aggregationCroustillante.js

aggregateHelper.js

// function to aggregate values of the last 24h of a given sensor, according to its strategy
var last24 = function(sensorConf, callback) {
	// get current hour in order to make some relative calculations
	var current = moment();
	var currentHour = current.utc().hour();
	// get yesterday date (from h-23 to h+1 to get the running hour, e.g. from 2h yesterday to 2h today when it's 1h)
	var yesterday = current.startOf('hour').add(1, 'h').subtract(24, 'h').toDate();

	var aggregate = Event.aggregate();
	if (sensorConf) {
		// match events from date and with the given name
		aggregate.match({
			date: { $gte : yesterday },
			name: sensorConf.name
		});
	}
	else {
		// match events from date
		aggregate.match({
			date: { $gte : yesterday }
		});
	}
	// only keep the hour part of the date, since we know all matched events happened during the last 24h
	aggregate.project({
		name: 1,
		value: 1,
		hour : {'$hour' : '$date'}
	});
	// get sum and avg for each name/hour tuple
	aggregate.group({
		_id: { name: '$name', hour: '$hour' },
		sum: { $sum: '$value' },
		avg: { $avg: '$value' }
	});
	// make a condition to calculate the sum or the avg according to the sensor name
	aggregate.project({
		_id: 1,
		value: {
			$cond: [
				{ $or: [
					{ $eq: [ '$_id.name', 'watt' ] },
					{ $eq: [ '$_id.name', 'sound' ] },
					{ $eq: [ '$_id.name', 'degrees' ] },
					{ $eq: [ '$_id.name', 'light' ] },
					{ $eq: [ '$_id.name', 'fridgeDegrees' ] },
					{ $eq: [ '$_id.name', 'devices' ] }
				]},
				'$avg',
				'$sum'
			]
		}
	});
	// if it's devices, we need to return an integer average value
	aggregate.project({
		_id: 1,
		value: {
			$cond: [
				{ $eq: [ '$_id.name', 'devices' ] },
				{ $subtract: [ '$value' , { $mod: [ '$value', 1 ] } ] },
				'$value'
			]
		}
	});
	// re-arrange data
	// calculate hour ago, instead of the plain hour
	// first subtract the hour returned by the query to the current hour
	aggregate.project({
		_id: '$_id.name',
		values: { 
			hour: { $subtract: [ currentHour, '$_id.hour' ] },
			value : '$value'
		}
	});
	// then if the result of the subtraction is negative, it means it's an hour of the day ago
	// if so remove 24h, else leave the hour as is
	aggregate.project({
		_id: '$_id',
		values: {
			hourAgo: {
				$cond: [
					{ $lt: [ '$values.hour', 0 ] },
					{ $add: ['$values.hour', 24] },
					'$values.hour'
				]
			},
			value : '$values.value'
		}
	});
	// sort the result by ascending values.hourAgo
	aggregate.sort('values.hourAgo');
	// then push each values in an array
	aggregate.group({
		_id: '$_id',
		values: {
			$push: { 
				hourAgo: '$values.hourAgo',
				value: '$values.value'
			}
		}
	});
	aggregate.exec(callback);
};