Added PersistentJsonStorageClass

PersistentJsonStorage is used to store persistent information in
json format. This class will be used by ReportManager to save
persistent report configuration.

Tested:
  - Added unit tests for new functionality
  - All other unit tests are passing

Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
Change-Id: Ib496e6782e849d910fe37c02c355047afda5c79c
diff --git a/src/interfaces/json_storage.hpp b/src/interfaces/json_storage.hpp
new file mode 100644
index 0000000..badd938
--- /dev/null
+++ b/src/interfaces/json_storage.hpp
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <boost/serialization/strong_typedef.hpp>
+#include <nlohmann/json.hpp>
+
+#include <filesystem>
+#include <optional>
+#include <string>
+
+namespace interfaces
+{
+
+class JsonStorage
+{
+  public:
+    BOOST_STRONG_TYPEDEF(std::filesystem::path, FilePath)
+    BOOST_STRONG_TYPEDEF(std::filesystem::path, DirectoryPath)
+
+    virtual ~JsonStorage() = default;
+
+    virtual void store(const FilePath& subPath, const nlohmann::json& data) = 0;
+    virtual bool remove(const FilePath& subPath) = 0;
+    virtual std::optional<nlohmann::json>
+        load(const FilePath& subPath) const = 0;
+    virtual std::vector<FilePath>
+        list(const DirectoryPath& subDirectory) const = 0;
+};
+
+} // namespace interfaces
diff --git a/src/persistent_json_storage.cpp b/src/persistent_json_storage.cpp
new file mode 100644
index 0000000..8fb3fe9
--- /dev/null
+++ b/src/persistent_json_storage.cpp
@@ -0,0 +1,144 @@
+#include "persistent_json_storage.hpp"
+
+#include <phosphor-logging/log.hpp>
+
+#include <fstream>
+#include <stdexcept>
+
+PersistentJsonStorage::PersistentJsonStorage(const DirectoryPath& directory) :
+    directory(directory)
+{}
+
+void PersistentJsonStorage::store(const FilePath& filePath,
+                                  const nlohmann::json& data)
+{
+    try
+    {
+        const auto path = join(directory, filePath);
+        std::error_code ec;
+
+        phosphor::logging::log<phosphor::logging::level::DEBUG>(
+            "Store to file", phosphor::logging::entry("path=%s", path.c_str()));
+
+        std::filesystem::create_directories(path.parent_path(), ec);
+        if (ec)
+        {
+            throw std::runtime_error(
+                "Unable to create directory for file: " + path.string() +
+                ", ec=" + std::to_string(ec.value()) + ": " + ec.message());
+        }
+
+        std::ofstream file(path);
+        file << data;
+        if (!file)
+        {
+            throw std::runtime_error("Unable to create file: " + path.string());
+        }
+
+        limitPermissions(path.parent_path());
+        limitPermissions(path);
+    }
+    catch (...)
+    {
+        remove(filePath);
+        throw;
+    }
+}
+
+bool PersistentJsonStorage::remove(const FilePath& filePath)
+{
+    const auto path = join(directory, filePath);
+    std::error_code ec;
+
+    auto removed = std::filesystem::remove(path, ec);
+    if (!removed)
+    {
+        phosphor::logging::log<phosphor::logging::level::ERR>(
+            "Unable to remove file",
+            phosphor::logging::entry("path=%s, ec= %lu: %s", path.c_str(),
+                                     ec.value(), ec.message().c_str()));
+        return false;
+    }
+
+    /* removes directory only if it is empty */
+    std::filesystem::remove(path.parent_path(), ec);
+
+    return true;
+}
+
+std::optional<nlohmann::json>
+    PersistentJsonStorage::load(const FilePath& filePath) const
+{
+    const auto path = join(directory, filePath);
+    if (!std::filesystem::exists(path))
+    {
+        return std::nullopt;
+    }
+
+    nlohmann::json result;
+
+    try
+    {
+        std::ifstream file(path);
+        file >> result;
+    }
+    catch (const std::exception& e)
+    {
+        phosphor::logging::log<phosphor::logging::level::ERR>(e.what());
+        return std::nullopt;
+    }
+
+    return result;
+}
+
+std::vector<interfaces::JsonStorage::FilePath>
+    PersistentJsonStorage::list(const DirectoryPath& subDirectory) const
+{
+    auto result = std::vector<FilePath>();
+    const auto path = join(directory, subDirectory);
+
+    if (!std::filesystem::exists(path))
+    {
+        return result;
+    }
+
+    for (const auto& p : std::filesystem::directory_iterator(path))
+    {
+        if (std::filesystem::is_directory(p.path()))
+        {
+            for (auto& item : list(DirectoryPath(p.path())))
+            {
+                result.emplace_back(std::move(item));
+            }
+        }
+        else
+        {
+            const auto item = std::filesystem::relative(
+                p.path().parent_path(), std::filesystem::path{directory});
+
+            if (std::find(result.begin(), result.end(), item) == result.end())
+            {
+                result.emplace_back(item);
+            }
+        }
+    }
+
+    return result;
+}
+
+std::filesystem::path
+    PersistentJsonStorage::join(const std::filesystem::path& left,
+                                const std::filesystem::path& right)
+{
+    return left / right;
+}
+
+void PersistentJsonStorage::limitPermissions(const std::filesystem::path& path)
+{
+    constexpr auto filePerms = std::filesystem::perms::owner_read |
+                               std::filesystem::perms::owner_write;
+    constexpr auto dirPerms = filePerms | std::filesystem::perms::owner_exec;
+    std::filesystem::permissions(
+        path, std::filesystem::is_directory(path) ? dirPerms : filePerms,
+        std::filesystem::perm_options::replace);
+}
diff --git a/src/persistent_json_storage.hpp b/src/persistent_json_storage.hpp
new file mode 100644
index 0000000..4b18aa1
--- /dev/null
+++ b/src/persistent_json_storage.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "interfaces/json_storage.hpp"
+
+class PersistentJsonStorage : public interfaces::JsonStorage
+{
+  public:
+    explicit PersistentJsonStorage(const DirectoryPath& directory);
+
+    void store(const FilePath& subPath, const nlohmann::json& data) override;
+    bool remove(const FilePath& subPath) override;
+    std::optional<nlohmann::json> load(const FilePath& subPath) const override;
+    std::vector<FilePath>
+        list(const DirectoryPath& subDirectory) const override;
+
+  private:
+    DirectoryPath directory;
+
+    static std::filesystem::path join(const std::filesystem::path&,
+                                      const std::filesystem::path&);
+    static void limitPermissions(const std::filesystem::path& path);
+};