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

import { degrees } from "pdf-lib";
import { PdfFile, RepresentationType } from "../wrappers/PdfFile";

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

export async function rotatePages(params: RotateParamsType): Promise<PdfFile> {
    const { file, rotation } = params;
    
    const pdfDoc = await file.pdfLibDocument;
    const pages = pdfDoc.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 new PdfFile(file.originalFilename, pdfDoc, RepresentationType.PDFLibDocument, file.filename+"_rotated");
}