var db string  // database per service function chain, so db is named after sfc

var rp = 'autogen'  // default value for the retention policy

var measurement string

var field string

var influxFunction string

var whereClause = 'TRUE'  // default value is TRUE, hence no filtering of the query result

var messageValue = 'TRUE'  // default value is TRUE, as this is what SFEMC expects as a notification for an event rule

var comparisonLambda lambda  // comparison function e.g. "diff" > 40

var alertPeriod duration

var topicID string


var current = batch
    |query('SELECT ' + influxFunction + '(' + field + ') AS value FROM "' + db + '"."' + rp + '"."' + measurement + '" WHERE ' + whereClause)
        .period(alertPeriod)
        .every(alertPeriod)

var past = current
    .offset(alertPeriod)
    | shift(alertPeriod)

past
    | join(current)
        .as('past', 'current')
    | eval(lambda: float("current.value" - "past.value"))
        .as('diff')
    | alert()
        .id(topicID)
        .details('db=' + db + ',measurement=' + measurement)
        .crit(comparisonLambda)
        .message(messageValue)
        .topic(topicID)
        .noRecoveries()