[Oracle/Client] Report card database download progress

Card database updates ran invisibly: MTGJSON parsing spun an indeterminate
bar on the UI thread and the set import blocked the window, while the
onboarding wizard spawned `oracle -b` with no progress to show at all.

- Add byte-level scan progress to `RawJson::scanSetRanges` via an optional
  callback, throttled to ~100 reports per scan.
- Emit `OracleImporter::dataReadProgress` during the scan and import sets on a
  worker thread, driving the wizard's progress bar per set.
- With `-b`, write machine-readable `PROGRESS <stage> <done> <total>` lines to
  stdout for the download/scan/import stages; stderr keeps the log output.
- Parse the oracle stdout in `MainWindow` and forward it to the onboarding
  wizard, giving the card database step a determinate bar with stage-specific
  status text.
- Guard the async workers against the wizard being closed mid-run.
- Add Google Test coverage for scan progress reporting.

oracle/src/oracleimporter.cpp

@@ -47,8 +47,14 @@ static CardSet::Priority getSetPriority(const QString &setType, const QString &s
 
 bool OracleImporter::readSetsFromByteArray(QByteArray data)
 {
+    const RawJson::ScanProgressCallback progress =
+        progressReporting ? RawJson::ScanProgressCallback([this](qsizetype bytesRead, qsizetype totalBytes) {
+            emit dataReadProgress(static_cast<int>(bytesRead), static_cast<int>(totalBytes));
+        })
+                          : RawJson::ScanProgressCallback();
+
     RawJson::ScanError error;
-    const QList<RawJson::SetRange> ranges = RawJson::scanSetRanges(data, &error);
+    const QList<RawJson::SetRange> ranges = RawJson::scanSetRanges(data, &error, progress);
     if (error.isError()) {
         qDebug() << "error: RawJson::scanSetRanges():" << error.message;
         return false;

oracle/src/oracleimporter.h

@@ -155,6 +155,14 @@ private:
      */
     QByteArray rawSetsData;
 
+    /**
+     * Whether readSetsFromByteArray() should report scan progress via
+     * dataReadProgress. A background run routes that signal to stdout (for the
+     * hosting Cockatrice client to parse); the flag exists to skip the scanner
+     * instrumentation entirely when no consumer needs it.
+     */
+    bool progressReporting = true;
+
     CardInfoPtr addCard(QString name,
                         const QString &text,
                         bool isToken,
@@ -167,6 +175,18 @@ signals:
 
 public:
     explicit OracleImporter(QObject *parent = nullptr);
+    /**
+     * @brief Controls whether readSetsFromByteArray() instruments the raw scan.
+     *
+     * When enabled (the default) the raw scanner reports progress via
+     * dataReadProgress(), which an interactive wizard shows on its progress bar
+     * and a background run routes to stdout for the hosting client. Switch it
+     * off only when nothing will consume scan progress.
+     */
+    void setProgressReporting(bool enabled)
+    {
+        progressReporting = enabled;
+    }
     /**
      * Scans the given JSON document for set metadata. Takes the data by value so
      * the wizard can hand over its decompressed buffer without copying it.

oracle/src/oraclewizard.cpp

@@ -110,6 +110,13 @@ void OracleWizard::accept()
     QDialog::accept();
 }
 
+void OracleWizard::runInBackground()
+{
+    backgroundMode = true;
+    hide();
+    currentPage()->initializePage();
+}
+
 void OracleWizard::enableButtons()
 {
     button(QWizard::NextButton)->setDisabled(false);

oracle/src/oraclewizard.h

@@ -52,12 +52,7 @@ public:
     }
     bool saveTokensToFile(const QString &fileName);
 
-    void runInBackground()
-    {
-        backgroundMode = true;
-        hide();
-        currentPage()->initializePage();
-    }
+    void runInBackground();
 
 public:
     OracleImporter *importer;

oracle/src/pages.cpp

@@ -12,6 +12,7 @@
 #include <QBuffer>
 #include <QCheckBox>
 #include <QComboBox>
+#include <QDebug>
 #include <QDir>
 #include <QFileDialog>
 #include <QGridLayout>
@@ -20,14 +21,17 @@
 #include <QMessageBox>
 #include <QNetworkAccessManager>
 #include <QNetworkReply>
+#include <QPointer>
 #include <QProgressBar>
 #include <QPushButton>
 #include <QRadioButton>
 #include <QScrollBar>
 #include <QStandardPaths>
 #include <QTextEdit>
+#include <QTextStream>
 #include <QtConcurrent>
 #include <QtGui>
+#include <cstdio>
 #include <libcockatrice/settings/personal_settings.h>
 
 #ifdef HAS_LZMA
@@ -53,6 +57,20 @@
 #define ALLSETS_URL "https://www.mtgjson.com/api/v5/AllPrintings.json"
 #endif
 
+/**
+ * @brief Emits one machine-readable background-run progress line to stdout.
+ *
+ * Used only in background mode, so the hosting Cockatrice client can parse these
+ * lines to drive a determinate progress bar. stderr stays reserved for
+ * human-readable log output.
+ */
+static void emitBackgroundProgress(const char *stage, qint64 done, qint64 total)
+{
+    QTextStream out(stdout);
+    out << "PROGRESS " << stage << ' ' << done << ' ' << total << '\n';
+    out.flush();
+}
+
 #define TOKENS_URL "https://raw.githubusercontent.com/Cockatrice/Magic-Token/master/tokens.xml"
 #define SPOILERS_URL "https://raw.githubusercontent.com/Cockatrice/Magic-Spoiler/files/spoiler.xml"
 
@@ -339,6 +357,9 @@ void LoadSetsPage::downloadSetsFile(const QUrl &url)
 
 void LoadSetsPage::actDownloadProgressSetsFile(qint64 received, qint64 total)
 {
+    if (wizard()->backgroundMode) {
+        emitBackgroundProgress("download", received, total);
+    }
     if (total > 0) {
         progressBar->setMaximum(static_cast<int>(total));
         progressBar->setValue(static_cast<int>(received));
@@ -384,6 +405,21 @@ void LoadSetsPage::actDownloadFinishedSetsFile()
     reply->deleteLater();
 }
 
+void LoadSetsPage::updateParsingProgress(int bytesRead, int totalBytes)
+{
+    if (totalBytes <= 0) {
+        return;
+    }
+    progressBar->setValue(bytesRead);
+    const int percent = static_cast<int>((100.0 * bytesRead) / totalBytes);
+    progressLabel->setText(tr("Parsing file (%1%)").arg(percent));
+}
+
+void LoadSetsPage::scanProgressToStdout(int bytesRead, int totalBytes)
+{
+    emitBackgroundProgress("scan", bytesRead, totalBytes);
+}
+
 void LoadSetsPage::readSetsFromByteArray(QByteArray _data)
 {
     // show an infinite progressbar
@@ -469,9 +505,23 @@ void LoadSetsPage::readSetsFromByteArrayRef(QByteArray &_data)
         return;
 #endif
     } else if (_data.startsWith("{")) {
-        // Start the computation.
-        jsonData = std::move(_data);
-        future = QtConcurrent::run([this] { return wizard()->importer->readSetsFromByteArray(std::move(jsonData)); });
+        if (wizard()->backgroundMode) {
+            qInfo() << tr("Parsing file");
+            connect(wizard()->importer, &OracleImporter::dataReadProgress, this, &LoadSetsPage::scanProgressToStdout,
+                    Qt::UniqueConnection);
+        } else {
+            // Start the computation.
+            progressBar->setRange(0, static_cast<int>(_data.size()));
+            progressBar->setValue(0);
+            progressLabel->setText(tr("Parsing file (0%)"));
+            connect(wizard()->importer, &OracleImporter::dataReadProgress, this, &LoadSetsPage::updateParsingProgress,
+                    Qt::UniqueConnection);
+        }
+
+        const QPointer<OracleImporter> importer = wizard()->importer;
+        future = QtConcurrent::run([importer, data = std::move(_data)]() mutable {
+            return importer ? importer->readSetsFromByteArray(std::move(data)) : false;
+        });
         watcher.setFuture(future);
     } else if (_data.startsWith("<")) {
         // save xml file and don't do any processing
@@ -514,7 +564,16 @@ void LoadSetsPage::importFinished()
     progressLabel->hide();
     progressBar->hide();
 
-    if (wizard()->downloadedPlainXml || watcher.future().result()) {
+    const bool hasData = wizard()->downloadedPlainXml || watcher.future().result();
+    if (wizard()->backgroundMode) {
+        if (!hasData) {
+            qWarning() << tr("The file was retrieved successfully, but it does not contain any sets data.");
+        }
+        emit readyToContinue();
+        return;
+    }
+
+    if (hasData) {
         wizard()->next();
     } else {
         QMessageBox::critical(this, tr("Error"),
@@ -527,16 +586,22 @@ SaveSetsPage::SaveSetsPage(QWidget *parent) : OracleWizardPage(parent)
     pathLabel = new QLabel(this);
     saveLabel = new QLabel(this);
 
+    progressBar = new QProgressBar(this);
+    progressBar->hide();
+
     defaultPathCheckBox = new QCheckBox(this);
 
     messageLog = new QTextEdit(this);
     messageLog->setReadOnly(true);
 
     auto *layout = new QGridLayout(this);
-    layout->addWidget(messageLog, 0, 0);
-    layout->addWidget(saveLabel, 1, 0);
-    layout->addWidget(pathLabel, 2, 0);
-    layout->addWidget(defaultPathCheckBox, 3, 0);
+    layout->addWidget(progressBar, 0, 0);
+    layout->addWidget(messageLog, 1, 0);
+    layout->addWidget(saveLabel, 2, 0);
+    layout->addWidget(pathLabel, 3, 0);
+    layout->addWidget(defaultPathCheckBox, 4, 0);
+
+    connect(&importWatcher, &QFutureWatcher<int>::finished, this, &SaveSetsPage::importFinished);
 
     setLayout(layout);
 }
@@ -549,27 +614,54 @@ void SaveSetsPage::cleanupPage()
 
 void SaveSetsPage::initializePage()
 {
-    messageLog->clear();
-
     retranslateUi();
     if (wizard()->downloadedPlainXml) {
         messageLog->hide();
-    } else {
-        messageLog->show();
-        connect(wizard()->importer, &OracleImporter::setIndexChanged, this, &SaveSetsPage::updateTotalProgress);
-
-        int setsImported = wizard()->importer->startImport();
-
-        // JSON data no longer needed after CardInfo objects are built
-        wizard()->importer->releaseSetData();
-
-        if (setsImported == 0) {
-            QMessageBox::critical(this, tr("Error"), tr("No set has been imported."));
+        progressBar->hide();
+        if (wizard()->backgroundMode) {
+            emit readyToContinue();
         }
+        return;
+    }
+
+    messageLog->clear();
+    messageLog->show();
+    progressBar->show();
+    progressBar->setRange(0, wizard()->importer->getSets().size());
+    progressBar->setValue(0);
+
+    connect(wizard()->importer, &OracleImporter::setIndexChanged, this, &SaveSetsPage::updateTotalProgress,
+            Qt::UniqueConnection);
+
+    wizard()->disableButtons();
+
+    const QPointer<OracleImporter> importer = wizard()->importer;
+    importFuture = QtConcurrent::run([importer] { return importer ? importer->startImport() : 0; });
+    importWatcher.setFuture(importFuture);
+}
+
+void SaveSetsPage::importFinished()
+{
+    wizard()->enableButtons();
+
+    const int setsImported = importWatcher.result();
+    const QPointer<OracleImporter> importer = wizard()->importer;
+    if (importer) {
+        importer->releaseSetData();
     }
 
     if (wizard()->backgroundMode) {
+        if (setsImported == 0) {
+            qWarning() << tr("No set has been imported.");
+        }
         emit readyToContinue();
+        return;
+    }
+
+    progressBar->setValue(progressBar->maximum());
+
+    if (setsImported == 0) {
+        QMessageBox::critical(this, tr("Error"), tr("No set has been imported."));
     }
 }
 
@@ -591,13 +683,27 @@ void SaveSetsPage::retranslateUi()
     setButtonText(QWizard::NextButton, tr("&Save"));
 }
 
-void SaveSetsPage::updateTotalProgress(int cardsImported, int /* setIndex */, const QString &setName)
+void SaveSetsPage::updateTotalProgress(int cardsImported, int setIndex, const QString &setName)
 {
+    const bool background = wizard()->backgroundMode;
+    const int totalSets = wizard()->importer->getSets().size();
     if (setName.isEmpty()) {
-        messageLog->append("<b>" + tr("Import finished: %1 cards.").arg(wizard()->importer->getCardList().size()) +
-                           "</b>");
+        progressBar->setValue(progressBar->maximum());
+        if (background) {
+            qInfo() << tr("Import finished: %1 cards.").arg(wizard()->importer->getCardList().size());
+            emitBackgroundProgress("import", totalSets, totalSets);
+        } else {
+            messageLog->append("<b>" + tr("Import finished: %1 cards.").arg(wizard()->importer->getCardList().size()) +
+                               "</b>");
+        }
     } else {
-        messageLog->append(tr("%1: %2 cards imported").arg(setName).arg(cardsImported));
+        progressBar->setValue(setIndex);
+        if (background) {
+            qInfo() << tr("%1: %2 cards imported").arg(setName).arg(cardsImported);
+            emitBackgroundProgress("import", setIndex, totalSets);
+        } else {
+            messageLog->append(tr("%1: %2 cards imported").arg(setName).arg(cardsImported));
+        }
     }
 
     messageLog->verticalScrollBar()->setValue(messageLog->verticalScrollBar()->maximum());

oracle/src/pages.h

@@ -83,13 +83,14 @@ private:
 
     QFutureWatcher<bool> watcher;
     QFuture<bool> future;
-    QByteArray jsonData;
 
 private slots:
     void actLoadSetsFile();
     void actRestoreDefaultUrl();
     void actDownloadProgressSetsFile(qint64 received, qint64 total);
     void actDownloadFinishedSetsFile();
+    void updateParsingProgress(int bytesRead, int totalBytes);
+    void scanProgressToStdout(int bytesRead, int totalBytes);
     void importFinished();
     void zipDownloadFailed(const QString &message);
 };
@@ -103,16 +104,21 @@ public:
 
 private:
     QTextEdit *messageLog;
+    QProgressBar *progressBar;
     QCheckBox *defaultPathCheckBox;
     QLabel *pathLabel;
     QLabel *saveLabel;
 
+    QFutureWatcher<int> importWatcher;
+    QFuture<int> importFuture;
+
 protected:
     void initializePage() override;
     void cleanupPage() override;
     bool validatePage() override;
 
 private slots:
+    void importFinished();
     void updateTotalProgress(int cardsImported, int setIndex, const QString &setName);
 };
 

oracle/src/raw_json_scanner.cpp

@@ -1,5 +1,6 @@
 #include "raw_json_scanner.h"
 
+#include <algorithm>
 #include <cstring>
 
 namespace
@@ -11,6 +12,43 @@ namespace
 // reason and reports DeepNesting).
 constexpr int kMaxNestingDepth = 1024;
 
+/**
+ * @brief Throttled byte-position reporting for scanSetRanges().
+ *
+ * Threaded through the skip walk so progress can be reported without materializing
+ * the whole document. Reports are rate-limited so a GUI showing progress isn't
+ * flooded with interrupts: a callback is invoked at most ~100 times per scan
+ * regardless of element count.
+ */
+struct ScanProgress
+{
+    const char *begin = nullptr;
+    qsizetype size = 0;
+    RawJson::ScanProgressCallback callback;
+    qsizetype step = 1;
+    qsizetype lastReported = 0;
+
+    /**
+     * @brief Reports the scanner's absolute offset, unless within @p step bytes
+     * of the previous report and not yet at the end of the document.
+     */
+    void report(const char *p)
+    {
+        if (!callback) {
+            return;
+        }
+        const qsizetype offset = p - begin;
+        if (offset == lastReported) {
+            return; // the final element often already sits exactly at the end
+        }
+        if (offset - lastReported < step && offset < size) {
+            return;
+        }
+        lastReported = offset;
+        callback(offset, size);
+    }
+};
+
 inline bool isWhitespace(char c)
 {
     return c == ' ' || c == '\t' || c == '\r' || c == '\n';
@@ -296,9 +334,9 @@ bool skipNumber(const char *&p, const char *end)
     return true;
 }
 
-bool skipValue(const char *&p, const char *end, int depth);
-bool skipObject(const char *&p, const char *end, int depth);
-bool skipArray(const char *&p, const char *end, int depth);
+bool skipValue(const char *&p, const char *end, int depth, ScanProgress &scan);
+bool skipObject(const char *&p, const char *end, int depth, ScanProgress &scan);
+bool skipArray(const char *&p, const char *end, int depth, ScanProgress &scan);
 
 bool skipPrimitive(const char *&p, const char *end)
 {
@@ -324,7 +362,7 @@ bool skipPrimitive(const char *&p, const char *end)
     return false;
 }
 
-bool skipObject(const char *&p, const char *end, int depth)
+bool skipObject(const char *&p, const char *end, int depth, ScanProgress &scan)
 {
     if (depth <= 0) {
         return false; // nest deeper than the cap
@@ -348,9 +386,10 @@ bool skipObject(const char *&p, const char *end, int depth)
             return false;
         }
         ++p;
-        if (!skipValue(p, end, depth - 1)) {
+        if (!skipValue(p, end, depth - 1, scan)) {
             return false;
         }
+        scan.report(p);
         p = skipWhitespace(p, end);
         if (p >= end) {
             return false;
@@ -367,7 +406,7 @@ bool skipObject(const char *&p, const char *end, int depth)
     }
 }
 
-bool skipArray(const char *&p, const char *end, int depth)
+bool skipArray(const char *&p, const char *end, int depth, ScanProgress &scan)
 {
     if (depth <= 0) {
         return false; // nest deeper than the cap
@@ -379,9 +418,10 @@ bool skipArray(const char *&p, const char *end, int depth)
         return true;
     }
     for (;;) {
-        if (!skipValue(p, end, depth - 1)) {
+        if (!skipValue(p, end, depth - 1, scan)) {
             return false;
         }
+        scan.report(p);
         p = skipWhitespace(p, end);
         if (p >= end) {
             return false;
@@ -398,7 +438,7 @@ bool skipArray(const char *&p, const char *end, int depth)
     }
 }
 
-bool skipValue(const char *&p, const char *end, int depth)
+bool skipValue(const char *&p, const char *end, int depth, ScanProgress &scan)
 {
     p = skipWhitespace(p, end);
     if (p >= end) {
@@ -407,10 +447,10 @@ bool skipValue(const char *&p, const char *end, int depth)
     const char c = *p;
     if (c == '{') {
         // pass depth through: skipObject consumes the single decrement for this level
-        return skipObject(p, end, depth);
+        return skipObject(p, end, depth, scan);
     }
     if (c == '[') {
-        return skipArray(p, end, depth);
+        return skipArray(p, end, depth, scan);
     }
     // a primitive is a leaf, so it never wastes a nesting level
     return skipPrimitive(p, end);
@@ -422,7 +462,8 @@ bool skipValue(const char *&p, const char *end, int depth)
  * For each member invokes @p memberCallback with the key and the byte range of
  * its value. Advancing @p p is unaffected by the callback.
  */
-template <typename F> bool forEachObjectMember(const char *&p, const char *end, int depth, F &&memberCallback)
+template <typename F>
+bool forEachObjectMember(const char *&p, const char *end, int depth, F &&memberCallback, ScanProgress &scan)
 {
     if (depth <= 0) {
         return false; // nest deeper than the cap
@@ -449,7 +490,7 @@ template <typename F> bool forEachObjectMember(const char *&p, const char *end,
         ++p;
         const char *valueStart = skipWhitespace(p, end);
         const char *valueEnd = valueStart;
-        if (!skipValue(valueEnd, end, depth - 1)) {
+        if (!skipValue(valueEnd, end, depth - 1, scan)) {
             return false;
         }
         if (!memberCallback(key, valueStart, valueEnd)) {
@@ -473,7 +514,7 @@ template <typename F> bool forEachObjectMember(const char *&p, const char *end,
 }
 
 // Counts the direct elements of an array value; returns -1 if the array is malformed.
-int countArrayElements(const char *p, const char *end, int depth)
+int countArrayElements(const char *p, const char *end, int depth, ScanProgress &scan)
 {
     if (depth <= 0) {
         return -1; // nest deeper than the cap
@@ -485,9 +526,10 @@ int countArrayElements(const char *p, const char *end, int depth)
         return 0;
     }
     for (;;) {
-        if (!skipValue(p, end, depth - 1)) {
+        if (!skipValue(p, end, depth - 1, scan)) {
             return -1;
         }
+        scan.report(p);
         ++count;
         p = skipWhitespace(p, end);
         if (p >= end) {
@@ -509,7 +551,7 @@ int countArrayElements(const char *p, const char *end, int depth)
 namespace RawJson
 {
 
-QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error)
+QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error, const ScanProgressCallback &progress)
 {
     QList<SetRange> ranges;
     if (error) {
@@ -529,6 +571,14 @@ QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error)
         return fail(QStringLiteral("empty JSON document"));
     }
 
+    // Throttle reports to ~100 per scan so a GUI thread unthrottling them never
+    // drowns under per-card interrupts, whatever the document size.
+    ScanProgress scan;
+    scan.begin = begin;
+    scan.size = end - begin;
+    scan.step = std::max<qsizetype>(1, scan.size / 100);
+    scan.callback = progress;
+
     const char *p = skipWhitespace(begin, end);
     if (p >= end || *p != '{') {
         return fail(QStringLiteral("top-level JSON must be an object"));
@@ -545,55 +595,57 @@ QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error)
                 return false;
             }
             const char *setP = valueStart;
-            const bool ok = forEachObjectMember(setP, valueEnd, kMaxNestingDepth - 1,
-                                                [&](const QString &setCode, const char *setStart, const char *setEnd) {
-                                                    if (setStart >= setEnd || *setStart != '{') {
-                                                        malformedSetData = true;
-                                                        return false;
-                                                    }
-                                                    SetRange range;
-                                                    range.dataRange.start = setStart - begin;
-                                                    range.dataRange.length = setEnd - setStart;
-                                                    range.code = setCode;
+            const bool ok = forEachObjectMember(
+                setP, valueEnd, kMaxNestingDepth - 1,
+                [&](const QString &setCode, const char *setStart, const char *setEnd) {
+                    if (setStart >= setEnd || *setStart != '{') {
+                        malformedSetData = true;
+                        return false;
+                    }
+                    SetRange range;
+                    range.dataRange.start = setStart - begin;
+                    range.dataRange.length = setEnd - setStart;
+                    range.code = setCode;
 
-                                                    const char *memberP = setStart;
-                                                    const bool metaOk = forEachObjectMember(
-                                                        memberP, setEnd, kMaxNestingDepth - 2,
-                                                        [&](const QString &field, const char *fs, const char *fe) {
-                                                            if (field == QStringLiteral("code")) {
-                                                                return decodeStringMember(fs, fe, range.code);
-                                                            }
-                                                            if (field == QStringLiteral("name")) {
-                                                                return decodeStringMember(fs, fe, range.name);
-                                                            }
-                                                            if (field == QStringLiteral("type")) {
-                                                                return decodeStringMember(fs, fe, range.type);
-                                                            }
-                                                            if (field == QStringLiteral("releaseDate")) {
-                                                                return decodeStringMember(fs, fe, range.releaseDate);
-                                                            }
-                                                            if (field == QStringLiteral("cards")) {
-                                                                if (fs >= fe) {
-                                                                    return false;
-                                                                }
-                                                                if (*fs != '[') {
-                                                                    // e.g. "cards": null — treat as an empty array,
-                                                                    // matching Qt's tolerance.
-                                                                    return true;
-                                                                }
-                                                                range.dataRange.cardCount =
-                                                                    countArrayElements(fs, fe, kMaxNestingDepth - 2);
-                                                                return range.dataRange.cardCount >= 0;
-                                                            }
-                                                            return true;
-                                                        });
-                                                    if (!metaOk) {
-                                                        malformedSetData = true;
-                                                        return false;
-                                                    }
-                                                    ranges.append(range);
-                                                    return true;
-                                                });
+                    const char *memberP = setStart;
+                    const bool metaOk = forEachObjectMember(
+                        memberP, setEnd, kMaxNestingDepth - 2,
+                        [&](const QString &field, const char *fs, const char *fe) {
+                            if (field == QStringLiteral("code")) {
+                                return decodeStringMember(fs, fe, range.code);
+                            }
+                            if (field == QStringLiteral("name")) {
+                                return decodeStringMember(fs, fe, range.name);
+                            }
+                            if (field == QStringLiteral("type")) {
+                                return decodeStringMember(fs, fe, range.type);
+                            }
+                            if (field == QStringLiteral("releaseDate")) {
+                                return decodeStringMember(fs, fe, range.releaseDate);
+                            }
+                            if (field == QStringLiteral("cards")) {
+                                if (fs >= fe) {
+                                    return false;
+                                }
+                                if (*fs != '[') {
+                                    // e.g. "cards": null — treat as an empty array,
+                                    // matching Qt's tolerance.
+                                    return true;
+                                }
+                                range.dataRange.cardCount = countArrayElements(fs, fe, kMaxNestingDepth - 2, scan);
+                                return range.dataRange.cardCount >= 0;
+                            }
+                            return true;
+                        },
+                        scan);
+                    if (!metaOk) {
+                        malformedSetData = true;
+                        return false;
+                    }
+                    ranges.append(range);
+                    return true;
+                },
+                scan);
             if (!ok) {
                 malformedSetData = true;
                 return false;
@@ -602,7 +654,7 @@ QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error)
         return true;
     };
 
-    if (!forEachObjectMember(p, end, kMaxNestingDepth, topLevelCallback)) {
+    if (!forEachObjectMember(p, end, kMaxNestingDepth, topLevelCallback, scan)) {
         return fail(malformedSetData ? QStringLiteral("malformed set data") : QStringLiteral("malformed JSON"));
     }
     p = skipWhitespace(p, end);
@@ -615,6 +667,7 @@ QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error)
     if (ranges.isEmpty()) {
         return fail(QStringLiteral("no sets found in \"data\""));
     }
+    scan.report(end);
     return ranges;
 }
 

oracle/src/raw_json_scanner.h

@@ -4,6 +4,7 @@
 #include <QByteArray>
 #include <QList>
 #include <QString>
+#include <functional>
 
 namespace RawJson
 {
@@ -42,6 +43,13 @@ struct ScanError
     QString message;
 };
 
+/**
+ * @brief Optional progress callback receiving @c (bytesRead, totalBytes) while
+ * the document is walked. Invoked from the scanning thread; the caller decides
+ * how the throttled offsets are relayed to a GUI event loop.
+ */
+using ScanProgressCallback = std::function<void(qsizetype bytesRead, qsizetype totalBytes)>;
+
 /**
  * @brief Scans a full MTGJSON document without materializing the JSON tree.
  *
@@ -67,9 +75,14 @@ struct ScanError
  * @param error Out parameter. Set to an error ScanError when the document
  *              cannot be parsed, otherwise left empty. Passing a null
  *              pointer disables error reporting.
+ * @param progress Optional progress callback. When non-empty it is invoked as
+ *                 the scanner advances through the document, throttled to a
+ *                 tiny fraction of the total size.
  * @return The detected per-set ranges, or an empty list on failure.
  */
-QList<SetRange> scanSetRanges(const QByteArray &json, ScanError *error = nullptr);
+QList<SetRange> scanSetRanges(const QByteArray &json,
+                              ScanError *error = nullptr,
+                              const ScanProgressCallback &progress = ScanProgressCallback());
 
 } // namespace RawJson