I'm Pepega too. Added two missing files.

src/util/NuulsUploader.cpp

@@ -0,0 +1,205 @@
+#include "NuulsUploader.hpp"
+
+#include "common/Env.hpp"
+#include "common/NetworkRequest.hpp"
+#include "providers/twitch/TwitchMessageBuilder.hpp"
+
+#include <boost/algorithm/string/replace.hpp>
+
+namespace chatterino {
+bool isUploading = false;
+
+std::queue<TypedBytes> uploadQueue;
+void uploadImageToNuuls(QByteArray imageData, ChannelPtr channel,
+                        ResizingTextEdit &textEdit)
+{
+    uploadImageToNuuls(imageData, channel, textEdit, "png");
+}
+void uploadImageToNuuls(TypedBytes imageData, ChannelPtr channel,
+                        ResizingTextEdit &textEdit)
+{
+    uploadImageToNuuls(imageData.data, channel, textEdit, imageData.type);
+}
+void uploadImageToNuuls(QByteArray imageData, ChannelPtr channel,
+                        ResizingTextEdit &textEdit, std::string format)
+{
+    QByteArray dataToSend;
+    const char *boundary = "thisistheboudaryasd";
+    static QUrl url(Env::get().imagePasteSiteUrl);
+
+    dataToSend.insert(0, "--");
+    dataToSend.append(boundary);
+    std::string temp = "\r\n"
+                       "Content-Disposition: form-data; name=\"attachment\"; "
+                       "filename=\"control_v.%\"\r\n"
+                       "Content-Type: image/%\r\n"
+                       "\r\n";
+    boost::replace_all(temp, "%", format);
+
+    dataToSend.append(temp.c_str());
+    dataToSend.append(imageData);
+    dataToSend.append("\r\n--");
+    dataToSend.append(boundary);
+    dataToSend.append("\r\n");
+
+    NetworkRequest(url, NetworkRequestType::Post)
+        .header("Content-Type", (std::string("multipart/form-data; boundary=") +
+                                 std::string(boundary))
+                                    .c_str())
+
+        .payload(dataToSend)
+        .onSuccess([&textEdit, channel](NetworkResult result) -> Outcome {
+            textEdit.insertPlainText(result.getData() + QString(" "));
+            //            this->input_->ui_.textEdit->insertPlainText(result.getData());
+            if (uploadQueue.size())
+            {
+                channel->addMessage(makeSystemMessage(
+                    QString("Your image has been uploaded. %1 left. Please "
+                            "wait until all of them are uploaded. About %2 "
+                            "seconds left.")
+                        .arg(uploadQueue.size())
+                        .arg(uploadQueue.size() * 3)));
+                // Argument number 2 is the ETA.
+                // 2 seconds for the timer that's there not to spam Nuuls' server
+                // and 1 second of actual uploading.
+            }
+            else
+            {
+                channel->addMessage(makeSystemMessage(
+                    QString("Your image has been uploaded.")));
+            }
+            isUploading = false;
+            QTimer::singleShot(2000, [channel, &textEdit]() {
+                if (uploadQueue.size())
+                {
+                    uploadImageToNuuls(uploadQueue.front(), channel, textEdit);
+                    uploadQueue.pop();
+                }
+            });
+            return Success;
+        })
+        .onError([channel](NetworkResult result) -> bool {
+            channel->addMessage(makeSystemMessage(
+                QString("An error happened while uploading your image: %1")
+                    .arg(result.status())));
+            isUploading = false;
+            return true;
+        })
+        .execute();
+}
+QString getImageFileFormat(QString path)
+{
+    static QStringList LIST_OF_IMAGE_FORMATS = {".png", ".jpg", ".jpeg"};
+    for (QString i : LIST_OF_IMAGE_FORMATS)
+    {
+        if (path.endsWith(i))
+        {
+            return i.replace('.', "");
+        }
+    }
+    return QString();
+}
+
+void pasteFromClipboard(const QMimeData *source, ChannelPtr channel,
+                        ResizingTextEdit &outputTextEdit)
+{
+    /*
+static QUrl url("http://localhost:7494/upload?password=xd");
+// default port and password for nuuls' filehost.
+*/
+    if (isUploading)
+    {
+        channel->addMessage(makeSystemMessage(
+            QString("You are already uploading an image. "
+                    "Please wait until the upload finishes.")));
+        return;
+    }
+
+    isUploading = true;
+    channel->addMessage(makeSystemMessage(QString("Started upload...")));
+
+    if (source->hasFormat("image/png"))
+    {
+        uploadImageToNuuls(source->data("image/png"), channel, outputTextEdit);
+    }
+    else if (source->hasFormat("text/uri-list"))
+    {
+        QStringList potientialPathsToSend =
+            QString(source->data("text/uri-list").toStdString().c_str())
+                .split("\r\n");
+
+        for (QString path : potientialPathsToSend)
+        {
+            if (path.isEmpty())
+            {
+                break;
+            }
+            else
+            {
+                if (getImageFileFormat(path) != QString())
+                {
+                    channel->addMessage(makeSystemMessage(
+                        QString("Uploading image: %1").arg(path)));
+                    QImage img = QImage(QUrl(path).toLocalFile());
+                    if (img.isNull())
+                    {
+                        channel->addMessage(makeSystemMessage(
+                            QString("Couldn't load image :(")));
+                        return;
+                    }
+                    QByteArray imageData;
+                    QBuffer buf(&imageData);
+                    buf.open(QIODevice::WriteOnly);
+                    img.save(&buf, "png");
+
+                    TypedBytes data = {imageData, "png"};
+                    uploadQueue.push(data);
+                }
+                else if (path.endsWith(".gif"))
+                {
+                    channel->addMessage(makeSystemMessage(
+                        QString("Uploading GIF: %1").arg(path)));
+                    QFile file(QUrl(path).toLocalFile());
+                    bool isOkay = file.open(QIODevice::ReadOnly);
+                    if (!isOkay)
+                    {
+                        channel->addMessage(makeSystemMessage(
+                            QString("Failed to open file. :(")));
+                        return;
+                    }
+                    TypedBytes data = {file.readAll(), "gif"};
+                    uploadQueue.push(data);
+                    file.close();
+                    // file.readAll() => might be a bit big but it /should/ work
+                }
+                else
+                {
+                    channel->addMessage(makeSystemMessage(
+                        QString("Cannot upload file: %1, not an image")
+                            .arg(path)));
+                }
+            }
+        }
+        if (uploadQueue.size())
+        {
+            uploadImageToNuuls(uploadQueue.front(), channel, outputTextEdit);
+            uploadQueue.pop();
+        }
+    }
+    else if (source->hasFormat("image/gif"))
+    {
+        TypedBytes data = {source->data("image/gif"), "gif"};
+        uploadImageToNuuls(data, channel, outputTextEdit);
+    }
+    else
+    {  // not PNG, try loading it into QImage and save it to a PNG.
+        QImage image = qvariant_cast<QImage>(source->imageData());
+        QByteArray imageData;
+        QBuffer buf(&imageData);
+        buf.open(QIODevice::WriteOnly);
+        image.save(&buf, "png");
+
+        uploadImageToNuuls(imageData, channel, outputTextEdit);
+    }
+}
+}  // namespace chatterino

src/util/NuulsUploader.hpp

@@ -0,0 +1,19 @@
+#include "common/Channel.hpp"
+#include "widgets/helper/ResizingTextEdit.hpp"
+
+#include <QMimeData>
+#include <QString>
+
+namespace chatterino {
+struct TypedBytes {
+    QByteArray data;
+    std::string type;
+};
+void uploadImageToNuuls(QByteArray imageData, ChannelPtr channel,
+                        ResizingTextEdit &textEdit, std::string format);
+void uploadImageToNuuls(TypedBytes imageData, ChannelPtr channel,
+                        ResizingTextEdit &textEdit);
+QString getImageFileFormat(QString path);
+void pasteFromClipboard(const QMimeData *source, ChannelPtr channel,
+                        ResizingTextEdit &outputTextEdit);
+}  // namespace chatterino