7 files changed, 350 insertions, 2 deletions

diff --git a/src/database/database-dummy.cpp b/src/database/database-dummy.cpp
index b56f341c5..629b2fb04 100644
--- a/src/database/database-dummy.cpp
+++ b/src/database/database-dummy.cpp
@@ -80,3 +80,41 @@ void Database_Dummy::listPlayers(std::vector<std::string> &res)
 		res.emplace_back(player);
 	}
 }
+
+bool Database_Dummy::getModEntries(const std::string &modname, StringMap *storage)
+{
+	const auto mod_pair = m_mod_meta_database.find(modname);
+	if (mod_pair != m_mod_meta_database.cend()) {
+		for (const auto &pair : mod_pair->second) {
+			(*storage)[pair.first] = pair.second;
+		}
+	}
+	return true;
+}
+
+bool Database_Dummy::setModEntry(const std::string &modname,
+	const std::string &key, const std::string &value)
+{
+	auto mod_pair = m_mod_meta_database.find(modname);
+	if (mod_pair == m_mod_meta_database.end()) {
+		m_mod_meta_database[modname] = StringMap({{key, value}});
+	} else {
+		mod_pair->second[key] = value;
+	}
+	return true;
+}
+
+bool Database_Dummy::removeModEntry(const std::string &modname, const std::string &key)
+{
+	auto mod_pair = m_mod_meta_database.find(modname);
+	if (mod_pair != m_mod_meta_database.end())
+		return mod_pair->second.erase(key) > 0;
+	return false;
+}
+
+void Database_Dummy::listMods(std::vector<std::string> *res)
+{
+	for (const auto &pair : m_mod_meta_database) {
+		res->push_back(pair.first);
+	}
+}
diff --git a/src/database/database-dummy.h b/src/database/database-dummy.h
index b69919f84..44b9e8d68 100644
--- a/src/database/database-dummy.h
+++ b/src/database/database-dummy.h
@@ -24,7 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "database.h"
 #include "irrlichttypes.h"
 
-class Database_Dummy : public MapDatabase, public PlayerDatabase
+class Database_Dummy : public MapDatabase, public PlayerDatabase, public ModMetadataDatabase
 {
 public:
 	bool saveBlock(const v3s16 &pos, const std::string &data);
@@ -37,10 +37,17 @@ public:
 	bool removePlayer(const std::string &name);
 	void listPlayers(std::vector<std::string> &res);
 
+	bool getModEntries(const std::string &modname, StringMap *storage);
+	bool setModEntry(const std::string &modname,
+			const std::string &key, const std::string &value);
+	bool removeModEntry(const std::string &modname, const std::string &key);
+	void listMods(std::vector<std::string> *res);
+
 	void beginSave() {}
 	void endSave() {}
 
 private:
 	std::map<s64, std::string> m_database;
 	std::set<std::string> m_player_database;
+	std::unordered_map<std::string, StringMap> m_mod_meta_database;
 };
diff --git a/src/database/database-files.cpp b/src/database/database-files.cpp
index d9d113b4e..9021ae61b 100644
--- a/src/database/database-files.cpp
+++ b/src/database/database-files.cpp
@@ -18,7 +18,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 */
 
 #include <cassert>
-#include <json/json.h>
 #include "convert_json.h"
 #include "database-files.h"
 #include "remoteplayer.h"
@@ -376,3 +375,138 @@ bool AuthDatabaseFiles::writeAuthFile()
 	}
 	return true;
 }
+
+ModMetadataDatabaseFiles::ModMetadataDatabaseFiles(const std::string &savedir):
+	m_storage_dir(savedir + DIR_DELIM + "mod_storage")
+{
+}
+
+bool ModMetadataDatabaseFiles::getModEntries(const std::string &modname, StringMap *storage)
+{
+	Json::Value *meta = getOrCreateJson(modname);
+	if (!meta)
+		return false;
+
+	const Json::Value::Members attr_list = meta->getMemberNames();
+	for (const auto &it : attr_list) {
+		Json::Value attr_value = (*meta)[it];
+		(*storage)[it] = attr_value.asString();
+	}
+
+	return true;
+}
+
+bool ModMetadataDatabaseFiles::setModEntry(const std::string &modname,
+	const std::string &key, const std::string &value)
+{
+	Json::Value *meta = getOrCreateJson(modname);
+	if (!meta)
+		return false;
+
+	(*meta)[key] = Json::Value(value);
+	m_modified.insert(modname);
+
+	return true;
+}
+
+bool ModMetadataDatabaseFiles::removeModEntry(const std::string &modname,
+		const std::string &key)
+{
+	Json::Value *meta = getOrCreateJson(modname);
+	if (!meta)
+		return false;
+
+	Json::Value removed;
+	if (meta->removeMember(key, &removed)) {
+		m_modified.insert(modname);
+		return true;
+	}
+	return false;
+}
+
+void ModMetadataDatabaseFiles::beginSave()
+{
+}
+
+void ModMetadataDatabaseFiles::endSave()
+{
+	if (!fs::CreateAllDirs(m_storage_dir)) {
+		errorstream << "ModMetadataDatabaseFiles: Unable to save. '" << m_storage_dir
+				<< "' tree cannot be created." << std::endl;
+		return;
+	}
+
+	for (auto it = m_modified.begin(); it != m_modified.end();) {
+		const std::string &modname = *it;
+
+		if (!fs::PathExists(m_storage_dir)) {
+			if (!fs::CreateAllDirs(m_storage_dir)) {
+				errorstream << "ModMetadataDatabaseFiles[" << modname
+						<< "]: Unable to save. '" << m_storage_dir
+						<< "' tree cannot be created." << std::endl;
+				++it;
+				continue;
+			}
+		} else if (!fs::IsDir(m_storage_dir)) {
+			errorstream << "ModMetadataDatabaseFiles[" << modname << "]: Unable to save. '"
+					<< m_storage_dir << "' is not a directory." << std::endl;
+			++it;
+			continue;
+		}
+
+		const Json::Value &json = m_mod_meta[modname];
+
+		if (!fs::safeWriteToFile(m_storage_dir + DIR_DELIM + modname, fastWriteJson(json))) {
+			errorstream << "ModMetadataDatabaseFiles[" << modname
+					<< "]: failed write file." << std::endl;
+			++it;
+			continue;
+		}
+
+		it = m_modified.erase(it);
+	}
+}
+
+void ModMetadataDatabaseFiles::listMods(std::vector<std::string> *res)
+{
+	// List in-memory metadata first.
+	for (const auto &pair : m_mod_meta) {
+		res->push_back(pair.first);
+	}
+
+	// List other metadata present in the filesystem.
+	for (const auto &entry : fs::GetDirListing(m_storage_dir)) {
+		if (!entry.dir && m_mod_meta.count(entry.name) == 0)
+			res->push_back(entry.name);
+	}
+}
+
+Json::Value *ModMetadataDatabaseFiles::getOrCreateJson(const std::string &modname)
+{
+	auto found = m_mod_meta.find(modname);
+	if (found == m_mod_meta.end()) {
+		fs::CreateAllDirs(m_storage_dir);
+
+		Json::Value meta(Json::objectValue);
+
+		std::string path = m_storage_dir + DIR_DELIM + modname;
+		if (fs::PathExists(path)) {
+			std::ifstream is(path.c_str(), std::ios_base::binary);
+
+			Json::CharReaderBuilder builder;
+			builder.settings_["collectComments"] = false;
+			std::string errs;
+
+			if (!Json::parseFromStream(builder, is, &meta, &errs)) {
+				errorstream << "ModMetadataDatabaseFiles[" << modname
+						<< "]: failed read data (Json decoding failure). Message: "
+						<< errs << std::endl;
+				return nullptr;
+			}
+		}
+
+		return &(m_mod_meta[modname] = meta);
+	} else {
+		return &found->second;
+	}
+}
diff --git a/src/database/database-files.h b/src/database/database-files.h
index e647a2e24..962e4d7bb 100644
--- a/src/database/database-files.h
+++ b/src/database/database-files.h
@@ -25,6 +25,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "database.h"
 #include <unordered_map>
+#include <unordered_set>
+#include <json/json.h>
 
 class PlayerDatabaseFiles : public PlayerDatabase
 {
@@ -69,3 +71,27 @@ private:
 	bool readAuthFile();
 	bool writeAuthFile();
 };
+
+class ModMetadataDatabaseFiles : public ModMetadataDatabase
+{
+public:
+	ModMetadataDatabaseFiles(const std::string &savedir);
+	virtual ~ModMetadataDatabaseFiles() = default;
+
+	virtual bool getModEntries(const std::string &modname, StringMap *storage);
+	virtual bool setModEntry(const std::string &modname,
+		const std::string &key, const std::string &value);
+	virtual bool removeModEntry(const std::string &modname, const std::string &key);
+	virtual void listMods(std::vector<std::string> *res);
+
+	virtual void beginSave();
+	virtual void endSave();
+
+private:
+	Json::Value *getOrCreateJson(const std::string &modname);
+	bool writeJson(const std::string &modname, const Json::Value &json);
+
+	std::string m_storage_dir;
+	std::unordered_map<std::string, Json::Value> m_mod_meta;
+	std::unordered_set<std::string> m_modified;
+};
diff --git a/src/database/database-sqlite3.cpp b/src/database/database-sqlite3.cpp
index 898acc265..e9442118e 100644
--- a/src/database/database-sqlite3.cpp
+++ b/src/database/database-sqlite3.cpp
@@ -779,3 +779,108 @@ void AuthDatabaseSQLite3::writePrivileges(const AuthEntry &authEntry)
 		sqlite3_reset(m_stmt_write_privs);
 	}
 }
+
+ModMetadataDatabaseSQLite3::ModMetadataDatabaseSQLite3(const std::string &savedir):
+	Database_SQLite3(savedir, "mod_storage"), ModMetadataDatabase()
+{
+}
+
+ModMetadataDatabaseSQLite3::~ModMetadataDatabaseSQLite3()
+{
+	FINALIZE_STATEMENT(m_stmt_remove)
+	FINALIZE_STATEMENT(m_stmt_set)
+	FINALIZE_STATEMENT(m_stmt_get)
+}
+
+void ModMetadataDatabaseSQLite3::createDatabase()
+{
+	assert(m_database); // Pre-condition
+
+	SQLOK(sqlite3_exec(m_database,
+		"CREATE TABLE IF NOT EXISTS `entries` (\n"
+			"	`modname` TEXT NOT NULL,\n"
+			"	`key` BLOB NOT NULL,\n"
+			"	`value` BLOB NOT NULL,\n"
+			"	PRIMARY KEY (`modname`, `key`)\n"
+			");\n",
+		NULL, NULL, NULL),
+		"Failed to create database table");
+}
+
+void ModMetadataDatabaseSQLite3::initStatements()
+{
+	PREPARE_STATEMENT(get, "SELECT `key`, `value` FROM `entries` WHERE `modname` = ?");
+	PREPARE_STATEMENT(set,
+		"REPLACE INTO `entries` (`modname`, `key`, `value`) VALUES (?, ?, ?)");
+	PREPARE_STATEMENT(remove, "DELETE FROM `entries` WHERE `modname` = ? AND `key` = ?");
+}
+
+bool ModMetadataDatabaseSQLite3::getModEntries(const std::string &modname, StringMap *storage)
+{
+	verifyDatabase();
+
+	str_to_sqlite(m_stmt_get, 1, modname);
+	while (sqlite3_step(m_stmt_get) == SQLITE_ROW) {
+		const char *key_data = (const char *) sqlite3_column_blob(m_stmt_get, 0);
+		size_t key_len = sqlite3_column_bytes(m_stmt_get, 0);
+		const char *value_data = (const char *) sqlite3_column_blob(m_stmt_get, 1);
+		size_t value_len = sqlite3_column_bytes(m_stmt_get, 1);
+		(*storage)[std::string(key_data, key_len)] = std::string(value_data, value_len);
+	}
+	sqlite3_vrfy(sqlite3_errcode(m_database), SQLITE_DONE);
+
+	sqlite3_reset(m_stmt_get);
+
+	return true;
+}
+
+bool ModMetadataDatabaseSQLite3::setModEntry(const std::string &modname,
+	const std::string &key, const std::string &value)
+{
+	verifyDatabase();
+
+	str_to_sqlite(m_stmt_set, 1, modname);
+	SQLOK(sqlite3_bind_blob(m_stmt_set, 2, key.data(), key.size(), NULL),
+		"Internal error: failed to bind query at " __FILE__ ":" TOSTRING(__LINE__));
+	SQLOK(sqlite3_bind_blob(m_stmt_set, 3, value.data(), value.size(), NULL),
+		"Internal error: failed to bind query at " __FILE__ ":" TOSTRING(__LINE__));
+	SQLRES(sqlite3_step(m_stmt_set), SQLITE_DONE, "Failed to set mod entry")
+
+	sqlite3_reset(m_stmt_set);
+
+	return true;
+}
+
+bool ModMetadataDatabaseSQLite3::removeModEntry(const std::string &modname,
+		const std::string &key)
+{
+	verifyDatabase();
+
+	str_to_sqlite(m_stmt_remove, 1, modname);
+	SQLOK(sqlite3_bind_blob(m_stmt_remove, 2, key.data(), key.size(), NULL),
+		"Internal error: failed to bind query at " __FILE__ ":" TOSTRING(__LINE__));
+	sqlite3_vrfy(sqlite3_step(m_stmt_remove), SQLITE_DONE);
+	int changes = sqlite3_changes(m_database);
+
+	sqlite3_reset(m_stmt_remove);
+
+	return changes > 0;
+}
+
+void ModMetadataDatabaseSQLite3::listMods(std::vector<std::string> *res)
+{
+	verifyDatabase();
+
+	char *errmsg;
+	int status = sqlite3_exec(m_database,
+		"SELECT `modname` FROM `entries` GROUP BY `modname`;",
+		[](void *res_vp, int n_col, char **cols, char **col_names) -> int {
+			((decltype(res)) res_vp)->emplace_back(cols[0]);
+			return 0;
+		}, (void *) res, &errmsg);
+	if (status != SQLITE_OK) {
+		DatabaseException e(std::string("Error trying to list mods with metadata: ") + errmsg);
+		sqlite3_free(errmsg);
+		throw e;
+	}
+}
diff --git a/src/database/database-sqlite3.h b/src/database/database-sqlite3.h
index d7202a918..5e3d7c96c 100644
--- a/src/database/database-sqlite3.h
+++ b/src/database/database-sqlite3.h
@@ -232,3 +232,28 @@ private:
 	sqlite3_stmt *m_stmt_delete_privs = nullptr;
 	sqlite3_stmt *m_stmt_last_insert_rowid = nullptr;
 };
+
+class ModMetadataDatabaseSQLite3 : private Database_SQLite3, public ModMetadataDatabase
+{
+public:
+	ModMetadataDatabaseSQLite3(const std::string &savedir);
+	virtual ~ModMetadataDatabaseSQLite3();
+
+	virtual bool getModEntries(const std::string &modname, StringMap *storage);
+	virtual bool setModEntry(const std::string &modname,
+		const std::string &key, const std::string &value);
+	virtual bool removeModEntry(const std::string &modname, const std::string &key);
+	virtual void listMods(std::vector<std::string> *res);
+
+	virtual void beginSave() { Database_SQLite3::beginSave(); }
+	virtual void endSave() { Database_SQLite3::endSave(); }
+
+protected:
+	virtual void createDatabase();
+	virtual void initStatements();
+
+private:
+	sqlite3_stmt *m_stmt_get = nullptr;
+	sqlite3_stmt *m_stmt_set = nullptr;
+	sqlite3_stmt *m_stmt_remove = nullptr;
+};
diff --git a/src/database/database.h b/src/database/database.h
index b7d551935..fbb5befea 100644
--- a/src/database/database.h
+++ b/src/database/database.h
@@ -25,6 +25,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "irr_v3d.h"
 #include "irrlichttypes.h"
 #include "util/basic_macros.h"
+#include "util/string.h"
 
 class Database
 {
@@ -84,3 +85,15 @@ public:
 	virtual void listNames(std::vector<std::string> &res) = 0;
 	virtual void reload() = 0;
 };
+
+class ModMetadataDatabase : public Database
+{
+public:
+	virtual ~ModMetadataDatabase() = default;
+
+	virtual bool getModEntries(const std::string &modname, StringMap *storage) = 0;
+	virtual bool setModEntry(const std::string &modname,
+		const std::string &key, const std::string &value) = 0;
+	virtual bool removeModEntry(const std::string &modname, const std::string &key) = 0;
+	virtual void listMods(std::vector<std::string> *res) = 0;
+};