Stirling-PDF/shared-operations/src/functions/rotatePages.ts

import { degrees } from 'pdf-lib';
import { PdfFile } from '../wrappers/PdfFile';

export type RotateParamsType = {
    file: PdfFile;
    rotation: number|number[];
}

export async function rotatePages(params: RotateParamsType): Promise<PdfFile> {
    const { file, rotation } = params;
    
    const pages = (await file.pdfLibDocument).getPages();

    if (Array.isArray(rotation)) {
        if (rotation.length != pages.length) {
            throw new Error(`Number of given rotations '${rotation.length}' is not the same as the number of pages '${pages.length}'`)
        }
        for (let i=0; i<rotation.length; i++) {
            const oldRotation = pages[i].getRotation().angle
            pages[i].setRotation(degrees(oldRotation + rotation[i]))
        }
    } else {
        pages.forEach(page => {
            // Change page size
            const oldRotation = page.getRotation().angle
            page.setRotation(degrees(oldRotation + rotation))
        });
    }

    return file;
};