current-bidi-paragraph-direction is a built-in function in `C source code'.

(current-bidi-paragraph-direction &optional BUFFER)

Return paragraph direction at point in BUFFER.
Value is either `left-to-right' or `right-to-left'.
If BUFFER is omitted or nil, it defaults to the current buffer.

Paragraph direction determines how the text in the paragraph is displayed.
In left-to-right paragraphs, text begins at the left margin of the window
and the reading direction is generally left to right. In right-to-left
paragraphs, text begins at the right margin and is read from right to left.

See also `bidi-paragraph-direction'.