mu: refactor labels code

Split labels-cache and store-labels.

lib/mu-labels-cache.hh

@@ -0,0 +1,148 @@
+/*
+** Copyright (C) 2025 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+** This program is free software; you can redistribute it and/or modify it
+** under the terms of the GNU General Public License as published by the
+** Free Software Foundation; either version 3, or (at your option) any
+** later version.
+**
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+** GNU General Public License for more details.
+**
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software Foundation,
+** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+**
+*/
+
+#ifndef MU_LABELS_CACHE_HH
+#define MU_LABELS_CACHE_HH
+
+#include <set>
+#include <string>
+#include <unordered_map>
+
+#include "utils/mu-utils.hh"
+#include "utils/mu-option.hh"
+#include "message/mu-labels.hh"
+
+#include "mu-config.hh"
+
+namespace Mu {
+
+class Store; // fwd declaration
+
+/**
+ * The cache keeps track of what labels are being used. This can be used
+ * for completion etc. and `mu label list`
+ */
+class LabelsCache {
+public:
+	// maps a label to a number of occurrences
+	using Map = std::unordered_map<std::string, size_t>;
+
+	/**
+	 * CTOR
+	 *
+	 * Deserialize the map from the configuration.
+	 *
+	 * @param serialized serialization string
+	 */
+	LabelsCache(Config& config): config_{config},
+				     label_map_{deserialize(config_.get<Config::Id::Labels>())},
+				     dirty_{false}{}
+
+	~LabelsCache() {
+		if (dirty_)
+			serialize();
+	};
+
+	/**
+	 * Add a label occurrence to the cache
+	 *
+	 * @param label some label
+	 */
+	void increase(const std::string& label) {
+		if (auto it = label_map_.find(label); it == label_map_.end())
+			label_map_.insert({label, 1});
+		else
+			++it->second;
+		++dirty_;
+	}
+	/**
+	 * Remove a label occurrence from the cache
+	 *
+	 * Removes the label completely if this was the _last_ occurence.
+	 *
+	 * @param label some label
+	 */
+	void decrease(const std::string& label) {
+		if (auto it = label_map_.find(label); it != label_map_.end()) {
+			if (it->second == 1)
+				label_map_.erase(it);
+			else
+				--it->second;
+			++dirty_;
+		}
+	}
+
+	/**
+	 * Update the cache with the label changes
+	 *
+	 * @param updates a vector of delta-labels
+	 */
+	void update(const Labels::DeltaLabelVec& updates) {
+		for(const auto& [delta, label]: updates) {
+			switch(delta) {
+			case Labels::Delta::Add:
+				increase(label);
+				break;
+			case Labels::Delta::Remove:
+				decrease(label);
+				break;
+			}
+		}
+	}
+
+	/**
+	 * Return a copy of the label-map
+	 *
+	 * @return the label-map
+	 */
+	Map label_map() const { return label_map_; }
+
+	// serialization/deserialization could be optimized, but is not super
+	// time-critical
+
+	/**
+	 * Serialize the cache into Config if there are changes.
+	 *
+	 */
+	void serialize() const;
+
+	/**
+	 * Restore the labels-cache from the labels seen in the store.
+	 *
+	 * @param store a store
+	 *
+	 * @return Ok() or some error
+	 */
+	Result<void> restore(const Store& store);
+
+private:
+	/**
+	 * Deserialize the cache into a Map
+	 *
+	 * @return serialized cache
+	 */
+	Map deserialize(const std::string& serialized) const;
+
+	Config& config_;
+	Map label_map_;
+	mutable size_t dirty_{};
+};
+
+} // namespace Mux
+#endif /*MU_LABELS_CACHE_HH*/