.moderator?.stop();
    });

    let simulateDate = (start: Date, progress: number = SAMPLE_SIZE) =>
        new Date(start.getTime() + 2 * progress * BUCKET_DURATION_MS / SAMPLE_SIZE);

    it('DetectFederationLag doesn\'t detect lag when there isn\'t any', async function() {
        this.timeout(60000);
        const MULTIPLIERS = [0, 0.5, 0.9];

        // In this test, all the events we send have a lag < {local, federated}HomeserverLagEnterWarningZoneMS.
        const start = new Date();

        // Ensure that no alert has been emitted yet.
        assert.equal(await this.getAlertEvent(), null, "Initially, there should be no alert");

        // First, let's send events from the local homeserver.
        const LOCAL_SENDERS = [`@local_user:${this.localDomain}`];
        for (let multiplier of MULTIPLIERS) {
            const LAG = multiplier * LOCAL_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS;
            await this.simulateLag(LOCAL_SENDERS, LAG, start);
            assert.equal(await this.getAlertEvent(), null, `We have sent lots of local pseudo-events with a small lag of ${LAG}, there should be NO alert`);
        }

        // Three distinct remote servers should be sufficient to trigger an alert, if they all lag.
        const REMOTE_SENDERS = [
            "@user2:left.example.com",
            "@user3:right.example.com",
            "@user4:middle.example.com",
        ];
        for (let multiplier of MULTIPLIERS) {
            const LAG = multiplier * FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS;
            await this.simulateLag(REMOTE_SENDERS, LAG, start);
            assert.equal(await this.getAlertEvent(), null, `We have sent lots of remote pseudo-events with a small lag of ${LAG}, there should be NO alert`);
        }

        const {protectedRoomStats, globalStats} = await this.getCommandStatus();
        assert.ok(protectedRoomStats, "We should see stats for our room");
        assert.ok(protectedRoomStats.min >= 0, `min ${protectedRoomStats.min} >= 0`);
        assert.ok(protectedRoomStats.min < protectedRoomStats.max);
        assert.ok(protectedRoomStats.mean > 0);
        assert.ok(protectedRoomStats.mean < protectedRoomStats.max);
        assert.ok(protectedRoomStats.median < protectedRoomStats.max);
        assert.ok(protectedRoomStats.median > 0);
        assert.ok(protectedRoomStats.max >= MULTIPLIERS[MULTIPLIERS.length - 1] * FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS);
        assert.ok(protectedRoomStats.max < FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS);
        assert.deepEqual(globalStats, { [this.protectedRoomId]: protectedRoomStats });
    });

    it('DetectFederationLag detects lag on local homeserver', async function() {
        this.timeout(60000);
        // In this test, all the events we send have a lag > localHomeserverLagEnterWarningZoneMS.
        const start = new Date();
        const stop = simulateDate(start);

        // Ensure that no alert has been emitted yet.
        assert.equal(await this.getAlertEvent(), null, "Initially, there should be no alert");

        // Simulate lagging events from the local homeserver. This should trigger an alarm.
        const SENDERS = [`@local_user_1:${this.localDomain}`];
        await this.simulateLag(SENDERS, 1.5 * LOCAL_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS, start);

        let lagEvent = await this.getAlertEvent();
        console.debug(lagEvent);

        assert(lagEvent, "Local lag should be reported");
        assert.equal(JSON.stringify(lagEvent.domains), JSON.stringify([this.localDomain]), "Lag report should mention only the local domain");
        assert.equal(lagEvent.roomId, this.protectedRoomId, "Lag report should mention the right room");
        assert(new Date(lagEvent.since) >= start, "Lag report should have happened since `now`");
        assert(new Date(lagEvent.since) < stop, "Lag should have been detected before the end of the bombardment");

        {
            const {protectedRoomStats, globalStats} = await this.getCommandStatus();
            assert.ok(protectedRoomStats, "We should see stats for our room");
            assert.ok(protectedRoomStats.min >= 0, `min ${protectedRoomStats.min} >= 0`);
            assert.ok(protectedRoomStats.min < protectedRoomStats.max);
            assert.ok(protectedRoomStats.mean > 0);
            assert.ok(protectedRoomStats.mean < protectedRoomStats.max);
            assert.ok(protectedRoomStats.median < protectedRoomStats.max);
            assert.ok(protectedRoomStats.median > 0);
            assert.ok(protectedRoomStats.max >= 1.5 * LOCAL_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS);
            assert.deepEqual(globalStats, { [this.protectedRoomId]: protectedRoomStats })
        }

        // Simulate non-lagging events from the local homeserver. After a while, this should rescind the alarm.
        // We switch to a new (pseudo-)user to simplify reading logs.
        const SENDERS_2 = [`@local_user_2:${this.localDomain}`];
        const start2 = new Date(stop.getTime() + 1_000);
        await this.simulateLag(SENDERS_2, 0.75 * LOCAL_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS, start2);

        assert.equal(await this.getAlertEvent(), null, "The alert should now be rescinded");

        {
            const {protectedRoomStats, globalStats} = await this.getCommandStatus();
            assert.ok(protectedRoomStats, "We should see stats for our room");
            assert.ok(protectedRoomStats.min >= 0, `min ${protectedRoomStats.min} >= 0`);
            assert.ok(protectedRoomStats.min < protectedRoomStats.max);
            assert.ok(protectedRoomStats.mean > 0);
            assert.ok(protectedRoomStats.mean < protectedRoomStats.max);
            assert.ok(protectedRoomStats.median < protectedRoomStats.max);
            assert.ok(protectedRoomStats.median > 0);
            assert.ok(protectedRoomStats.max >= 0.75 * LOCAL_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS);
            assert.ok(protectedRoomStats.max < FEDERATED_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS);
            assert.deepEqual(globalStats, { [this.protectedRoomId]: protectedRoomStats })
        }
    });

    it('DetectFederationLag doesn\'t report lag when only one federated homeserver lags', async function() {
        this.timeout(60000);
        // In this test, all the events we send have a lag > federatedHomeserverLagEnterWarningZoneMS.
        const start = new Date();

        // Ensure that no alert has been emitted yet.
        assert.equal(await this.getAlertEvent(), null, "Initially, there should be no alert");

        // First, let's send events from the local homeserver.
        const SENDERS = ["@left:left.example.com"];
        await this.simulateLag(SENDERS, 1.5 * FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS, start);

        let lagEvent = await this.getAlertEvent();
        assert.equal(lagEvent, null, "With only one federated homeserver lagging, we shouldn't report any lag");
    });

    it('DetectFederationLag reports lag when three federated homeservers lag', async function() {
        this.timeout(60000);
        // In this test, all the events we send have a lag > federatedHomeserverLagEnterWarningZoneMS.
        const start = new Date();
        const stop = simulateDate(start);

        // Ensure that no alert has been emitted yet.
        assert.equal(await this.getAlertEvent(), null, "Initially, there should be no alert");

        // Simulate lagging events from remote homeservers. This should trigger an alarm.
        const SENDERS = [
            "@left:left.example.com",
            "@middle:middle.example.com",
            "@right:right.example.com",
        ];
        await this.simulateLag(SENDERS, 1.5 * FEDERATED_HOMESERVER_LAG_ENTER_WARNING_ZONE_MS, start);

        let lagEvent = await this.getAlertEvent();
        console.debug(lagEvent);
        assert(lagEvent, "Local lag should be reported");
        assert.equal(JSON.stringify(lagEvent.domains.sort()), JSON.stringify(["left.example.com", "middle.example.com", "right.example.com"]), "Lag report should mention only the local domain");
        assert.equal(lagEvent.roomId, this.protectedRoomId, "Lag report should mention the right room");
        assert(new Date(lagEvent.since) >= start, "Lag report should have happened since `now`");
        assert(new Date(lagEvent.since) < stop, "Lag should have been detected before the end of the bombardment");

        // Simulate non-lagging events from remote homeservers. After a while, this should rescind the alarm.
        // We switch to new (pseudo-)users to simplify reading logs.
        const SENDERS_2 = [
            "@left_2:left.example.com",
            "@middle_2:middle.example.com",
            "@right_2:right.example.com",
        ];
        const start2 = new Date(stop.getTime() + 1_000);
        await this.simulateLag(SENDERS_2, 0.75 * FEDERATED_HOMESERVER_LAG_EXIT_WARNING_ZONE_MS, start2);

        assert.equal(await this.getAlertEvent(), null, "The alert should now be rescinded");
    });
});