refactor: add a HashUtils place for hashing stuff

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/modplatform/helpers/HashUtils.cpp

@@ -0,0 +1,81 @@
+#include "HashUtils.h"
+
+#include <QDebug>
+#include <QFile>
+
+#include "FileSystem.h"
+
+#include <MurmurHash2.h>
+
+namespace Hashing {
+
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+Hasher::Ptr createHasher(QString file_path, ModPlatform::Provider provider)
+{
+    switch (provider) {
+        case ModPlatform::Provider::MODRINTH:
+            return createModrinthHasher(file_path);
+        case ModPlatform::Provider::FLAME:
+            return createFlameHasher(file_path);
+        default:
+            qCritical() << "[Hashing]"
+                        << "Unrecognized mod platform!";
+            return nullptr;
+    }
+}
+
+Hasher::Ptr createModrinthHasher(QString file_path)
+{
+    return new ModrinthHasher(file_path);
+}
+
+Hasher::Ptr createFlameHasher(QString file_path)
+{
+    return new FlameHasher(file_path);
+}
+
+void ModrinthHasher::executeTask()
+{
+    QFile file(m_path);
+
+    try {
+        file.open(QFile::ReadOnly);
+    } catch (FS::FileSystemException& e) {
+        qCritical() << QString("Failed to open JAR file in %1").arg(m_path);
+        qCritical() << QString("Reason: ") << e.cause();
+
+        emitFailed("Failed to open file for hashing.");
+        return;
+    }
+
+    auto hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+    m_hash = ProviderCaps.hash(ModPlatform::Provider::MODRINTH, &file, hash_type);
+
+    file.close();
+
+    if (m_hash.isEmpty()) {
+        emitFailed("Empty hash!");
+    } else {
+        emitSucceeded();
+    }
+}
+
+void FlameHasher::executeTask()
+{
+    // CF-specific
+    auto should_filter_out = [](char c) { return (c == 9 || c == 10 || c == 13 || c == 32); };
+
+    std::ifstream file_stream(m_path.toStdString(), std::ifstream::binary);
+    // TODO: This is very heavy work, but apparently QtConcurrent can't use move semantics, so we can't boop this to another thread.
+    // How do we make this non-blocking then?
+    m_hash = QString::number(MurmurHash2(std::move(file_stream), 4 * MiB, should_filter_out));
+
+    if (m_hash.isEmpty()) {
+        emitFailed("Empty hash!");
+    } else {
+        emitSucceeded();
+    }
+}
+
+}  // namespace Hashing