#include <qpdf/QPDF.hh>
#include <qpdf/QPDFAcroFormDocumentHelper.hh>
#include <qpdf/QPDFPageDocumentHelper.hh>
#include <qpdf/QPDFWriter.hh>
#include <qpdf/QUtil.hh>
#include <cstdlib>
#include <iostream>

static char const* whoami = nullptr;

void
usage()
{
    std::cerr << "Usage: " << whoami << " infile.pdf outfile.pdf value" << std::endl
              << "Set the value of all text fields to a specified value" << std::endl;
    exit(2);
}

int
main(int argc, char* argv[])
{
    whoami = QUtil::getWhoami(argv[0]);

    if (argc != 4) {
        usage();
    }

    char const* infilename = argv[1];
    char const* outfilename = argv[2];
    char const* value = argv[3];

    // This is a contrived example that just goes through a file page
    // by page and sets the value of any text fields it finds to a
    // fixed value as given on the command line. The purpose here is
    // to illustrate use of the helper classes around interactive
    // forms.

    try {
        QPDF qpdf;
        qpdf.processFile(infilename);

        // We will iterate through form fields by starting at the page
        // level and looking at each field for each page. We could
        // also called QPDFAcroFormDocumentHelper::getFormFields to
        // iterate at the field level, but doing it as below
        // illustrates how we can map from annotations to fields.

        QPDFAcroFormDocumentHelper afdh(qpdf);
        for (auto const& page: QPDFPageDocumentHelper(qpdf).getAllPages()) {
            // Get all widget annotations for each page. Widget
            // annotations are the ones that contain the details of
            // what's in a form field.
            for (auto& annot: afdh.getWidgetAnnotationsForPage(page)) {
                // For each annotation, find its associated field. If
                // it's a text field, set its value.
                QPDFFormFieldObjectHelper ffh = afdh.getFieldForAnnotation(annot);
                if (ffh.getFieldType() == "/Tx") {
                    // Set the value. Passing false as the second
                    // value prevents qpdf from setting
                    // /NeedAppearances to true (but will not turn it
                    // off if it's already on), so we call
                    // generateAppearance after setting the value. You
                    // may or may not want to do this depending on
                    // whether the appearance streams generated by
                    // qpdf are good enough for your purposes. For
                    // additional details, please see comments in
                    // QPDFFormFieldObjectHelper.hh for this method.
                    ffh.setV(value, false);
                    ffh.generateAppearance(annot);
                }
            }
        }

        // Write out a new file
        QPDFWriter w(qpdf, outfilename);
        w.setStaticID(true); // for testing only
        w.write();
    } catch (std::exception& e) {
        std::cerr << whoami << " processing file " << infilename << ": " << e.what() << std::endl;
        exit(2);
    }

    return 0;
}