[Oracle] Skip low-memory prompt in background mode, guard with HAS_LZMA

Use QRegularExpression behind the same Qt version guard as
totalMemoryBytes() in availableMemoryBytes(), where a bare QRegExp
broke every Qt6 Linux build. hasAtLeastGiB() now treats a 0 reading
(unsupported platform or failed query) as unknown and skips the
low-memory prompt instead of misreading it as low memory.

libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp

@@ -166,7 +166,7 @@ bool DeckList::readElement(QXmlStreamReader *xml)
     return true;
 }
 
-void writeMetadata(QXmlStreamWriter *xml, const DeckList::Metadata &metadata)
+static void writeMetadata(QXmlStreamWriter *xml, const DeckList::Metadata &metadata)
 {
     xml->writeTextElement("lastLoadedTimestamp", metadata.lastLoadedTimestamp);
     xml->writeTextElement("deckname", metadata.name);

libcockatrice_network/libcockatrice/network/server/remote/server_player_reference.h

@@ -24,7 +24,7 @@ public:
     {
         return playerId;
     }
-    bool operator==(const PlayerReference &other)
+    bool operator==(const PlayerReference &other) const
     {
         return ((roomId == other.roomId) && (gameId == other.gameId) && (playerId == other.playerId));
     }

libcockatrice_utility/CMakeLists.txt

@@ -6,12 +6,17 @@ set(CMAKE_AUTOUIC ON)
 set(CMAKE_AUTORCC ON)
 
 set(UTILITY_SOURCES libcockatrice/utility/expression.cpp libcockatrice/utility/levenshtein.cpp
-                    libcockatrice/utility/passwordhasher.cpp
+                    libcockatrice/utility/passwordhasher.cpp libcockatrice/utility/system_memory_querier.cpp
 )
 
 set(UTILITY_HEADERS
-    libcockatrice/utility/color.h libcockatrice/utility/expression.h libcockatrice/utility/levenshtein.h
-    libcockatrice/utility/macros.h libcockatrice/utility/passwordhasher.h libcockatrice/utility/trice_limits.h
+    libcockatrice/utility/color.h
+    libcockatrice/utility/expression.h
+    libcockatrice/utility/levenshtein.h
+    libcockatrice/utility/macros.h
+    libcockatrice/utility/passwordhasher.h
+    libcockatrice/utility/system_memory_querier.h
+    libcockatrice/utility/trice_limits.h
 )
 
 add_library(libcockatrice_utility STATIC ${UTILITY_SOURCES} ${UTILITY_HEADERS})

libcockatrice_utility/libcockatrice/utility/system_memory_querier.cpp

@@ -0,0 +1,116 @@
+#include "system_memory_querier.h"
+
+#ifdef Q_OS_WIN
+#include <windows.h>
+#endif
+
+#ifdef Q_OS_LINUX
+#include <QFile>
+#include <QRegularExpression>
+#include <QTextStream>
+#endif
+
+#ifdef Q_OS_MACOS
+#include <mach/mach.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
+qulonglong SystemMemoryQuerier::totalMemoryBytes()
+{
+#if defined(Q_OS_WIN)
+
+    MEMORYSTATUSEX statex;
+    statex.dwLength = sizeof(statex);
+    if (GlobalMemoryStatusEx(&statex))
+        return statex.ullTotalPhys;
+    return 0;
+
+#elif defined(Q_OS_LINUX)
+
+    QFile file("/proc/meminfo");
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
+        return 0;
+
+    QTextStream in(&file);
+    while (!in.atEnd()) {
+        QString line = in.readLine();
+        if (line.startsWith("MemTotal:")) {
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+            QStringList parts = line.split(QRegExp("\\s+"), QString::SkipEmptyParts);
+#else
+            QStringList parts = line.split(QRegularExpression("\\s+"), Qt::SkipEmptyParts);
+#endif
+            if (parts.size() >= 2)
+                return parts[1].toULongLong() * 1024; // kB → bytes
+        }
+    }
+    return 0;
+
+#elif defined(Q_OS_MACOS)
+
+    int mib[2] = {CTL_HW, HW_MEMSIZE};
+    qulonglong memsize = 0;
+    size_t len = sizeof(memsize);
+
+    if (sysctl(mib, 2, &memsize, &len, nullptr, 0) == 0)
+        return memsize;
+
+    return 0;
+
+#else
+    return 0;
+#endif
+}
+
+qulonglong SystemMemoryQuerier::availableMemoryBytes()
+{
+#if defined(Q_OS_WIN)
+
+    MEMORYSTATUSEX statex;
+    statex.dwLength = sizeof(statex);
+    if (GlobalMemoryStatusEx(&statex))
+        return statex.ullAvailPhys;
+    return 0;
+
+#elif defined(Q_OS_LINUX)
+
+    QFile file("/proc/meminfo");
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
+        return 0;
+
+    QTextStream in(&file);
+    while (!in.atEnd()) {
+        QString line = in.readLine();
+        if (line.startsWith("MemAvailable:")) {
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+            QStringList parts = line.split(QRegExp("\\s+"), QString::SkipEmptyParts);
+#else
+            QStringList parts = line.split(QRegularExpression("\\s+"), Qt::SkipEmptyParts);
+#endif
+            if (parts.size() >= 2)
+                return parts[1].toULongLong() * 1024;
+        }
+    }
+    return 0;
+
+#elif defined(Q_OS_MACOS)
+
+    vm_size_t pageSize;
+    host_page_size(mach_host_self(), &pageSize);
+
+    mach_msg_type_number_t count = HOST_VM_INFO_COUNT;
+    vm_statistics64_data_t vmstat;
+
+    if (host_statistics64(mach_host_self(), HOST_VM_INFO, (host_info64_t)&vmstat, &count) != KERN_SUCCESS)
+        return 0;
+
+    qulonglong freeBytes = (qulonglong)vmstat.free_count * (qulonglong)pageSize;
+
+    return freeBytes;
+
+#else
+    return 0;
+#endif
+}

libcockatrice_utility/libcockatrice/utility/system_memory_querier.h

@@ -0,0 +1,25 @@
+#ifndef COCKATRICE_SYSTEM_MEMORY_QUERIER_H
+#define COCKATRICE_SYSTEM_MEMORY_QUERIER_H
+
+#include <QtGlobal>
+
+class SystemMemoryQuerier
+{
+public:
+    static qulonglong totalMemoryBytes();
+    static qulonglong availableMemoryBytes();
+
+    static bool hasAtLeastGiB(int gib)
+    {
+        const qulonglong total = totalMemoryBytes();
+        // 0 means the amount could not be determined (unsupported platform or failed query).
+        // Treat it as unknown and skip the check instead of misreading it as low memory.
+        if (total == 0) {
+            return true;
+        }
+        const qulonglong GiB = 1024ull * 1024ull * 1024ull;
+        return total >= (qulonglong)gib * GiB;
+    }
+};
+
+#endif // COCKATRICE_SYSTEM_MEMORY_QUERIER_H

oracle/src/pages.cpp

@@ -1,6 +1,7 @@
 #include "pages.h"
 
 #include "client/settings/cache_settings.h"
+#include "libcockatrice/utility/system_memory_querier.h"
 #include "main.h"
 #include "oracleimporter.h"
 #include "oraclewizard.h"
@@ -43,6 +44,7 @@
 #define MTGJSON_V4_URL_COMPONENT "mtgjson.com/files/"
 #define ALLSETS_URL_FALLBACK "https://www.mtgjson.com/api/v5/AllPrintings.json"
 #define MTGJSON_VERSION_URL "https://www.mtgjson.com/api/v5/Meta.json"
+#define MTGXML_URL "https://github.com/ebbit1q/mtgxml/releases/latest/download/mtg.xml.xz"
 
 #ifdef HAS_LZMA
 #define ALLSETS_URL "https://www.mtgjson.com/api/v5/AllPrintings.json.xz"
@@ -185,6 +187,32 @@ void LoadSetsPage::initializePage()
 {
     urlLineEdit->setText(wizard()->settings->value("allsetsurl", ALLSETS_URL).toString());
 
+    // Memory check because Oracle parsing fails on systems with less than 4GiB for MTGJsons allPrintings.json
+    // The fallback URL is xz-compressed, so only offer it in builds that can read it.
+    // During background (automatic) updates there is no user to answer, so switch silently.
+#ifdef HAS_LZMA
+    if (!SystemMemoryQuerier::hasAtLeastGiB(4) && urlLineEdit->text() == ALLSETS_URL) {
+        if (wizard()->backgroundMode) {
+            urlLineEdit->setText(MTGXML_URL);
+        } else {
+            // Ask user whether to switch URL
+            QMessageBox msgBox(
+                QMessageBox::Question, tr("Low Memory Detected"),
+                tr("Your system has less than 4 GiB of memory.\n"
+                   "Using the default AllPrintings URL may cause high memory usage and is known to fail as a "
+                   "result.\n\n"
+                   "Would you like to switch to the direct-download pre-parsed URL instead? (Updated daily)"),
+                QMessageBox::Yes | QMessageBox::No, this);
+
+            msgBox.setDefaultButton(QMessageBox::Yes);
+
+            if (msgBox.exec() == QMessageBox::Yes) {
+                urlLineEdit->setText(MTGXML_URL);
+            }
+        }
+    }
+#endif
+
     progressLabel->hide();
     progressBar->hide();