function getBatchRanges()

in index.js [400:441]
29 lines of code
6 McCabe index (conditional complexity)

function getBatchRanges(records) {
    var batches = [];
    var currentLowOffset = 0;
    var batchCurrentBytes = 0;
    var batchCurrentCount = 0;
    var recordSize;
    var nextRecordSize;

    for (var i = 0; i < records.length; i++) {
        // need to calculate the total record size for the call to Firehose on
        // the basis of of non-base64 encoded values
        recordSize = Buffer.byteLength(records[i].toString(targetEncoding), targetEncoding);

        // batch always has 1 entry, so add it first
        batchCurrentBytes += recordSize;
        batchCurrentCount += 1;

        // To get next record size inorder to calculate the FIREHOSE_MAX_BATCH_BYTES
        if(i === records.length - 1) {
		    nextRecordSize = 0;
	    } else {
		    nextRecordSize = Buffer.byteLength(records[i+1].toString(targetEncoding), targetEncoding);
	    }
        
        // generate a new batch marker every 4MB or 500 records, whichever comes
        // first
        if (batchCurrentCount === FIREHOSE_MAX_BATCH_COUNT || batchCurrentBytes + nextRecordSize > FIREHOSE_MAX_BATCH_BYTES || i === records.length - 1) {
            batches.push({
                lowOffset: currentLowOffset,
                // annoying special case handling for record sets of size 1
                highOffset: i + 1,
                sizeBytes: batchCurrentBytes
            });
            // reset accumulators
            currentLowOffset = i + 1;
            batchCurrentBytes = 0;
            batchCurrentCount = 0;
        }
    }

    return batches;
}