'use strict';

exports = module.exports = {
    get,
    add,
    update,
    setCompleted,
    setCompletedByType,
    listByTypePaged,

    getLogs,

    startTask,
    stopTask,
    stopAllTasks,

    removePrivateFields,

    _del: del,

    // task types. if you add a task here, fill up the function table in taskworker and dashboard client.js
    TASK_APP: 'app',
    TASK_BACKUP: 'backup',
    TASK_UPDATE: 'update',
    TASK_CHECK_CERTS: 'checkCerts',
    TASK_SYNC_DYNDNS: 'syncDyndns',
    TASK_PREPARE_DASHBOARD_LOCATION: 'prepareDashboardLocation',
    TASK_CLEAN_BACKUPS: 'cleanBackups',
    TASK_SYNC_EXTERNAL_LDAP: 'syncExternalLdap',
    TASK_CHANGE_MAIL_LOCATION: 'changeMailLocation',
    TASK_SYNC_DNS_RECORDS: 'syncDnsRecords',
    TASK_UPDATE_DISK_USAGE: 'updateDiskUsage',

    // error codes
    ESTOPPED: 'stopped',
    ECRASHED: 'crashed',
    ETIMEOUT: 'timeout',

    // testing
    _TASK_IDENTITY: '_identity',
    _TASK_CRASH: '_crash',
    _TASK_ERROR: '_error',
    _TASK_SLEEP: '_sleep'
};

const assert = require('assert'),
    BoxError = require('./boxerror.js'),
    constants = require('./constants.js'),
    database = require('./database.js'),
    debug = require('debug')('box:tasks'),
    fs = require('fs'),
    logs = require('./logs.js'),
    path = require('path'),
    paths = require('./paths.js'),
    safe = require('safetydance'),
    shell = require('./shell.js')('tasks'),
    _ = require('underscore');

let gTasks = {}; // indexed by task id

const START_TASK_CMD = path.join(__dirname, 'scripts/starttask.sh');
const STOP_TASK_CMD = path.join(__dirname, 'scripts/stoptask.sh');

const TASKS_FIELDS = [ 'id', 'type', 'argsJson', 'percent', 'message', 'errorJson', 'creationTime', 'resultJson', 'ts' ];

function postProcess(task) {
    assert.strictEqual(typeof task, 'object');

    assert(task.argsJson === null || typeof task.argsJson === 'string');
    task.args = safe.JSON.parse(task.argsJson) || [];
    delete task.argsJson;

    task.id = String(task.id);

    task.result = JSON.parse(task.resultJson);
    delete task.resultJson;

    task.error = safe.JSON.parse(task.errorJson);
    delete task.errorJson;

    return task;
}

function updateStatus(result) {
    assert.strictEqual(typeof result, 'object');

    // running means actively running
    // pending means not actively running
    // active mean task is 'done' or not. at this point, clients can stop polling this task. 
    // the apptaskmanager sets percent=1 when queued. just a hack to figure non-started but scheduled tasks
    result.running = !!gTasks[result.id];
    result.active = result.running || result.percent === 1;
    result.pending = !gTasks[result.id] && result.active;

    // we rely on 'percent' to determine success. maybe this can become a db field
    result.success = result.percent === 100 && !result.error;

    // the error in db will be empty if we didn't get a chance to handle task exit
    if (!result.active && result.percent !== 100 && !result.error) {
        result.error = { message: 'Task was stopped because the server was restarted or crashed', code: exports.ECRASHED };
    }

    return result;
}

async function get(id) {
    assert.strictEqual(typeof id, 'string');

    const result = await database.query(`SELECT ${TASKS_FIELDS} FROM tasks WHERE id = ?`, [ id ]);
    if (result.length === 0) return null;

    return updateStatus(postProcess(result[0]));
}

async function update(id, task) {
    assert.strictEqual(typeof id, 'string');
    assert.strictEqual(typeof task, 'object');

    debug(`update ${id}: ${JSON.stringify(task)}`);

    const args = [], fields = [];
    for (const k in task) {
        if (k === 'result' || k === 'error') {
            fields.push(`${k}Json = ?`);
            args.push(JSON.stringify(task[k]));
        } else {
            fields.push(k + ' = ?');
            args.push(task[k]);
        }
    }
    args.push(id);

    const result = await database.query('UPDATE tasks SET ' + fields.join(', ') + ' WHERE id = ?', args);
    if (result.affectedRows !== 1) throw new BoxError(BoxError.NOT_FOUND, 'Task not found');
}

async function setCompleted(id, task) {
    assert.strictEqual(typeof id, 'string');
    assert.strictEqual(typeof task, 'object');

    debug(`setCompleted - ${id}: ${JSON.stringify(task)}`);

    await update(id, Object.assign({ percent: 100 }, task));
}

async function setCompletedByType(type, task) {
    assert.strictEqual(typeof type, 'string');
    assert.strictEqual(typeof task, 'object');

    const results = await listByTypePaged(type, 1, 1);
    if (results.length !== 1) throw new BoxError(BoxError.NOT_FOUND, 'No such task');

    await setCompleted(results[0].id, task);
}

async function add(type, args) {
    assert.strictEqual(typeof type, 'string');
    assert(Array.isArray(args));

    const result = await database.query('INSERT INTO tasks (type, argsJson, percent, message) VALUES (?, ?, ?, ?)', [ type, JSON.stringify(args), 0, 'Queued' ]);
    return String(result.insertId);
}

function startTask(id, options, onTaskFinished) {
    assert.strictEqual(typeof id, 'string');
    assert.strictEqual(typeof options, 'object');
    assert(typeof onTaskFinished === 'undefined' || typeof onTaskFinished === 'function');

    const logFile = options.logFile || `${paths.TASKS_LOG_DIR}/${id}.log`;
    debug(`startTask - starting task ${id} with options ${JSON.stringify(options)}. logs at ${logFile}`);

    let killTimerId = null, timedOut = false;

    const sudoOptions = { preserveEnv: true, logStream: null };
    if (constants.TEST) sudoOptions.logStream = fs.createWriteStream('/dev/null'); // without this output is messed up, not sure why
    gTasks[id] = shell.sudo([ START_TASK_CMD, id, logFile, options.nice || 0, options.memoryLimit || 400, options.oomScoreAdjust || 0 ], sudoOptions, async function (sudoError) {
        if (!gTasks[id]) return; // ignore task exit since we are shutting down. see stopAllTasks

        const code = sudoError ? sudoError.code : 0;

        debug(`startTask: ${id} completed with code ${code}`);

        if (options.timeout) clearTimeout(killTimerId);

        const [getError, task] = await safe(get(id));

        let taskError = null;
        if (!getError && task.percent !== 100) { // taskworker crashed or was killed by us
            if (code === 0) {
                taskError = {
                    message: `Task ${id} ${timedOut ? 'timed out' : 'stopped'}` ,
                    code: timedOut ? exports.ETIMEOUT : exports.ESTOPPED
                };
            } else { // task crashed. for code, maybe we can check systemctl show box-task-1707 -p ExecMainStatus
                taskError = {
                    message: code === 2 ? `Task ${id} crashed as it ran out of memory` : `Task ${id} crashed with code ${code}`,
                    code: exports.ECRASHED
                };
            }

            // note that despite the update() here, we should handle the case where the box code was restarted and never got taskworker exit
            await safe(setCompleted(id, { error: taskError }));
        } else if (!getError && task.error) {
            taskError = task.error;
        } else if (!task) { // db got cleared in tests
            taskError = new BoxError(BoxError.NOT_FOUND, `No such task ${id}`);
        }

        delete gTasks[id];

        if (onTaskFinished) onTaskFinished(taskError, task ? task.result : null);

        debug(`startTask: ${id} done. error: %o`, taskError);
    });

    if (options.timeout) {
        killTimerId = setTimeout(async function () {
            debug(`startTask: task ${id} took too long. killing`);
            timedOut = true;
            const [error] = await safe(stopTask(id));
            if (error) debug(`startTask: error stopping task: ${error.message}`);
        }, options.timeout);
    }
}

async function stopTask(id) {
    assert.strictEqual(typeof id, 'string');

    if (!gTasks[id]) throw new BoxError(BoxError.BAD_STATE, 'task is not active');

    debug(`stopTask: stopping task ${id}`);

    await shell.promises.sudo([ STOP_TASK_CMD, id, ], {});
}

async function stopAllTasks() {
    debug('stopAllTasks: stopping all tasks');

    gTasks = {}; // this signals startTask() to not set completion status as "crashed"
    const [error] = await safe(shell.promises.sudo([ STOP_TASK_CMD, 'all' ], { cwd: paths.baseDir() }));
    if (error) debug(`stopAllTasks: error stopping stasks: ${error.message}`);
}

async function listByTypePaged(type, page, perPage) {
    assert(typeof type === 'string' || type === null);
    assert.strictEqual(typeof page, 'number');
    assert.strictEqual(typeof perPage, 'number');

    const data = [];
    let query = `SELECT ${TASKS_FIELDS} FROM tasks`;

    if (type) {
        query += ' WHERE TYPE=?';
        data.push(type);
    }

    query += ' ORDER BY creationTime DESC, id DESC LIMIT ?,?'; // put latest task first

    data.push((page-1)*perPage);
    data.push(perPage);

    const results = await database.query(query, data);
    results.forEach(postProcess);
    results.forEach(updateStatus);
    return  results;
}

async function getLogs(task, options) {
    assert.strictEqual(typeof task, 'object');
    assert(options && typeof options === 'object');

    assert.strictEqual(typeof options.lines, 'number');
    assert.strictEqual(typeof options.format, 'string');
    assert.strictEqual(typeof options.follow, 'boolean');

    const logFile = `${paths.TASKS_LOG_DIR}/${task.id}.log`;

    if (!task.active && !safe.fs.existsSync(logFile)) throw new BoxError(BoxError.FS_ERROR, 'Log file removed/missing'); // logrotated

    const cp = logs.tail([`${paths.TASKS_LOG_DIR}/${task.id}.log`], { lines: options.lines, follow: options.follow });
    const logStream = new logs.LogStream({ format: options.format || 'json', source: task.id });
    logStream.on('close', () => cp.terminate()); // the caller has to call destroy() on logStream. destroy() of Transform emits 'close'

    cp.stdout.pipe(logStream);

    return logStream;
}

// removes all fields that are strictly private and should never be returned by API calls
function removePrivateFields(task) {
    return _.pick(task, 'id', 'type', 'percent', 'message', 'error', 'active', 'pending', 'creationTime', 'result', 'ts', 'success');
}

async function del(id) {
    assert.strictEqual(typeof id, 'string');

    const result = await database.query('DELETE FROM tasks WHERE id = ?', [ id ]);
    if (result.affectedRows !== 1) throw new BoxError(BoxError.NOT_FOUND, 'Task not found');
}