ChanViewer: Fetch the list of boards and allow switching the board

We put the list of boards in a combo box and allow the user to switch
boards that way. :^)

Applications/ChanViewer/BoardListModel.cpp

@@ -0,0 +1,90 @@
+#include "BoardListModel.h"
+#include <AK/JsonArray.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
+#include <LibCore/CHttpRequest.h>
+#include <LibCore/CNetworkJob.h>
+#include <LibCore/CNetworkResponse.h>
+#include <stdio.h>
+
+BoardListModel::BoardListModel()
+{
+    update();
+}
+
+BoardListModel::~BoardListModel()
+{
+}
+
+void BoardListModel::update()
+{
+    CHttpRequest request;
+    request.set_hostname("a.4cdn.org");
+    request.set_path("/boards.json");
+
+    auto* job = request.schedule();
+
+    job->on_finish = [job, this](bool success) {
+        auto* response = job->response();
+        dbg() << "Board list download finished, success=" << success << ", response=" << response;
+
+        if (!success)
+            return;
+
+        dbg() << "Board list payload size: " << response->payload().size();
+
+        auto json = JsonValue::from_string(response->payload());
+
+        if (json.is_object()) {
+            auto new_boards = json.as_object().get("boards");
+            if (new_boards.is_array())
+                m_boards = move(new_boards.as_array());
+        }
+
+        did_update();
+    };
+}
+
+int BoardListModel::row_count(const GModelIndex&) const
+{
+    return m_boards.size();
+}
+
+String BoardListModel::column_name(int column) const
+{
+    switch (column) {
+    case Column::Board:
+        return "Board";
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+GModel::ColumnMetadata BoardListModel::column_metadata([[maybe_unused]] int column) const
+{
+    return {};
+}
+
+GVariant BoardListModel::data(const GModelIndex& index, Role role) const
+{
+    auto& board = m_boards.at(index.row()).as_object();
+    if (role == Role::Display) {
+        switch (index.column()) {
+        case Column::Board:
+            return String::format("/%s/ - %s",
+                board.get("board").to_string().characters(),
+                board.get("title").to_string().characters());
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    }
+    if (role == Role::Custom) {
+        switch (index.column()) {
+        case Column::Board:
+            return board.get("board").to_string();
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    }
+    return {};
+}