'use strict';

const apps = require('./apps.js'),
    assert = require('assert'),
    AuditSource = require('./auditsource.js'),
    BoxError = require('./boxerror.js'),
    constants = require('./constants.js'),
    debug = require('debug')('box:apphealthmonitor'),
    docker = require('./docker.js'),
    eventlog = require('./eventlog.js'),
    safe = require('safetydance'),
    superagent = require('superagent');

exports = module.exports = {
    run
};

const UNHEALTHY_THRESHOLD = 20 * 60 * 1000; // 20 minutes

const OOM_EVENT_LIMIT = 60 * 60 * 1000; // will only raise 1 oom event every hour
let gStartTime = null; // time when apphealthmonitor was started
let gLastOomMailTime = Date.now() - (5 * 60 * 1000); // pretend we sent email 5 minutes ago

async function setHealth(app, health) {
    assert.strictEqual(typeof app, 'object');
    assert.strictEqual(typeof health, 'string');

    // app starts out with null health
    // if it became healthy, we update immediately. this is required for ui to say "running" etc
    // if it became unhealthy/error/dead, wait for a threshold before updating db

    const now = new Date(), lastHealth = app.health;
    let healthTime = gStartTime > app.healthTime ? gStartTime : app.healthTime; // on box restart, clamp value to start time

    if (health === apps.HEALTH_HEALTHY) {
        healthTime = now;
        if (lastHealth && lastHealth !== apps.HEALTH_HEALTHY) { // app starts out with null health
            debug(`setHealth: ${app.id} (${app.fqdn}) switched from ${lastHealth} to healthy`);

            // do not send mails for dev apps
            if (!app.debugMode) await eventlog.add(eventlog.ACTION_APP_UP, AuditSource.HEALTH_MONITOR, { app: app });
        }
    } else if (Math.abs(now - healthTime) > UNHEALTHY_THRESHOLD) {
        if (lastHealth === apps.HEALTH_HEALTHY) {
            debug(`setHealth: marking ${app.id} (${app.fqdn}) as unhealthy since not seen for more than ${UNHEALTHY_THRESHOLD/(60 * 1000)} minutes`);

            // do not send mails for dev apps
            if (!app.debugMode) await eventlog.add(eventlog.ACTION_APP_DOWN, AuditSource.HEALTH_MONITOR, { app: app });
        }
    } else {
        debug(`setHealth: ${app.id} (${app.fqdn}) waiting for ${(UNHEALTHY_THRESHOLD - Math.abs(now - healthTime))/1000} to update health`);
        return;
    }

    const [error] = await safe(apps.setHealth(app.id, health, healthTime));
    if (error && error.reason === BoxError.NOT_FOUND) return; // app uninstalled?
    if (error) throw error;

    app.health = health;
    app.healthTime = healthTime;
}


// callback is called with error for fatal errors and not if health check failed
async function checkAppHealth(app, options) {
    assert.strictEqual(typeof app, 'object');
    assert.strictEqual(typeof options, 'object');

    if (app.installationState !== apps.ISTATE_INSTALLED || app.runState !== apps.RSTATE_RUNNING) return;

    const manifest = app.manifest;

    const [error, data] = await safe(docker.inspect(app.containerId));
    if (error || !data || !data.State) return await setHealth(app, apps.HEALTH_ERROR);
    if (data.State.Running !== true) return await setHealth(app, apps.HEALTH_DEAD);

    // non-appstore apps may not have healthCheckPath
    if (!manifest.healthCheckPath) return await setHealth(app, apps.HEALTH_HEALTHY);

    const healthCheckUrl = `http://${app.containerIp}:${manifest.httpPort}${manifest.healthCheckPath}`;
    const [healthCheckError, response] = await safe(superagent
        .get(healthCheckUrl)
        .set('Host', app.fqdn) // required for some apache configs with rewrite rules
        .set('User-Agent', 'Mozilla (CloudronHealth)') // required for some apps (e.g. minio)
        .redirects(0)
        .ok(() => true)
        .timeout(options.timeout * 1000));

    if (healthCheckError) {
        await setHealth(app, apps.HEALTH_UNHEALTHY);
    } else if (response.status > 403) { // 2xx and 3xx are ok. even 401 and 403 are ok for now (for WP sites)
        await setHealth(app, apps.HEALTH_UNHEALTHY);
    } else {
        await setHealth(app, apps.HEALTH_HEALTHY);
    }
}

async function getContainerInfo(containerId) {
    const result = await docker.inspect(containerId);

    const appId = safe.query(result, 'Config.Labels.appId', null);
    if (appId) return { app: await apps.get(appId) }; // don't get by container id as this can be an exec container

    if (result.Name.startsWith('/redis-')) {
        return { app: await apps.get(result.Name.slice('/redis-'.length)), addonName: 'redis' };
    } else {
        return { addonName: result.Name.slice(1) }; // addon . Name has a '/' in the beginning for some reason
    }
}

/*
    OOM can be tested using stress tool like so:
        docker run -ti -m 100M cloudron/base:3.0.0 /bin/bash
        stress --vm 1 --vm-bytes 200M --vm-hang 0
*/
async function processDockerEvents(options) {
    assert.strictEqual(typeof options, 'object');

    const since = ((new Date().getTime() / 1000) - options.intervalSecs).toFixed(0);
    const until = ((new Date().getTime() / 1000) - 1).toFixed(0);

    const stream = await docker.getEvents({ since: since, until: until, filters: JSON.stringify({ event: [ 'oom' ] }) });
    stream.setEncoding('utf8');
    stream.on('data', async function (data) { // this is actually ldjson, we only process the first line for now
        const event = safe.JSON.parse(data);
        if (!event) return;
        const containerId = String(event.id);

        const [error, info] = await safe(getContainerInfo(containerId));
        const program = error ? containerId : (info.addonName || info.app.fqdn);
        const now = Date.now();

        // do not send mails for dev apps
        const notifyUser = !(info.app && info.app.debugMode) && ((now - gLastOomMailTime) > OOM_EVENT_LIMIT);

        debug(`OOM ${program} notifyUser: ${notifyUser}. lastOomTime: ${gLastOomMailTime} (now: ${now})`);

        if (notifyUser) {
            await eventlog.add(eventlog.ACTION_APP_OOM, AuditSource.HEALTH_MONITOR, { event, containerId, addonName: info?.addonName || null, app: info?.app || null });

            gLastOomMailTime = now;
        }
    });

    stream.on('error', function (error) {
        debug('Error reading docker events', error);
    });

    stream.on('end', function () {
        // debug('Event stream ended');
    });

    // safety hatch if 'until' doesn't work (there are cases where docker is working with a different time)
    setTimeout(stream.destroy.bind(stream), options.timeout); // https://github.com/apocas/dockerode/issues/179
}

async function processApp(options) {
    assert.strictEqual(typeof options, 'object');

    const allApps = await apps.list();

    const healthChecks = allApps.map((app) => checkAppHealth(app, options)); // start healthcheck in parallel

    await Promise.allSettled(healthChecks); // wait for all promises to finish

    const alive = allApps
        .filter(function (a) { return a.installationState === apps.ISTATE_INSTALLED && a.runState === apps.RSTATE_RUNNING && a.health === apps.HEALTH_HEALTHY; });

    debug(`app health: ${alive.length} alive / ${allApps.length - alive.length} dead.`);
}

async function run(intervalSecs) {
    assert.strictEqual(typeof intervalSecs, 'number');

    if (constants.TEST) return;

    if (!gStartTime) gStartTime = new Date();

    await processApp({ timeout: (intervalSecs - 3) * 1000 });
    await processDockerEvents({ intervalSecs, timeout: 3000 });
}