#!/usr/node/bin/node

"use strict";

var CronJob = require('cron').CronJob;
var async = require('async');
var fs = require('fs')
var minimatch = require('minimatch')
var util = require('util');
var zfs = require('zfs')

// Generate a snapshot name given a base.
function snapshotName(base) {
    var when = (new Date()).toISOString().replace(/[-:]|(\.\d\d\d)/g, '');
    return base + '-' + when;
}

// Create a snapshot on the specified dataset with the specified name, exluding all datasets in excl.
function createSnapshot(ds, sn, cb) {
    util.log('Create snapshot ' + ds + '@' + sn);
    zfs.snapshot({ dataset: ds, name: sn, recursive: true }, cb);
}

// Keep only num snapshots with the specified base on the specified dataset
function cleanSnapshots(patterns, base, num, cb) {
    zfs.list({ type: 'snapshot' }, function (err, snaps) {
        var allSnaps = {};
        patterns.forEach(function (pat) {
            snaps.forEach(function (s) {
                var fields = s.name.split('@');
                var parts = fields[1].split('-');
                if (minimatch(fields[0], pat) && parts[0] === base) {
                    var l = allSnaps[fields[0]] || [];
                    l.push(s.name);
                    allSnaps[fields[0]] = l;
                }
            });
        });

        async.eachLimit(Object.keys(allSnaps), 10, function (dsName, cb) {
            var snapNames = allSnaps[dsName];
            if (snapNames.length > num) {
                snapNames.sort();

                // Get the ones that exceed the specified number of snapshots.
                var toDestroy = snapNames.slice(0, snapNames.length - num);

                // Destroy them, one after the other.
                async.eachSeries(toDestroy, function (sn, cb) {
                    util.log('Destroy snapshot ' + sn + ' (cleaned)');
                    zfs.destroy({ name: sn, recursive: true }, cb);
                }, cb);
            } else {
                cb(null);
            }
        }, cb);
    });
}

function loadConfig() {
    var data = fs.readFileSync(process.argv[2], 'utf-8');
    var confObj = JSON.parse(data);
    return confObj;
}

function snap(datasets, snapBase, num) {
    var snapId = snapshotName(snapBase);
    zfs.list({type: 'filesystem,volume'}, function (err, dss) {
        dss = dss.map(function (s) { return s.name; });
        var toSnap = dss.filter(function (ds) {
            return datasets.filter(function (pat) { return minimatch(ds, pat) }).length > 0;
        });

        async.eachLimit(toSnap, 10, function (ds, cb) {
            createSnapshot(ds, snapId, cb);
        }, function () {
            cleanSnapshots(datasets, snapBase, num, function () {
                util.log("Done " + snapId);
            });
        });
    });
}

var cronJobs = [];
var conf = loadConfig();
Object.keys(conf).forEach(function (snapBase) {
    var config = conf[snapBase];
    var job = new CronJob('00 ' + config.when, function () {
        snap(config.datasets, snapBase, parseInt(config.count, 10));
    }, null, true);
    cronJobs.push(job);
});

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