mu: refactor labels code

Split labels-cache and store-labels.

9 files changed, 251 insertions, 186 deletions

diff --git a/lib/meson.build b/lib/meson.build
index 35b61be..eb772ef 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -1,4 +1,4 @@
-## Copyright (C) 2021-2023 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+## Copyright (C) 2021-2025 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
@@ -24,6 +24,7 @@ lib_mu=static_library(
     # db
     'mu-config.cc',
     'mu-contacts-cache.cc',
+    'mu-labels-cache.cc',
     'mu-store.cc',
     'mu-store-labels.cc',
     'mu-xapian-db.cc',
diff --git a/lib/mu-contacts-cache.cc b/lib/mu-contacts-cache.cc
index b422ed9..66cb4d7 100644
--- a/lib/mu-contacts-cache.cc
+++ b/lib/mu-contacts-cache.cc
@@ -273,7 +273,6 @@ ContactsCache::size() const
 	return priv_->contacts_.size();
 }
 
-
 /**
 * Wrapper to allow for Contact sorting
 * (needed due to reference_wrapper)
diff --git a/lib/mu-labels-cache.cc b/lib/mu-labels-cache.cc
new file mode 100644
index 0000000..0e4fa83
--- /dev/null
+++ b/lib/mu-labels-cache.cc
@@ -0,0 +1,79 @@
+/*
+** 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.
+**
+*/
+
+#include "mu-labels-cache.hh"
+#include "mu-store.hh"
+#include "message/mu-labels.hh"
+
+using namespace Mu;
+
+void
+Mu::LabelsCache::serialize() const
+{
+	std::string s;
+	for (const auto&[label, n]: label_map_)
+		s += mu_format("{}{}{}\n", label, SepaChar2, n);
+
+	config_.set<Config::Id::Labels>(s);
+	mu_debug("labels: serialized {} change(s)", dirty_);
+	dirty_ = 0;
+}
+
+Mu::LabelsCache::Map
+Mu::LabelsCache::deserialize(const std::string& serialized) const
+{
+	Map  map;
+
+	std::stringstream ss{serialized, std::ios_base::in};
+	std::string       line;
+
+	while (std::getline(ss, line)) {
+		if (const auto parts =
+		    Mu::split(line, SepaChar2); parts.size() != 2)
+			mu_warning("error: '{}'", line);
+		else
+			map.emplace(std::move(parts[0]),
+				    static_cast<std::size_t>(
+					    g_ascii_strtoll(parts[1].c_str(),{}, 10)));
+	}
+	return map;
+}
+
+Result<void>
+Mu::LabelsCache::restore(const Store& store)
+{
+	const auto res{store.run_query("")};
+	if (!res)
+		return Err(Error{Error::Code::Query,
+				"failed to run query: {}",
+				 *res.error().what()});
+	label_map_.clear();
+	++dirty_;
+
+	for (auto&& item: *res) {
+		if (auto &&msg{item.message()}; msg) {
+			for (const auto& label: msg->labels())
+				increase(label);
+		}
+	}
+
+	serialize();
+
+	return Ok();
+}
diff --git a/lib/mu-labels-cache.hh b/lib/mu-labels-cache.hh
new file mode 100644
index 0000000..9f95d09
--- /dev/null
+++ b/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*/
diff --git a/lib/mu-store-labels.cc b/lib/mu-store-labels.cc
index 8653c84..a08f3b4 100644
--- a/lib/mu-store-labels.cc
+++ b/lib/mu-store-labels.cc
@@ -18,30 +18,14 @@
 */
 
 #include "mu-store-labels.hh"
+
+#include <istream>
+#include <sstream>
+
 #include "mu-store.hh"
-#include "message/mu-labels.hh"
 
 using namespace Mu;
 
-Result<void>
-Mu::LabelsCache::restore(const Store& store)
-{
-	const auto res{store.run_query("")};
-	if (!res)
-		return Err(Error{Error::Code::Query,
-				"failed to run query: {}",
-				 *res.error().what()});
-	label_map_.clear();
-
-	for (auto&& item: *res) {
-		if (auto &&msg{item.message()}; msg) {
-			for (const auto& label: msg->labels())
-				increase(label);
-		}
-	}
-	return Ok();
-}
-
 namespace {
 constexpr std::string_view	path_key       = "path:";
 constexpr std::string_view	message_id_key = "message-id:";
diff --git a/lib/mu-store-labels.hh b/lib/mu-store-labels.hh
index 6104973..919e9de 100644
--- a/lib/mu-store-labels.hh
+++ b/lib/mu-store-labels.hh
@@ -17,160 +17,16 @@
 **
 */
 
-#ifndef MU_LABELS_CACHE_HH
-#define MU_LABELS_CACHE_HH
-
-#include <set>
 #include <string>
-#include <unordered_map>
+#include "mu-option.hh"
+#include "mu-result.hh"
 
-#include "utils/mu-utils.hh"
-#include "utils/mu-option.hh"
-#include "message/mu-labels.hh"
+#ifndef MU_STORE_LABELS_HH
+#define MU_STORE_LABELS_HH
 
 namespace Mu {
 
-class Store;
-
-/**
- * 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 a string
-	 *
-	 * @param serialized serialization string
-	 */
-	LabelsCache(const std::string serialized = {}): label_map_{deserialize(serialized)} {
-	}
-
-	/**
-	 * 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_ = true;
-	}
-	/**
-	 * 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_ = true;
-		}
-	}
-
-	/**
-	 * 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 a string.
-	 *
-	 * Note: this also marks the cache a _non_ dirty;
-	 *
-	 * @return serialized cache
-	 */
-	[[nodiscard]] std::string serialize() const {
-		std::string s;
-		for (const auto&[label, n]: label_map_)
-			s += mu_format("{}{}{}\n", label, SepaChar2, n);
-		dirty_ = false;
-		return s;
-	}
-
-	/**
-	 * Deserialize the cache into a Map
-	 *
-	 * @return serialized cache
-	 */
-	Map deserialize(const std::string& serialized) const {
-
-		Map       map;
-		std::stringstream ss{serialized, std::ios_base::in};
-		std::string       line;
-
-		while (std::getline(ss, line)) {
-			if (const auto parts =
-			    Mu::split(line, SepaChar2); parts.size() != 2)
-				mu_warning("error: '{}'", line);
-			else
-				map.emplace(std::move(parts[0]),
-					    static_cast<std::size_t>(
-						    g_ascii_strtoll(parts[1].c_str(),{}, 10)));
-		}
-		return map;
-	}
-
-
-	/**
-	 * 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);
-
-
-	/**
-	 * Is the cache "dirty"?
-	 *
-	 * I.e. have there been changes since "serialize()" was called?
-	 *
-	 * @return true or false
-	 */
-	bool dirty() const {
-		return dirty_;
-	}
-
-private:
-	Map label_map_;
-	mutable bool dirty_{};
-};
+class Store; // fwd declaration
 
 /**
  * Export labels to a file
@@ -187,7 +43,6 @@ private:
 Result<std::string> export_labels(const Store& store,
 				  const std::string& query="",
 				  Option<std::string> path={});
-
 /**
  * Import labels from a file
  *
@@ -203,6 +58,7 @@ Result<std::string> export_labels(const Store& store,
  */
 Result<void> import_labels(Store&, const std::string& path, bool dry_run,
 			   bool quiet, bool verbose);
+} // Mu
+
 
-} // namespace Mux
-#endif /*MU_LABELS_CACHE_HH*/
+#endif /*MU_STORE_LABELS_HH*/
diff --git a/lib/mu-store.cc b/lib/mu-store.cc
index de148af..e5ba902 100644
--- a/lib/mu-store.cc
+++ b/lib/mu-store.cc
@@ -35,10 +35,10 @@
 #include "mu-query.hh"
 #include "mu-xapian-db.hh"
 #include "mu-scanner.hh"
+#include "mu-store-labels.hh"
 
 #include "utils/mu-error.hh"
 
-
 #include "utils/mu-utils.hh"
 #include <utils/mu-utils-file.hh>
 
@@ -66,7 +66,7 @@ struct Store::Private {
 				    : XapianDb::Flavor::Open)},
 		config_{xapian_db_},
 		contacts_cache_{config_},
-		labels_cache_{config_.get<Config::Id::Labels>()},
+		labels_cache_{config_},
 		root_maildir_{remove_slash(config_.get<Config::Id::RootMaildir>())},
 		message_opts_{make_message_options(config_)}
 		{}
@@ -76,7 +76,7 @@ struct Store::Private {
 		xapian_db_{XapianDb(path, XapianDb::Flavor::CreateOverwrite)},
 		config_{make_config(xapian_db_, root_maildir, conf)},
 		contacts_cache_{config_},
-		labels_cache_{config_.get<Config::Id::Labels>()},
+		labels_cache_{config_},
 		root_maildir_{remove_slash(config_.get<Config::Id::RootMaildir>())},
 		message_opts_{make_message_options(config_)} {
 		// so tell xapian-db to update its internal cached values from
@@ -85,10 +85,6 @@ struct Store::Private {
 	}
 
 	~Private() try {
-		if (!xapian_db_.read_only()) {
-			if (const auto res = serialize(); !res)
-				mu_critical("failed to serialize: {}", res.error().what());
-		}
 		mu_debug("closing store @ {}", xapian_db_.path());
 	} catch (...) {
 		mu_critical("caught exception in store dtor");
@@ -156,9 +152,7 @@ Store::Private::serialize()
 	mu_debug("serialize data into store @ {}", xapian_db_.path());
 
 	contacts_cache_.serialize(); // does the 'dirty' check internally.
-
-	if (labels_cache_.dirty())
-		config_.set<Config::Id::Labels>(labels_cache_.serialize());
+	labels_cache_.serialize();
 
 	return Ok();
 }
@@ -697,6 +691,9 @@ Store::clear_labels(Message& message)
 Result<void>
 Store::restore_label_map()
 {
+	if (xapian_db().read_only())
+		throw Error{Error::Code::Store, "store is read-only"};
+
 	std::unique_lock lock{priv_->lock_};
 
 	return priv_->labels_cache_.restore(*this);
diff --git a/lib/mu-store.hh b/lib/mu-store.hh
index 9aff22c..8a7f13c 100644
--- a/lib/mu-store.hh
+++ b/lib/mu-store.hh
@@ -27,6 +27,8 @@
 #include <memory>
 
 #include "mu-contacts-cache.hh"
+#include "mu-labels-cache.hh"
+
 #include "mu-xapian-db.hh"
 #include "mu-config.hh"
 #include "mu-indexer.hh"
@@ -35,7 +37,6 @@
 #include <utils/mu-utils.hh>
 #include <utils/mu-utils.hh>
 #include <utils/mu-option.hh>
-#include "mu-store-labels.hh"
 
 #include <message/mu-message.hh>
 
diff --git a/lib/mu-xapian-db.hh b/lib/mu-xapian-db.hh
index e6f6557..1f727a3 100644
--- a/lib/mu-xapian-db.hh
+++ b/lib/mu-xapian-db.hh
@@ -480,7 +480,7 @@ private:
 		if ((++changes_ < batch_size_) && !force)
 			return;
 		xapian_try([&]{
-			mu_debug("committing {} changes; transaction={}; "
+			mu_debug("committing {} change(s); transaction={}; "
 				 "forced={}", changes_,
 				 in_transaction() ? "yes" : "no",
 				 force ? "yes" : "no");