base: Add get_active_transaction_info() method

The method returns unique_ptr to ActiveTransactionInfo if a transaction
is running, nullptr otherwise.

Author: m-blaha

include/libdnf5/base/base.hpp

@@ -20,6 +20,7 @@
 #ifndef LIBDNF5_BASE_BASE_HPP
 #define LIBDNF5_BASE_BASE_HPP
 
+#include "libdnf5/base/active_transaction_info.hpp"
 #include "libdnf5/base/base_weak.hpp"
 #include "libdnf5/common/exception.hpp"
 #include "libdnf5/common/impl_ptr.hpp"
@@ -132,6 +133,10 @@ class LIBDNF_API Base {
     /// Gets base variables. They can be used in configuration files. Syntax in the config - ${var_name} or $var_name.
     VarsWeakPtr get_vars();
 
+    /// Returns information about the currently active transaction, if any.
+    /// @return unique_ptr to ActiveTransactionInfo if a transaction is running, nullptr otherwise
+    std::unique_ptr<base::ActiveTransactionInfo> get_active_transaction_info();
+
     libdnf5::BaseWeakPtr get_weak_ptr();
 
 private:

libdnf5/base/base.cpp

@@ -38,6 +38,7 @@
 #include "libdnf5/conf/config_parser.hpp"
 #include "libdnf5/conf/const.hpp"
 #include "libdnf5/utils/bgettext/bgettext-mark-domain.h"
+#include "libdnf5/utils/locker.hpp"
 
 #include <atomic>
 #include <cstdlib>
@@ -300,6 +301,29 @@ VarsWeakPtr Base::get_vars() {
     return {&p_impl->vars, &p_impl->vars_guard};
 }
 
+std::unique_ptr<base::ActiveTransactionInfo> Base::get_active_transaction_info() {
+    std::filesystem::path lock_file_path = get_config().get_installroot_option().get_value();
+    lock_file_path /= std::filesystem::path(libdnf5::TRANSACTION_LOCK_FILEPATH).relative_path();
+
+    libdnf5::utils::Locker locker(lock_file_path.string());
+
+    // Try to acquire read lock - if successful, no write lock exists (no active transaction)
+    if (locker.read_lock()) {
+        return nullptr;
+    }
+
+    // Read lock failed - write lock exists, read content from the opened file descriptor
+    std::string content = locker.read_content();
+
+    if (content.empty()) {
+        // Empty lock file means no valid transaction info
+        return nullptr;
+    }
+
+    // Parse TOML content
+    return std::make_unique<base::ActiveTransactionInfo>(base::ActiveTransactionInfo::from_toml(content));
+}
+
 libdnf5::BaseWeakPtr Base::get_weak_ptr() {
     return {this, &base_guard};
 }