/* Utility to "un-patch" Qt5Core.dll, so that the cryptographic signature becomes valid.
   Issue: https://bugreports.qt.io/browse/QTBUG-76985
*/
#include <fstream>
#include <iterator>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

/** Replace the value in a "key=value" segment within the buffer. */
static bool PatchSegment (string & buffer, string key, string value) {
    key += "=";

    size_t idx = buffer.find(key);
    if (idx == std::string::npos)
        return false;

    idx += key.size();
    for (size_t i = 0; i < value.size(); ++i)
        buffer[idx + i] = value[i];

    return true;
}


/** Change specfic Qt5Core.dll sections hack to their original values from when the file was signed.
    Based on suggestions from in Patrick Morgenstern in https://bugreports.qt.io/browse/QTBUG-76985 */
static bool UnPatchQt5CoreDLL (string & buffer) {
    std::string instdate = "2012-12-20";
    instdate.resize(11); // zero-extend to match size in https://github.com/qt/qtbase/blob/dev/configure.pri
    PatchSegment(buffer, "qt_instdate", instdate); // discard return-value, since the field is being removed

    std::string prfxpath = "c:/Users/qt/work/install";
    prfxpath.resize(256); // zero-extend to match size in https://github.com/qt/qtbase/blob/dev/configure.pri
    return PatchSegment(buffer, "qt_prfxpath", prfxpath);
}


int main (int argc, char *argv[]) {
    if (argc != 3) {
        cout << "QtUnpatcher - Utility to un-patch Qt5Core.dll, so that the cryptographic signature becomes valid.\n";
        cout << "Usage: QtUnpatcher <in-file> <out-file>\n";
        return 1;
    }

    ifstream input(argv[1], ios::binary);
    if (!input) {
        cerr << "ERROR: Unable to open input file\n";
        return -1;
    }

    // load file content into a string instead of a vector to ease search
    // this is safe, because std::string may contain '\0' characters
    string content(istreambuf_iterator<char>(input), {});
    bool patched = UnPatchQt5CoreDLL(content);
    if (!patched) {
        cerr << "ERROR: Unable to patch " << argv[1] << "\n";
        return -2;
    }

    ofstream output(argv[2], ios::binary);
    if (!output) {
        cerr << "ERROR: Unable to open output file\n";
        return -3;
    }
    output.write(content.data(), content.size());

    cout << "Patched file " << argv[2] << " successfully written.\n";
    return 0;
}