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 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 working, could be improved

        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 +199,12 @@ 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;
 

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>
@@ -395,9 +396,95 @@ 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));
+        }
+
+        // Snapshot Progress GUI display
+        COutPoint outpoint;
+        Coin coin;
+        const uint64_t coins_count = metadata.m_coins_count;
+        uint64_t coins_left = metadata.m_coins_count;
+
+        LogPrintf("[loadsnapshot] Loading %d coins from snapshot %s\n", coins_count, base_blockhash.ToString());
+        int64_t coins_processed{0};
+        m_snapshot_progress.store(0.0);
+
+        while (coins_left > 0) {
+            --coins_left;
+            ++coins_processed;
+
+            if (coins_processed > 0) {
+                double progress = static_cast<float>(coins_processed) / static_cast<float>(coins_count);
+                m_snapshot_progress.store(progress);
+                if (coins_processed % 1000000 == 0) {
+                    LogPrintf("[loadsnapshot] Progress: %.2f%% (%d/%d coins)\n",
+                      progress * 100, coins_processed, coins_count);
+                }
+            }
+        }
+        m_snapshot_progress.store(1.0);
+
+        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 +597,7 @@ 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/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 +5,40 @@
 import QtQuick 2.15
 import QtQuick.Controls 2.15
 import QtQuick.Layouts 1.15
+import QtQuick.Dialogs 1.3
 
 import "../controls"
 
+// This QML component manages the snapshot loading process in the GUI.
+// It provides visual feedback to the user about the snapshot's loading state.
+
 ColumnLayout {
+    // The snapshotLoading property indicates if the snapshot is currently being loaded.
+    // When true, the UI will show a loading indicator.
+    property bool snapshotLoading: nodeModel.snapshotLoading
     signal snapshotImportCompleted()
     property int snapshotVerificationCycles: 0
     property real snapshotVerificationProgress: 0
-    property bool snapshotVerified: false
+    property bool onboarding: false
+
+    // The snapshotVerified property indicates if the snapshot has been successfully loaded and verified.
+    // When true, the UI will transition to the "Snapshot Loaded" page.
+    property bool snapshotVerified: onboarding ? false : chainModel.isSnapshotActive
+
+    // The snapshotFileName property holds the name of the snapshot file being loaded.
+    // It is set when a file is selected in the FileDialog.
+    property string snapshotFileName: ""
+
+    // The snapshotInfo property holds information about the loaded snapshot.
+    // It is updated when the snapshot is loaded and verified.
+    property var snapshotInfo: ({})
 
     id: columnLayout
     width: Math.min(parent.width, 450)
     anchors.horizontalCenter: parent.horizontalCenter
 
-
+    // The Timer component simulates snapshot verification progress for testing purposes.
+    // It updates the snapshotVerificationProgress property, which can be used to display a progress bar.
     Timer {
         id: snapshotSimulationTimer
         interval: 50 // Update every 50ms
@@ -29,7 +49,7 @@ ColumnLayout {
                 snapshotVerificationProgress += 0.01
             } else {
                 snapshotVerificationCycles++
-                if (snapshotVerificationCycles < 1) {
+                if (snapshotVerificationCycles < 3) {
                     snapshotVerificationProgress = 0
                 } else {
                     running = false
@@ -40,9 +60,11 @@ ColumnLayout {
         }
     }
 
+    // The StackLayout component manages the different pages of the snapshot settings UI.
+    // It determines which page to display based on the snapshotLoading and snapshotVerified properties.
     StackLayout {
         id: settingsStack
-        currentIndex: 0
+        currentIndex: onboarding ? 0 : snapshotVerified ? 2 : snapshotLoading ? 1 : 0
 
         ColumnLayout {
             Layout.alignment: Qt.AlignHCenter
@@ -69,6 +91,8 @@ ColumnLayout {
                 " It will be automatically verified in the background.")
             }
 
+            // The ContinueButton component is used to trigger the snapshot file selection process.
+            // When clicked, it opens a FileDialog for the user to choose a snapshot file.
             ContinueButton {
                 Layout.preferredWidth: Math.min(300, columnLayout.width - 2 * Layout.leftMargin)
                 Layout.topMargin: 40
@@ -78,8 +102,25 @@ ColumnLayout {
                 Layout.alignment: Qt.AlignCenter
                 text: qsTr("Choose snapshot file")
                 onClicked: {
-                    settingsStack.currentIndex = 1
-                    snapshotSimulationTimer.start()
+                    fileDialog.open()
+                }
+            }
+
+            // The FileDialog component is used to allow the user to select a snapshot file from their system.
+            FileDialog {
+                id: fileDialog
+                folder: shortcuts.home
+                selectMultiple: false
+                onAccepted: {
+                    console.log("File chosen:", fileDialog.fileUrls)
+                    snapshotFileName = fileDialog.fileUrl.toString()
+                    console.log("Snapshot file name:", snapshotFileName)
+                    if (snapshotFileName.endsWith(".dat")) {
+                        nodeModel.initializeSnapshot(true, snapshotFileName)
+                        // nodeModel.presyncProgress
+                    } else {
+                        console.error("Snapshot loading failed")
+                    }
                 }
             }
         }
@@ -102,17 +143,40 @@ ColumnLayout {
                 Layout.leftMargin: 20
                 Layout.rightMargin: 20
                 header: qsTr("Loading Snapshot")
+                description: qsTr("This might take a while...")
             }
 
+            // The ProgressIndicator component displays the progress of the snapshot verification process.
             ProgressIndicator {
                 id: progressIndicator
                 Layout.topMargin: 20
                 width: 200
                 height: 20
-                progress: snapshotVerificationProgress
+                progress: nodeModel.snapshotProgress
                 Layout.alignment: Qt.AlignCenter
                 progressColor: Theme.color.blue
             }
+
+            // The Connections component listens for signals from the nodeModel
+            // to update the UI based on snapshot loading progress.
+            Connections {
+                target: nodeModel
+                function onSnapshotProgressChanged() {
+                    progressIndicator.progress = nodeModel.snapshotProgress
+                }
+
+                function onSnapshotLoaded(success) {
+                    if (success) {
+                        chainModel.isSnapshotActiveChanged()
+                        snapshotVerified = chainModel.isSnapshotActive
+                        snapshotInfo = chainModel.getSnapshotInfo()
+                        settingsStack.currentIndex = 2  // Move to the "Snapshot Loaded" page
+                    } else {
+                        // Handle snapshot loading failure
+                        console.error("Snapshot loading failed")
+                    }
+                }
+            }
         }
 
         ColumnLayout {
@@ -137,8 +201,11 @@ 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 {
@@ -153,6 +220,7 @@ ColumnLayout {
                 }
             }
 
+            // The Setting component provides a toggleable view for detailed snapshot information.
             Setting {
                 id: viewDetails
                 Layout.alignment: Qt.AlignCenter
@@ -188,16 +256,26 @@ 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...")
+                    // The CoreText component displays the hash of the loaded snapshot.
+                    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()
+                    }
+                }
             }
         }
     }