From b2f4192a4f9f69667ec283bed71b0755389dce7e Mon Sep 17 00:00:00 2001
From: "Dr. Patrick Urbanke" <patrick@getml.com>
Date: Fri, 9 May 2025 18:17:51 +0200
Subject: [PATCH] Added to_sql

---
 include/sqlgen.hpp                         |  2 +
 include/sqlgen/CreateTable.hpp             | 15 +++++++
 include/sqlgen/Insert.hpp                  | 15 +++++++
 include/sqlgen/postgres.hpp                |  1 +
 include/sqlgen/postgres/Connection.hpp     |  4 +-
 include/sqlgen/postgres/to_sql.hpp         | 14 ++++++-
 include/sqlgen/sqlite/Connection.hpp       |  2 +-
 include/sqlgen/sqlite/to_sql.hpp           | 13 +++++-
 include/sqlgen/transpilation/to_sql.hpp    | 48 ++++++++++++++++++++++
 src/sqlgen/postgres/Connection.cpp         |  2 +-
 src/sqlgen/postgres/to_sql.cpp             |  2 +-
 src/sqlgen/sqlite/Connection.cpp           |  4 +-
 src/sqlgen/sqlite/to_sql.cpp               |  2 +-
 tests/postgres/test_create_table_dry.cpp   | 23 +++++++++++
 tests/postgres/test_insert_dry.cpp         | 24 +++++++++++
 tests/postgres/test_to_select_from.cpp     | 30 --------------
 tests/postgres/test_to_select_from_dry.cpp | 24 +++++++++++
 tests/postgres/test_where_dry.cpp          | 29 +++++++++++++
 18 files changed, 214 insertions(+), 40 deletions(-)
 create mode 100644 include/sqlgen/CreateTable.hpp
 create mode 100644 include/sqlgen/Insert.hpp
 create mode 100644 include/sqlgen/transpilation/to_sql.hpp
 create mode 100644 tests/postgres/test_create_table_dry.cpp
 create mode 100644 tests/postgres/test_insert_dry.cpp
 delete mode 100644 tests/postgres/test_to_select_from.cpp
 create mode 100644 tests/postgres/test_to_select_from_dry.cpp
 create mode 100644 tests/postgres/test_where_dry.cpp

diff --git a/include/sqlgen.hpp b/include/sqlgen.hpp
index 2921460..d51595b 100644
--- a/include/sqlgen.hpp
+++ b/include/sqlgen.hpp
@@ -2,7 +2,9 @@
 #define SQLGEN_HPP_
 
 #include "sqlgen/Connection.hpp"
+#include "sqlgen/CreateTable.hpp"
 #include "sqlgen/Flatten.hpp"
+#include "sqlgen/Insert.hpp"
 #include "sqlgen/Iterator.hpp"
 #include "sqlgen/IteratorBase.hpp"
 #include "sqlgen/Literal.hpp"
diff --git a/include/sqlgen/CreateTable.hpp b/include/sqlgen/CreateTable.hpp
new file mode 100644
index 0000000..1f59291
--- /dev/null
+++ b/include/sqlgen/CreateTable.hpp
@@ -0,0 +1,15 @@
+#ifndef SQLGEN_CREATETABLE_HPP_
+#define SQLGEN_CREATETABLE_HPP_
+
+#include <rfl.hpp>
+
+namespace sqlgen {
+
+/// Helper class for to_sql.
+template <class T>
+struct CreateTable {};
+
+};  // namespace sqlgen
+
+#endif
+
diff --git a/include/sqlgen/Insert.hpp b/include/sqlgen/Insert.hpp
new file mode 100644
index 0000000..481ed1d
--- /dev/null
+++ b/include/sqlgen/Insert.hpp
@@ -0,0 +1,15 @@
+#ifndef SQLGEN_INSERT_HPP_
+#define SQLGEN_INSERT_HPP_
+
+#include <rfl.hpp>
+
+namespace sqlgen {
+
+/// Helper class for to_sql.
+template <class T>
+struct Insert {};
+
+};  // namespace sqlgen
+
+#endif
+
diff --git a/include/sqlgen/postgres.hpp b/include/sqlgen/postgres.hpp
index 5ee513b..1ff83b4 100644
--- a/include/sqlgen/postgres.hpp
+++ b/include/sqlgen/postgres.hpp
@@ -4,5 +4,6 @@
 #include "../sqlgen.hpp"
 #include "postgres/Credentials.hpp"
 #include "postgres/connect.hpp"
+#include "postgres/to_sql.hpp"
 
 #endif
diff --git a/include/sqlgen/postgres/Connection.hpp b/include/sqlgen/postgres/Connection.hpp
index 2a9824e..46f76b8 100644
--- a/include/sqlgen/postgres/Connection.hpp
+++ b/include/sqlgen/postgres/Connection.hpp
@@ -41,11 +41,11 @@ class Connection : public sqlgen::Connection {
   Result<Ref<IteratorBase>> read(const dynamic::SelectFrom& _query) final;
 
   std::string to_sql(const dynamic::Statement& _stmt) noexcept final {
-    return postgres::to_sql(_stmt);
+    return postgres::to_sql_impl(_stmt);
   }
 
   Result<Nothing> start_write(const dynamic::Insert& _stmt) final {
-    return execute(to_sql(_stmt));
+    return execute(postgres::to_sql_impl(_stmt));
   }
 
   Result<Nothing> end_write() final;
diff --git a/include/sqlgen/postgres/to_sql.hpp b/include/sqlgen/postgres/to_sql.hpp
index 2323405..da663b4 100644
--- a/include/sqlgen/postgres/to_sql.hpp
+++ b/include/sqlgen/postgres/to_sql.hpp
@@ -2,13 +2,25 @@
 #define SQLGEN_POSTGRES_TO_SQL_HPP_
 
 #include <string>
+#include <type_traits>
 
 #include "../dynamic/Statement.hpp"
+#include "../transpilation/to_sql.hpp"
 
 namespace sqlgen::postgres {
 
 /// Transpiles a dynamic general SQL statement to the postgres dialect.
-std::string to_sql(const dynamic::Statement& _stmt) noexcept;
+std::string to_sql_impl(const dynamic::Statement& _stmt) noexcept;
+
+/// Transpiles any  SQL statement to the postgres dialect.
+template <class T>
+std::string to_sql(const T& _t) noexcept {
+  if constexpr (std::is_same_v<std::remove_cvref_t<T>, dynamic::Statement>) {
+    return to_sql_impl(_t);
+  } else {
+    return to_sql_impl(transpilation::to_sql(_t));
+  }
+}
 
 }  // namespace sqlgen::postgres
 
diff --git a/include/sqlgen/sqlite/Connection.hpp b/include/sqlgen/sqlite/Connection.hpp
index 562807a..0ba0851 100644
--- a/include/sqlgen/sqlite/Connection.hpp
+++ b/include/sqlgen/sqlite/Connection.hpp
@@ -37,7 +37,7 @@ class Connection : public sqlgen::Connection {
   Result<Ref<IteratorBase>> read(const dynamic::SelectFrom& _query) final;
 
   std::string to_sql(const dynamic::Statement& _stmt) noexcept final {
-    return sqlite::to_sql(_stmt);
+    return sqlite::to_sql_impl(_stmt);
   }
 
   Result<Nothing> start_write(const dynamic::Insert& _stmt) final;
diff --git a/include/sqlgen/sqlite/to_sql.hpp b/include/sqlgen/sqlite/to_sql.hpp
index 2fd5079..9959e30 100644
--- a/include/sqlgen/sqlite/to_sql.hpp
+++ b/include/sqlgen/sqlite/to_sql.hpp
@@ -4,11 +4,22 @@
 #include <string>
 
 #include "../dynamic/Statement.hpp"
+#include "../transpilation/to_sql.hpp"
 
 namespace sqlgen::sqlite {
 
 /// Transpiles a dynamic general SQL statement to the sqlite dialect.
-std::string to_sql(const dynamic::Statement& _stmt) noexcept;
+std::string to_sql_impl(const dynamic::Statement& _stmt) noexcept;
+
+/// Transpiles any  SQL statement to the sqlite dialect.
+template <class T>
+std::string to_sql(const T& _t) noexcept {
+  if constexpr (std::is_same_v<std::remove_cvref_t<T>, dynamic::Statement>) {
+    return to_sql_impl(_t);
+  } else {
+    return to_sql_impl(transpilation::to_sql(_t));
+  }
+}
 
 }  // namespace sqlgen::sqlite
 
diff --git a/include/sqlgen/transpilation/to_sql.hpp b/include/sqlgen/transpilation/to_sql.hpp
new file mode 100644
index 0000000..d6c67ca
--- /dev/null
+++ b/include/sqlgen/transpilation/to_sql.hpp
@@ -0,0 +1,48 @@
+#ifndef SQLGEN_TRANSPILATION_TO_SQL_HPP_
+#define SQLGEN_TRANSPILATION_TO_SQL_HPP_
+
+#include <vector>
+
+#include "../CreateTable.hpp"
+#include "../Insert.hpp"
+#include "../dynamic/Statement.hpp"
+#include "../read.hpp"
+#include "to_create_table.hpp"
+#include "to_insert.hpp"
+#include "to_select_from.hpp"
+#include "value_t.hpp"
+
+namespace sqlgen::transpilation {
+
+template <class T>
+struct ToSQL;
+
+template <class T>
+struct ToSQL<CreateTable<T>> {
+  dynamic::Statement operator()(const auto&) const {
+    return to_create_table<T>();
+  }
+};
+
+template <class T>
+struct ToSQL<Insert<T>> {
+  dynamic::Statement operator()(const auto&) const { return to_insert<T>(); }
+};
+
+template <class ContainerType, class WhereType, class OrderByType,
+          class LimitType>
+struct ToSQL<Read<ContainerType, WhereType, OrderByType, LimitType>> {
+  dynamic::Statement operator()(const auto& _read) const {
+    return to_select_from<value_t<ContainerType>, WhereType, OrderByType,
+                          LimitType>(_read.where_, _read.limit_);
+  }
+};
+
+template <class T>
+dynamic::Statement to_sql(const T& _t) {
+  return ToSQL<std::remove_cvref_t<T>>{}(_t);
+}
+
+}  // namespace sqlgen::transpilation
+
+#endif
diff --git a/src/sqlgen/postgres/Connection.cpp b/src/sqlgen/postgres/Connection.cpp
index d5cedd6..bfa741b 100644
--- a/src/sqlgen/postgres/Connection.cpp
+++ b/src/sqlgen/postgres/Connection.cpp
@@ -46,7 +46,7 @@ typename Connection::ConnPtr Connection::make_conn(
 }
 
 Result<Ref<IteratorBase>> Connection::read(const dynamic::SelectFrom& _query) {
-  const auto sql = postgres::to_sql(_query);
+  const auto sql = postgres::to_sql_impl(_query);
   try {
     return Ref<IteratorBase>(Ref<Iterator>::make(sql, conn_));
   } catch (std::exception& e) {
diff --git a/src/sqlgen/postgres/to_sql.cpp b/src/sqlgen/postgres/to_sql.cpp
index 08a770c..3706d74 100644
--- a/src/sqlgen/postgres/to_sql.cpp
+++ b/src/sqlgen/postgres/to_sql.cpp
@@ -223,7 +223,7 @@ std::string select_from_to_sql(const dynamic::SelectFrom& _stmt) noexcept {
   return stream.str();
 }
 
-std::string to_sql(const dynamic::Statement& _stmt) noexcept {
+std::string to_sql_impl(const dynamic::Statement& _stmt) noexcept {
   return _stmt.visit([&](const auto& _s) -> std::string {
     using S = std::remove_cvref_t<decltype(_s)>;
     if constexpr (std::is_same_v<S, dynamic::CreateTable>) {
diff --git a/src/sqlgen/sqlite/Connection.cpp b/src/sqlgen/sqlite/Connection.cpp
index 969e60f..b6ac28d 100644
--- a/src/sqlgen/sqlite/Connection.cpp
+++ b/src/sqlgen/sqlite/Connection.cpp
@@ -42,7 +42,7 @@ typename Connection::ConnPtr Connection::make_conn(const std::string& _fname) {
 }
 
 Result<Ref<IteratorBase>> Connection::read(const dynamic::SelectFrom& _query) {
-  const auto sql = to_sql(_query);
+  const auto sql = to_sql_impl(_query);
 
   sqlite3_stmt* p_stmt = nullptr;
 
@@ -70,7 +70,7 @@ Result<Nothing> Connection::start_write(const dynamic::Insert& _stmt) {
         ".end_write() before you can start another.");
   }
 
-  const auto sql = to_sql(_stmt);
+  const auto sql = to_sql_impl(_stmt);
 
   sqlite3_stmt* p_stmt = nullptr;
 
diff --git a/src/sqlgen/sqlite/to_sql.cpp b/src/sqlgen/sqlite/to_sql.cpp
index d89cd79..167a20f 100644
--- a/src/sqlgen/sqlite/to_sql.cpp
+++ b/src/sqlgen/sqlite/to_sql.cpp
@@ -210,7 +210,7 @@ std::string select_from_to_sql(const dynamic::SelectFrom& _stmt) noexcept {
   return stream.str();
 }
 
-std::string to_sql(const dynamic::Statement& _stmt) noexcept {
+std::string to_sql_impl(const dynamic::Statement& _stmt) noexcept {
   return _stmt.visit([&](const auto& _s) -> std::string {
     using S = std::remove_cvref_t<decltype(_s)>;
     if constexpr (std::is_same_v<S, dynamic::CreateTable>) {
diff --git a/tests/postgres/test_create_table_dry.cpp b/tests/postgres/test_create_table_dry.cpp
new file mode 100644
index 0000000..b2705cc
--- /dev/null
+++ b/tests/postgres/test_create_table_dry.cpp
@@ -0,0 +1,23 @@
+#include <gtest/gtest.h>
+
+#include <sqlgen.hpp>
+#include <sqlgen/postgres.hpp>
+
+namespace test_create_table_dry {
+
+struct TestTable {
+  std::string field1;
+  int32_t field2;
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::optional<std::string> nullable;
+};
+
+TEST(postgres, test_create_table_dry) {
+  const auto query = sqlgen::CreateTable<TestTable>{};
+
+  const auto expected =
+      R"(CREATE TABLE IF NOT EXISTS "TestTable" ("field1" TEXT NOT NULL, "field2" INTEGER NOT NULL, "id" INTEGER NOT NULL, "nullable" TEXT, PRIMARY KEY ("id"));)";
+
+  EXPECT_EQ(sqlgen::postgres::to_sql(query), expected);
+}
+}  // namespace test_create_table_dry
diff --git a/tests/postgres/test_insert_dry.cpp b/tests/postgres/test_insert_dry.cpp
new file mode 100644
index 0000000..4ee7335
--- /dev/null
+++ b/tests/postgres/test_insert_dry.cpp
@@ -0,0 +1,24 @@
+#include <gtest/gtest.h>
+
+#include <sqlgen.hpp>
+#include <sqlgen/postgres.hpp>
+
+namespace test_insert_dry {
+
+struct TestTable {
+  std::string field1;
+  int32_t field2;
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::optional<std::string> nullable;
+};
+
+TEST(postgres, test_insert_dry) {
+  const auto query = sqlgen::Insert<TestTable>{};
+
+  const auto expected =
+      "COPY \"public\".\"TestTable\"(\"field1\", \"field2\", \"id\", "
+      "\"nullable\") FROM STDIN WITH DELIMITER '\t' NULL '\e' QUOTE '\a';";
+
+  EXPECT_EQ(sqlgen::postgres::to_sql(query), expected);
+}
+}  // namespace test_insert_dry
diff --git a/tests/postgres/test_to_select_from.cpp b/tests/postgres/test_to_select_from.cpp
deleted file mode 100644
index 1aadbe1..0000000
--- a/tests/postgres/test_to_select_from.cpp
+++ /dev/null
@@ -1,30 +0,0 @@
-#include <gtest/gtest.h>
-
-#include <sqlgen.hpp>
-#include <sqlgen/postgres.hpp>
-#include <sqlgen/transpilation/to_select_from.hpp>
-
-namespace test_to_select_from {
-
-struct TestTable {
-  std::string field1;
-  int32_t field2;
-  sqlgen::PrimaryKey<uint32_t> id;
-  std::optional<std::string> nullable;
-};
-
-TEST(postgres, test_to_select_from) {
-  const auto select_from_stmt =
-      sqlgen::transpilation::to_select_from<TestTable>();
-  const auto credentials = sqlgen::postgres::Credentials{.user = "postgres",
-                                                         .password = "postgres",
-                                                         .host = "localhost",
-                                                         .dbname = "postgres",
-                                                         .port = 5432};
-  const auto conn = sqlgen::postgres::connect(credentials).value();
-  const auto expected =
-      R"(SELECT "field1", "field2", "id", "nullable" FROM "TestTable";)";
-
-  EXPECT_EQ(conn->to_sql(select_from_stmt), expected);
-}
-}  // namespace test_to_select_from
diff --git a/tests/postgres/test_to_select_from_dry.cpp b/tests/postgres/test_to_select_from_dry.cpp
new file mode 100644
index 0000000..18a818d
--- /dev/null
+++ b/tests/postgres/test_to_select_from_dry.cpp
@@ -0,0 +1,24 @@
+#include <gtest/gtest.h>
+
+#include <sqlgen.hpp>
+#include <sqlgen/postgres.hpp>
+#include <sqlgen/transpilation/to_select_from.hpp>
+
+namespace test_to_select_from_dry {
+
+struct TestTable {
+  std::string field1;
+  int32_t field2;
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::optional<std::string> nullable;
+};
+
+TEST(postgres, test_to_select_from_dry) {
+  const auto query = sqlgen::read<std::vector<TestTable>>;
+
+  const auto expected =
+      R"(SELECT "field1", "field2", "id", "nullable" FROM "TestTable";)";
+
+  EXPECT_EQ(sqlgen::postgres::to_sql(query), expected);
+}
+}  // namespace test_to_select_from_dry
diff --git a/tests/postgres/test_where_dry.cpp b/tests/postgres/test_where_dry.cpp
new file mode 100644
index 0000000..284099d
--- /dev/null
+++ b/tests/postgres/test_where_dry.cpp
@@ -0,0 +1,29 @@
+#include <gtest/gtest.h>
+
+#include <sqlgen.hpp>
+#include <sqlgen/postgres.hpp>
+#include <vector>
+
+namespace test_where_dry {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  int age;
+};
+
+TEST(postgres, test_where_dry) {
+  using namespace sqlgen;
+
+  const auto query = sqlgen::read<std::vector<Person>> |
+                     where("age"_c < 18 and "first_name"_c != "Hugo") |
+                     order_by("age"_c);
+
+  const auto expected =
+      R"(SELECT "id", "first_name", "last_name", "age" FROM "Person" WHERE ("age" < 18) AND ("first_name" != 'Hugo') ORDER BY "age";)";
+
+  EXPECT_EQ(sqlgen::postgres::to_sql(query), expected);
+}
+
+}  // namespace test_where_dry