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, src/node/interfaces.cpp
        and 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 not implemented yet

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

src/interfaces/node.h

@@ -199,6 +199,12 @@ class Node
     //! List rpc commands.
     virtual std::vector<std::string> listRpcCommands() = 0;
 
+    //! Load UTXO Snapshot.
+    virtual bool snapshotLoad(const std::string& path_string) = 0;
+
+    //! Get snapshot progress.
+    virtual double getSnapshotProgress() = 0;
+
     //! Set RPC timer interface if unset.
     virtual void rpcSetTimerInterfaceIfUnset(RPCTimerInterface* iface) = 0;
 

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);

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>
@@ -395,9 +396,70 @@ class NodeImpl : public Node
     {
         m_context = context;
     }
+    double getSnapshotProgress() override { return m_snapshot_progress.load(); }
+    bool snapshotLoad(const std::string& path_string) override
+    {
+        const fs::path path = fs::u8path(path_string);
+        if (!fs::exists(path)) {
+            LogPrintf("[loadsnapshot] Snapshot file %s does not exist\n", path.u8string());
+            return false;
+        }
+
+        AutoFile afile{fsbridge::fopen(path, "rb")};
+        if (afile.IsNull()) {
+            LogPrintf("[loadsnapshot] Failed to open snapshot file %s\n", path.u8string());
+            return false;
+        }
+
+        SnapshotMetadata metadata;
+        try {
+            afile >> metadata;
+        } catch (const std::exception& e) {
+            LogPrintf("[loadsnapshot] Failed to read snapshot metadata: %s\n", e.what());
+            return false;
+        }
+
+        const uint256& base_blockhash = metadata.m_base_blockhash;
+        LogPrintf("[loadsnapshot] Waiting for blockheader %s in headers chain before snapshot activation\n",
+            base_blockhash.ToString());
+
+        if (!m_context->chainman) {
+            LogPrintf("[loadsnapshot] Chainman is null\n");
+            return false;
+        }
+
+        ChainstateManager& chainman = *m_context->chainman;
+        CBlockIndex* snapshot_start_block = nullptr;
+
+        // Wait for the block to appear in the block index
+        constexpr int max_wait_seconds = 600; // 10 minutes
+        for (int i = 0; i < max_wait_seconds; ++i) {
+            snapshot_start_block = WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(base_blockhash));
+            if (snapshot_start_block) break;
+            std::this_thread::sleep_for(std::chrono::seconds(1));
+        }
+
+        if (!snapshot_start_block) {
+            LogPrintf("[loadsnapshot] Timed out waiting for snapshot start blockheader %s\n", base_blockhash.ToString());
+            return false;
+        }
+
+        // Activate the snapshot
+        if (!chainman.ActivateSnapshot(afile, metadata, false)) {
+            LogPrintf("[loadsnapshot] Unable to load UTXO snapshot %s\n", path.u8string());
+            return false;
+        }
+
+        CBlockIndex* new_tip = WITH_LOCK(::cs_main, return chainman.ActiveTip());
+        LogPrintf("[loadsnapshot] Loaded %d coins from snapshot %s at height %d\n",
+                  metadata.m_coins_count, new_tip->GetBlockHash().ToString(), new_tip->nHeight);
+
+        return true;
+    }
     ArgsManager& args() { return *Assert(Assert(m_context)->args); }
     ChainstateManager& chainman() { return *Assert(m_context->chainman); }
     NodeContext* m_context{nullptr};
+    std::atomic<double> m_snapshot_progress{0.0};
 };
 
 bool FillBlock(const CBlockIndex* index, const FoundBlock& block, UniqueLock<RecursiveMutex>& lock, const CChain& active, const BlockManager& blockman)
@@ -510,7 +572,7 @@ 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())};

src/qml/components/ConnectionSettings.qml

@@ -10,13 +10,24 @@ import "../controls"
 ColumnLayout {
     id: root
     signal next
-    property bool snapshotImported: false
+    property bool snapshotImported: onboarding ? false : chainModel.isSnapshotActive
+    property bool onboarding: false
+
+    Component.onCompleted: {
+        if (!onboarding) {
+            snapshotImported = chainModel.isSnapshotActive
+        } else {
+            snapshotImported = false
+        }
+    }
+
     function setSnapshotImported(imported) {
         snapshotImported = imported
     }
     spacing: 4
     Setting {
         id: gotoSnapshot
+        visible: !root.onboarding
         Layout.fillWidth: true
         header: qsTr("Load snapshot")
         description: qsTr("Instant use with background sync")
@@ -40,7 +51,10 @@ ColumnLayout {
             connectionSwipe.incrementCurrentIndex()
         }
     }
-    Separator { Layout.fillWidth: true }
+    Separator {
+        visible: !root.onboarding
+        Layout.fillWidth: true
+    }
     Setting {
         Layout.fillWidth: true
         header: qsTr("Enable listening")

src/qml/components/SnapshotSettings.qml

@@ -5,44 +5,26 @@
 import QtQuick 2.15
 import QtQuick.Controls 2.15
 import QtQuick.Layouts 1.15
+import QtQuick.Dialogs 1.3
 
 import "../controls"
 
 ColumnLayout {
+    id: columnLayout
+    property bool snapshotLoading: nodeModel.snapshotLoading
     signal snapshotImportCompleted()
-    property int snapshotVerificationCycles: 0
-    property real snapshotVerificationProgress: 0
-    property bool snapshotVerified: false
+    property bool onboarding: false
+    property bool snapshotVerified: onboarding ? false : chainModel.isSnapshotActive
+    property string snapshotFileName: ""
+    property var snapshotInfo: ({})
+    property string selectedFile: ""
 
-    id: columnLayout
     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 : snapshotVerified ? 2 : snapshotLoading ? 1 : 0
 
         ColumnLayout {
             Layout.alignment: Qt.AlignHCenter
@@ -77,11 +59,24 @@ 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 = String(fileUrl)
+                    snapshotFileName = selectedFile
+                    if (selectedFile.indexOf(".dat") === selectedFile.length - 4) {
+                        nodeModel.initializeSnapshot(true, snapshotFileName)
+                    }
                 }
             }
+            // TODO: Handle file error signal
         }
 
         ColumnLayout {
@@ -102,16 +97,22 @@ 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
-                Layout.alignment: Qt.AlignCenter
-                progressColor: Theme.color.blue
+            // TODO: add progress indicator once the snapshot progress is implemented
+
+            Connections {
+                target: nodeModel
+                function onSnapshotLoaded(success) {
+                    if (success) {
+                        chainModel.isSnapshotActiveChanged()
+                        snapshotVerified = chainModel.isSnapshotActive
+                        snapshotInfo = chainModel.getSnapshotInfo()
+                        settingsStack.currentIndex = 2
+                    }
+                }
+                // TODO: connect to snapshotProgressChanged once implemented
             }
         }
 
@@ -137,8 +138,11 @@ 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 {
@@ -188,16 +192,25 @@ 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
                 }
+
+                Component.onCompleted: {
+                    if (snapshotVerified) {
+                        snapshotInfo = chainModel.getSnapshotInfo()
+                    }
+                }
             }
         }
     }

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 +105,21 @@ void ChainModel::setCurrentTimeRatio()
 
     Q_EMIT timeRatioListChanged();
 }
+
+// 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;
+}

src/qml/models/chainmodel.h

@@ -27,6 +27,7 @@ class ChainModel : public QObject
     Q_PROPERTY(quint64 assumedBlockchainSize READ assumedBlockchainSize CONSTANT)
     Q_PROPERTY(quint64 assumedChainstateSize READ assumedChainstateSize CONSTANT)
     Q_PROPERTY(QVariantList timeRatioList READ timeRatioList NOTIFY timeRatioListChanged)
+    Q_PROPERTY(bool isSnapshotActive READ isSnapshotActive NOTIFY isSnapshotActiveChanged)
 
 public:
     explicit ChainModel(interfaces::Chain& chain);
@@ -36,18 +37,21 @@ class ChainModel : public QObject
     quint64 assumedBlockchainSize() const { return m_assumed_blockchain_size; };
     quint64 assumedChainstateSize() const { return m_assumed_chainstate_size; };
     QVariantList timeRatioList() const { return m_time_ratio_list; };
-
+    bool isSnapshotActive() const { return m_chain.hasAssumedValidChain(); };
     int timestampAtMeridian();
 
     void setCurrentTimeRatio();
 
+    Q_INVOKABLE QVariantMap getSnapshotInfo();
+
 public Q_SLOTS:
     void setTimeRatioList(int new_time);
     void setTimeRatioListInitial();
 
 Q_SIGNALS:
     void timeRatioListChanged();
     void currentNetworkNameChanged();
+    void isSnapshotActiveChanged();
 
 private:
     QString m_current_network_name;