wip: Add minimal support for loading signet UTXO snapshots

        Adds minimal wiring to connect QML GUI to loading a signet UTXO snapshot via
        the connection settings. Uses SnapshotSettings.qml to allow user interaction.
	Modifies src/interfaces/node.h to src/node/interfaces.cpp
        Also modifies src/validation.cpp to enable showing the snapshot loading
	progress.
	And touches chainparams.cpp (temporarily for signet snapshot testing)
        to expose snapshot loading functionality through the node model.

        Current limitations:
        - Not integrated with onboarding process
        - Requires manual navigation to connection settings after initial startup
        - Snapshot verification progress is working via notifications

        Testing:
        1. Start the node
        2. Complete onboarding
        3. Navigate to connection settings
        4. Load snapshot from provided interface

Author: D33r-Gee

Diff for: src/interfaces/node.h

@@ -11,6 +11,7 @@
 #include <net_types.h>                 // For banmap_t
 #include <netaddress.h>                // For Network
 #include <netbase.h>                   // For ConnectionDirection
+#include <node/utxo_snapshot.h>         // For SnapshotMetadata
 #include <support/allocators/secure.h> // For SecureString
 #include <util/translation.h>
 
@@ -199,6 +200,9 @@ class Node
     //! List rpc commands.
     virtual std::vector<std::string> listRpcCommands() = 0;
 
+    //! Load UTXO Snapshot.
+    virtual bool loadSnapshot(AutoFile& afile, const node::SnapshotMetadata& metadata, bool in_memory) = 0;
+
     //! Set RPC timer interface if unset.
     virtual void rpcSetTimerInterfaceIfUnset(RPCTimerInterface* iface) = 0;
 
@@ -234,6 +238,10 @@ class Node
     using ShowProgressFn = std::function<void(const std::string& title, int progress, bool resume_possible)>;
     virtual std::unique_ptr<Handler> handleShowProgress(ShowProgressFn fn) = 0;
 
+    //! Register handler for snapshot load progress.
+    using SnapshotLoadProgressFn = std::function<void(double progress)>;
+    virtual std::unique_ptr<Handler> handleSnapshotLoadProgress(SnapshotLoadProgressFn fn) = 0;
+
     //! Register handler for wallet loader constructed messages.
     using InitWalletFn = std::function<void()>;
     virtual std::unique_ptr<Handler> handleInitWallet(InitWalletFn fn) = 0;

Diff for: src/kernel/chainparams.cpp

@@ -371,6 +371,13 @@ class SigNetParams : public CChainParams {
 
         vFixedSeeds.clear();
 
+        m_assumeutxo_data = MapAssumeutxo{
+            {
+                160000,
+                {AssumeutxoHash{uint256S("0x5225141cb62dee63ab3be95f9b03d60801f264010b1816d4bd00618b2736e7be")}, 1278002},
+            },
+        };
+
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
         base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
         base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);

Diff for: src/kernel/notifications_interface.h

@@ -40,6 +40,7 @@ class Notifications
     [[nodiscard]] virtual InterruptResult blockTip(SynchronizationState state, CBlockIndex& index) { return {}; }
     virtual void headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync) {}
     virtual void progress(const bilingual_str& title, int progress_percent, bool resume_possible) {}
+    virtual void snapshotLoadProgress(double progress) {}
     virtual void warning(const bilingual_str& warning) {}
 
     //! The flush error notification is sent to notify the user that an error

Diff for: src/node/interface_ui.cpp

@@ -21,6 +21,7 @@ struct UISignals {
     boost::signals2::signal<CClientUIInterface::NotifyNetworkActiveChangedSig> NotifyNetworkActiveChanged;
     boost::signals2::signal<CClientUIInterface::NotifyAlertChangedSig> NotifyAlertChanged;
     boost::signals2::signal<CClientUIInterface::ShowProgressSig> ShowProgress;
+    boost::signals2::signal<CClientUIInterface::SnapshotLoadProgressSig> SnapshotLoadProgress;
     boost::signals2::signal<CClientUIInterface::NotifyBlockTipSig> NotifyBlockTip;
     boost::signals2::signal<CClientUIInterface::NotifyHeaderTipSig> NotifyHeaderTip;
     boost::signals2::signal<CClientUIInterface::BannedListChangedSig> BannedListChanged;
@@ -44,6 +45,7 @@ ADD_SIGNALS_IMPL_WRAPPER(ShowProgress);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyBlockTip);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyHeaderTip);
 ADD_SIGNALS_IMPL_WRAPPER(BannedListChanged);
+ADD_SIGNALS_IMPL_WRAPPER(SnapshotLoadProgress);
 
 bool CClientUIInterface::ThreadSafeMessageBox(const bilingual_str& message, const std::string& caption, unsigned int style) { return g_ui_signals.ThreadSafeMessageBox(message, caption, style).value_or(false);}
 bool CClientUIInterface::ThreadSafeQuestion(const bilingual_str& message, const std::string& non_interactive_message, const std::string& caption, unsigned int style) { return g_ui_signals.ThreadSafeQuestion(message, non_interactive_message, caption, style).value_or(false);}
@@ -53,6 +55,7 @@ void CClientUIInterface::NotifyNumConnectionsChanged(PeersNumByType newNumConnec
 void CClientUIInterface::NotifyNetworkActiveChanged(bool networkActive) { return g_ui_signals.NotifyNetworkActiveChanged(networkActive); }
 void CClientUIInterface::NotifyAlertChanged() { return g_ui_signals.NotifyAlertChanged(); }
 void CClientUIInterface::ShowProgress(const std::string& title, int nProgress, bool resume_possible) { return g_ui_signals.ShowProgress(title, nProgress, resume_possible); }
+void CClientUIInterface::SnapshotLoadProgress(double progress) { return g_ui_signals.SnapshotLoadProgress(progress); }
 void CClientUIInterface::NotifyBlockTip(SynchronizationState s, const CBlockIndex* i) { return g_ui_signals.NotifyBlockTip(s, i); }
 void CClientUIInterface::NotifyHeaderTip(SynchronizationState s, int64_t height, int64_t timestamp, bool presync) { return g_ui_signals.NotifyHeaderTip(s, height, timestamp, presync); }
 void CClientUIInterface::BannedListChanged() { return g_ui_signals.BannedListChanged(); }

Diff for: src/node/interface_ui.h

@@ -109,6 +109,9 @@ class CClientUIInterface
      */
     ADD_SIGNALS_DECL_WRAPPER(ShowProgress, void, const std::string& title, int nProgress, bool resume_possible);
 
+    /** Snapshot load progress. */
+    ADD_SIGNALS_DECL_WRAPPER(SnapshotLoadProgress, void, double progress);
+
     /** New block has been accepted */
     ADD_SIGNALS_DECL_WRAPPER(NotifyBlockTip, void, SynchronizationState, const CBlockIndex*);
 

Diff for: src/node/interfaces.cpp

@@ -29,6 +29,7 @@
 #include <node/context.h>
 #include <node/interface_ui.h>
 #include <node/transaction.h>
+#include <node/utxo_snapshot.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
@@ -356,6 +357,10 @@ class NodeImpl : public Node
     {
         return MakeSignalHandler(::uiInterface.ShowProgress_connect(fn));
     }
+    std::unique_ptr<Handler> handleSnapshotLoadProgress(SnapshotLoadProgressFn fn) override
+    {
+        return MakeSignalHandler(::uiInterface.SnapshotLoadProgress_connect(fn));
+    }
     std::unique_ptr<Handler> handleInitWallet(InitWalletFn fn) override
     {
         return MakeSignalHandler(::uiInterface.InitWallet_connect(fn));
@@ -395,6 +400,10 @@ class NodeImpl : public Node
     {
         m_context = context;
     }
+    bool loadSnapshot(AutoFile& afile, const node::SnapshotMetadata& metadata, bool in_memory) override
+    {
+        return chainman().ActivateSnapshot(afile, metadata, in_memory);
+    }
     ArgsManager& args() { return *Assert(Assert(m_context)->args); }
     ChainstateManager& chainman() { return *Assert(m_context->chainman); }
     NodeContext* m_context{nullptr};
@@ -510,7 +519,7 @@ class RpcHandlerImpl : public Handler
 class ChainImpl : public Chain
 {
 public:
-    explicit ChainImpl(NodeContext& node) : m_node(node) {}
+    explicit ChainImpl(node::NodeContext& node) : m_node(node) {}
     std::optional<int> getHeight() override
     {
         const int height{WITH_LOCK(::cs_main, return chainman().ActiveChain().Height())};

Diff for: src/node/kernel_notifications.cpp

@@ -78,6 +78,11 @@ void KernelNotifications::progress(const bilingual_str& title, int progress_perc
     uiInterface.ShowProgress(title.translated, progress_percent, resume_possible);
 }
 
+void KernelNotifications::snapshotLoadProgress(double progress)
+{
+    uiInterface.SnapshotLoadProgress(progress);
+}
+
 void KernelNotifications::warning(const bilingual_str& warning)
 {
     DoWarning(warning);

Diff for: src/node/kernel_notifications.h

@@ -31,6 +31,8 @@ class KernelNotifications : public kernel::Notifications
 
     void progress(const bilingual_str& title, int progress_percent, bool resume_possible) override;
 
+    void snapshotLoadProgress(double progress) override;
+
     void warning(const bilingual_str& warning) override;
 
     void flushError(const std::string& debug_message) override;

Diff for: src/qml/components/ConnectionSettings.qml

@@ -11,13 +11,13 @@ ColumnLayout {
     id: root
     signal next
     signal gotoSnapshot
-    property bool snapshotImported: false
-    function setSnapshotImported(imported) {
-        snapshotImported = imported
-    }
+    property bool snapshotImportCompleted: chainModel.isSnapshotActive
+    property bool onboarding: false
+
     spacing: 4
     Setting {
         id: gotoSnapshot
+        visible: !root.onboarding
         Layout.fillWidth: true
         header: qsTr("Load snapshot")
         description: qsTr("Instant use with background sync")
@@ -26,19 +26,22 @@ ColumnLayout {
             height: 26
             CaretRightIcon {
                 anchors.centerIn: parent
-                visible: !snapshotImported
+                visible: !snapshotImportCompleted
                 color: gotoSnapshot.stateColor
             }
             GreenCheckIcon {
                 anchors.centerIn: parent
-                visible: snapshotImported
+                visible: snapshotImportCompleted
                 color: Theme.color.transparent
                 size: 30
             }
         }
         onClicked: root.gotoSnapshot()
     }
-    Separator { Layout.fillWidth: true }
+    Separator {
+        visible: !root.onboarding
+        Layout.fillWidth: true
+    }
     Setting {
         Layout.fillWidth: true
         header: qsTr("Enable listening")

Diff for: src/qml/components/SnapshotSettings.qml

@@ -5,44 +5,28 @@
 import QtQuick 2.15
 import QtQuick.Controls 2.15
 import QtQuick.Layouts 1.15
+import QtQuick.Dialogs 1.3
 
 import "../controls"
 
 ColumnLayout {
-    signal snapshotImportCompleted()
-    property int snapshotVerificationCycles: 0
-    property real snapshotVerificationProgress: 0
-    property bool snapshotVerified: false
-
     id: columnLayout
+    signal back
+    property bool snapshotLoading: nodeModel.snapshotLoading
+    property bool snapshotLoaded: nodeModel.isSnapshotLoaded
+    property bool snapshotImportCompleted: chainModel.isSnapshotActive
+    property bool onboarding: false
+    property bool snapshotVerified: onboarding ? false : chainModel.isSnapshotActive
+    property string snapshotFileName: ""
+    property var snapshotInfo: (snapshotVerified || snapshotLoaded) ? chainModel.getSnapshotInfo() : ({})
+    property string selectedFile: ""
+
     width: Math.min(parent.width, 450)
     anchors.horizontalCenter: parent.horizontalCenter
 
-
-    Timer {
-        id: snapshotSimulationTimer
-        interval: 50 // Update every 50ms
-        running: false
-        repeat: true
-        onTriggered: {
-            if (snapshotVerificationProgress < 1) {
-                snapshotVerificationProgress += 0.01
-            } else {
-                snapshotVerificationCycles++
-                if (snapshotVerificationCycles < 1) {
-                    snapshotVerificationProgress = 0
-                } else {
-                    running = false
-                    snapshotVerified = true
-                    settingsStack.currentIndex = 2
-                }
-            }
-        }
-    }
-
     StackLayout {
         id: settingsStack
-        currentIndex: 0
+        currentIndex: onboarding ? 0 : snapshotLoaded ? 2 : snapshotVerified ? 2 : snapshotLoading ? 1 : 0
 
         ColumnLayout {
             Layout.alignment: Qt.AlignHCenter
@@ -77,11 +61,22 @@ ColumnLayout {
                 Layout.bottomMargin: 20
                 Layout.alignment: Qt.AlignCenter
                 text: qsTr("Choose snapshot file")
-                onClicked: {
-                    settingsStack.currentIndex = 1
-                    snapshotSimulationTimer.start()
+                onClicked: fileDialog.open()
+            }
+
+            FileDialog {
+                id: fileDialog
+                folder: shortcuts.home
+                selectMultiple: false
+                selectExisting: true
+                nameFilters: ["Snapshot files (*.dat)", "All files (*)"]
+                onAccepted: {
+                    selectedFile = fileUrl.toString()
+                    snapshotFileName = selectedFile
+                    nodeModel.snapshotLoadThread(snapshotFileName)
                 }
             }
+            // TODO: Handle file error signal
         }
 
         ColumnLayout {
@@ -102,14 +97,15 @@ ColumnLayout {
                 Layout.leftMargin: 20
                 Layout.rightMargin: 20
                 header: qsTr("Loading Snapshot")
+                description: qsTr("This might take a while...")
             }
 
             ProgressIndicator {
                 id: progressIndicator
                 Layout.topMargin: 20
                 width: 200
                 height: 20
-                progress: snapshotVerificationProgress
+                progress: nodeModel.snapshotProgress
                 Layout.alignment: Qt.AlignCenter
                 progressColor: Theme.color.blue
             }
@@ -137,8 +133,11 @@ ColumnLayout {
                 descriptionColor: Theme.color.neutral6
                 descriptionSize: 17
                 descriptionLineHeight: 1.1
-                description: qsTr("It contains transactions up to January 12, 2024. Newer transactions still need to be downloaded." +
-                " The data will be verified in the background.")
+                description: snapshotInfo && snapshotInfo["date"] ?
+                    qsTr("It contains transactions up to %1. Newer transactions still need to be downloaded." +
+                    " The data will be verified in the background.").arg(snapshotInfo["date"]) :
+                    qsTr("It contains transactions up to DEBUG. Newer transactions still need to be downloaded." +
+                    " The data will be verified in the background.")
             }
 
             ContinueButton {
@@ -147,9 +146,8 @@ ColumnLayout {
                 Layout.alignment: Qt.AlignCenter
                 text: qsTr("Done")
                 onClicked: {
-                    snapshotImportCompleted()
-                    connectionSwipe.decrementCurrentIndex()
-                    connectionSwipe.decrementCurrentIndex()
+                    chainModel.isSnapshotActiveChanged()
+                    back()
                 }
             }
 
@@ -188,14 +186,17 @@ ColumnLayout {
                         font.pixelSize: 14
                     }
                     CoreText {
-                        text: qsTr("200,000")
+                        text: snapshotInfo && snapshotInfo["height"] ?
+                            snapshotInfo["height"] : qsTr("DEBUG")
                         Layout.alignment: Qt.AlignRight
                         font.pixelSize: 14
                     }
                 }
                 Separator { Layout.fillWidth: true }
                 CoreText {
-                    text: qsTr("Hash: 0x1234567890abcdef...")
+                    text: snapshotInfo && snapshotInfo["hashSerialized"] ?
+                        qsTr("Hash: %1").arg(snapshotInfo["hashSerialized"].substring(0, 13) + "...") :
+                        qsTr("Hash: DEBUG")
                     font.pixelSize: 14
                 }
             }

Diff for: src/qml/models/chainmodel.cpp

@@ -9,9 +9,13 @@
 #include <QThread>
 #include <QTime>
 #include <interfaces/chain.h>
+#include <node/utxo_snapshot.h>
+#include <kernel/chainparams.h>
+#include <validation.h>
 
 ChainModel::ChainModel(interfaces::Chain& chain)
     : m_chain{chain}
+    //   m_params{Params()}
 {
     QTimer* timer = new QTimer();
     connect(timer, &QTimer::timeout, this, &ChainModel::setCurrentTimeRatio);
@@ -101,3 +105,22 @@ void ChainModel::setCurrentTimeRatio()
 
     Q_EMIT timeRatioListChanged();
 }
+
+// TODO: Change this once a better solution has been found.
+// Using hardcoded snapshot info to display in SnapshotSettings.qml
+QVariantMap ChainModel::getSnapshotInfo() {
+    QVariantMap snapshot_info;
+
+   const MapAssumeutxo& valid_assumeutxos_map = Params().Assumeutxo();
+    if (!valid_assumeutxos_map.empty()) {
+        const int height = valid_assumeutxos_map.rbegin()->first;
+        const auto& hash_serialized = valid_assumeutxos_map.rbegin()->second.hash_serialized;
+        int64_t date = m_chain.getBlockTime(height);
+
+        snapshot_info["height"] = height;
+        snapshot_info["hashSerialized"] = QString::fromStdString(hash_serialized.ToString());
+        snapshot_info["date"] = QDateTime::fromSecsSinceEpoch(date).toString("MMMM d yyyy");
+    }
+
+    return snapshot_info;
+}