Implement filter

Add a proxy model class with filter logic, and use it as the model for
events ListView.

event_filter.cpp

@@ -0,0 +1,79 @@
+#include "event_filter.h"
+
+#include <QAbstractItemModel>
+#include <QMetaType>
+#include <QRegularExpression>
+
+void EventFilter::setFilter(const QString& text)
+{
+	filters.clear();
+	if (!text.isEmpty()) {
+		for (const auto &s : text.split(QRegularExpression{"\\s+"})) {
+			if (const int split = s.indexOf(":"); split == -1)
+				filters.append({"", s.trimmed()});
+			else
+				filters.append({s.left(split).trimmed(), s.mid(split+1).trimmed()});
+		}
+	}
+	invalidateFilter();
+}
+
+bool EventFilter::remove(int row)
+{
+	return removeRows(row, 1);
+}
+
+// Check if any of the given values match name: value.
+static bool matches(const QVariantMap& values, const QString& name, const QString& value)
+{
+	for (auto kv = values.constKeyValueBegin(); kv != values.constKeyValueEnd(); kv++) {
+		const auto& [fieldName, fieldValue] = *kv;
+		if (!name.isEmpty() && !fieldName.startsWith(name))
+			continue;
+
+		switch (fieldValue.type()) {
+		case QMetaType::QString:
+			// Prepend = to value for exact match.
+			if (value.startsWith("=")) {
+				if (fieldValue.toString() == value.mid(1))
+					return true;
+			} else {
+				if (fieldValue.toString().contains(value))
+					return true;
+			}
+			break;
+		case QMetaType::Bool:
+			// Prepend ! to value for inverted match.
+			if (value.startsWith("!")) {
+				if (fieldName.startsWith(value.mid(1)) && !fieldValue.toBool())
+					return true;
+			} else {
+				if (fieldName.startsWith(value) && fieldValue.toBool())
+					return true;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+	return false;
+}
+
+bool EventFilter::filterAcceptsRow(int sourceRow, const QModelIndex& sourceParent) const
+{
+	const auto& model = sourceModel();
+	const auto& index = model->index(sourceRow, 0, sourceParent);
+
+	const auto& roles = model->roleNames();
+	const auto& tag = model->data(index, roles.key("tag")).toString();
+	const auto& values = model->data(index, roles.key("values")).toMap();
+
+	for (const auto& filter : filters) {
+		if (filter.first.isEmpty() && tag.startsWith(filter.second))
+			continue;
+		if (matches(values, filter.first, filter.second))
+			continue;
+		return false;
+	}
+	return true;
+}