some first thoguhts of receiving actual data

API/models/CMakeLists.txt

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+# SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+set(HEADERS
+    assets.h
+)
+
+set(SOURCES
+    assets.cpp
+)
+
+target_sources(magpie PRIVATE ${SOURCES})

API/models/assets.cpp

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+//SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
+//SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "assets.h"
+
+#include "../helpers.h"
+
+Models::Assets::Assets (QObject* parent):
+    QAbstractListModel(parent),
+    records(),
+    state(State::initial)
+{}
+
+void Models::Assets::clear () {
+    beginResetModel();
+    records.clear();
+    endResetModel();
+}
+
+void Models::Assets::addAsset (const Asset& asset) {
+    QModelIndex index = getIndex(asset.id);
+    if (index.isValid())
+        throw std::runtime_error("An attempt to insert a duplicating Asset to an asset model");
+
+    beginInsertRows(QModelIndex(), records.size(), records.size() + 1);
+    records.push_back(asset);
+    endInsertRows();
+}
+
+void Models::Assets::addAssets (const std::deque<Asset>& assets) {
+    if (assets.empty())
+        return;
+
+    for (const Asset& asset : assets)
+        if (getIndex(asset.id).isValid())
+            throw std::runtime_error("An attempt to insert a duplicating Asset to an asset model (bulk)");
+
+    beginInsertRows(QModelIndex(), records.size(), records.size() + assets.size());
+    for (const Asset& asset : assets)
+        records.push_back(asset);
+
+    endInsertRows();
+}
+
+void Models::Assets::deleteAsset (unsigned int id) {
+    QModelIndex index = getIndex(id);
+    if (!index.isValid())
+        throw std::runtime_error("An attempt to insert to delete non existing Asset from asset model");
+
+    int row = index.row();
+    beginRemoveRows(QModelIndex(), row, row + 1);
+    records.erase(records.begin() + row);
+    if (state == State::syncronized)    //give a second thought
+        state = State::initial;
+
+    endRemoveRows();
+}
+
+int Models::Assets::rowCount (const QModelIndex& parent) const {
+    //For list models only the root node (an invalid parent) should return the
+    //list's size. For all other (valid) parents, rowCount() should return 0 so
+    //that it does not become a tree model.
+    if (parent.isValid())
+        return 0;
+
+    return records.size();
+}
+
+QHash<int, QByteArray> Models::Assets::roleNames () const {
+    static const QHash<int, QByteArray> roleNames{
+        {Title, "title"}, {Icon, "icon"}, {Balance, "balance"}, {Archived, "archived"}
+    };
+    return roleNames;
+}
+
+bool Models::Assets::canFetchMore (const QModelIndex& parent) const {
+    return state == State::initial;
+}
+
+void Models::Assets::fetchMore (const QModelIndex& parent) {
+    if (state != State::initial)
+        return;
+
+    state = State::requesting;
+}
+
+QVariant Models::Assets::data (const QModelIndex& index, int role) const {
+    if (!index.isValid())
+        return QVariant();
+
+    int row = index.row();
+    if (row >= 0 && row < records.size()) {
+        switch (role) {
+            case Qt::DisplayRole:
+            case Title:
+                return records[row].title;
+            case Icon:
+                return records[row].icon;
+            case Balance:
+                return records[row].balance;
+            case Archived:
+                return records[row].archived;
+        }
+    }
+
+    return QVariant();
+}
+
+bool Models::Assets::deserialize (const QVariantList& from, std::deque<Asset>& out) {
+    for (const QVariant& item : from) {
+        if (!item.canConvert<QVariantMap>())
+            return false;
+
+        const QVariantMap& ser = qast<QVariantMap>(item);
+        Asset& asset = out.emplace_back();
+        asset.title = ser.value("title").toString();
+        asset.icon = ser.value("icon").toString();
+        asset.archived = ser.value("archived").toBool();
+        asset.id = ser.value("archived").toUInt();
+    }
+
+    return true;
+}
+
+void Models::Assets::receivedAssets (const std::deque<Asset>& assets) {
+    beginResetModel();
+    records = assets;
+    state = State::syncronized;
+    endResetModel();
+}
+
+QModelIndex Models::Assets::getIndex (unsigned int id) const {
+    for (std::size_t i = 0; i < records.size(); ++i) {
+        if (records[i].id == id)
+            return createIndex(i, 0, &records[i]);
+    }
+    return QModelIndex();
+}

API/models/assets.h

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+//SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
+//SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <deque>
+
+#include <QString>
+#include <QAbstractListModel>
+#include <qqmlregistration.h>
+
+namespace Models {
+struct Asset {
+    unsigned int id;
+    QString title;
+    QString icon;
+    double balance;
+    bool archived;
+    unsigned int currency;
+};
+
+class Assets : public QAbstractListModel {
+    Q_OBJECT
+    QML_ELEMENT
+
+public:
+    explicit Assets (QObject* parent = nullptr);
+
+    enum Roles {
+        Title = Qt::UserRole + 1,
+        Icon,
+        Balance,
+        Archived
+    };
+
+    void clear();
+    void addAsset(const Asset& asset);
+    void addAssets(const std::deque<Asset>& assets);
+    void deleteAsset(unsigned int id);
+
+    //Basic functionality:
+    int rowCount (const QModelIndex& parent = QModelIndex()) const override;
+    QHash<int, QByteArray> roleNames () const override;
+
+    //Fetch data dynamically:
+    bool canFetchMore (const QModelIndex& parent) const override;
+    void fetchMore (const QModelIndex& parent) override;
+    QVariant data (const QModelIndex& index, int role = Qt::DisplayRole) const override;
+
+    static bool deserialize(const QVariantList& from, std::deque<Asset>& out);
+
+signals:
+    void requestAssets();
+
+public slots:
+    void receivedAssets(const std::deque<Asset>& assets);
+
+private:
+    QModelIndex getIndex(unsigned int id) const;
+
+private:
+    enum class State {
+        initial,
+        requesting,
+        syncronized
+    };
+
+    State state;
+    std::deque<Asset> records;
+};
+}