clean up using directives and type alias

Most C++ style guides try to avoid using directives in headers and also
suggest using type alias carefully, according to which, this change does
the following clean up:

1. used Enum class to represent Certificate type
2. removed all using directives: e.g. the phosphor logging namespace;
instead, this change uses using declarations
3. removed unnecessary type alias; in existing codes, we only support
strings as types of UnitToRestart, InstallPath, UploadPath, etc; this
change uses std::string directly
4. moved all alias outside any class scope into source files or an
internal namespace
5. renamed types, constants, classes as per OpenBMC style guide
6. fixed all compilation errors and some warnings after the refactoring;
built with both Clang & GCC

Reference:
https://docs.microsoft.com/en-us/cpp/cpp/header-files-cpp?view=msvc-170#what-to-put-in-a-header-file
https://google.github.io/styleguide/cppguide.html#Namespaces

Tested:
Unit tests

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I58e026934a4e969f4d8877801c8f3c671990468a
diff --git a/certificate.hpp b/certificate.hpp
index ce2a737..46479e4 100644
--- a/certificate.hpp
+++ b/certificate.hpp
@@ -5,6 +5,9 @@
 #include <openssl/x509.h>
 
 #include <filesystem>
+#include <functional>
+#include <memory>
+#include <optional>
 #include <phosphor-logging/elog.hpp>
 #include <xyz/openbmc_project/Certs/Certificate/server.hpp>
 #include <xyz/openbmc_project/Certs/Replace/server.hpp>
@@ -12,45 +15,68 @@
 
 namespace phosphor::certs
 {
-using DeleteIface = sdbusplus::xyz::openbmc_project::Object::server::Delete;
-using CertificateIface =
-    sdbusplus::xyz::openbmc_project::Certs::server::Certificate;
-using ReplaceIface = sdbusplus::xyz::openbmc_project::Certs::server::Replace;
-using CertIfaces = sdbusplus::server::object::object<CertificateIface,
-                                                     ReplaceIface, DeleteIface>;
 
-using CertificateType = std::string;
-using CertInstallPath = std::string;
-using CertUploadPath = std::string;
-using InputType = std::string;
+// Certificate types
+enum class CertificateType
+{
+    Authority,
+    Server,
+    Client,
+    Unsupported,
+};
+
+inline constexpr const char* certificateTypeToString(CertificateType type)
+{
+    switch (type)
+    {
+        case CertificateType::Authority:
+            return "authority";
+        case CertificateType::Server:
+            return "server";
+        case CertificateType::Client:
+            return "client";
+        default:
+            return "unsupported";
+    }
+}
+
+inline constexpr CertificateType stringToCertificateType(std::string_view type)
+{
+    if (type == "authority")
+    {
+        return CertificateType::Authority;
+    }
+    if (type == "server")
+    {
+        return CertificateType::Server;
+    }
+    if (type == "client")
+    {
+        return CertificateType::Client;
+    }
+    return CertificateType::Unsupported;
+}
+
+namespace internal
+{
+using CertificateInterface = sdbusplus::server::object_t<
+    sdbusplus::xyz::openbmc_project::Certs::server::Certificate,
+    sdbusplus::xyz::openbmc_project::Certs::server::Replace,
+    sdbusplus::xyz::openbmc_project::Object::server::Delete>;
 using InstallFunc = std::function<void(const std::string&)>;
 using AppendPrivKeyFunc = std::function<void(const std::string&)>;
-using CertWatchPtr = std::unique_ptr<Watch>;
-using namespace phosphor::logging;
-
-// for placeholders
-using namespace std::placeholders;
-namespace fs = std::filesystem;
+using X509Ptr = std::unique_ptr<X509, decltype(&::X509_free)>;
+} // namespace internal
 
 class Manager; // Forward declaration for Certificate Manager.
 
-// Supported Types.
-static constexpr auto SERVER = "server";
-static constexpr auto CLIENT = "client";
-static constexpr auto AUTHORITY = "authority";
-
-// RAII support for openSSL functions.
-using X509_Ptr = std::unique_ptr<X509, decltype(&::X509_free)>;
-using X509_STORE_CTX_Ptr =
-    std::unique_ptr<X509_STORE_CTX, decltype(&::X509_STORE_CTX_free)>;
-
 /** @class Certificate
  *  @brief OpenBMC Certificate entry implementation.
  *  @details A concrete implementation for the
  *  xyz.openbmc_project.Certs.Certificate DBus API
  *  xyz.openbmc_project.Certs.Install DBus API
  */
-class Certificate : public CertIfaces
+class Certificate : public internal::CertificateInterface
 {
   public:
     Certificate() = delete;
@@ -66,12 +92,12 @@
      *  @param[in] type - Type of the certificate
      *  @param[in] installPath - Path of the certificate to install
      *  @param[in] uploadPath - Path of the certificate file to upload
-     *  @param[in] watchPtr - watch on self signed certificate pointer
+     *  @param[in] watchPtr - watch on self signed certificate
+     *  @param[in] parent - the manager that owns the certificate
      */
     Certificate(sdbusplus::bus::bus& bus, const std::string& objPath,
-                const CertificateType& type, const CertInstallPath& installPath,
-                const CertUploadPath& uploadPath, const CertWatchPtr& watchPtr,
-                Manager& parent);
+                CertificateType type, const std::string& installPath,
+                const std::string& uploadPath, Watch* watch, Manager& parent);
 
     /** @brief Validate and Replace/Install the certificate file
      *  Install/Replace the existing certificate file with another
@@ -127,7 +153,7 @@
      *
      * @return void
      */
-    void validateCertificateStartDate(const X509_Ptr& cert);
+    void validateCertificateStartDate(X509& cert);
 
     /**
      * @brief Populate certificate properties by parsing given certificate file
@@ -142,7 +168,7 @@
      *  @param[in] filePath - Certificate and key full file path.
      *  @return pointer to the X509 structure.
      */
-    X509_Ptr loadCert(const std::string& filePath);
+    internal::X509Ptr loadCert(const std::string& filePath);
 
     /** @brief Check and append private key to the certificate file
      *         If private key is not present in the certificate file append the
@@ -222,10 +248,7 @@
     std::string generateCertFilePath(const std::string& certSrcFilePath);
 
     /** @brief Type specific function pointer map */
-    std::unordered_map<InputType, InstallFunc> typeFuncMap;
-
-    /** @brief sdbusplus handler */
-    sdbusplus::bus::bus& bus;
+    std::unordered_map<CertificateType, internal::InstallFunc> typeFuncMap;
 
     /** @brief object path */
     std::string objectPath;
@@ -240,13 +263,16 @@
     std::string certFilePath;
 
     /** @brief Certificate file installation path */
-    CertInstallPath certInstallPath;
+    std::string certInstallPath;
 
     /** @brief Type specific function pointer map for appending private key */
-    std::unordered_map<InputType, AppendPrivKeyFunc> appendKeyMap;
+    std::unordered_map<CertificateType, internal::AppendPrivKeyFunc>
+        appendKeyMap;
 
-    /** @brief Certificate file create/update watch */
-    const CertWatchPtr& certWatchPtr;
+    /** @brief Certificate file create/update watch
+     * Note that Certificate object doesn't own the pointer
+     */
+    Watch* certWatch;
 
     /** @brief Reference to Certificate Manager */
     Manager& manager;