Google Sheets Apps: insert new data while shifting old rows down

Question

I have a Google Sheet with a table that looks something like this:

date	value1	value2
day 2	foo	foo
day 1	bar	bar

Every day has a certain amount of records, and from time to time I add new records. The way I do it currently is:

1. Shift existing rows down depending on how many rows I need to insert;
2. Insert new records into the freed up cells.

I'd like to automate this with Google Scripts by making it be this way:

1. Click on B1 and paste from clipboard;
2. Have all the old rows automatically move down depending on how many rows are in what I'm pasting, and new rows be inserted into the freed up cells.

I wonder if there is a way to do this.

This is a good reference code, but I'm stuck on the "depending on" part.