From 20f3972ce08dd71cf309ad34e6a8d00dbdc69209 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 18 Feb 2019 20:39:31 +0000
Subject: Add traits based generic bindParam function

---
 libdbpp/command.h               | 55 +++++++++++++++++++++++++++++++++++++++++
 libdbpp/unittests/testUtils.cpp | 48 +++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)

diff --git a/libdbpp/command.h b/libdbpp/command.h
index 6f66559..09377a9 100644
--- a/libdbpp/command.h
+++ b/libdbpp/command.h
@@ -103,6 +103,61 @@ namespace DB {
 			/// The SQL statement.
 			const std::string sql;
 
+			/// Bind a parameter by type based on C++ traits to parameter i.
+			template<typename O>
+			inline auto bindParam(unsigned int i, const O & o)
+			{
+				if constexpr (std::is_null_pointer<O>::value) {
+					bindNull(i);
+				}
+				else if constexpr (std::is_same<O, std::nullopt_t>::value) {
+					bindNull(i);
+				}
+				else if constexpr (std::is_same<O, bool>::value) {
+					bindParamB(i, o);
+				}
+				else if constexpr (std::is_floating_point<O>::value) {
+					bindParamF(i, o);
+				}
+				else if constexpr (std::is_same<O, boost::posix_time::time_duration>::value) {
+					bindParamT(i, o);
+				}
+				else if constexpr (std::is_same<O, boost::posix_time::ptime>::value) {
+					bindParamT(i, o);
+				}
+				else if constexpr (std::is_same<O, Blob>::value) {
+					bindParamBLOB(i, o);
+				}
+				else if constexpr (std::is_integral<O>::value && !std::is_pointer<O>::value) {
+					bindParamI(i, o);
+				}
+				else if constexpr (std::is_convertible<O, std::string_view>::value && std::is_pointer<O>::value) {
+					if (o) {
+						bindParamS(i, o);
+					}
+					else {
+						bindNull(i);
+					}
+				}
+				else if constexpr (std::is_same<O, Glib::ustring>::value) {
+					bindParamS(i, o);
+				}
+				else if constexpr (std::is_convertible<O, std::string_view>::value) {
+					bindParamS(i, o);
+				}
+				else if constexpr (std::is_constructible<bool, const O &>::value) {
+					if (o) {
+						bindParam(i, *o);
+					}
+					else {
+						bindNull(i);
+					}
+				}
+				else {
+					static_assert(!&o, "No suitable trait");
+				}
+			}
+
 #define OPTWRAPPER(func) \
 			template<typename O> \
 			inline auto \
diff --git a/libdbpp/unittests/testUtils.cpp b/libdbpp/unittests/testUtils.cpp
index 0e90a94..67c1751 100644
--- a/libdbpp/unittests/testUtils.cpp
+++ b/libdbpp/unittests/testUtils.cpp
@@ -302,6 +302,54 @@ BOOST_AUTO_TEST_CASE( bindIntPtr )
 	BOOST_REQUIRE_EQUAL(159, total);
 }
 
+BOOST_FIXTURE_TEST_CASE( traits_bind, DB::TestCore )
+{
+	auto db = DB::ConnectionPtr(DB::MockDatabase::openConnectionTo("pqmock"));
+	auto cmd = db->select("select x is null, format('%s', x) from (select ? x) d");
+	auto check = [cmd](int line, const auto & v, bool isNull, const auto & strval) {
+		BOOST_TEST_CONTEXT("line " << line) {
+			cmd->bindParam(0, v);
+			for (const auto & [null, str] : cmd->as<bool, std::string_view>()) {
+				BOOST_CHECK_EQUAL(null, isNull);
+				BOOST_CHECK_EQUAL(str, strval);
+			}
+		}
+	};
+	check(__LINE__, std::nullopt, true, "");
+	check(__LINE__, nullptr, true, "");
+	check(__LINE__, testInt, false, "43");
+	check(__LINE__, std::make_unique<short>(testInt), false, "43");
+	check(__LINE__, std::unique_ptr<short>(), true, "");
+	check(__LINE__, (unsigned int)testInt, false, "43");
+	check(__LINE__, &testInt, false, "43");
+	check(__LINE__, testDouble, false, "3.14");
+	check(__LINE__, std::make_shared<float>(testDouble), false, "3.14");
+	check(__LINE__, std::shared_ptr<float>(), true, "");
+	check(__LINE__, (float)testDouble, false, "3.14");
+	check(__LINE__, &testDouble, false, "3.14");
+	check(__LINE__, testString, false, testString);
+	check(__LINE__, &testString, false, testString);
+	check(__LINE__, "str", false, "str");
+	check(__LINE__, "", false, "");
+	const char * const nullstr = nullptr;
+	check(__LINE__, nullstr, true, "");
+	const char * const str = "str";
+	check(__LINE__, str, false, "str");
+	check(__LINE__, std::string(), false, "");
+	check(__LINE__, std::string_view(), false, "");
+	check(__LINE__, Glib::ustring(), false, "");
+	check(__LINE__, Glib::ustring("foo"), false, "foo");
+	check(__LINE__, testDateTime, false, "2015-05-02T01:36:33");
+	check(__LINE__, testInterval, false, "01:02:03");
+	check(__LINE__, &testInterval, false, "01:02:03");
+	decltype(testInterval) * nullInterval = nullptr;
+	check(__LINE__, nullInterval, true, "");
+	check(__LINE__, true, false, "1");
+	check(__LINE__, false, false, "0");
+	check(__LINE__, std::optional<int>(4), false, "4");
+	check(__LINE__, std::optional<int>(), true, "");
+}
+
 BOOST_AUTO_TEST_CASE( testBlobRaw )
 {
 	DB::Blob ptr(this, 1);
-- 
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