Replay: deterministic record & playback (#4)

Add deterministic record/playback for a run.

Recording captures `(seed, config hash, ordered tick-tagged commands)` and re-simulates on playback — no state snapshots. `DotaFactory.exe --replay <file>` re-plays a recorded run view-only with manual speed/pause.

Reviewed-on: #4
Co-authored-by: Malte Langkabel <malte.langkabel@gmail.com>
Co-committed-by: Malte Langkabel <malte.langkabel@gmail.com>

src/lib/sim/ReplayRecorder.cpp

@@ -0,0 +1,130 @@
+#include "ReplayRecorder.h"
+
+#include <iomanip>
+#include <sstream>
+#include <utility>
+
+#include <QByteArray>
+#include <QDateTime>
+#include <QDir>
+#include <QFile>
+#include <QString>
+#include <QStringList>
+
+#include "Command.h"
+#include "CommandSerializer.h"
+#include "StateChecksum.h"
+
+namespace
+{
+constexpr const char* kReplayFormatVersion = "1";
+
+// Build fingerprint: even a new local build can desync old replays (float
+// reasons), so the header carries a per-build tag to warn on mismatch.
+const std::string kBuildTag = std::string(__DATE__) + " " + __TIME__;
+
+std::string toHex(std::uint64_t value)
+{
+    std::ostringstream out;
+    out << std::hex << std::setw(16) << std::setfill('0') << value;
+    return out.str();
+}
+}  // namespace
+
+ReplayRecorder::ReplayRecorder(std::string configDir, std::string outputDir)
+    : m_configDir(std::move(configDir))
+    , m_outputDir(std::move(outputDir))
+{
+}
+
+ReplayRecorder::~ReplayRecorder()
+{
+    close();
+}
+
+std::string computeReplayConfigHash(const std::string& configDir)
+{
+    Hasher hasher;
+    QDir dir(QString::fromStdString(configDir));
+    const QStringList files =
+        dir.entryList(QStringList() << "*.toml", QDir::Files, QDir::Name);
+    for (const QString& name : files)
+    {
+        hasher.append(name.toStdString());
+        QFile file(dir.filePath(name));
+        if (file.open(QIODevice::ReadOnly))
+        {
+            const QByteArray bytes = file.readAll();
+            hasher.appendBytes(bytes.constData(), static_cast<std::size_t>(bytes.size()));
+        }
+    }
+    return toHex(hasher.value());
+}
+
+void ReplayRecorder::startNewRun(unsigned int seed, std::uint64_t initialRngFingerprint)
+{
+    close();
+
+    QDir().mkpath(QString::fromStdString(m_outputDir));
+    const QString timestamp = QDateTime::currentDateTime().toString("yyyyMMdd_HHmmss");
+    const QString fileName  = timestamp + "_" + QString::number(seed) + ".replay";
+    m_filePath = QDir(QString::fromStdString(m_outputDir)).filePath(fileName).toStdString();
+
+    m_stream.open(m_filePath, std::ios::out | std::ios::trunc);
+    if (!m_stream.is_open())
+    {
+        return;
+    }
+
+    m_stream << "# dota_factory replay\n";
+    m_stream << "version "     << kReplayFormatVersion << "\n";
+    m_stream << "build "       << kBuildTag << "\n";
+    m_stream << "seed "        << seed << "\n";
+    m_stream << "config_hash " << computeReplayConfigHash(m_configDir) << "\n";
+    m_stream << "timestamp "
+             << QDateTime::currentDateTime().toString(Qt::ISODate).toStdString() << "\n";
+    m_stream << "---\n";
+    m_stream << "# checksum 0 " << toHex(initialRngFingerprint) << "\n";
+    m_stream.flush();
+}
+
+void ReplayRecorder::recordCommand(Tick tick, const Command& command,
+                                   std::uint64_t rngFingerprint)
+{
+    if (!m_stream.is_open())
+    {
+        return;
+    }
+    m_stream << tick << ' ' << serializeCommand(command) << "\n";
+    m_stream << "# checksum " << tick << ' ' << toHex(rngFingerprint) << "\n";
+    m_stream.flush();
+}
+
+void ReplayRecorder::recordChecksum(Tick tick, std::uint64_t rngFingerprint)
+{
+    if (!m_stream.is_open())
+    {
+        return;
+    }
+    m_stream << "# checksum " << tick << ' ' << toHex(rngFingerprint) << "\n";
+    m_stream.flush();
+}
+
+void ReplayRecorder::close()
+{
+    if (m_stream.is_open())
+    {
+        m_stream.flush();
+        m_stream.close();
+    }
+}
+
+bool ReplayRecorder::isOpen() const
+{
+    return m_stream.is_open();
+}
+
+const std::string& ReplayRecorder::currentFilePath() const
+{
+    return m_filePath;
+}