Merge #430: Allow IPv6 in Proxy settings and moving validation out from the UI into the model/ interface

7bd7d1c qml, proxy: Allow IPv6 and move out UI validation (pablomartin4btc)

Pull request description:

  The main purposes of this PR are:
  - Allow configure proxy server with IPv6 (after testing exhaustively in current `bitcoin-qt` [repo](https://github.com/bitcoin-core/gui/) and `bitcoind` - e.g. [IPv6 on Qt](bitcoin-core/gui#836 (comment)); [IP validation in Qt](bitcoin-core/gui#813))
  - More importantly: moving the validation logic out from the UI (component/ control/ widget) into the back-end (model/ interfaces). It seemed currently in [Qt](https://github.com/bitcoin-core/gui/) all this logic (validation, network classes) was coupled to the UI since the beginning (more than [12y ago](https://github.com/bitcoin-core/gui/blame/c4443c2be141e5f45bb10376056f3083e97cde50/src/qt/optionsmodel.cpp)) instead of using interfaces (introduced much later) that would be the correct thing to do.

  Feedback and suggestions are very welcome and will help establish a foundation for leaving business logic out of the UI going forward.

  ---
  <details>
  <summary>In order to test it, if it's the first time you run <code>./src/qt/bitcoin-qt</code> you need to go thru the on-boarding flow (<i>start->next->next->next->next->connection settings->Proxy settings</i>) otherwise you need to go to the settings (top right gear icon) then <i>Connection->Proxy settings</i>.</summary>

  ![image](https://github.com/user-attachments/assets/9f10c4b7-b7e4-4807-b895-1c03d9c00037)

  </details>

  Before this change, only IPv4 address were allow in the value input, now also IPv6 can be entered.

  ---
  There are some [look and feel kind of issues](#430 (comment)) that will be handled on follow-ups (issues: #437 and #438).

ACKs for top commit:
  D33r-Gee:
    tACK [7bd7d1c](7bd7d1c) on Ubuntu 20.04 works as expected.
  vasild:
    ACK 7bd7d1c
  johnny9:
    ACK 7bd7d1c

Tree-SHA512: f633f5729f4ca2a8433560b15722bccd5938bfa55643cd3d925b75ed01006dbc7a56fe3a20766a6bb9e2bb601c8a3828c177de3cccc7728959eb48987838e90c

Author: hebasto

qml/components/ProxySettings.qml

@@ -7,7 +7,12 @@ import QtQuick.Controls 2.15
 import QtQuick.Layouts 1.15
 import "../controls"
 
+import org.bitcoincore.qt 1.0
+
 ColumnLayout {
+    property string ipAndPortHeader: qsTr("IP and Port")
+    property string invalidIpError: qsTr("Invalid IP address or port format. Use '255.255.255.255:65535' or '[ffff::]:65535'")
+
     spacing: 4
     Header {
         headerBold: true
@@ -41,14 +46,17 @@ ColumnLayout {
     Setting {
         id: defaultProxy
         Layout.fillWidth: true
-        header: qsTr("IP and Port")
-        errorText: qsTr("Invalid IP address or port format. Please use the format '255.255.255.255:65535'.")
+        header: ipAndPortHeader
+        errorText: invalidIpError
         state: !defaultProxyEnable.loadedItem.checked ? "DISABLED" : "FILLED"
         showErrorText: !defaultProxy.loadedItem.validInput && defaultProxyEnable.loadedItem.checked
         actionItem: IPAddressValueInput {
             parentState: defaultProxy.state
-            description: "127.0.0.1:9050"
+            description: nodeModel.defaultProxyAddress()
             activeFocusOnTab: true
+            onTextChanged: {
+                validInput = nodeModel.validateProxyAddress(text);
+            }
         }
         onClicked: {
             loadedItem.filled = true
@@ -89,14 +97,17 @@ ColumnLayout {
     Setting {
         id: torProxy
         Layout.fillWidth: true
-        header: qsTr("IP and Port")
-        errorText: qsTr("Invalid IP address or port format. Please use the format '255.255.255.255:65535'.")
+        header: ipAndPortHeader
+        errorText: invalidIpError
         state: !torProxyEnable.loadedItem.checked ? "DISABLED" : "FILLED"
         showErrorText: !torProxy.loadedItem.validInput && torProxyEnable.loadedItem.checked
         actionItem: IPAddressValueInput {
             parentState: torProxy.state
-            description: "127.0.0.1:9050"
+            description: nodeModel.defaultProxyAddress()
             activeFocusOnTab: true
+            onTextChanged: {
+                validInput = nodeModel.validateProxyAddress(text);
+            }
         }
         onClicked: {
             loadedItem.filled = true

qml/controls/IPAddressValueInput.qml

@@ -16,9 +16,9 @@ TextInput {
     property bool validInput: true
     enabled: true
     state: root.parentState
-    validator: RegExpValidator { regExp: /[0-9.:]*/ } // Allow only digits, dots, and colons
+    validator: RegularExpressionValidator { regularExpression: /^[\][0-9a-f.:]+$/i } // Allow only IPv4/ IPv6 chars
 
-    maximumLength: 21
+    maximumLength: 47
 
     states: [
         State {
@@ -53,30 +53,4 @@ TextInput {
     Behavior on color {
         ColorAnimation { duration: 150 }
     }
-
-    function isValidIPPort(input)
-    {
-        var parts = input.split(":");
-        if (parts.length !== 2) return false;
-        if (parts[1].length === 0) return false; // port part is empty
-        var ipAddress = parts[0];
-        var ipAddressParts = ipAddress.split(".");
-        if (ipAddressParts.length !== 4) return false;
-        for (var i = 0; (i < ipAddressParts.length); i++) {
-            if (ipAddressParts[i].length === 0) return false; // ip group number part is empty
-            if (parseInt(ipAddressParts[i]) > 255) return false;
-        }
-        var port = parseInt(parts[1]);
-        if (port < 1 || port > 65535) return false;
-        return true;
-    }
-
-    // Connections element to ensure validation on editing finished
-    Connections {
-        target: root
-        function onTextChanged() {
-            // Validate the input whenever editing is finished
-            validInput = isValidIPPort(root.text);
-        }
-    }
 }

qml/models/nodemodel.cpp

@@ -166,3 +166,13 @@ void NodeModel::ConnectToNumConnectionsChangedSignal()
             setNumOutboundPeers(new_num_peers.outbound_full_relay + new_num_peers.block_relay);
         });
 }
+
+bool NodeModel::validateProxyAddress(QString address_port)
+{
+    return m_node.validateProxyAddress(address_port.toStdString());
+}
+
+QString NodeModel::defaultProxyAddress()
+{
+    return QString::fromStdString(m_node.defaultProxyAddress());
+}

qml/models/nodemodel.h

@@ -62,6 +62,9 @@ class NodeModel : public QObject
     void startShutdownPolling();
     void stopShutdownPolling();
 
+    Q_INVOKABLE bool validateProxyAddress(QString addr_port);
+    Q_INVOKABLE QString defaultProxyAddress();
+
 public Q_SLOTS:
     void initializeResult(bool success, interfaces::BlockAndHeaderTipInfo tip_info);