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. Modifies src/interfaces/node.h, src/node/interfaces.cpp
        and chainparams.cpp (temporarily for signet snapshot testing)
        to implement 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 working yet

        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

@@ -199,6 +199,9 @@ class Node
     //! List rpc commands.
     virtual std::vector<std::string> listRpcCommands() = 0;
 
+    //! Load UTXO Snapshot.
+    virtual bool snapshotLoad(const std::string& path_string) = 0;
+
     //! Set RPC timer interface if unset.
     virtual void rpcSetTimerInterfaceIfUnset(RPCTimerInterface* iface) = 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/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>
@@ -395,6 +396,65 @@ class NodeImpl : public Node
     {
         m_context = context;
     }
+    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};

Diff for: 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")

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

@@ -5,20 +5,22 @@
 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
+    property bool onboarding: false
+    property bool snapshotVerified: onboarding ? false : chainModel.isSnapshotActive
 
     id: columnLayout
     width: Math.min(parent.width, 450)
     anchors.horizontalCenter: parent.horizontalCenter
 
-
+    // TODO: Remove this once the verification progress is available
     Timer {
         id: snapshotSimulationTimer
         interval: 50 // Update every 50ms
@@ -29,7 +31,7 @@ ColumnLayout {
                 snapshotVerificationProgress += 0.01
             } else {
                 snapshotVerificationCycles++
-                if (snapshotVerificationCycles < 1) {
+                if (snapshotVerificationCycles < 3) {
                     snapshotVerificationProgress = 0
                 } else {
                     running = false
@@ -42,7 +44,7 @@ ColumnLayout {
 
     StackLayout {
         id: settingsStack
-        currentIndex: 0
+        currentIndex: onboarding ? 0 : snapshotVerified ? 2 : 0
 
         ColumnLayout {
             Layout.alignment: Qt.AlignHCenter
@@ -78,8 +80,22 @@ ColumnLayout {
                 Layout.alignment: Qt.AlignCenter
                 text: qsTr("Choose snapshot file")
                 onClicked: {
-                    settingsStack.currentIndex = 1
-                    snapshotSimulationTimer.start()
+                    fileDialog.open()
+                }
+            }
+
+            FileDialog {
+                id: fileDialog
+                folder: shortcuts.home
+                selectMultiple: false
+                onAccepted: {
+                    console.log("File chosen:", fileDialog.fileUrls)
+                    var snapshotFileName = fileDialog.fileUrl.toString()
+                    console.log("Snapshot file name:", snapshotFileName)
+                    if (snapshotFileName.endsWith(".dat")) {
+                        nodeModel.initializeSnapshot(true, snapshotFileName)
+                        settingsStack.currentIndex = 1
+                    }
                 }
             }
         }
@@ -109,10 +125,31 @@ ColumnLayout {
                 Layout.topMargin: 20
                 width: 200
                 height: 20
-                progress: snapshotVerificationProgress
+                // TODO: uncomment this once the verification progress is available
+                // progress: nodeModel.verificationProgress
+                progress: 0
                 Layout.alignment: Qt.AlignCenter
                 progressColor: Theme.color.blue
             }
+
+            Connections {
+                target: nodeModel
+                // TODO: uncomment this once the verification progress is available
+                // function onVerificationProgressChanged() {
+                //     progressIndicator.progress = nodeModel.verificationProgress
+                // }
+                function onSnapshotLoaded(success) {
+                    if (success) {
+                        chainModel.isSnapshotActiveChanged()
+                        snapshotVerified = chainModel.isSnapshotActive
+                        progressIndicator.progress = 1
+                        settingsStack.currentIndex = 2  // Move to the "Snapshot Loaded" page
+                    } else {
+                        // Handle snapshot loading failure
+                        console.error("Snapshot loading failed")
+                    }
+                }
+            }
         }
 
         ColumnLayout {
@@ -137,6 +174,7 @@ ColumnLayout {
                 descriptionColor: Theme.color.neutral6
                 descriptionSize: 17
                 descriptionLineHeight: 1.1
+                // TODO: Update this description once the snapshot is verified
                 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.")
             }
@@ -153,6 +191,9 @@ ColumnLayout {
                 }
             }
 
+            // TODO: Update this with the actual snapshot details
+            // TODO: uncomment this once the snapshot details are available
+            /*
             Setting {
                 id: viewDetails
                 Layout.alignment: Qt.AlignCenter
@@ -188,17 +229,20 @@ ColumnLayout {
                         font.pixelSize: 14
                     }
                     CoreText {
+                        // TODO: Update this with the actual block height
                         text: qsTr("200,000")
                         Layout.alignment: Qt.AlignRight
                         font.pixelSize: 14
                     }
                 }
                 Separator { Layout.fillWidth: true }
                 CoreText {
+                    // TODO: Update this with the actual snapshot file hash
                     text: qsTr("Hash: 0x1234567890abcdef...")
                     font.pixelSize: 14
                 }
             }
+            */
         }
     }
 }

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

@@ -12,6 +12,7 @@
 #include <QString>
 #include <QTimer>
 #include <QVariant>
+#include <QDebug>
 
 namespace interfaces {
 class FoundBlock;
@@ -27,6 +28,7 @@ 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);
@@ -36,7 +38,7 @@ 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();
@@ -48,6 +50,7 @@ public Q_SLOTS:
 Q_SIGNALS:
     void timeRatioListChanged();
     void currentNetworkNameChanged();
+    void isSnapshotActiveChanged();
 
 private:
     QString m_current_network_name;

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

@@ -7,6 +7,7 @@
 #include <interfaces/node.h>
 #include <net.h>
 #include <node/interface_ui.h>
+#include <node/utxo_snapshot.h>
 #include <validation.h>
 
 #include <cassert>
@@ -16,6 +17,8 @@
 #include <QMetaObject>
 #include <QTimerEvent>
 #include <QString>
+#include <QUrl>
+#include <QThread>
 
 NodeModel::NodeModel(interfaces::Node& node)
     : m_node{node}
@@ -166,3 +169,33 @@ void NodeModel::ConnectToNumConnectionsChangedSignal()
             setNumOutboundPeers(new_num_peers.outbound_full_relay + new_num_peers.block_relay);
         });
 }
+
+// Loads a snapshot from a given path using FileDialog
+void NodeModel::initializeSnapshot(bool initLoadSnapshot, QString path_file) {
+    if (initLoadSnapshot) {
+        // TODO: this is to deal with FileDialog returning a QUrl
+        path_file = QUrl(path_file).toLocalFile();
+        // TODO: Remove this before release
+        // qDebug() << "path_file: " << path_file;
+        QThread* snapshot_thread = new QThread();
+
+        // Capture path_file by value
+        auto lambda = [this, path_file]() {
+            bool result = this->snapshotLoad(path_file);
+            Q_EMIT snapshotLoaded(result);
+        };
+
+        connect(snapshot_thread, &QThread::started, lambda);
+        connect(snapshot_thread, &QThread::finished, snapshot_thread, &QThread::deleteLater);
+
+        snapshot_thread->start();
+    }
+}
+
+void NodeModel::setSnapshotProgress(double new_snapshot_progress)
+{
+    if (new_snapshot_progress != m_snapshot_progress) {
+        m_snapshot_progress = new_snapshot_progress;
+        Q_EMIT snapshotProgressChanged();
+    }
+}